REVISTA CONSTRUCŢIA DE MAŞINI SERIE NOUĂ form TI 3_4_2014.pdfTRANSMISII MECANICE / TRANSMISSIONS . 7. AN EXTENSION OF THE ELECTROMECHANICAL ANALOGY IN THE DOMAIN OF HYDROSTATIC

REVISTA CONSTRUCŢIA DE MAŞINI - SERIE NOUĂ

Anul 66, Nr. 3-4 / 2014

Din sumar

TEHNOLOGIE INOVATIVĂ / INNOVATIVE TECHNOLOGY

TRANSMISII MECANICE / TRANSMISSIONS MECANICĂ / MECHANICS

MODELARE & SIMULARE / MODELLING &SIMULATION

ECONOMIE INDUSTRIALĂ / INDUSTRIAL ECONOMY

• "Tehnologia Inovativa" printed form: ISSN 2248 - 0420; ISSN-L 2248 - 0420 • "Tehnologia Inovativa" online form: ISSN 2248 - 0420; ISSN-L 2248 - 0439 EDITOR: ICTCM – CITAf 041303 Bucuresti Şos. Olteniţei nr. 103, sector 4, O.P. 8 Tel: 021 332.37.70/234 Fax: 021 332.07.75 / 021 332.31.95 E-mail: [email protected]

RESPONSABIL EDITOR Florica Costin REDACTOR- ŞEF Irina Rădulescu INFORMAŢII, ABONAMENTE: Revista este evaluată CNCSIS la categoria B+, apare trimestrial. Abonamentele se fac direct, prin dispoziţie de plată sau mandat poştal, trimis pe adresa revistei. CONT – ICTCM: nr. RO58 RNCB 0075 0352 1240 0001; BCR sector 4 TIPAR: ICTCM – CITAf COPYRIGHT 2003 Toate drepturile asupra acestei ediţii sunt rezervate ICTCM – CITAf. Nu este permisă reproducerea integrală sau parţială a articolelor din revista „Tehnologia Inovativă” fără consimţământul scris al editorului. Opiniile exprimate în revistă aparţin semnatarilor articolelor, fără să reflecte obligatoriu şi punctul de vedere al editorului. Toate drepturile asupra acestei ediţii sunt rezervate ICTCM – CITAf. Nu este permisă reproducerea integrală sau parţială a articolelor din revista „Tehnologia Inovativă” fără consimţământul scris al editorului. Opiniile exprimate în revistă aparţin semnatarilor articolelor, fără să reflecte obligatoriu şi punctul de vedere al editorului.

TEHNOLOGIA INOVATIVĂ – Revista „Construcţia de maşini” nr. 3-4 / 2014

ANUL 66 / 2014 – NR. 3 - 4

TEHNOLOGIA INOVATIVĂ

REVISTA CONSTRUCŢIA DE MAŞINI

COLEGIUL DE REDACŢIE Octavian BOLOGA - Universitatea „Lucian Blaga” din Sibiu

Olivier BONNEAU – Universitatea din Poitiers, Franţa

Ion BOSTAN – Universitatea Tehnică a Moldovei

K.D. BOUZAKIS – Aristoteles University of Thessaloniki, Grecia

Doug BRANHAM - Lubrication Systems Company, Houston, Texas, USA

Dan BRÎNDAŞU - Universitatea „Lucian Blaga” din Sibiu

Radu Mircea CARP – CIOCÂRDIA - Universitatea POLITEHNICA din Bucureşti

Mircea CIOBANU - Universitatea „Ştefan cel Mare” din Suceava

Valeriu DULGHERU – Universitatea Tehnică a Moldovei

Ioan Dan FILIPOIU - Universitatea POLITEHNICA din Bucureşti

Michel FILLON – Universitatea din Poitiers, Franţa

Mohamed HAJJAM – Universitatea din Poitiers, Franţa

Tudor ICLĂNZAN - Universitatea „Politehnica” din Timişoara

Nicolae Valentin IVAN - Universitatea „TRANSILVANIA” din Braşov

Gheorghe MOGAN – Universitatea „TRANSILVANIA” din Braşov

Ilie MUSCĂ - Universitatea „Ştefan cel Mare” din Suceava

Nicolae OANCEA - Universitatea „Dunărea de Jos” din Galaţi

Dumitru OLARU - Universitatea Tehnică „Gheorghe Asachi” din Iaşi

Juozas PADGURSKAS – Lithuanian University of Agriculture, Lithuania

Radu POPESCU – Academia Română - INCE – CEIS, Bucureşti

Tudor PRISECARU - Universitatea POLITEHNICA din Bucureşti

Vasile PUIU - Universitatea din Bacău

Stanisław PYTKO - University of Science and Technology, Kraków, Poland

Alexandru RĂDULESCU - Universitatea POLITEHNICA din Bucureşti

Minodora RÎPĂ - Universitatea „Dunărea de Jos” din Galaţi

Lucian TUDOSE - Universitatea din Cluj

Thami ZEGHLOUL – Universitatea din Poitiers, Franţa


COMITET ONORIFIC

Niculae Napoleon ANTONESCU – Universitatea „Petrol şi Gaze” din Ploieşti

Traian AURITE - Universitatea POLITEHNICA din Bucureşti

Gavrilă CALEFARIU - Universitatea „TRANSILVANIA” din Braşov

Mircea COZMÎNCĂ - Universitatea Tehnică „Gheorghe Asachi” din Iaşi

Marian GHEORGHE - Universitatea POLITEHNICA din Bucureşti

Constantin ISPAS - Universitatea POLITEHNICA din Bucureşti

Valeriu JINESCU - Universitatea POLITEHNICA din Bucureşti

Aurel JULA - Universitatea „TRANSILVANIA” din Braşov

Constantin MINCIU - Universitatea POLITEHNICA din Bucureşti

Eugen PAY - Universitatea de Nord din Baia Mare

Iulian POPESCU - Universitatea din Craiova

Aurelian VLASE - Universitatea POLITEHNICA din Bucureşti

Ioan VOICA - Universitatea POLITEHNICA din Bucureşti

EDITOR Oficiul de Informare Documentară pentru Industrie, Cercetare, Management

din cadrul S.C. ICTCM S.A. BUCUREŞTI

RESPONSABIL EDITOR Irina Rădulescu

REDACTOR - ȘEF Irina Rădulescu


CUPRINS TEHNOLOGIE INOVATIVĂ / INNOVATIVE TECHNOLOGY

1. PERFORMANCES OF THE LAYERS OBTAIN BY THE HVOF THERMAL SPRAYING PROCEDURE pag. 9 Valeriu Avramescu, Raluca Magdalena Nita, Waltraut Brandl, Loredana Theodora Paun, Daniel Bobe, Sebastian Rosulescu, Luminita Elena Olteanu, Marius Costin Manea SC ICTCM SA Bucharest, Bucharest, ROMANIA

2. MONITORING THE HVOF THERMAL SPRAYING PROCESS FOR QUALITY IMPROVEMENT OF THE DEPOSITED COATINGS pag. 17 V. Avramescu, S. Roşulescu, R. Niţă, L. Păun, D. Bobe, L. Olteanu, M. Manea SC ICTCM SA Bucharest, Bucharest, ROMANIA

3. FRICTION STIR PROCESSING AS A NEW SURFACE FINISHING TECHINOLOGY pag. 25 Milena Folea Transilvania University of Brașov, Brașov, ROMANIA

4. DETECTION EFFICIENCY OF ROAD VEHICLES IN MOTION pag. 31 FOR TRANSPORT COMPANIES Nicolae Răzvan, Alexandru Valentin Rădulescu POLITEHNICA University of Bucharest, Bucharest, ROMANIA

5. ADDITIVE MANUFACTURING TECHNOLOGIES USED FOR SUPERALLOYS PROCESSING pag. 35 Răzvan Udroiu Transilvania University of Brașov, Brașov, ROMANIA

6. INNOVATIVE TECHNOLOGIES IN DENTISTRY AND DENTAL TECHNIQUE pag. 42 Stamate Valentin-Marian, Lancea Camil Transilvania University of Braşov, Braşov, ROMANIA TRANSMISII MECANICE / TRANSMISSIONS

7. AN EXTENSION OF THE ELECTROMECHANICAL ANALOGY IN THE DOMAIN OF HYDROSTATIC TRANSMISSIONS pag. 50 Mircea Radulescu University of Craiova, Craiova, ROMANIA MECANICĂ / MECHANICS

8. OVERVIEW ON FEATURE-BASED DESIGN pag. 66 Chicoş Lucia Antoneta Transilvania University of Braşov, Braşov, ROMANIA

9. COMPORTAREA ÎN FUNCŢIONARE A GRUPURILOR DE REZEMARE ALE CUPTOARELOR ROTATIVE (BEHAVIOR IN OPERATION OF ROTARY FURNACES BEARING GROUPS) pag. 72 Gheorghe Ene, Teodor Sima University Politehnica of Bucharest, Bucharest, ROMANIA


10. INFLUENCE OF THE FEED ON THE PRINCIPLE QUALITY AND ACCURACY INDICATORS AT THE SPD PROCESSING OF THE INVOLUTES TOOTH pag. 80 Gheorghe Mareş TRANSILVANIA Univesity of Braşov, Brașov, ROMANIA

11. PRINCIPALELE PROBLEME ALE TEHNOLOGIEI PRELUCRĂRII METALELOR PRIN

DEFORMARE PLASTICĂ LA RECE (MAIN PROBLEMS OF METALS PROCESSING TECHNOLOGY BY COLD PLASTICAL DEFORMATION) pag. 86 Teodor Sima University Politehnica of Bucharest, Bucharest, ROMANIA

12. REZEMAREA CIURURILOR VIBRATOARE PE ELEMENTE ELASTICE DIN CAUCIUC (THE VIBRATING SCREENS BEARING SYSTEM WITH ELASTIC RUBBER ELEMENTS) pag. 92 Ene I. Gheorghe, Prodea Iuliana-Marlena University Politehnica of Bucharest, Bucharest, ROMANIA

MODELARE & SIMULARE / MODELLING & SIMULATION

13. CAD-CAM SOLUTIONS FOR CNC MILLING OF 3D SURFACES USING

FASC-14 SOFTWARE SYSTEM pag. 98 Camil Lancea, Valentin-Marian Stamate Transilvania University of Brașov, Brașov, ROMANIA

14. RESTITUŢIA STEREOSCOPICĂ A ACOPERIŞURILOR (STEREOSCOPIC RESTITUTION ROOFS) pag. 106 Adina Oprea, Alexandru Valentin Rădulescu University POLITEHNICA of Bucharest, Bucharest, ROMANIA

15. NONLINEAR FINITE ELEMENT ANALYSIS FOR ENGINEERING APPLICATIONS OF COMPRESSIBLE METALLIC FOAMS pag. 112 I. Carciog1, A. Gavrus2, A. Belhadj3, S. Cananau1, F. Bernard2 1. Dep. Machine Elements and Tribology, Polytechnic University from Bucharest, ROMANIA 2. Laboratory of Civil and Mechanical Engineering (LGCGM, EA3913), INSA Rennes, FRANCE 3. Laboratory of Materials Science and Engineering (LSGM), Univ. of Sciences & Technologies Houari Boumediene, Bab-Ezzouar, Alger, ALGERIA ECONOMIE INDUSTRIALĂ / INDUSTRIAL ECONOMY

16. RESEARCHES REGARDING THE ACHIEVEMENT OF AN INTERVIEW QUESTIONNAIRE FOR BUSINESS ENVIRONMENT AGAINST AN ECO-INNOVATION HUB pag. 119 Irina Rădulescu1, Florica Costin2 1POLITEHNICA University of Bucharest, 2S.C. ICTCM S.A. Bucharest, ROMANIA

TEHNOLOGIA INOVATIVĂ – Revista „Construcţia de maşini” nr. 3 - 4 / 2014

ABSTRACTS “INNOVATIVE TECHNOLOGY” 3 -4 / 2014

PERFORMANCES OF THE LAYERS OBTAIN BY THE HVOF THERMAL SPRAYING

PROCEDURE

Valeriu Avramescu, Raluca Magdalena Nita, Waltraut Brandl, Loredana Theodora Paun,

Daniel Bobe, Sebastian Rosulescu, Luminita Elena Olteanu, Marius Costin Manea SC ICTCM SA Bucharest, Bucharest, ROMANIA

The article “Performances of the layers obtain by the HVOF thermal spraying procedure” has as objective the evaluation of the sprayed deposit performances obtain by thermal spraying. Were realised deposits on paralipipedic plates, from OL37, using 3 different powders. Technologic parameters were chosen taking into consideration the GTV specifications.

MONITORING THE HVOF THERMAL SPRAYING PROCESS FOR QUALITY

IMPROVEMENT OF THE DEPOSITED COATINGS

V. Avramescu, S. Roşulescu, R. Niţă, L. Păun, D. Bobe, L. Olteanu, M. Manea

SC ICTCM SA Bucharest, Bucharest, ROMANIA

The article Monitoring the HVOF thermal spraying process for quality improvement of the deposited coatings shows the approach regarding assessment of sources of variation, such as vibrations and temperature, concerning the quality of the deposited coatings by HVOF process and proposes the modification of the parameters of technological process to mitigate the sources of variation monitored and quality improving of the HVOF coatings produced by thermal spraying.

FRICTION STIR PROCESSING AS A NEW SURFACE FINISHING

TECHINOLOGY

Milena Folea Transilvania University of Braşov, Braşov,

ROMANIA

The paper presents Friction stir processing (FSP) as a specific method for surface engineering. This method is derived from Friction stir welding (FSW) patented in 1991 by British scientists of The Welding Institute (TWI). Later on it was found that the method can be effectively used for surface finishing, specifically to obtain a very fine grain surface layer with far superior mechanical and tribological properties compared to the base material of the workpiece.

DETECTION EFFICIENCY OF ROAD VEHICLES IN MOTION FOR TRANSPORT

COMPANIES

Nicolae Răzvan, Alexandru Valentin Rădulescu POLITEHNICA University of Bucharest, Bucharest,

ROMANIA

Automation became necessary in the road since the authorities have realized that the number of road accidents and material losses of life have increased alarmingly long. The complexity of these processes, the extent of large geography, transport systems and road infrastructure to achieve scale automation in this area is needed a large merger of several specific technologies: Capture information, Information processing, Submit Information,Use of information. The general objectives of the latest research and development programs in the field were directed to obtaining and exploitation of new knowledge on the applicability of traffic control systems in major cities, traffic management . Research has focused mainly on the applicability of self-training these types of embedded systems, auto optimization urban traffic control strategies.

ADDITIVE MANUFACTURING TECHNOLOGIES USED FOR SUPERALLOYS

PROCESSING

Răzvan Udroiu Transilvania University of Braşov, Braşov,

ROMANIA

The paper presents Additive Manufacturing (AM) technologies used for building parts from superalloys. The main objective of this article is the state of the art of AM used for metal parts, of presentation of the working principle of the metal AM, of the types and characteristics of AM machines used and also of the applications for superalloys.

INNOVATIVE TECHNOLOGIES IN DENTISTRY AND DENTAL TECHNIQUE

Stamate Valentin-Marian, Lancea Camil Transivania University of Braşov, Braşov,

ROMANIA

Investments made during the last decades in dentistry field and borrowing advanced industrial technologies have led to spectacular and irreplaceable results. The most advanced methods, such as three-dimensional digital photography, using virtual working models and building models of laser sintered metal powder by Rapid prototyping method were immediately assimilated.


AN EXTENSION OF THE ELECTROMECHANICAL ANALOGY

IN THE DOMAIN OF HYDROSTATIC TRANSMISSIONS

(Part II. THE ELECTROHYDRAULIC ANALOGY AND ITS EXTENSION)

Mircea Rădulescu University of Craiova, Craiova, ROMANIA

This paper represents the part II of a research: “The Transmission Coefficient of Hydrostatic Drives”, which is published in Power Transmissions, Proc. Of the 4th International Conference, June 20 – 23, Sinaia, 2012, pp.399 – 415. The paper aims to expand the electromechanical analogy in other domains of technology: hydraulic, pneumatic, acoustic, sonic, and even in thermodynamics. In addition to the similarity of the equations and mathematical models, in the domain of fluidic systems we have highlighted the analogy of the circuit elements and some basic structures, for which the equivalent schemes are given. Analogy tables are presented, including the important sizes, units, symbols and generalized mathematical models applicable in all domains above and the advantages of the analogy and its limits of application are highlighted.

OVERVIEW ON FEATURE-BASED DESIGN

Chicoş Lucia Antoneta Transilvania University of Braşov, Braşov,

ROMANIA

Concurrent/simultaneous engineering admits that the design and manufacturing are strongly interdependent. Concurrent engineering argues that critical manufacturing issues should be considered early in design stage in order to reduce the number of design iterations. Therefore the information provided by a CAD system must contain, in addition to the geometric information, information for process planning, manufacturing, NC programming etc. Feature-based design has received much attention in last decade because the features are considered the connection elements among CAD, CAPP and CAM systems. This paper presents an overview of the research carried out in feature-based design (FBD), the evolution of their definitions, representation techniques as well as their role in design and manufacturing.

COMPORTAREA ÎN FUNCŢIONARE A GRUPURILOR DE REZEMARE ALE CUPTOARELOR ROTATIVE

(BEHAVIOR IN OPERATION OF ROTARY FURNACES BEARING GROUPS)

Gheorghe Ene, Teodor Sima University Politehnica of Bucharest, Bucharest,

ROMANIA

In the present work is presented the functional behavior of bindings and roles as parts in the bearing groups of rotational ovens. The influence of manufacturing precision, installation and adjustment of bearing groups is considered.

INFLUENCE OF THE FEED ON THE PRINCIPLE QUALITY AND

ACCURACY INDICATORS AT THE SPD PROCESSING OF THE INVOLUTES TOOTH

Gheorghe Mareş TRANSILVANIA Univesity of Braşov,

Braşov, ROMANIA

The processing trough Superficial Plastic Deforming (SPD) of the spur gear is a final cold-work hardening and finishing process of the superficial stratum. Quality and accuracy of the processing are influenced by the deforming parameters regime, deforming force, physical and mechanical properties of the work piece and by the cooling and lubricating regime. In this paper the author presents the influence of the feed over the roughness Ra, micro hardness HV of the tooth flank and over the processing accuracy. This influence is given by the next terms: length over the tooth W, teeth thickness Sc, profile error Ffr and tolerance from teeth striker Fk.

PRINCIPALELE PROBLEME ALE TEHNOLOGIEI PRELUCRĂRII METALELOR

PRIN DEFORMARE PLASTICĂ LA RECE (MAIN PROBLEMS OF METALS

PROCESSING TECHNOLOGY BY COLD PLASTICAL DEFORMATION)

Teodor Sima University Politehnica of Bucharest, Bucharest,

ROMANIA

In this paper the main technological parameters of manufacturing through plastic cold deformation are reviewed and their calculation in the specific case of bending on machines with rotational cylinders is considered.

REZEMAREA CIURURILOR VIBRATOARE PE ELEMENTE ELASTICE DIN CAUCIUC /

THE VIBRATING SCREENS BEARING SYSTEM WITH ELASTIC RUBBER

ELEMENTS

Ene I. Gheorghe, Prodea Iuliana-Marlena University Politehnica of Bucharest, Bucharest,

ROMANIA

The paper focuses on design issues related to the vibrating screens bearing system with elastic rubber elements. A calculation method for this elastic support systems is presented. Finally, a numerical example is used to illustrate the application of this methodology.


CAD-CAM SOLUTIONS FOR CNC MILLING OF 3D SURFACES USING FASC-14

SOFTWARE SYSTEM

Camil Lancea, Valentin-Marian Stamate Transilvania University of Brasov, Brasov,

ROMANIA

Absolutely, the manufacturing of complex 3D surfaces should be performed nowadays in accordance with the newest scientific and technical conditions. This implies that the parts manufacturing should be performed according with the CAD / CAM techniques. Hence, as well as the new engineering concepts such as modelling and simulation engineering and also because of the need to consider the technological impact over the constructive phase, it is necessary that the geometric information, generated within the CAD-C (CAD - Conception) stage to be used in the CAD-T (CAD - Technology) stage. This paper proposes an alternative for using established CAD / CAM / CAE systems, for CNC processing, by milling complex shape surfaces, generated with 4 spline curves, using end mills or ball nose mills. The software package presented in this paper offers facilities both for the surfaces designing phase and also for the manufacturing process phase, through the design of customized pull-down menus and commands specific the CAD CAPP and CAM phases in Romanian language. Another advantage, far from being insignificant, of this system, is a significantly lower acquisition cost than dedicated systems existing nowadays on the market: CATIA, ProEngineer, Solid Works etc.

RESTITUŢIA STEREOSCOPICĂ A ACOPERIŞURILOR

(STEREOSCOPIC RESTITUTION ROOFS)

Adina Oprea, Alexandru Valentin Rădulescu University POLITEHNICA of Bucharest,

ROMANIA

For 3D models, it is necessary to use some effective methods to reduce working time and lighten the work of operators. In this context it creates a continuous flow technology to bring the ease of achievin g realistic virtual models.

NONLINEAR FINITE ELEMENT ANALYSIS FOR ENGINEERING APPLICATIONS

OF COMPRESSIBLE METALLIC FOAMS

I. Carciog1, A. Gavrus2, A. Belhadj3, S. Cănănău1, F. Bernard2

1. Dep. Machine Elements and Tribology, Polytechnic University from Bucharest, ROMANIA 2. Laboratory of Civil and Mechanical Engineering

(LGCGM, EA3913), INSA Rennes, FRANCE

3. Laboratory of Materials Science and Engineering (LSGM), Univ. of Sciences & Technologies Houari

Boumediene, Bab-Ezzouar, Alger, ALGERIA

The present article proposes the improvement of a Finite Element Analysis (FEA) applied to the study of a metallic foam material submitted to a compression loading. The purpose of the study is to achieve a compressible model using the finite element method that will reproduce the experimental conditions and physical phenomena resulted while testing the sample on a test bench. Based on identified rheological input data, the model is used for two different samples geometries. The corresponding simulation results are compared with those obtained from a test bench. Starting from the obtained numerical results, conclusions will be made concerning the used numerical mesh and its geometry morphology.

RESEARCHES REGARDING THE ACHIEVEMENT

OF AN INTERVIEW QUESTIONNAIRE FOR BUSINESS ENVIRONMENT

AGAINST AN ECO-INNOVATION HUB

Irina Rădulescu1, Florica Costin2 1 POLITEHNICA University of Bucharest, 2 S.C. ICTCM S.A. Bucharest, ROMANIA

Development of a questionnaire for enterprises that is working in the Romanian recycling of waste electrical and electronic equipment raises many issues. It is necessary to increase organizational competitiveness of firms operating in this area, also to increase the degree of involvement of these entities in promoting eco-innovation for green economy development. By creating an eco-innovation hub prototype will get a transparent, easy to access infrastructure for collecting and analysing data. It will be facilitated the transfer of eco-innovation know-how, in order to improve the recycling of Electrical and Electronic Equipment Wastes and promote eco-innovation. The questionnaire is sent to companies that operate operating in this field, whose experience and competence may be useful to other stakeholders in the WEEE area.


PERFORMANCES OF THE LAYERS OBTAIN BY THE HVOF THERMAL SPRAYING PROCEDURE

Valeriu Avramescu, Raluca Magdalena Nita, Waltraut Brandl, Loredana Theodora Paun, Daniel Bobe, Sebastian Rosulescu,

Luminita Elena Olteanu, Marius Costin Manea

SC ICTCM SA Bucharest, Bucharest, ROMANIA, [email protected]

REZUMAT Articolul “Performantele straturilor depuse prin procedeul de pulverizare termica HVOF”are ca obiectiv evaluarea performanţelor straturilor obtinute prin procedeul de pulverizare termica. Au fost realizate depuneri pe placute de forma paralelipedica, din OL 37, utilizându-se 3 pulberi diferite. Parametrii tehnologici alesi au fost stabiliti in functiile de specificatiile GTV.

ABSTRACT The article “Performances of the layers obtain by the HVOF thermal spraying procedure” has as objective the evaluation of the sprayed deposit performances obtain by thermal spraying. Were realised deposits on paralipipedic plates, from OL37, using 3 different powders. Technologic parameters were chosen taking into consideration the GTV specifications.

KEYWORDS: HVOF installation, integrated technologic system, thermal spraying process, spraying parameters, thermal spraying process structure, metallographic analysis. CUVINTE CHEIE: instalatie HVOF, sistem tehnologic integrat, proces pulverizare termica, parametru de pulverizare, structura procesului de pulverizare termica, analiza metalografica.

1. INTRODUCTION

In S.C. ICTCM – Mechanical Engineering and Research Institute - SA by project no. 614 SMIS code / NSRF: 12537 "Applied researches, technology and technological equipment for high strength thermal spraying by HVOF process used in industrial and medical applications", co-funded by the Regional Development European Fund, under the contract financing 270/27.10.2010, was achieved an integrated technological system for thermal spraying by HVOF process (High Velocity Oxygen Fuel). 2. HVOF – THERMAL SPRAYING PROCESS

Thermal spraying is a processes for making thin layers in which fine powders, metal, non-metal or ceramics are deposited as a thin layer, adherent, with imposed properties required by the domain of interest (industrial or medical applications).

The process consists in introducing continuously a mixture of powder, gas and liquid fuel (kerosene), in a combustion chamber. The great pressure in the combustion chamber, resulted from the combustion of a mixture from oxygen – kerosene, correlate with its expansion through the combustion nozzle from the output spraying torch contribute at obtaining a jet with very high speed (2 … 4 Mach).

As a result, the metal/non-metal/ceramics particles from the powder, at the very high obtain temperatures, are accelerated at the obtained speed in the output nozzle of the spraying torch, which results in layers with high density of particles and good adhesion. The characteristics of HVOF thermal spray process [1] are briefly presented in the following ideas: The energy source is oxygen in gaseous form and the fuel gas is kerosene; the jet has a temperature of up to 2700° C and the speeds up to 1600 m/s; the deposited material is a powder with particle size of 5-45 μm;

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the type of the deposited powder is: carbide with metal alloys matrix; the particle velocity during deposition: 400-800 m/s; the spraying distance: 150 – 300 mm; The characteristics of the deposited layers by HVOF process [1] are the following: high density: less than 2% porosity and in special conditions up to 0.2% porosity; high adhesion with the base material (for example, for tungsten and cobalt carbide) - 1100 ... 1350 HV0,3 DPH300; good fatigue resistance; greater thickness; the layers coated by HVOF process (for ex. layers of tungsten carbides can be up to 6.4 mm); excellent wear resistance; superior corrosion resistance; The parameters that characterise the HVOF process are process parameters respectively technologic parameters. Process parameters are the ones that describe the process components that realise the jet of the depose material, like: HVOF flame, used powder and powder spraying parameters. 3. HVOF LABORATORY: MAIN ELEMENTS, FEATURES AND FUNCTIONALITY

The laboratory is an integrated technological system - prototype - which allows applied research in order to achieve high strength metal coatings, thermal, for corrosion protection and the surface of new or used parts, for industrial and medical applications using HVOF process (High Velocity Oxygen Fuel).

For the laboratory were provided the following equipments and accessories: compressor, blasting cabin, containers and distribution networks for kerosene, oxygen, nitrogen, water, compressed air and powders, security system for containers, cooling system for the HVOF torch, feeding/dosing powder system, HVOF controller, parts handling devices (horizontal axis and vertical axis connected to the exhaust system and exhaust filter, electric actuated), thermal spraying cabin, with specific security systems for the HVOF process, parts cooling system, K2 spraying torch and cooling nozzle – figure 1, FANUC robot with command controller, a filtration system and ventilations pipes, electric installation for the command of the hole HVOF technologic system, performing systems for data acquisition, others accessories.

K2 Spraying tourch

Cooling nozzle

FanucRobot

Figure 1. Fanuc Robot Arm, with K2 spraying torch

In the laboratory can be realised different types

of laying on the parts surface, for industrial applications (for example: the shank of the pomp of very high pressure used in the installation of water jet cutting, moulds for glass of for metal plastic deformation; cylinders, shanks, valves, others components, etc.) and for medical applications (for example: surgical devices; laparoscopic surgical devices; others types of devices).

It can be processed by thermal spraying rotation parts (with a maximum diameter of 300 mm and maximum lengths of 1200 mm, handled with a device with horizontal axis) and also shell parts (with a maximum diameter of 1000 mm, handled with a device with vertical axis). 4. TYPES OF USED POWDERS. HVOF THERMAL SPRAYING PROCESS PARAMETERS

The used powders are specific to the applications that are taken into view and depend by the beneficiary requests, support material and the laying process specifications. From the identified applications point of view these can be classified: a) Industrial applications: WC-Co or WC-Co-Cr

carbide; nickel based alloys (ex: NiCrBSi); oxide, like A1203.

b) Medical applications: carbides like WC-Co or C-Co-Cr for surgical devices; oxide like AI203 for electrostatic isolation.

c) Others types of applications requested by the necessity of assuring some specific properties. The laying of the HVOF process is the one that is

specific for GTV and is characterised by a thermal spraying torch, K2 variant, mounted by indexing, on the Fanuc Robot arm and assisted by a cooling air system in the zone of the spraying process.

As a result were done laying with powders recommended by GTV and acquired from the same firm: 80.76.1, WC/Co/Cr GTV powder, 80.15.1, NICrBSi GTV powder, respectively 80.46.1, 316L/CrNiMo GTV powder. These powders characteristics [2,3] are presented in the following tables 1, 2, 3:

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Tab. 1. Powder GTV 80.76.1, WC/Co/Cr, -45+15µm Chemical analysis in weight %

W Co Ct Cf O Fe Cr Balance 10,0 5,08 0,11 0,089 0,0191 3,91 Hall flow 20,6 sec/50g Apparent density 4,78 g/cc Tab.2. Powder GTV 80.15.1, NICrBSi, -53+20µm Chemical analysis in weight %

C Ni Fe Cr Si B O 0,71 Balance 3,69 14,06 4,26 3,15 0,037 Hall flow 12,0 sec/50g Apparent density 4,22 g/cc Hardness 63 HRc Tab.3.Powder GTV 80.46.1, 316L/CrNiMo, -53+20µm Chemical analysis in weight %

C Cr Si Fe Ni Mn Mo O 0,015 17,5 0,7 Balance 13,1 1,5 2,5 0,065 Sieve analysis Grain size (µm) +53 +45 +36 +20 -20 Distribution (%) 1.76 12,99 26.64 50,86 7,75 Hall flow 17,1 sec/50g Apparent density 4,18 g/cc Parameters of the HVOF thermal spraying process for the 3 types of GTV powders: 80.76.1 (WC/Co/Cr), 80.15.1 (NICrBSi) and 80.46.1 (316L/CrNiM), using the K2 system and supplementary air cooling, established during the thermal spraying process, are presented in tables 4, 5, 6, for every used powders: Tab. 4. Powder GTV 80.76.1, WC/Co/Cr, -45+15µm Oxygen [L/min] 870 Kerosene [L/h] 24 λ 1,05 Combustion chamber pressure [bar] 8,3 nozzle [mm] 150/11 Carrier gas [l/min] 7 Stipper NL Stirrer [%] 50 Feed rate [g/min] 2x50 Surface speed [m/min] 38 Spray distance [mm] 420 Rotation Speed [mm/sec] 60 Hardness HV0.3 1300 DE [%] 50 Vaverage [m/s] 600 Taverage [°C] 1800 Tab.5. Powder GTV 80.15.1, NICrBSi, -53+20µm

Oxygen [L/min] 900 Kerosene [L/h] 26 λ 1,0 Combustion chamber pressure [bar] 8,5 nozzle [mm] 150/14 Carrier gas [l/min] 6 Stipper NL Disk rotation speed [RPM] 1,7 Stirrer [%] 50 Feed rate [g/min] 2x50 Linear speed [m/min] 38 Spray distance [mm] 300 Hardness HV0.3 890 DE [%] 65 Tab.6. Powder GTV 80.46.1, 316L/CrNiMo,-53+20µm Oxygen [L/min] 900 Kerosene [L/h] 24 Λ 1,1 Combustion chamber pressure [bar] 8,3 nozzle [mm] 150/14 Carrier gas [l/min] 8 Stipper NL Disk rotation speed [RPM] 2,6 Stirrer [%] 50 Feed rate [g/min] 2x75 Linear speed [m/min] 38 Spray distance [mm] 350 Hardness HV0.3 350 DE [%] 65-70 5. PARTS – THERMAL SPRAYING

Parts on which were realised laying from GTV powders, GTV 80.76.1, GTV 80.15.1, respectively GTV 80.46.1, using the HVOF thermal spraying process – K2 system, are from OL 37, have a parallelepiped form and have the following dimensions 50x30x4. For fixing the parts on the handling device for the parts with horizontal axe was design and executed a support clamping device for the Sample parts, represented in figure 2.

Figure 2. Support for clamping the Sample parts

On the support represented in figure 2 can be fix 22 parts, as represented in figure 3. The device is realised in order the laying to be efficient and the loss of powders to be minimum.

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Figure 3. Assembly parts for spraying-support for

clamping the parts

6. RECCOMANDATIONS AND RECIPE FOR METALLOGRAPHIC PREPARATION OF THE LAYERS

Cutting is preferred to be done with automatic cutting machines, with cooling-lubricate system for the saw blade, function of the substrate material. Saw blades based on aluminium oxide are in general used for cutting the metallic materials with high hardness. It is recommended that between the Sample and the clamping mechanism to be set wood spatulas or from polymeric material for protecting the very fragile layers. It is very important to set the Sample a saw blade to advance from the layer to the sub layer.

Packing is recommended to be realised at cold, with acrylic resin (ex. DuroCit) or under vacuum, with epoxide resin (ex. EpoFix, SpeciFix-20). Metallographic samples can be obtained also through warm packing, procedure that can introduce cracks in the fragile layers because of the high pressure.

Abrasion and polish is recommended to be realised on an automatic machine with rotated plates. Rotopol-V machine is gifted adaptable clamping systems for the parts, with adjustment for the working speed of the support disc and samples. It can be established them sense of rotation (the same or contrary sense) and the pressing force. For the abrasion of the samples, the rotation sense of the disc and of the samples is the same, for 1 min, for every passing, the force is 20 N and the speed 300 rot/min.

Using the abrasive paper from SiC is done respecting the following rules:

• at first is used a paper with high granulation, and after is used paper with more and more fine granulation (paper-SiC 320, 500, 800, 1000, 1200, 2000, 4000);

• at every change of paper granulation the Sample is turned with 90º for discarding the scratching from the anterior stage;

• after every polishing stage, the samples are washed with water.

The polishing process is executed at 150rot/min, for 5 minutes for every stage, with a pressing force of 25N, using the dosage system for the diamond suspension and lubricant of the Rotopol-V machine.

Between the successive polishing operations (6μm, 3μm, 1μm), the samples are washed with water for residuum discarding, that with ethanol, that are dried in hot air jet. The same procedure of washing and during it is applied at the end of the abrasion and polish processes.

Table 7. Standard recipe for metallographic preparation of the layers

Abrasion

Stage 1 2*

SiC paper - from 320

MD-Largo

Suspension - DiaPro Allegro/Largo

Lubricant Water - Rpm 300 150 Force [N] 20 20 Time As in plane 2 min

Polishing Stage 1 2 MD-Dac MD-Nap Suspension DiaPro-Dac** DiaPro-Nap B***

Rpm 150 150 Force [N] 20 20 Time 5 min 5 min * Just in some of the cases. ** DiaPro Dac can be replaced with diamond suspension of 6, 3, 1μm in combination with alcohol based lubricant. *** DiaPro Nap B can be replaced with diamond suspension of 1μm in combination with alcohol based lubricant or OP-S suspension in case of ceramic sub layers or OP-U for the metallic ones. 7. REQUESTS – TESTS FOR THE HVOF LAYERS

The layers obtain by the HVOF procedure deposit on the parts, by thermal spraying, using the HVOF procedure, the K2 system and the powders GTV 80.76.1, GTV 80.15.1, respectively GTV 80.46.1, must respond to the following requests: A. Micro hardness: HV0,3, minimum 1.000, as in

ISO 6507-1:2005; B. Adherence: Minimum 75 MPa, as in ISO 4624 or

ASTM / C633-01:2008; C. Porosity: Maximum 2%, as in ISO / TR

29946:2011. A. Metallographic analysis

Requests are in concordance with recommendations and international regulations and them revering assure the process framing in the characteristic domain of the performances of the HVOF procedure, allowing comparison with others

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similar procedures or in the frame of the same procedure for different laying. A very important characteristic is the obtain porosity.

For every of the 3 samples are presented the representatives results for the evidenced oxides in the microstructure with black or gray –first image and the marked porosity - second image. The oxide appears, as a rule, because of the process parameter variation or of same imperfect combustion or incomplete laying. The existence of a less or more quantity of powders, the incorrect nozzle chosen, the working pressure variance, the oxygen and/or kerosene debit and also others working and process parameter variation could produce imperfect combustion and/or incomplete laying favouring oxides appearance. Then measure could be as micron order which has no influence on the properties of the layer. There are recipes that assure the process parameters adjustment in an acceptable area but exist also the possibility of process parameters optimization. The surface occupied by the oxides related to the total layed surface represent the characteristic porosity, which should not be great than 2%.

Figure 4. Sample: Nr.2 (80.76.1) WC/Co/Cr 86 10 4;

20-45 µm

Figure 5. Sample: Nr.4 (80.15.1) NiCrBSi 60HRC;

20-53 µm

Figure 6. Sample: Nr.6 (80.46.1) Steel 316L (CrNiMo-Stahl); 20-53 µm

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The metallographic analysis and the porosity tests, shown in figure 4, 5, 6, were realised at the Gelsenkirchen University Metallographic Laboratory. For the porosity results are conclusive. It can be observed that in the anterior figures the fact that porosity is framed up in the ISO/TR 29946:2011request, being under 2% in all cases. The best porosity was obtained for Sample: Nr.4 (80.15.1) NiCrBSi 60HRC; 20-53 µm, which means that also the respective process parameters are almost optimal. From hardness point of view is desired to obtain laying for which the micro hardness HV0, 3 should be minimum 1.000, as in ISO 6507-1:2005.Regarding the layer adherence deposed this should be at least 75 MPa, as in ISO 4624 or ASTM / C633-01:2008. The same samples were analysed in the GTV specialised laboratory and the results are (figures 7, 8, 9 and tables 8, 9, 10):

Tab. 8. Sample: Nr.2 (80.76.1) WC/Co/Cr 86 10 4; Sample: Nr.2 80.76.1 Porosity [%] 1.6 standard deviation 0.3 Min/Max 1.2/2.0 Coating thickness [µm] 169.8 standard deviation [µm] 35.6 Min/Max 111.4/230.4 Hardness HV0,3 1300.0 standard deviation 65.7 Min/Max 1245.0/1425.0

Figure 7. Sample: Nr.2 (80.76.1) WC/Co/Cr 86 10 4

Porosity = 1,6%, Coating thickness = 169,8 µm Hardness = 1300 HV0,3

Tab. 9. Sample: Nr.4 (80.15.1) NiCrBSi 60HRC Sample: Nr.4 80.15.1 Porosity [%] 1.9 standard deviation 0.2 Min/Max 1.5/2.2 Coating thickness [µm] 509.1 standard deviation [µm] 109.3 Min/Max 309.5/617.5 Hardness HV0,3 1020.7 standard deviation 31.7 Min/Max 959.0/1067.0

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Fig. 8. Sample: Nr.4 (80.15.1) NiCrBSi 60HRC

Porosity = 1,9% Coating thickness = 509,1 µm Hardness = 1020,7 HV0,3

Tab. 10. Sample: Nr.6 (80.46.1) Steel 316L (CrNiMo) Sample: Nr.6 80.46.1 Porosity [%] 0.8 standard deviation 0.2 Min/Max 0.5/1.1 Coating thickness [µm] 446.8 standard deviation [µm] 82.6 Min/Max 332.3/541.1 Hardness HV0,3 406.7 standard deviation 24.9 Min/Max 374.0/438.0

Fig. 9. Sample: Nr.6 (80.46.1) Steel 316L (CrNiMo)

Porosity = 0,8% Coating thickness = 446,8 µm Hardness = 406,7 HV0,3

The Laboratory of metallographic testing – LAMET of University Politehnica of Bucharest has obtained just partial results (table 11) for the samples metallographic analysis:

Tab. 11. LAMET Laboratory results Sample 2: 80.76.1 Hardness -- HV0,3 Sample 4: 80.15.1 Hardness 1033 HV0,3 Sample 6: 80.46.1 Hardness 424 HV0,3

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CONCLUSIONS

The HVOF procedure used for the deposion of performant layers on different surfaces is based on the GTV equipment and on already tested powders. From the performances taken into view it is mentioned the microhardness [HV0,3], adherence [MPa] and porosity [%].

These ensure for the deposed layers characteristics that permit the choosing of the HVOF procedure for obtain hard layers of with specific performances assuring them superior quality and performances in comparison with others similar technologies.

The experience permit establishing the specific optimal parameters specific for a certain deposion using the HVOK K2 system and powders based on WC/Co/Cr, NiCrBSi and 316L/CrNiMo.

The various numbers of process parameters and them pre-established values lead on to obtaining performances more or less representatives.

Metallographic processing properly done can ensure a better precision or not when are determined microhardness, porosity and adherence.

Correlating the process parameters with the obtain results from the deposed sample analysis it can be observed that the best porosity 1,120%, is represented the NiCrBSi deposion in the opinion of Gelsenkirchen University, and respectively 0,8% for the 316L/CrNiMo deposion in the GTV case.

Taking into consideration micro hardness the

best value it has the WC/Co/Cr deposion, of 1300 HV0,3, in GTV case.

For the NiCrBSi deposions, microhardness values are approximately 1020 HV0,3, GTV case and also in Gelsenkirchen University.

At a first analysis of the obtain results it can be concluded that the process parameters influence and the deposed characteristic powders, together with surface preparing for the deposion process lead to obtain the performances desired by the beneficiary.

Metallographic preparing method can influence in a direct way the performance evaluation of the deposed layers.

A correct evaluation of the deposed layers influence in a direct mode the applicability of the HVOF procedure in conformity with the beneficiary requests. REFERENCES [1]. "Study regarding the theoretical determination of specific

technological parameters for HVOF process on application" project no. 614 SMIS code / CNRS: 12537, contract no.: 270/27.10.2010, project "Applied researches, technology and technological equipment for high strength thermal spraying by HVOF process used in industrial and medical applications".

[2] Technical Documentation GTV Coating System HVOF-MF-K 1000, Project ICTCM, 662.013.

[3]. http://www.gtv-mbh.com

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MONITORING THE HVOF THERMAL SPRAYING PROCESS FOR QUALITY IMPROVEMENT OF THE DEPOSITED

COATINGS

V. Avramescu, S. Roşulescu, R. Niţă, L. Păun, D. Bobe, L. Olteanu, M. Manea

Mechanical Engineering and Research Institute, Bucharest. ROMANIA, [email protected]

REZUMAT Articolul Monitorizarea procesului de pulverizare termică HVOF în vederea îmbunătăţirii calităţii straturilor depuse prezintă modul de evaluare a unor surse de variaţii, cum ar fi vibraţiile şi temperatura, asupra calităţii stratului depus prin procedeul HVOF şi propune modificarea unor parametrii tehnologici ai procesului pentru atenuarea surselor de variaţii monitorizate şi îmbunătăţirea calităţii straturilor realizate prin pulverizare termică HVOF.

ABSTRACT The article Monitoring the HVOF thermal spraying process for quality improvement of the deposited coatings shows the approach regarding assessment of sources of variation, such as vibrations and temperature, concerning the quality of the deposited coatings by HVOF process and proposes the modification of the parameters of technological process to mitigate the sources of variation monitored and quality improving of the HVOF coatings produced by thermal spraying. KEYWORDS: HVOF, thermal spraying, technological parameters, quality, deposited coating.

CUVINTE CHEIE: HVOF, pulverizare termică, paramerii tehnologici, calitate, strat depus.

1. INTRODUCTION

In the project „Applied researches, technology and technological equipment for high strength thermal spraying by HVOF process used in industrial and medical applications", co-funded by the Regional Development European Fund, whose beneficiary is SC ICTCM SA, were conducted experimental coatings by HVOF thermal spraying (High Velocity Oxygen Fuel) on a series of prismatic and revolution parts.

It have been used various types of powders and different processing parameters.

The quality of the deposited coatings is determined through removal by cutting of the specimens and cross-sectional evaluation of the quality characteristics: HV0,3 Vickers hardness (≈3N test force); porosity; metallographic structure.

Also it will evaluate other quality characteristics: the adhesion of the coating through destructive tests on a series of specimens; the roughness of the surfaces with coatings, measured before processing.

In this article we show how monitoring of

sources of variation, such as vibration and temperature, which can influence some of these quality characteristics and what actions can be taken to improve quality. 2. THE PROCESS EQUIPMENT AND TECHNOLOGICAL PARAMETERS The coatings were made on two types of parts:

- prismatic parts: 30 x 50 x 4 mm; - revolution part: Ø98 x 220 mm.

The material of the pieces is carbon steel for general use. In order to coat by HVOF the surfaces of the parts were blasted in a Fervi blasting cabin with corundum grain 80 μm and a pressure of 6 bars. The prismatic parts were fixed on a milling holder which was mounted within the universal chuck and in the rotary centre of the footstock in the horizontal axis handling device. The revolution part was fixed within the universal chuck and the rotary centre of the footstock.

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The metallic coating was performed with HVOF thermal spray equipment with liquid (kerosene) supplied by GTV (Germany) consisting of: - HVOF spray gun with accessories;

Ignition box fuel mixture (oxygen + kerosene); Monitoring combustion chamber pressure box

(from the gun); Monitoring cooling water box (of the gun). Nozzles + stay-in-place hoses for air cooling

during metallization of the parts. - Powder supply / dosing system (carrier gas:

nitrogen) - Cooling system (heat exchanger) of gun supply

water; - Control gas cabinet (oxygen, nitrogen,

compressed air and kerosene); - Accessories: hoses with quick connections for

supply with oxygen, nitrogen + powder, compressed air, kerosene; power supply cables.

- PLC control cabinet (Programmable Logic Controller) - industrial process computer;

- Kerosene pumping unit; - Accessories: hoses with quick connections for

supply with oxygen, nitrogen + powder, compressed air, kerosene; power supply cables.

The path for HVOF spraying is done by means of a FANUC robot with 6 axes (J1 ... J6) + corresponding controller and mobile device for programming (teach pendant). The gun is mounted on the mechanical interface of the J6 joint through a fixing holder. Technological process parameters for the three types of powder are as follows: Table 1. Technological process parameters

Powder Denomination Composition Grain GTV 80.76.1 WC/Co-Cr +45+15 μm

Oxygen flowrate [l/min] 870

Kerosene flowrate [l/h] 24

λ Oxygen / kerosene

equivalence ratio

- 1,0

Combustion chamber pressure [bar] 8,3

Nozzle (Length/diameter) [mm] 150/11

Nytrogen flowrate [l/min] 7

Stripper - NL Powder feed disk

rotation speed [rot/min] 1,5

Stirrer [%] 50 Powder feed rate [g/min] 2 x 50

Surface speed [m/min] 38 Spray distance [mm] 420

Feed/rotation [mm/rot] 12 Robot linear

velocity [mm/s] 60

Number of - 3

cycles/Robot

Number of passes/Robot - 12

Powder Denomination Composition Grain 80.46.1 316L +53+20 μm

Oxygen flowrate [l/min] 900 Kerosene flowrate [l/h] 24 λ - 1,1 Oxygen / kerosene equivalence ratio [bar] 8,3

Combustion chamber pressure [mm] 150/14

Nozzle (Length/diameter) [l/min] 8

Nytrogen flowrate - NL Stripper [rot/min] 2,6 Powder feed disk rotation speed [%] 50

Stirrer [g/min] 2 x 75 Powder feed rate [m/min] 38 Surface speed [mm] 350 Spray distance [mm/rot] 5 Feed/rotation [mm/s] 30 Robot linear velocity

- 3

Number of cycles/Robot

- 12

Powder Denomination Composition Grain GTV 80.15.1 NiCrBSi +53+20 μm

Oxygen flowrate [l/min] 900 Kerosene flowrate [l/h] 24 λ - 1,1 Oxygen / kerosene equivalence ratio [bar] 8,5

Combustion chamber pressure [mm] 150/14

Nozzle (Length/diameter) [l/min] 6

Nytrogen flowrate - NL Stripper [rot/min] 1,7 Powder feed disk rotation speed [%] 50

Stirrer [g/min] 2 x 50 Powder feed rate [m/min] 38 Surface speed [mm] 300 Spray distance [mm/rot] Feed/rotation [mm/s] 30 Robot linear velocity

- 5

Number of cycles/Robot

- 20

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3. INFLUENCE OF VIBRATION AND TEMPERATURE ON THE QUALITY CHARACTERISTICS OF DEPOSITED COATING The quality characteristics of the deposited coating which can be achieved by the GTV equipment are: - HV0,3 hardness at reduced test force (≈3N test

force) according to ISO 6507-1:2005 : min. 1000 HV0,3; except NiCrBSi coating for which HV0,3 (according to DVS 2318:2011) is min. 800

- adhesion according to ASTM C633-01:2008 (TAT method – Tension Adhesion Test) or equivalent standard: min 75 N/mm2

- porosity according to ISO / TR 26946:2011 or equivalent standard: max. 2%

- Ra roughness according to ISO 4287:1997 or equivalent standard without processing after deposition: max. 3,2 µm. In the HVOF deposing process can occur a

number of variability of quality characteristics of the deposited coating that can translate inevitably to poor quality and financial losses during the lifetime of the product on which the HVOF coating was performed.

It was identified a number of factors which will vary during the HVOF process, and which will be monitored in order to determine their influence on the quality of the deposited coating (porosity and surface roughness), as follows: - the vibration level of FANUC robot on the gun

without performing coating; - the vibration level of the gun during performing

of metallization process; - the vibration level of the horizontal axis handling

device on the part without performing coating; - the vibration level of the horizontal axis handling

device on the part during performing of metallization process;

- the temperature level of the part during performing of metallization process. The vibrations of the robot, the horizontal axis

handling device (assimilated to a lathe) and the gun affects the surface roughness of the metallized part by vibration roughness.

The mechanism of roughness as described in [2] states that "because the composition of the vibrations with rotational frequency and with different frequencies occurring in the rotation shaft of the machine - tool, rotation axis of the part moving on a cyclic path known as vibration trochoid ".

The vibrations transmitted to surface of the HVOF coated part are a resultant of vibration generated by the horizontal axis handling device, the robot on the spaying path and the HVOF gun due to the sprayed jet velocity.

The high level of vibration generated by the robot when moving on the path shows that it is necessary to carry out tests to determine the performance criteria of the robot, that are important in thermal spray applications, respectively path repeatability, path velocity repeatability and path velocity fluctuation. Tests are carried out according to ISO 9283: 1998 standard [1].

The part temperature during coating by HVOF is an important parameter, when are sprayed cermets, due the generation of residual stresses [3] which may increase coating porosity. In such cases the temperature should be maintained at 373-473 K [3]. When is melted self-fluxing layer the temperature can rise up to 1000 K [3].

Also, will be monitor the reference distance from which will move the robot arm, until reaching the recommended distance for a specific HVOF spraying process on the entire length of the part to be covered. 4. DATA ACQUISITION SYSTEM FOR MONITORING THE HVOF PROCESS 4.1 COMPONENTS AND CHARACTERISTICS

In order to monitor vibration and temperature of the HVOF process was created a data acquisition system consisting of: - temperature sensor: IR thermographic camera

(infrared) : ThermoVision™ A20M + ThermaCAM Researcher Software, from Flir Systems + FireWire cable;

- vibration sensors: 2 accelerometers IMI Industrial, 2-Pin Accelerometer, 100mV/g, ICP® (IEPE) from IMI Sensors – a PCB Piezotronics Division + power cables BNC;

- laser sensors: 3 photoelectric sensors (Pepperl-Fuchs) MLV11-8-LAS-150/47/112 + cords -Female Cordset, M12, 5-pin, PUR cable V15-G-10M-PUR;

- PXI platform for data acquisition (National Instruments) consisting of: Chassis: NI PXIe-1071, 4-Slot 3U PXI

Express Chassis; Controller: NI PXIe-8820 2.2 GHz Celeron

1020E Dual-Core, Windows 7; NI PXI-8252, IEEE 1394 Board with Vision

Acquisition SW - the data acquisition module from thermographic camera; NI PXI-6220, M Series DAQ (16

Analog Inputs, 24 Digital I/O0 with NI-DAQmx driver software) – the data acquisition module from laser sensors;

SCB-68A Noise Rejecting, Shielded I/O Connector Block – connector;

SHC68-68-EPM Shielded Cable, 68-D-Type to 68 VHDCI Offset, 2 m – cable;

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Software: LabVIEW Real-Time Deployment License for NI PXI Controllers (ETS RTOS);

USB English Keyboard and Optical USB Mouse;

External USB CD/DVD-ROM for use with PXI & VXI Emb Controllers.

- Supply voltage divider: 24 V D.C. - photoelectric sensors, 3 x 5 V D.C. - NI PXI- 6220 module.

Software for application development of virtual instrumentation:

NI Developer Suite Core (English); Image Acquisition and Machine Vision

Option; Sound and Vibration Option;

- Monitor DELL 20inch (2007WFP). Technical and functional characteristics of the sensors used: - Thermographic camera: ThermoVision™ A20M

(figure 1) [4]:

Figure 1. Thermographic camera

Table 2. Thrmograpic camera technical and functional characteristics Characteristics U/M Technical Data Temperature Range ºC -20 ...+900 Thermal sensitivity ºC < 0,1 Frequency Hz 50 Detector Type: - FPA (Focal Plane

Array) uncooled microbolometer,

Spectral Range µm. 7,5...13 Detector Resolution: - 160x120 phisical

pixels Digital Video Interface - Ethernet or Firewire Control Interfaces - RS232, Firewire sau

Ethernet Analogic Output Video PAL, voltage Exchangeable Lenses - 17mm Standard

Telescope x2 Wide angle x0,5/x0,25

Real-time storage and analysis software

- ThermaCAM Researcher

Measurement:

- Capability for thermographic image analysis in real time (possibility

whereabouts temperature at any point during the process of image) Spot movable, area, isothermal, alarms, Delta-T

Voltage V 12/24 D.C. Environmental Specifications

Temperature °C -15...+55 Humidity % 10...95 Shock g 25 Vibration g 2 - IMI Industrial Accelerometer ICP® (IEPE)

(figure 2) [5]:

Figure 2. Accelerometer

Table 3. Accelerometer technical and functional characteristics Characteristics U/M Technical Data Sensitivity (± 10%) mV/g 100 Measurement Range g ± 50 FrequencyRange (± 3 dB) Hz 0,5...10000 Resonant Frequency kHz 25 Non-Linearity % ± 1 Excitation Voltage V 18...28 cc Constant Current Excitation mA 2...20 Electrical Connector - 2-Pin MIL--5015C

Environmental Specifications Temperature °C -54...+121 Shock g 5000 Photoelectric sensor MLV11-8-LAS-150/47/112 (figure 3) [6]:

Figure 3. Photoelectric sensor

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Table 4. Photoelectric sensor technical and functional characteristics Characteristics U/M Technical

Data Detection range mm 0 ... 150 Light source - laser diode Laser class - 2 Adjustment range mm 50 ... 150 Reference target - standard white

10 mm x 10 mm Light type - red, modulated

light Laser class 2, eyesafe

Diameter of the light spot mm 0,1 at a distance of 60 mm ± 2

Ambient light limit lux 10000 Operating display - LED green Function display - TEACH-IN:

LED green flashing switching state: LED yellow pre-fault indicator: LED red flashing

Operating elements - membrane keys for setting sensitivity and TEACH IN

Operating voltage V 10 ... 30 D.C. Ripple % 10 No-load supply current mA ≤ 25 Switching voltage V max. 30 D.C. Switching current mA max. 200 Connection 5-pin M12 x 1

connector, 90° adjustable position

Environmental Specifications Ambient temperature °C -10 ... 40 4.2 THE LAYOUT AND MODE OF OPERATION.

The layout of the PXI monitoring system is shown in figure 4.

It is noted that vibration sensors (IMI accelerometers) are mounted: - The first one on the HVOF gun holder fixed on

the FANUC robot flange that performs the path for coating (fig. 5), as close to the spray gun to capture the vibrations generated by it during metallization and on the same axis with it (fig. 5);

- The second one on the screw head that secures the rotary centre of the footstock in the horizontal axis handling device; this captures vibration of the parts fixed in the universal chuck and the rotary centre (fig. 6).

For assembly the accelerometers it is necessary that [5]: - the mounting surface shall have roughness up to

1.6 μm and have to be lubricated with a thin layer of grease or oil;

- to be drilled on the capture surface of vibration a threaded hole 1/4-28 UNF in which will be fixed the threaded sensor stud. IR (infrared) camera is mounted on an adjustable

tripod, located in the laboratory spraying booth and it is oriented to sprayed part to capture the deposited coating temperature during the technological process (figure 4).

The laser sensors are fixed on dovetail holders, which are mounted on the HVOF gun holder (figure 7), so that it can deliver the laser beam towards the sprayed parts on the centering axis of HVOF gun.

The sensor adjustment procedure (TEACH IN - static objects) is as follows (figure 8) [7]:

1) If the sensor is blocked, simultaneously push the "+" and "-" buttons for 5 seconds until the green LED flashes once;

2) Place the piece to be detected at the desired distance within the sensing range. Simultaneously push the "+" and "-" buttons (approx. 1 s) until the red LED goes out. The sensor is now in teach mode (learning) as indicated by the flashing green LED. Note: If the red LED does not flash when the key is pushed, then the keypad is still locked.

3) The green LED flashes briefly at a higher frequency (4Hz). When the LED flashes again at the initial frequency of 2 Hz, the teaching process has finished.

4) To end the TEACH IN process, use either the „+” or the „-” key. The sensor then resumes normal operation.

Photoelectric sensors are adjusted to generate signal for a reference distance, so that when the support of the HVOF gun and the spray gun is moved together with the FANUC robot arm for adjusting the spraying distance, at the time when the distance to the piece coincides with the reference distance, the yellow LED lights up and the robot is stopped.

After that, the robot starts the movement from the reference distance until reaching spray distance, effective adjusted for specific HVOF process.

In the developed data acquisition application, can be viewed extinction of a LED, indicating that it have been reached the established reference distance.

In the same LabVIEW application will see vibration captured by the two accelerometers and the temperature of the part during thermal spraying process.

21


Figure 4. PXI monitoring system layout

Figure 5. Installation detail HVOF gun

22


Figure 6. Installation detail footstock

Figure 7. Installation detail photoelectric sensor

23


Figure 8. Manual setting photoelectric sensors [8]

CONCLUSIONS

During the monitoring of the specific HVOF processes have resulted the following: - the robot do not exhibit abnormal vibration

during moving on the path without and at the time the HVOF gun acts;

- the horizontal axis handling device generates vibrations due to misalignment of the universal chuck centre axis and of the rotating peak mounted in the footstock and due to the sprayed jet;

- the part temperature during the spraying process exceeds the recommended range for the substrate.

Proposed improvement actions: - Alignment of fixing axes of the universal chuck

and the footstock, in the horizontal axis handling device for refocusing of the part that is sprayed;

- Reducing the velocity of sprayed jet by decreasing pressure in the combustion chamber of the HVOF gun;

- Mounting on the horizontal axis handling device of compressed-air nozzles, additional to the existing ones off the HVOF gun for cooling improvement of the thermal sprayed part.

REFERENCES [1]*** ISO 9283: 1998 Manipulating industrial robots. Performance criteria and related test methods, ASRO, 2007 [2]. Dodoc, Petre Metode şi mijloace de măsurare moderne în mecanica fină şi construcţia de maşini, Editura Tehnică, Bucureşti, , 1978 [3]. Pawlowski Lech- The Science and Engineering of Thermal Spray Coatings, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, 2008 [4].*** ThermoVisionTM A20 M, Operator’ manual, FLIR Systems, October, 29, 2004; [5].*** Model 603C01, Platinum Low-cost Industrial ICP® Accelerometer, Installation and Operating Manual, IMI SENSORS, A PCB Piezotronics, Inc. Div., http://www.pcb.com/Products.aspx?m=603C01, PCB Group, Inc. 2014, USA [6]. *** Diffusive sensor, MLV11-8-LAS-150/47/112, with 5-pin M12 connector, 90° adjustable position; http://www.pepperl-fuchs.com/global/en/classid_47.htm?view=productdetails&prodid=1635, Pepperl+Fuchs Group, Date of issue: 2006-02-20, Germany [7]. *** MLV11 Series - Introduction; http://www.pepperl-fuchs.com/global/en/classid_47.htm?view=productdetails&prodid=1635, Pepperl+Fuchs Group, Germany.

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FRICTION STIR PROCESSING AS A NEW SURFACE FINISHING TECHINOLOGY

Milena Folea

Transilvania University of Brasov, Brasov, ROMANIA, [email protected]

REZUMAT Articolul prezintă procedeul de prelucrare a suprafeţelor prin frecare cu element activ rotitor (en. Friction stir processing – FSP) ca procedeu specific ingineriei suprafeţelor. Acest procedeu este derivat din procedeul de sudare prin frecare cu element activ rotitor (en. Friction stir welding - FSW) brevetat în anul 1991 de cercetătorii britanici de la The Welding Institute (TWI).Ulterior, s-a constatat că procedeul poate fi folosit eficient la finisarea suprafeţelor, mai precis la obţinerea unui strat superficiali cu grăunţi foarte fini cu proprietăţi mecanice şi tribologice mult superioare faţă de materialul de bază al piesei.

ABSTRACT The paper presents Friction stir processing (FSP) as a specific method for surface engineering. This method is derived from Friction stir welding (FSW) patented in 1991 by British scientists of The Welding Institute (TWI). Later on it was found that the method can be effectively used for surface finishing, specifically to obtain a very fine grain surface layer with far superior mechanical and tribological properties compared to the base material of the workpiece.

KEYWORDS: Friction stir processing, microhardness, grain size, tribological properties, multipass processing CUVINTE CHEIE: Prelucrare prin frecare cu element activ rotitor, microduritate, mărimea grăunţilor cristalini, proprietăţi tehnologice, prelucrare multitrecere

1. INTRODUCTION

Friction stir processing

Friction stir processing was developed as a surface engineering technique using the same simple principle as Friction stir welding [1]: a rotating tool is moved along the workpiece surface while applying an axial load to increase generated heat (Figure 1).

The result is a solid state localized surface modification with improved properties and refined microstructure obtained after recrystallization.

Very important for the quality and accuracy of finished surface are process parameters: tool rotation speed (rpm), traverse speed (mm/tr) and normal force (N) and tilt angle.

Beside these parameters, other factors contribute to the final result: surface preparation previous to FSP (initial surface roughness, preheating), tool shape and tool material, cooling strategy (using or not using lubrication, underwater processing, etc.) and process control.

Similarity of friction stir process kinematics with milling process kinematics makes possible the use of conventional machine tools equipped with force control devices. This is one of major advantages of

friction stir processing, because it allows finishing the surface and in the meantime it applies in-situ localized heat treatment.

Figure 1. Principle of Friction Stir Processing If friction stir process is well designed and

controlled important economic and environmental advantages are added to technical benefits such as:

• increased microhardness • superior wear resistance • better corrosion resistance

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• microstructural refinement, densification, and homogeneity of surface layer

As shown in Figure 2, on an aluminium alloy workpiece [2] different processing parameters led to different surface quality.

Figure 2. Surface appearance after FSP with various rotation and traverse speeds[2]

Friction stir tools

As for Friction Stir Welding, in the case of Friction Stir Processing the technique was used in the early days on aluminium, aluminium alloys and other lightweight materials. Most tools were made of steel tools and studies demonstrated that tool wear was not significant. Z.Y. Ma even stated that in friction stir welding a “A no consumable rotating tool with a specially designed pin and shoulder is inserted into the abutting edges of plates to be joined…” [1].

For harder workpiece materials, tool materials for FSW/FSP had to be upgraded since superior properties were required [3]: high compressive strength at elevated temperature, high thermal fatigue resistance, good dimensional stability and creep resistance at high temperatures and good fracture toughness.

Unfortunately all these requirements are characteristics of superior and expensive materials with low machinability. For example, nickel and cobalt superalloys are materials that preserve their properties (strength, hardness, fatigue resistance, etc.) at very high working temperatures.

Other refractory metals (W, Mo, Ta, etc.) and their alloys might be suitable for friction stir tools, but manufacturing cost of such tools would be elevated.

A reasonable choice from economic point of view might be carbide materials which offer acceptable toughness and good wear resistance [3].

Regarding the shape of friction stir processing tools, they are generally made up of three parts: shank, shoulder and pin [4] as seen in Figure 3. Sometimes different parts of tools are made of different materials. For the shank are used tool steels, while for the shoulder and pin are used more wear

resistant and temperature resistant materials (ceramics, PCBN, etc.).

Numerous studies were focused on the influence of friction stir welding and processing tools shape on weld or processed surface properties [3].

Figure 3.General appearance of friction stir tools

Shoulder’s outer surface may be conical or cylindrical, while the end surface may be flat and or with various features like scrolls, ridges, grooves or concentric circles designated to enhance friction with the surface of the workpiece.

The pin shape may also have different shapes: cylindrical, conical, prismatic or pyramidal shape, with smooth surface or threaded. Recently, pinless tools were tested during FSP of carbide and stainless steel plates with satisfactory results [5,6]. 2. FSP OF DIFFERENT METALS AND ALLOYS-LITERATURE REVIEW FSP of aluminium and aluminium alloys

Low melting temperature, high flow and ductility of lightweight materials such as aluminium alloys corroborated with very good heat conductivity allow smooth processing of surface layers by friction stir. After friction stir cast alloys defects like porosity and cold flakes are eliminated from the surface of the workpiece, while tensile strength and hardness increase due to grain refinement.

Significant improvement of microstructural, tribological and mechanical properties was observed after friction stir processing of as-cast A413 aluminium alloy [2]. Along with a structurally refined superficial layer, reduction of pores and cavities contributed to ameliorate wear resistance.

Ultrafine-grained microstructure with an average grain size of 100nm was produced on aluminium alloy 7075Al-T651by using water, ice and methanol as coolant immediately after friction stir [7]. Nakata et al. [8] obtained significant surface improvement by multi-pass friction stir processing of ADC12 when tensile strength and hardness almost doubled. They also experimentally confirmed the Hall-Petch relationship (Eq. 1) between the grain size d and hardness Hv in the stirred zone:

1/20v HH H k d −= + ⋅ (1)

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with H0 and kH specific material constants.

In Figure 4 can be observed the difference before (a) and after (b) friction stir processing of A356 aluminium alloy [9]:

Figure 4. Microstructure of an Al alloy: (a) base material and (b) friction stir processed [9]

FSP of copper and copper alloys

Su et al. developed nanocrystalline structures in oxygen-free high thermal conductivity (OFHC) copper by using FSP with rapid cooling and a small diameter tool [10]. FSP of steels

During steel FSP, for an actual temperature of approximately 900ºC in the workpiece material, tool tip temperature is expected to be higher than 1200º C [11]. To avoid rapid wear, generally for FSP of steel are used carbide and polycrystalline boron nitride tools. Peak temperature and cooling rate determine the type and grain size of recrystallized structure. High temperature and too rapid cooling rate produce unwanted brittle martensite structure.

Figure 5. Microstructure of tool steel (a) base material and (b) friction stir processed [12]

Very interesting results were obtained by

Dehghani and Chabok [12, 13] who studied nanolayers obtained by friction stir processing on interstitial free steels. They established an optimal rotating speed for which very fine grains (50–120 nm) were produced and demonstrated that rotating speed above and below this rate increased the grain size.

Morisada et al. [14] applied friction stir processing on a previously melted surface on a SKD11 tool steel plate. They obtained a 0.7 mm thick surface layer with hardness four time higher than base material hardness and a homogenous ultrarefined microstructure with carbide particle size of 100nm and steel matrix particle size of 200nm (Figure 5). FSP of Ti and Ti alloys

Concerning titanium alloys, studies on friction stir processing [1,15, 16, 17] confirmed that these alloys have a good potential to provide enhanced mechanical properties.

Most of the published works are dedicated to friction stir of Ti-6Al-4V, the most used titanium alloy, and describe the microstructure and the mechanical behaviour after FSP. For example, Zhang et al. found that mean hardness value, strength and elongation of the stirred zone SZ (Figure 6b) decrease with increasing rotational speed.

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Figure 6. Microstructure of Ti-6Al-4V (a) base material and (b) stirred zone SZ [17]

FSP of superalloys

Progress in tool materials recently enabled friction stir processing of superalloys. Using polycrystalline cubic boron nitride (PCBN) tools [18] or boron nitride tools [19], friction stir processing was applied to nickel based superalloys Inconel 600, respectively Inconel 738. Barabash et al. Higher found that FSP completely alters Inconel 738 microstructure (Figure7) and that cooling rate during FSP of the IN738 suppresses new grains growth.

Figure 7. Microstructure of Inconel 738 (a) base material and (b) stirred zone SZ [19]

3. CONCLUSIONS

Friction stir processing is a thermo mechanical process that offers numerous technical, environmental and economic benefits:

• produces surface layers thick from tens of millimeter to several millimeters with enhanced improved properties;

• is a simple technique that leads to refined and homogenous microstructure in the processed zone;

• heat input is generated by friction between tool and workpiece and plastic deformation of processed material, therefore FSP is energy efficient;

• the effects on stirred zone can replace heat treatments, so costs are decreased and productivity is increased due to in-situ processing on machine tools such as milling machines.

However, there are still problems to be solved by future research due to current studies limitations: • Studies revealed the influence of various process

parameters, but optimal process parameters for most commonly used materials are not yet determined. Regarding the tool material and manufacturing more cost effective solutions must be found. Tool shape for processing remains an issue for the future. Pinless tools with simple geometry and capable to produce more uniform surface layers might be an acceptable solution.

• In the area of understanding and numerical simulation of friction stir processing is a long way to go since until now it is not very clear which modification of microstructure and properties are due to mechanical effect, which are due to thermal effect and how can be balanced the two effects. Nevertheless, from technical, economic and

environmental point of view, friction stir processing is a promising surface finish technology.

REFERENCES [1]. Ma, Z.Y., ”Friction Stir Processing Technology: A Review”,

Metallurgical and Materials Transactions A., vol 39, 2008. [2]. Mahmoud, T.S. , Mohamed, S.S., “Improvement of

microstructural, mechanical and tribological characteristics of A413 cast Al alloys using friction stir processing”, Materials Science & Engineering A, vol 558, 2012.

[3]. Zhang, Y. N., Cao, X., Larose, S., Wanjara, P., “Review of tools for friction stir welding and processing”, Canadian Metallurgical Quarterly, vol 51/ no 3, 2012.

[4]. Folea,M, Roman, A., Langlade, C., Schlegel, D., Gete, E., Charmoret, D., “Producing nanograin surface layers by friction stir processing- Chapter in Comprehensive guide for nano-coatings technology”, in press, N.Y., 2014.

[5]. Langlade C., Schlegel D., Gete, E., Roman, A., Folea, M., “Formation of a TTS layer on Steel Samples by Friction Stir Processing”. Proceedings of the26th International Conference on Surface Modification Technologies, Ecully, France, June 20-22, 2012.

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[6]. Langlade C., Schlegel D., Gete, E., Roman, A., Folea, M., „Study of stirred layers on 316L steel created by friction stir processing”, IOP Conf. Series: Materials Science and Engineering 63, 2014.

[7]. Su, J.Q., Nelson, T.W., Mishra, R, Mahoney, M., "Microstructural investigation of friction stir welded 7050-T651 aluminum",Acta Materialia, vol. 51, 2003.

[8] Nakata, K., Kim, Y.G., H. Fujii, H.,T.,Tsumura, T. Komazaki, T., “Improvement of mechanical properties of aluminum die casting alloy by multi-pass friction stir processing”, Materials Science and Engineering A, vol. 437, 2006.

[9]. Alidokht, S.A., Abdollah-zadeh, A., Soleymani, S., Saeid, T., Assadi, H., “Evaluation of microstructure and wear behavior of friction stir processed cast aluminum alloy”, Materials characterization, vol. 63, 2012.

[10]. Su, J.Q., Nelson, T.W., McNelley, T.R., Mishra, R.S., “Development of nanocrystalline structure in Cu during friction stir processing (FSP)”, Materials Science and Engineering A, vol. 528, 2011.

[11]. Ohashi, R., Fujimoto, M., “Friction Stir Welding Apparatus and Method”, U.S. Patent 8,528,803 B2, Sep. 10, 2013.

[12]. Chabok, A., Dehghani, K., “Formation of nanograin in IF steels by friction stir processing”, Materials Science and Engineering A, vol. 528, 2010.

[13]. Dehghani, K., Chabok, A., “Dependence of Zener parameter on the nanograins formed during friction stir processing of interstitial free steels”, Materials Science and Engineering A, vol. 528, 2011.

14. Morisada, Y., Fujii, H., Mizuno, T., Abe, G., Nagaoka, T., Fukusumi, M., “Nanostructured tool steel fabricated by combination of laser melting and friction stir processing”, Materials Science and Engineering A, vol. 505, 2009.

[15]. Pilchak L., Williams J.C., “Microstructure and Texture Evolution during Friction Stir Processing of Fully Lamellar Ti-6Al-4V”, Metallurgical and Materials Transactions vol. 42A, 2011.

[16]. Farias, A., Batalha, G.F., Prados, E.F., Magnabosco, R., Delijaicov, S., “Tool wear evaluations in friction stir processing of commercial titanium Ti–6Al–4V”, Wear vol. 302, 2013.

[17]. Zhang, Y., Sato, Y.S., Kokawa, Park, H., S.H.C., Hirano, S., “Microstructural characteristics and mechanical properties of Ti–6Al–4V friction stir welds”, Materials Science and Engineering A, vol. 485, 2008.

[18] Sato, Y.S., Arkom, P., Kokawa, H., Nelson, T.W., Steel, R.J., “ Effect of microstructure on properties of friction stir welded Inconel Alloy 600”, Materials Science and Engineering A, vol. 477, 2008.

[19] Barabash, O.M., Barabash, R.I., Ice, G. E., Feng, Z., Gandy, D., “X-ray microdiffraction and EBSD study of FSP induced structural/phase transitions in a Ni-based superalloy”, Materials Science and Engineering A, vol. 524, 2009.

Quick Info

Piezo Engineering Tutorial

1.0 The Direct and Inverse Piezoelectric Effect

In 1880, while performing experiments with tourmaline, quartz, topaz, cane sugar and Rochelle salt crystals, Pierre and Jacques Curie discovered that when mechanical stress was applied to a crystal, faint electric charges developed on the surface of that crystal.

The prefix “piezo” comes from the Greek piezein,which means to squeeze or press. As a result, piezoelectricity is electrical charge that is produced on certain materials when that material is subjected to an applied mechanical stress or pressure. This is known as the direct piezoelectric effect.

The converse or inverse piezoelectric effect, or the application of an electric field to induce strain, was discovered using thermodynamic principles in 1881 by Gabriel Lippmann. It is the inverse piezoelectric effect that enables piezoelectric materials to be used in positioning applications.

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Reliable Linear Motion For Packaging Machines

In the productivity-driven packaging industry, there are many possible sources of downtime. You can eliminate many of them by selecting failure-resistant linear motion components.

These robust guides and positioning tables have design features that prevent premature failure due to poor lubrication practices or contamination. At the same time, these linear motion components still have to meet the necessary accuracy, precision and load requirements—all of which are on the upswing in packaging applications.

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Why bigger isn’t always better: the case for thin section bearings

For applications that demand maximum performance despite space and/or weight restrictions, designers should consider thin section bearings. While conventional bearings often have more load capacity, thin section bearings have more than enough for a wide range of applications and offer exceptional design flexibility with opportunities for significant reductions in overall system size and cost.

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A new white paper from Kaydon Bearings, an SKF Group company, examines thin section bearing styles and features, with a discussion of design considerations, fit, lubrication, and other useful information. (more in: http://www.techbriefs.com/component/content/article/14-ntb/white-papers/mechanics-and-machinery/21104-doc-6120)

NASA Tests Revolutionary Shape-Changing Aircraft Flap

NASA's green aviation project is one step closer to developing technology that could make future airliners quieter and more fuel-efficient with the successful flight test of a wing surface that can change shape in flight.

Researchers replaced an airplane’s conventional aluminum flaps with advanced, shape-changing assemblies that form seamless bendable and twistable surfaces.

Flight testing will determine whether flexible trailing-edge wing flaps are a viable approach to improve aerodynamic efficiency and reduce noise generated during takeoffs and landings.

The ACTE flap was extended to 20 degrees deflection for testing. Flight results will validate whether the design can reduce wing structural weight, improve fuel economy, and reduce environmental impact. (NASA/Ken Ulbrich)

The Adaptive Compliant Trailing Edge (ACTE) project is a joint effort between NASA and the U.S. Air Force Research Laboratory (AFRL), using flaps designed and built by FlexSys of Ann Arbor, MI. FlexSys developed a variable geometry airfoil system called FlexFoil that can be retrofitted to existing airplane wings or integrated into brand new airframes.

During the initial ACTE flight, the experimental control surfaces were locked at a specified setting.

Different flap settings will be employed on subsequent flights to collect a variety of data demonstrating the capability of the flexible wings to withstand a real flight environment.

The flaps have the potential to be retrofitted to existing airplane wings or integrated into new airframes.

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DETECTION EFFICIENCY OF ROAD VEHICLES IN MOTION FOR TRANSPORT COMPANIES

Nicolae Răzvan, Alexandru Valentin Rădulescu

POLITEHNICA University of Bucharest, Bucharest, ROMANIA, e-mail: [email protected]

ABSTRACT Automation became necessary in the road since the authorities have realized that the number of road accidents and material losses of life have increased alarmingly long. The complexity of these processes, the extent of large geography, transport systems and road infrastructure to achieve scale automation in this area is needed a large merger of several specific technologies: Capture information, Information processing, Submit Information,Use of information. The general objectives of the latest research and development programs in the field were directed to obtaining and exploitation of new knowledge on the applicability of traffic control systems in major cities, traffic management . Research has focused mainly on the applicability of self-training these types of embedded systems, auto optimization urban traffic control strategies.

KEYWORDS: detection efficiency, road vehicles, motion, transport companies

1. INTRODUCTION

Choosing sensors and transducers must be monitored taking into account the property , the area in which it varies , to be observed size or geometry , special environmental conditions or work , such as output size , not the least of cost . The sensor is a system for determining one or some properties , including both the transducer, which converts the input into useful electrical signal and circuit to adapt and convert the signals , and possibly for processing and evaluation .

Sensors and transducers are used and if the research laboratory is included in chains of complex instruments that are managed automatically. 2. INTELLIGENT SYSTEMS TECHNOLOGIES FOR ROAD TRANSPORT

Automation became necessary in the road since the

authorities have realized that the number of road accidents and material losses of life have increased alarmingly long. The complexity of these processes, the extent of large geography, transport systems and road infrastructure to achieve scale automation in this area is needed a large merger of several specific technologies:

• Capture information • Information processing

• Submit Information • Use of information

The general objectives of the latest research and development programs in the field were directed to obtaining and exploitation of new knowledge on the applicability of traffic control systems in major cities, traffic management .

Research has focused mainly on the applicability of self-training these types of embedded systems, autooptimizării urban traffic control strategies.

It seeks to develop a system that can respond effectively to permutations and change the general characteristics of Tafic . Such a system would need to be able to act on a semaphore traffic signal duration on the basis of algorithms for minimizing the duration of transit vehicles and the traffic lights waiting durations.

Usability urban traffic control systems depends heavily on their ability to react properly and timely to changes in the general characteristics of the traffic. The essence of an adaptive type UTC is based on the integrated operation of a number of blocks traffic signaling at intersections ( BSTI ) and several agents Authority (AA).

The expert " in the middle of a working BSTI a block contoler. Acest contolează the functioning optical and determine strategy.

Order signaling dependence traffic intersection normally work in closed loop fast - response model with internal systems . Detectors that provide data feeds with information control algorithm.

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Based on predetermined rules is chosen control strategy and road signs is controlled as such. 3. CAPTURE PARAMETERS CHANGE OF ROAD VEHICLES

Capturing information from the field on the conduct

of traffic is one of the most important processes in regulating its adaptive. You can not discuss adaptively adjusting traffic with vehicle detection and / or their identification. Vehicle detection is a process of collecting traffic information knowing so any time is the effectiveness of the system in the process of regulating traffic.

Can capture traffic information in real time or with further analysis of traffic data . There are several technologies used to capture traffic data derived from these detectors.

They are quite diverse methodologies and sensor accuracy depends on many factors, including: • Environment • Vehicle type • Distance • Vehicle speed unfold

Intelligent Transport systems like ATMS include subsystems traffic detection, communications, and control tehnlogii (components of traffic management strategies). These technologies serve to satisfy the growing demands of the surface transportation system. Vehicle detection and surveillance systems are entirely of ITS parts, because they collect all or at least part of the data used by STIs.

Are constantly improved vehicle detection technologies and create new technologies for monitoring speed , vehicle count , presence detection , direction of travel, and vehicle classification data acquisition relative to the moving vehicle weighing .

The processes of abstraction of information about how the avehiculelor displacement can be described as having three components:

Fig 1. Components required detection / surveillance vehicles

Detector or sensor, transducer, as it is often called, is designed to detect the passage or presence of a vehicle or its axles via a specific point. Signal processing device converts the transducer output sizes into electrical signals.

The data processing is typically made up of hardware / software for converting these electrical signals into parameters of the traffic.

These traffic parameters include: the presence of vehicles, vehicle count , speed , classification, interval between vehicles, direction of travel, gauge , weight and length of transit.

Data processing device can be constituii as part of the sensor (transducer) or may be represented by a controller outside it, bound by galvanic separation of control devices, such as, for example, optocuploaele or electromagnetic relays.

Detection/surveillance systems can best classify according to how it is affecting traffic to their attachment.

Sensing/monitoring systems with interaction in traffic-are those the echipamanete, for installation it is necessary to carry out specific works (ditches, potholes in the road, etc.) and which have the effect of cross sectional area traffic and a low degree of detection systems removability.

Detection systems and traffic monitoring without interaction cheap and reliable equipment; are those that can be installed and maintained with minimal intervention in the flow of traffic and the accuracy of detection is at least the level of inductive loops. 4. DATA ACQUISITION SYSTEMS

An acquisition and management system (SAC)

contains the following functional blocks: - analog data acquisition system (SADA) which is

designed to read data in analog data that can come from measuring transducers and adapters ;

- Analog data generation system (SGDA) is the primary means of obtaining orders to analog form ; signals thus obtained can be applied to the actuators or can be displayed on analog monitors

- Numerical system inputs and outputs used in connection with digital equipment or interfacing with electrically controlled actuators

- Microcomputer that performs both local data processing and communication with other systems. By microcomputer means a single or multiprocessor computing architecture, equipped with microprocessors or microcontrollers.

The transducers are designed to sample sizes measured and convert them into electrical signals, signal conditioning circuits performing analog signal processing.

Analog signals are taken from the analog input circuit that converts digital signals using analog- digital conversion circuits and digital signals are taken from digital input circuits. Finally, the computer receives sizes taken from the process in the form of digital signals that they process their analysis and developing decision making.

Industrial digital control systems generally involve a large number of sensors and actuators , analog and digital . Sensing elements ( sensors ) of the transducer converts quantities measured in voltage, current , resistance, Whose values differ widely from one device to another.

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Data acquisition systems start with transducers , devices that convert measurable physical quantities such as temperature , pressure, force, acceleration , vibration , sound , humidity , flow , level , humidity , pH, chemical composition , and others , in a electrical signal.

Any installation of transducers for industrial automation has its specific requirements . Besides sensors are available for a wide range of measurements, are presented in a variety of shapes, sizes and features.

5. CAPACITIVE SENSOR

Broadly proximity refers to the closeness between

two objects , one of which is the reference system. Proximity sensors are sensors to investigate whose features consist of small distances Action ( tenths of mm and mm ) , and that in many cases are used in the notification of the presence in the action.

Capacitive sensors are based on variaţtia electric capacity in a circuit, and have the advantage that they can detect nonmetallic objects. There are, however, sensitive to the disruptive factors such as soiling active face.

Capacitive sensors and transducers are part of parametric transducers and sensors Mohammad and they covertesc the size of electrical measurement in a variation of capacitance.In terms of geometrical and constructive, capacitive transducers and sensors can be Planar or cylindrical.

Capacitive sensors are designed to detect insulating materials and conductive current. They are able to detect most of the materials , particularly of paper, glass, plastic, water, oil, and all metal materials.

Capacitive proximity contain four main parts: the board , the oscillator circuit detection sensor and solid state switch operates in a manner similar to a simple capacitor.

When the oscillator is started, it detects the amount of capacitance between the target and the metal plate of the sensor.

To approach the target, the ability increases. When ability reaches a certain point, the oscillator starts to work (the opposite of inductive sensors, the oscillator stops working when approaching the target).

6. IMPLEMENTATION OF MANUFACTURING A PROXIMITY SENSOR

An IT company profits received by the sensor

provides a model for detecting trucks, such magnetic sensors provide a low- cost solution for vehicle recognition and vehicle detection systems. If mounted in the pavement, or with vehicle lanes, magnetoresistive sensor technology provides solutions highly sensitive for the detection of vehicles and traffic management.

From bikes and cars to forklifts and aircraft, vehicles containing ferrous materials that disrupts uniform intensity and direction of the magnetic field. Depending on the content of ferrous materials and proximity sensors , disturbance of Earth's magnetic field vehicles from 15 feet or more can be detected. Cars can be easily detected within a meter of the sensor without discrimination circuits significantly.

Since the magnetic sensors are very small and robust environment , make cost -effective vehicle detection and traffic management solutions.

Typical applications include door opening, bar operating safety , traffic management and monitoring , detection and vehicle parking space location / positioning.

Combinations of sensors could be used to enhance the signal processing and sensors than the same targeted movement can be used to determine vehicle heading and speed information.

7. SMOOTH TRAFFIC FLOW WITH ADVANTECH’S PC - BASED INTELLIGENT TRANSPORTATION SYSTEMS [4]

Advantech offers advanced product solutions for the

Intelligent Transportation System market. Our open Architecture solutions include robust designs that are manufactured specifically for outdoor installations and can sustain extended temperature, extreme shock and vibration tolerance.

Advantech has shown plenty of field proven solutions in:

Vehicle detection Advanced Traffic Management System Traffic Video Monitoring Environment Monitoring Automated Parking In-vehicle Control and Monitoring

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Fig.2. Traffic management system

Fig.3. Advantech's Intelligent Transportation System Solutions Main Products

CONCLUSIONS

Traffic monitoring system provides the following functions such as collecting information from sensors installed on the process flow, verify whether the parameters read preset limits and reporting alarms; saving regularly read the journals state values; presentation in graphical form status information and configuration process elements; it generates reports of values, status reports, elements reports alarms and graphical variation and reconfiguration of the dispatching process , control loops, alarm thresholds.

REFERENCES [1].Constantin Calinoiu, Senzori si traductoare , vol. I, Editura Tehnica,2009. [2]. Lucian Ciobanu ,Tratat de inginerie electrica.Senzori si tradutoare, Editura Matrix Rom. [3]. Dragomir, N.D., Research Center for Intelligent Instrumentation and Sensors, SENET 2000, Ljubliana, Nov. 2000. [4].http://www.advantech.com.tw/ia/newsletter/Transportation_page2.htm [5].Crisan, T.E. – Cercetari in domeniul traductoarelor inteligente pentru pozitionari de precizie, Referat de doctorat, 1999. [6].C.G.Saracin,M.Saracin,Traductoare. Interfete. Achizitii de date, Editura Matrixrom.

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ADDITIVE MANUFACTURING TECHNOLOGIES USED FOR SUPERALLOYS PROCESSING

Răzvan Udroiu

Transilvania University of Brasov, Brasov, ROMANIA, e-mail: [email protected]

REZUMAT Articolul prezintă tehnologiile de fabricatie aditiva utilizate pentru realizarea pieselor din superaliaje. Obiectivul principal al acestui articol este stadiul actual al fabricatiei additive utilizate pentru piese metalice, prezentarea principiului de lucru a fabricatiei additive, a tipurilor si caracteristicilor masinilor de fabricatie rapida cat si a aplicatiilor acestora pentru obtinerea superaliajelor.

ABSTRACT The paper presents Additive Manufacturing (AM) technologies used for building parts from superalloys. The main objective of this article is the state of the art of AM used for metal parts, of presentation of the working principle of the metal AM, of the types and characteristics of AM machines used and also of the applications for superalloys.

KEYWORDS: additive manufacturing, rapid manufacturing, powder bed fusion, powder melted deposition, metal powders, supperaloys CUVINTE CHEIE: fabricatie aditiva, fabricatie rapida, fuziune in pat de pulbere, depunere pulbere topita, pulberi metalice, superaliaje

1. INTRODUCTION

Additive manufacturing (AM) [1, 2, 3, 5] was developed as a automated fabrication of physically complex shapes directly from three dimensional (3D) computer aided design (CAD) data or data from 3D scanning system, using a layer-by-layer deposition principle. AM can reduce the manufacturing time of new products with 8-10 times in comparison with the conventional technologies and it reduces the costs of the products [2]. According to ASTM F42 Committee, AM is defined as “process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies, such as traditional machining” [4]. There are many terms commonly used for AM, such as rapid prototyping (RP), rapid manufacturing (RM), additive layered manufacturing (ALM) and 3D printing [5, 6]. Rapid Prototyping (RP) is the use of additive fabrication technique to obtained prototypes as communication tools, functional testing and inspection tools. Based on additive manufacturing principles, Rapid manufacturing (RM) produces end products made of plastic, composites, ceramics or metal [1].

The main methods for additive manufacturing of metals can be divided into non-melting, partially melting and fully melting processes [6, 7]. The solidification process can be softening or partial melting, complete melting and resolidification, liquid-phase sintering, chemical reaction, curing of a resin binder, etc. The additive manufacturing technologies, Figure 1, for metals can be divided into three main categories: indirect AM technologies, direct AM technologies and hybrid technologies [3]. Indirect AM technologies are no or partial melting technologies that require post-processing and infiltration, in order to increase the final density of the part [6]. Direct AM technologies are based on full melting processes, obtaining final properties directly from machine. Hybrid technologies combines AM and subtractive manufacturing technology like as CNC milling. Direct AM technologies [4] are classified in powder bed fusion (PBF) technologies and powder melted deposition technologies. Powder melted deposition are also known as Laser Cladding, Directed Energy Deposition (DED) [4] and Laser Metal Deposition.

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In PBF based technologies, thermal energy selectively fuses regions of powder bed [4, 9]. In DED based technologies focused thermal energy is used to fuse materials (powder or wire form) by melting as they are being deposited [4, 10]. The above AM technologies allows to process a wide range of metal materials, light metals, stainless, tooling steel and superalloys.

Figure 1. Metal additive manufacturing process

Superalloys are generally either nickel or cobalt based alloys beeing a class of metals having very high strength and typically also very good performance at high temperatures. Nickel-based superalloys are mainly used in aerospace, nuclear and automotive applications, whereas cobalt-based superalloys are used for aerospace and biomedical applications. The most knowns superalloys used in additive manufacturing are: Cobalt – Crom, Inconel, Hastelloy, Waspalloy, Stellite, MERL 72

2. ADDITIVE MANUFACTURING PROCESS CHAIN OF METAL PARTS Generally, the AM process of metal parts consists in the following main steps: pre-processing, processing and post-processing [2]. The industry standard exchange format for additive manufacturing is the STL (STereoLithography or Standard Triangulation Language) file. Basically, it is a file that replaces the original surface of solid, surface or scanned model with a mesh of triangulated surface segments.

Almost all of today's CAD systems are capable of producing a STL file, as selecting File, Save As and STL [2]. In the pre-processing stage a 3D file (STL) is imported into specific AM software, scale it (if necessary), generate the support structure (if necessary), orientate the part and simulate the manufacturing process layer by layer etc. Before starting the processing stage it is necessary to set up the laser power and choose the metal powder. Processing stage consists in prints the part, layer by layer from the bottom of the design to the top. When the printing process is completed wait a time to consolidate the 3D model. Post-processing process [8] consist in removing of the part from the powder bed or build platform. Metal parts can be supplied ‘as-built’ or finished using various post processing and finishing techniques. Dependent upon the material used, there are various forms of finishing available such as shot-peening and metal polishing. Shot-peening [3, 8] is a cold working process used to produce a compressive residual stress layer and modify mechanical properties of metals. Metal Polishing [8] is the process of smoothing metals and alloys and polishing to a bright, smooth, mirror-like finish. 3. AM OF SUPERALLOYS PARTS LITERATURE REVIEW Powder bed additive manufacturing process [3, 9] , generally consists in melting layer by layer of a powder spreaded by a roller or blade onto the build try. The energy used for powder melting is generated by a laser or electron beam. Material properties of the end part are very dependent on process parameters. The most known powder bed AM technologies are: Selective laser melting (SLM), Direct metal laser sintering (DMLS), LaserCUSING, Electron Beam Melting (EBM) and Laser sintered in solid phase. SLM SLM [10, 11, 12, 13] uses a high powered ytterbium fiber laser to fuse metallic powders together to form functional 3D parts. SLM 250HL system, from Transilvania University of Brasov, allows building parts from superalloys (Figure 2).

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Figure 2. SLM 250HL system, PRO-DD Institute, Transilvania University of Brasov The SLM process offers a quick and low cost method of producing components in Inconel (Figure 3) and in Cobalt Chrome Alloy (Co212 - ASTM F75) materials. Aerospace application such as turbine blade with internal conformal cooling channels to improve performance of jet engines, rocket motors, spacecraft, space shuttles, nuclear reactors, pumps, turbo pump seals use Inconel 625, Inconel 718 and Inconel HX (2.4665) [13].

Figure 3. Stator of a micro gas turbine out of Inconel

718 made by SLM [13]

Figure 4. Cobalt Chrome Superalloy turbine blade

made by DMLS [8] DMLS (EOS) Direct metal laser sintering (DMLS) is an additive metal fabrication technology developed by EOS from Germany [3, 15, 16, 17].

In718 Alloy (EOS 718 Alloy) is a nickel based heat resistant alloy in fine powder form. Its composition corresponds to UNS N07718, AMS 5662, AMS 5664, W.Nr 2.4668, DIN NiCr19Fe19NbMo3 [15]. This kind of precipitation-hardening nickel-chromium alloy is characterized by having good tensile, fatigue, creep and rupture strength at temperatures up to 700°C [8]. Cobalt Chrome Alloy (EOS CC MP1) is a fine powder mixture which produces parts in a cobalt-chrome-molybdenum-based [8]. This class of superalloy is characterized by having excellent mechanical properties (strength, hardness etc.), corrosion and temperature resistance, having applications on turbine blade (Figure 4). EOS CC SP2 is a cobalt-chrome-molybdenum-based superalloy powder which has been especially developed to fulfill the requirements of dental restorations which have to be veneered with dental ceramic material [16]. ARCAM In the EBM process [3, 18], fully dense metal parts are built up, in a vacuum, layer-by-layer of metal powder melted by a magnetically directed electron beam energy source. The Arcam ASTM F75 CoCr alloy powder [18] for EBM is produced by gas atomization and the chemical composition complies with the ASTM F75 standard’s specification. Concept Laser GmbH from Germany used a term derived from cladding and fusing: “LaserCusing”. LaserCUSING [19, 20] made up of the letter C from CONCEPT Laser and the word FUSING (complete melting). Nickel-based alloy CL 100NB (Inconel 718) offered by LaserCusing are used for the production of heat-resistant components in the power generation and aerospace industries. Metal Powder Deposition [21, 22] process has a much larger potential than bed-based systems. A complex deposition head mounted on 3, 5 or 6-axis robotic arm, jettes the metal powder into a melt-pool created by a laser or an electrode beam. The powder is injected into the system by either coaxial or lateral nozzles (Figure 5). The interaction of the metallic powder stream and the laser causes melting the powder. Full melting and weldable materials in combination with rapid solidification gives fine crystalline structure and excellent material properties [21]. The metal powder deposition applications are multiple: to build new metal part, to repair, add features to an existing part and to build functional graded materials.

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Figure 5. The different feeding systems available [23] The process of metal powder deposition is known by several names, most of which are trademarks of various machine manufacturers or research establishments. These include: Laser engineered net shaping (LENS) [27], Direct metal deposition (DMD) [28], Construction laser additive directe (CLAD) [29], Laser aided direct metal tooling, Laser powder fusion welding, Electron beam free form fabrication (welding wire not powder) and Laser consolidation [36]. Laser engineered net shaping (LENS) is a technology developed by Sandia National Laboratories USA, and commercialized by Optomec Design Company, USA, for fabricating metal parts directly from a computer-aided design (CAD) solid model by using a metal powder injected into a molten pool created by a focused, high-powered laser beam [25, 26, 27]. Concerning superalloys [24], LENS provides powders of nickel based alloys (625, 713, 718, 600, 690, Hastelloy X, Haynes 188 & 230, MarM 247, CMSX-3, Waspalloy, Rene 142 & N5) and cobalt based alloys (CoCr – Stellite). In Figure 6 is presented the LENS manufacturing process of a turbine blade [27].

Figure 6. Processing a blade using LENS system [27] POM (Precision Optical Manufacturing) based on a laser-aided surface treatment process known as laser cladding, has adapted it to create free form metal parts, known today as Direct Metal Deposition (DMD) [28]. DMD is the blending of five common technologies: lasers, computer-aided design, computer-aided manufacturing, sensors, and powder metallurgy. The main applications are restoration of gas turbine blade squealer tips, application of wear resistant cladding in Z-notch welding and restoration of blisks. The superalloys used in DMD process are Co alloys (Stellite 21, MERL 72, Stellite 6, Stellite 706) and Ni alloys (IN 718, Waspalloy, Inc 738, IN 625, C-276, Nistelle C). CLAD® technology (French acronym for ‘Construction Laser Additive Directe’ – direct additive manufacturing by laser) consists in manufacturing functional parts with metallic powder melted by laser [30]. CLAD technology provide a large operating flexibility for: deposits on warped parts, 3D direct manufacturing, addition of functions on existing parts, additive repair and build multi-material structure. Direct Metal Tooling (DMT) is an innovative technology in the field of RP and rapid tooling (RT) that consists in the injection of metallic powders into a nozzle and melted by a laser [31]. Sciaky [32] utilized the electron beam direct manufacturing (EBDM) or electron beam free form fabrication (EBFFF or EBF3) technology to produce metal parts by combining additive manufacturing principles, computer-aided design and electron beam welding technology. A wide range of alloys are compatible with the EBDM process and are available in the form of welding wire. These include superalloys such as Cobalt alloys and Nickel alloys.

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LPW Technology [33] offers a complete range of metal powders relating to Laser Metal Deposition and Powder Bed Additive Metal Manufacture within the Aerospace, Turbine, Medical, and Petrochemical industries. A synthesis regarding AM of superalloys is presented in the tables 1, 2 and 3. 4. CONCLUSIONS In this paper a review of additive manufacturing of metal parts with application on superalloys was presented. Aditive manufacturing are moving from rapid prototyping and rapid tooling to rapid manufacturing. The production of end-use parts made of metal in a fast way, keeping a freedom to design, support of green manufacturing, without using additional tools is one of the most promising applications for these techniques. Rapid manufacturing of metal parts of high density and excellent mechanical properties has main applications in aerospace, automotive, nuclear and medical industries. However, there are still problems to be solved by future research such as: bigger build envelopes, accuracy improvements, micro sintering for fine detail resolution, reduced cost, medium to high volume production and new materials. REFERENCES [1]. Wohlers, T., “Wohlers Report 2012: Executive summary,

Rapid prototyping & manufacturing. State of the industry”, TCT Magazine, Rapid News Publications plc, UK. 2012,

[2]. Udroiu R. Nedelcu A.,. “Optimization of Additive Manufacturing Processes Focused on 3D Printing”, In: Rapid Prototyping Technology - Principles and Functional Requirements, Muhammad Enamul Hoque (Ed.), ISBN: 978-953-307-970-7, InTech, available from: http://www.intechopen.com/articles/show/title/optimization-of-additive-manufacturing-processes-focused-on-3d-printing, 2011,

[3]. Udroiu, R., “Powder bed additive manufacturing systems and its applications”, Academic journal of manufacturing engineering, Vol. 10, Issue 4, 2012,

[4]. ASTM, “ASTM F2792-12a, Standard Terminology for Additive Manufacturing Technologies”

[5]. Verquin, B., “From rapid prototyping to Rapid manufacturing”, CETIM, 2006

[6]. Levy, G., N.; Schindel, R.; Kruth, J.P, “Rapid Manufacturing and Rapid Tooling with Layer Manufacturing technologies, state of the art and Future Perspective”, Annals of the CIRP 52/2, 589-609, 2003

[7]. Santosa, E.C., Shiomia M., Osakadaa, K., Laouib, T., “Rapid manufacturing of metal components by laser forming”, International Journal of Machine Tools & Manufacture 46 1459–1468, 2006

[8]. 3T RPD Ltd, “Direct Metal Laser Sintering (DMLS)”, available online: www.3trpd.co.uk/dmls, 2011

[9]. Woodcock, L., “Additive manufacturing in metals. Part 1: Powder bed systems”, The TCT Magazine 6/2011, pp. 27-32

[10]. SLM Solution GmbH, “Discover the variety. SLM® Materials Non Ferrous Metals, Tool Steel, Stainless Steel and Light Alloys”, 2011

[11]. Realizer, “Selective laser melting”, available online: http://www.realizer.com, 2012

[12]. Renishaw, “Additive manufacturing”, available online: http://www.renishaw.com/en/additive-manufacturing--15239, 2011

[13]. Meiners W.; Wissenbach, K. “Selective laser melting of superalloys”, available online: http://www.ilt.fraunhofer.de/en/technology-focus/laser-material-processing/rapid-manufacturing.html#tabpanel-3, 2011

[14]. Vilaro, T. ; Abed1, S. ; Knapp, W., “Direct manufacturing of technical parts using selective laser melting: example of automotive application”., In: Proc. of 12th European Forum on Rapid Prototyping, , France, 2008

[15]. EOS, “EOSINT M Materials for Direct Metal Laser-Sintering (DMLS)”, EOS GmbH - Electro Optical Systems, pp.1-58, 2010

[16]. EOS, “EOSINT M Technology for Direct Metal Laser-Sintering (DMLS)”, EOS GmbH - Electro Optical Systems, pp.1-22, 2010

[17]. EOS, “Additive Manufacturing System for the Industrial Production of High-Quality Large Metal Parts”, http://www.eos.info/systems_solutions/metal/systems_equipment/eos_m_400 , 2014

[18]. Arcam, “ASTM F75 CoCr Alloy”, available online: www.arcam.com, 2012

[19]. Hofmann & Engel Produktentwicklung GmbH, “Overview of materials”, http://www.cusing24.de/en/Materials.html, 2011

[20]. Concept Laser, “The technology”, available online: http://www.concept-laser.de/, 2011

[21]. Woodcock, L., “Additive manufacturing in metals. Part 2: Powder deposition systems”, The TCT Magazine 8/2011, pp. 45-48

[22]. Dutta, B., “New Advancements in Direct Metal Deposition Technology”,https://www.lia.org/laserinsights/2011/02/16/new-advancements-in-direct-metal-deposition-technology, 2011,

[23]. Wikipedia, “Cladding (metalworking)”, available online: http://en.wikipedia.org/wiki/Cladding_(metalworking), 2014

[24]. Hedges, M., Calder, N. , “Near net shape rapid manufacturing and repair by LENS”, AVT139/ RSM 019, NASA, 2006

[25]. LENS, “Laser Powder Forming”, available online: http://www.additive3d.com/lens.htm, 2010

[26]. Optomec, “Optomec_LENS_Superalloy_Datasheet”, available online: http://www.optomec.com, 2012

[27]. Gill, D., “Laser Engineered Net Shaping. Manufacturing Technologies”, contract DE-AC04-94AL85000, Sandia Corporation, 2002

[28]. POM, “Direct metal deposition (DMD)”, available online: http://www.pomgroup.com/index.php?option=com_content&task=view&id=15&Itemid=86, 2012

[29]. EasyCLAD systems, “Produits & services”, available online: http://www.easyclad.com , 2012

[30]. IREPA LASER, “Fabrication directe”, available online: http://www.irepa-laser.com/index.php/fra/fabrication-directe, 2011

[31]. Insstek, “DMT”, available online: http://www.insstek.com/tech/index02.htm, 2012

[32]. Sciaky, “Sciaky's Direct Manufacturing” available online: http://www.sciaky.com/direct_manufacturing.html, 2012

[33]. LPW Technology Ltd , “Metal additive manufacturing powders”, The TCT Magazine 11/2011

[34]. ProMetal , “Functional direct metal parts printed directly from CAD”, available online: http://www.exone.com/eng/technology/x1-prometal/index.html, 2011

[35]. Matsuura Machinery Corporation, “LUMEX25C,”, http://www.matsuura.co.jp/index.shtm., 2012

[36]. Accufusion Inc. “ Accurate parts, tools, prototypes, repairs – in one step”, available online: http://www.accufusion.com/ , 2012.

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http://www.intechopen.com/articles/show/title/optimization-of-additive-manufacturing-processes-focused-on-3d-printing

http://www.intechopen.com/articles/show/title/optimization-of-additive-manufacturing-processes-focused-on-3d-printing

http://www.3trpd.co.uk/dmls

http://www.realizer.com/

http://www.renishaw.com/en/additive-manufacturing--15239

http://www.ilt.fraunhofer.de/en/technology-focus/laser-material-processing/rapid-manufacturing.html#tabpanel-3

http://www.ilt.fraunhofer.de/en/technology-focus/laser-material-processing/rapid-manufacturing.html#tabpanel-3

http://www.eos.info/systems_solutions/metal/systems_equipment/eos_m_400

http://www.eos.info/systems_solutions/metal/systems_equipment/eos_m_400

http://www.arcam.com/

http://www.cusing24.de/en/Materials.html

http://www.concept-laser.de/

http://en.wikipedia.org/wiki/Cladding_(metalworking)

http://www.additive3d.com/lens.htm

http://www.optomec.com/

http://www.pomgroup.com/index.php?option=com_content&task=view&id=15&Itemid=86

http://www.pomgroup.com/index.php?option=com_content&task=view&id=15&Itemid=86

http://www.easyclad.com/

http://www.irepa-laser.com/index.php/fra/fabrication-directe

http://www.insstek.com/tech/index02.htm

http://www.sciaky.com/direct_manufacturing.html

http://www.exone.com/eng/technology/x1-prometal/index.html

http://www.exone.com/eng/technology/x1-prometal/index.html

http://www.matsuura.co.jp/index.shtm

http://www.accufusion.com/


Table 1. Hybrid Metal manufacturing systems (AM powder bed + CNC milling)

AM technology Manufacturer AM machine name

Build envelope X x Y x Z

(mm x mm x mm)

Power source type

(thermal energy)

Layer thickness

(µm)

Build materials

SLM + CNC milling Matsuura [35]

LUMEX25C W250 / D250 pulsed CO2 laser (500 W

- 1.5 kW)

- superalloys

DMD + dry microEDM POM Group Inc. SYNERGY5 300x300x300

(3 and 5 axis) - - superalloys

Table 2. Direct additive manufacture matrix for superalloys in the case of powder bed fusion systems



(mm x mm x mm)

Power source type

(thermal energy)

Layer thickness

(µm)

Build materials

LaserCUSING Concept Laser

M1 cusing M2 cusing M3 linear

250x250x250 250x250x280 300x350x300

YAG laser

20 - 100 20 - 100 20 - 100

Nickel-based alloy CL 100NB (Inconel 718); cobalt chrome

Direct metal laser sintering (DMLS)

EOS GmbH Electro Optical Systems

EOSINT M270 EOSINT M280 EOSINT M290 EOSINT M400

250x250x215 250x250x325 250 x 250 x 325 400 x 400 x 400

Yb-fibre laser, 200 W 200 or 400 400 W 1 kW

20 - 40 20 – 80

EOS Cobalt Chrome MP1; EOS Cobalt Chrome SP2; EOS Nickel alloy HX; EOS Nickel alloy IN625; EOS Nickel alloy IN718

Laser sintered in solid phase Phenix Systems

PXL PXM PXS PXS Dental

250x250x300 140x140x100 100x100x80 100x100x80

Fiber laser, 500W 300 W 50 W 50 W

10 - 60 10 - 60 10 - 60 10 - 60

superalloys

Selective laser melting (SLM)

SLM Solutions GmbH (Germany)

SLM 125 HL SLM 250 HL SLM 280 HL SLM 500 HL

125 x 125 x 75 248 x 248 x 250 280 x 280 x 350 500 x 280 x 325

400 to 1000 W, YLR- fiber-laser 2 x 400W, and optional 2 x 1000W YLR- fiber-laser

20–75 20-75 20-75/100 20-200

Cobalt Chrome; Inconel

Renishaw Group (UK)

AM 125 AM 250

120 x 120 x 125 250 x 250 x 300 (Z axis extendable to 360 mm)

Fibre laser

20 - 100 20 - 100

Realizer GmbH (Germany)

Realizer SLM 50 Realizer SLM 100 Realizer SLM 250 Realizer SLM 300

70 x 40 (Diam x Z) 125 x 120 x 100 250 x 250 x 300 300 x 300 x 300

Fibre laser

20 – 50 20 – 100 20 – 100 20 – 100

Phenix systems Phenix PM100 100 x 150(Ø/H) Ytterbium

doped fiber (P=50 W)

50

Electron Beam Melting (EBM) Arcam AB

Arcam S12 Arcam A1 Arcam A2 Arcam Q10 Arcam Q20 Arcam A2X i

200x200x180 200x200x350 200x200x180 350 x 380 (Ø/H) 200x200x380

Electron Beam max beam power 3000 W

50 - 100 50 - 100 Arcam ASTM

F75 Co Cr alloy

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Table 3. Direct additive manufacture matrix for superalloys in the case of metal powder deposition systems



(mm x mm x mm)

Power source type

(thermal energy)

Layer thickness

(µm)

Build materials

Laser engineered net shaping (LENS)

OPTOMEC Inc.

LENS 850-R 1000x1500x 1000 Laser, 500W - 4kW

500 LENS superalloys: IN625; IN718; IN713LC;IN738 Hastelloy; Waspalloy; MarM247

LENS 750

300x300x300 500

LENS MR7 Materials reseach

300x300x300 500

Direct metal deposition (DMD)

POM Group Inc.

DMD IC 106

800 (6axis robot)

Up to 1kW Fiber coupled laser Diode or Disc Laser

100-500 Cobalt base:

Stellite 21; Stellite 6; Stellite 31; MERL 72; Nickel base : IN 718; IN 625; Inc 738; Waspalloy; C-276; Nistelle C

DMD 44R/66R

2000-3000 (6 axis robot)

1 to 5kW

500-1800

DMD 103/105D

300x300x300 (3 and 5 axis)

1kW

250-700

DMD505D

1200x1200x 600 (5 axis)

5kW 400-1500

Construction laser additive directe (CLAD)

EasyCLAD Systems

VC LF300 VH LF4000 VI LF4000

MAGIC LF6000

400x350x200 650x700x500 950x900x500

1500x800x800 5 axes

Fiber or Disc laser 0,75-4kW

100-300 1000-1500

/3000-4000

100-300 /500-1200

200-800

INCO 718; INCO 625;

Stellite 6-12-21-25; H13;

Waspalloy

Laser aided direct metal tooling

Insstek MX 3 5axis 3-4kW

TRUMPF CO2 Laser

- Superalloys

Laser powder fusion welding Huffman Corp.

HC 205

5 axis PRC CO2 laser, max 2KW

-

Inconel 738 HC 115CL

5 axis -

Electron beam free form fabrication

Sciaky VX

VX.2 VX.4

1727x838x1575 2692x1016x1676 4978x2286x1778

Electron beam welding

- Cobalt alloys, Nickel alloys -

Laser consoled. Accufusion Inc. laser - IN625, IN738

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INNOVATIVE TECHNOLOGIES IN DENTISTRY AND DENTAL TECHNIQUE

Stamate Valentin-Marian1, Lancea Camil1

1Transivania University of Braşov, Braşov, ROMANIA, [email protected], [email protected]

REZUMAT Investițiile făcut în ultimele decenii în domeniul stomatologiei și împrumutarea tehnologiilor industriale avansate au dus la rezultate spectaculoase şi de neînlocuit. Metodele cele mai evoluate, cum ar fi fotografierea digitală tridimensională, utilizarea modelelor virtuale de lucru sau construirea unor modele din pulberi metalice sinterizate cu laser prin metoda Rapid prototyping au fost imediat asimilate. ABSTRACT Investments made during the last decades in dentistry field and borrowing advanced industrial technologies have led to spectacular and irreplaceable results. The most advanced methods, such as three-dimensional digital photography, using virtual working models and building models of laser sintered metal powder by Rapid prototyping method were immediately assimilated.

KEYWORDS: CAD/CAPP/CAM, dental technique, additive manufacturing, prosthetic works, galvanoforming, baro-thermo-polymerization CUVINTE CHEIE: CAD/CAPP/CAM, tehnică dentară, fabricaţie aditivă, lucrări protetice, depunere galvanică, barotermopolimerizare

1. INTRODUCTION

According to [1], [2], [3] the new CAD / CAM technology points out an area based on the use of information in the technical field. It is about the computerization of industrial activities, primarily of design and manufacture by using the computer in an extensive process of information processing, a process that became the basic coordinating component, in an efficient system and the other two components, meaning the flows of materials and energy are transformed with maximum efficiency [5], [21].

Some special technologies of these systems will attract our attention [11], [4]. Rapid Prototyping, Reverse Engineering and Virtual Engineering technology. CAD / CAM technology [17], [22] appeared in aerospace engineering, automotive engineering and electronics, expanding successfully in the medical field.

CEREC system is the most advanced prosthetic restoration treatment in dentistry, which uses the CAD / CAM system.

It allows making during one single session full

ceramic crowns, inlays, onlays or sides. Ceramic materials that are used are more resistant than ordinary fillings, but they are not tougher than dental enamel and therefore do not grind opposing teeth. According to statistics, every 20 seconds a CEREC restoration is achieved in the world. 2. MAKING PROSTHETIC WORKS BY USING CAD / CAMSYSTEM

CAD / CAM systems used by dental offices and dental labs allow achieving exceptional treatments sincethe new materials and products created by using new systems offer more comfort to users with their dimensional accuracy, esthetic appearance and physical and chemical properties of dentures which are confused with natural elements. Biocompatibility is increasingly felt by replacing metal with new types of materials accepted by the body.

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One of the most important stages of dental treatment is to analyze the patient's prosthetic field and develop a work strategy, presenting virtual treatment plans [13], [23]. Dental digital sheet allows storing all data on the clinical situation of the patient. This includes the real situation of the mouth, with previous processing, fillings, extractions, pins, crown-root devices, implants and any type of fixed works, date and location thereof.

The sheet contains information on the conditions that may create allergies to certain impression substances and also to some heart disease - cases where the use of certain injection products to anaesthesia is contraindicated [37].

For an optimum analysis of the situation in the patient's mouth intraoral cameras are used. The intraoral camera system and 2D images allow viewing the entire mouth on the monitors attached to dental units, connected to computers with specialized software for dentistry.

The patient can see on the screen dentures options that can be tailored to his personal situation. The variety is due to the different situations from individual to individual and the multitude of new materials and technologies.

By using CAD system, the dentist is able to scan certain types of cavities previously processed and to correct on the monitor the contour of the cavity, in order to send the information to the CNC device [37]. Using 3D intraoral cameras (figure 1) prosthetic field will be scanned, detecting with the laser beam any type of cavity, and one can see its evolution and depth.

Figure 1. 3D CEREC Bluecam,[42] With digital cameras photo, video and radiological images will be made before and after treatment and will be stored in patient’s electronic sheet. After 3D scanning, the virtual model of the prosthetic field is obtained from the oral cavity (figure 2).

Figure 2: Virtual model of prosthetic field

After obtaining the virtual model of the prosthetic field, different execution options of the prosthetic work can be chosen.

A working method frequently used in prosthetic work uses the mobile abutment model. It has a high dimensional accuracy, complying with the real situation of the patient's mouth, abutments are resistant to mechanical stress during prosthetic work test and the repositioning of mobile elements after taking them off the support [8]. 3. THE METHOD OF MAKING THE MOBILE ABUTMENTS MODEL

It is used in dentistry, and has to do with the use of CAD / CAM technologyforobtaining the virtual model of the prosthetic field of the oral cavity by 3D scanning, the use of 3D CAD design environments to process it and obtain virtual mobile abutment, and themanufactureof mobile elements of the prosthetic field using rapid prototyping technologies. To this end there were designed a "method and device for making dental prosthetic abutments using mobile abutment models".

The method involves digitization of a prosthetic field [35], [38] its import to CAD environment, its processing in order to achieve virtual mobile abutments and physical achievement through rapid prototyping. In order to apply the method a special device was developed consisting of a support (A), where mobile abutments are placed(D) and the other elements of the prosthetic field (E) and they are secured with clips (B) as shown in figure 3.

Figure 3. Support device

On the mobile abutments detached from the support by means of thepeg plate (C), layouts of prosthetic elements are made. Checking prosthetic work is done by repositioning the mobileelements intothe support and placing it on them.

To achieve virtual sectioning of prosthetic field elements to be used with the device (figure 4) a software system was required created as a development in AutoCAD, VisualLISP and DCL environments (Dialog Control Language).

43


Figure 4. Virtual abutments separation

To user-computer interface, the system uses customized dialog boxes. The dialog boxes were created using DCL (Dialog Control Language) and Visual LISPlanguages, and the images presented were made in AutoCAD, as "slide"type images. Programs created in DCL describe the structure of dialog boxes and the programs made in AutoLISP display and exploit these boxes [35]. Data required for prosthetic field sectioning are introduced through the dialog box shown in figure 5, containing the following elements:

Figure 5. Dialog box for entering data Select prosthetic field button - is an active DCL button type element by means of which the user must select the prosthetic field that he seeks to section.

The validation element - is an active DCL toggle typeelement, which automatically changes its status in active / marked when a valid prosthetic field was selected (prosthetic field must be a solid entity).

The buttons Point P1 and Point P2 - active DCL button typeelements that allow the selection on the prosthetic field model of the points the section plan will go through. The fields labeled with X1, Y1, Z1, X2, Y2, Z2 - active DCL edit_box type elements which, in this case, allow displaying coordinates of the previously selected points P1 and P2. The preview area - is an inactive imagetype element. In this element a slide type image is displayed withadvisory nature.

OK and Cancel buttons - DCL active elements. OK - validates the data entered in the dialog box. Cancel - abandons the current activity.

Two types of support-devices were made by rapid prototyping technology.

In the first variant the achievement of the shaped element takes place on a "3D ELITE" printer with an "ABSplus"thermoplastic material.

In the workingdevice of the machine there are cartridges with basic material and supportmaterial, while moving simultaneously "printing" layer by layer and UV light sources placed at ends provide almost instantaneous polymerization of each deposited layer. Figure 6 shows the informative dialog box of 3D printer.

Figure 6. Dialog box/ virtual model 4. SUPPORT DEVICE OF MOBILE ABUTMENTS MODEL

Two variants of support device were developed for the model with mobile abutments, each of thembeing designed in three constructive dimensions for an optimum adaptation to the prosthetic field of each patient. In figure 7 we can seethesupport device for a whole dental arch.

Figure 7. Physical model of support device for a whole arch

For smaller prostheses, such as dentures for a side group of 2-4 elements a support device may be used as in figure 8, physically made on a 3D printer with ultraviolet light polymerizable composite, figure 9 [12].

44


Figure 8. Virtual model

Figure 9. Real model

In order to simultaneously respond toaesthetic,prophylactic, and resistance requirements of coating crowns it was accepted to joinmanufacturing technology of metal crowns (non-physiognomic) with that of physiognomic crowns manufacture ofacrylic, composites or ceramics materials thus obtaining mixed coating crowns [8], [9], [14], [32].

By sing the support model a fixed bridgewill be manufactured, totally physiognomic, on thesuperior molars 1 and 2 prepared in cabinet as abutments, in order to recover. Using CAD / CAM system, mobile abutments can be obtained that can slide along the model support keeping constant the distance between dental elements. Using each abutment,layouts are made by using preformed blue wax of 0.3mm thick.

The final layout is packed and poured being made of chromium-cobalt alloy, thus resulting the prosthetic metal support (figure 10). This is positioned on the abutments model and dental baro polymerizable compositeelements are shaped.

Figure 10. Metal support

Mobile and fixed prostheses made in dentistry technique are ceramic works, photopolymerizable works and works made of composite or baro-thermo-polymerizable acrylic material. The polymerization of such materials requires creating an environment with preset pressure and temperatureconditions [36], [37]. Superpont and chromasit made by Ivoclar in Lichtenstein are composite baro-thermo-polymerizablematerials, unicomponents, pasty materials, which polymerize at a temperature of 120° C and a pressure of 6 atm. For total dentures we have materials that polymerizeat a minimum temperature of 55° C (plus the temperatureresulting from the exothermic reaction 30-35° C) and a pressure of 2.5 atm, [41], [16]. 5. ELECTROMAGNETIC INDUCTION DEVICE FOR POLYMERIZATION TO TEMPERATURE AND PRESSURE

In order to achieve polymerization conditions a device was created, (figure 11) whose particularity is the use an induction electromagnetic field for heating the working container fluid, [34], [29], [40].

Figure 11. Baro-thermo-polymerization device

By using this method it is heated only the

bottom part of the container and then the fluid/air from the working container [36], [33].

45


A thermoregulator controls maintenance of working temperature to a predetermined value, and the timer helps setting the polymerization time, it is set according to the leaflet instructions of the material chosen to manufacture a specific type of work. It is also set the operating pressure required for polymerization. 6. PROSTHETIC WORKS MADE ON METALIC SUPPORT

Metal-ceramic prosthetic works [20], [30] require the use of special alloys developed by producers for that purpose, compatible with certain ceramic masses. Until recently the metal component of a prosthetic work could be achieved only in a conventional manner, by casting noble, non-noble alloys and more recently from titanium. In recent years other methods of making metal skeletons of dentures imposed, such as galvanization, sintering, foliation technique, CAD / CAM milling techniques and Rapid Prototyping technology. Each of these techniques presents advantages and disadvantages [39]. 7. ELECTROGALVANICDEPOSIT

In order to obtain dental prostheses with a high mechanical strength, [28] with increased manufacture accuracy with a greater biocompatibility and aesthetic aspect, modern dental technologies used in engineering were implemented.

There is an electroforming system of the WIELAND Company which uses gold electrolyte and is intended for inlays, partial crowns, anchorage crowns for small bridges covered with ceramic or resin and for structures used in implants, for dentures and secondary crowns base in telescopic crowns techniques. Galvanic gold crowns have a lower mechanical resistance compared to classic metallic crowns, gold is a soft metal, but clinical experience showed that provides sufficient stability both in the front and lateral side, have an aesthetic effect and high biocompatibility and achieve a better marginal closing.

When considering the quality of dentures obtained by electro galvanic deposit it was taken into account the manufacture of work components, by using innovative technologies of Reverse Engineering and Rapid Prototyping (CAD / CAM).

A method of making such works requires the use of a positive virtual model of the patient's prosthetic field (figure 12), a model obtained by 3D scanning of the oral cavity following the preparation made by the physician on the abutments of the bridge.

Figure 12. Virtual model of prosthetic field For the physical achievement of the prosthetic field, first the virtual model obtained in the previous step, is imported into CAM PowerMILL system where processing trajectories and CNC files are generated. The physical model (figure 13) is made of synthetic resin, by milling, on a CNC machining center.

Figure 13. Prosthetic field model after milling

Prosthetic dental bridge will be made from the side of the cape fastened on abutments and intermediate connecting elements.

The prosthetic dental work will be a bridge consisting of the lateral area, copings fixed on abutment teeth and intermediate connection elements.

As connection elements between components of the bridge preformed strips or drop-shaped components made of chromium alloy can be used.

For metal deposit by electro galvanic technology the surfaces to be coated must have a good electrical conductivity. For this purpose the abutments surfaces, on which copings will be made and the connection elements will be coated with a silver solution (figure 14).

Figure 14. Model coated with silver

Also, on the model, holes were made (a) where electric conductors are mounted thus making the

46


connection between the surface to be coated with chromium and power source. The work will be inserted into the galvanic bath, which contains chromic anhydride (CrO3) as electrolyte and anodes are of lead-tin alloy. Subsequently, working conditions are set in order to achieve a metal deposit thickness of 0.25 mm.

Chromium is resistant to corrosion and is a basic element in support structures of composite materials depositor ceramic masses burning. In order to ensure biocompatibility the support can be covered electrogalvanic with gold. Chromium has a high strength that ensures the integrity of prosthetic work at stresses from the oral cavity. The methodology proposed in the current paper, aims to obtaining the multi dental bridges by galvanoforming. 8. METALLIC STRUCTURE ACHIEVED BY MILLING

Two new types of technologies for making the metal support of a prosthetic work using the CAD / CAM, are presented below. In the first variant, the metal support is obtained by using a CNC milling machine. This machine (figure 15) mills with metal discs according to figure 16, the shapes made by using a computer and they are so disposed, as to achieve a maximum material economy.

Figure 15. CNC milling machine for milling metal discs [43]

The resulted layouts are of top quality, but there are drawbacks. Metal alloys involve high costs and since they are very tough drills wear rapidly [27].

Figure 16. Milling metal discs [44]

9. METALLIC STRUCTURES ACHIEVED BY ADDITION A second option for achieving the metal support of a prosthetic work uses 3D printing machine. This type of machine, by using the latest Rapid prototyping technology has the option to three-dimensional build paper, plastic, wax, ceramic or metal products [27]. In order to achieve the metallic components of prostheses used in dentistry, such a machine is used (figure 17).

Figure 17. SLM 250 machine [45] It uses a metal powder of chrome-cobalt alloy after sintering with a laser beam, thus obtaining the metal models according to figure 18. When using this technology, unused powder is fully recovered and costs are lower than in the case of milling systems where removed material is lost. Control of deposition is calculated in microns and quality of models is great.

Figure 18. Metal models for future prosthetics works

[46] The use of chromium-cobalt as working material ensures the required strength of dentures. Finally the metal support is coated with ceramic materials or composite [6].

47

http://raps.se/wp-content/uploads/SLM_250er_solo.jpg


10. FULL CERAMIC DENTURES

Currently, the first option when choosing the material for ceramic crowns is either zirconium or alumina. By removing the support metallic core, an aesthetic ceramic crown, can be created with a reduced thickness of material. This makes it a favorable treatment option in areas with space limit.

Full ceramic dentures, in turn, can be achieved in two ways. If we have to make a work on the side group which is less visible, one can choose zirconium materialswith a certain hue and the work is made entirely by processing the final form (figure 19).

Figure 19. Zirconium block [43] If the work we have to make includes the central group that is clearly visible, the resistance support is made of zirconium oxide, (figure 20) is sintered and, because it still does not allow proper coloring in layers as required, continues with the processing of the final form of theporcelain work applied on resistancesupport, the porcelain currently allowing the use of full color graphics.

Figure 20. Milling of zirconium oxide disc [47]

In addition, the removal of metallic core allows the emission of light through porcelain, thereby increasing the effect of naturalness [10]. 11. CAD / CAM SYSTEMS IN DENTAL IMPLANTOLOGY

Implantology is a surgical specialty that is designed to replace missing or severely damagedteeth, safely. A dental implant has the same function as the root of a natural tooth, providing solid support for a new tooth, or a prosthetic work.

The first step in implantology is to insert the implant. Dental implants are designed to imitate natural

tooth root structure [26], [31]. They are placed directly into the patient's jaw as toundertakeforces distributed by prosthetics during mastication. Anessential fact for a correct positioning of the implant in the jaw bone is bone shape and size viewing and direction of implantation [25].This need has led to further modernization of dental radiology [24]. The current trend is to reduce as much as possible radiation exposure to both patient and user [18], [19], [24], [7], [15]. Radiography system has evolved, leading to the use of panoramic radiography cameras, small portable devices, and the possibility of three-dimensional visualization of the affected areas. Due to the existing software 3D images of bone support and implant correct direction are seen, figure 21.

Figure 21. Virtual images [48]

After determining the position and direction of implantation on the virtual model of bone structure virtual modeling of a mouth guard takes placesformill precise directionas regards the implantation hole. CAM technology enables accurate and rapid manufacture of the mouth guard made of plastic or photo polymerizable materials (figure 22).

Figure 22. Guide [49]

The mouth guard is placed on the patient's prosthetic field and secured with various fastening systems, ensuring optimum processing, such as positions and the working depth.

CONCLUSIONS

CAD / CAM technology constantly evolves making possible more complex, more accurate works which meet the requirements of working areas aiming to reduce the execution time and the selling price.

48

http://www.lucianoretana.com/computed_guided_implant_surgery

http://www.lucianoretana.com/computed_guided_implant_surgery


Recent studies are focused on achieving by using CAD / CAM technology, prosthetic components of damaged areas of the body, going as far as to 3D printing of organs of biocompatible materials.

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T. Edit. Didactică şi Pedagogică, Bucureşti, 2001. [2] Ivan, N.V., Drăgoi, M.V., Oancea, Gh. ş.a., Sisteme

CAD/CAPP/CAM. Teorie şi practică, Editura Tehnică, Bucureşti, 2004.

[3] Chicoş, L.A., Stadiul actual privind tehnica CAD/CAM şi utilizarea conceptului de inginerie simultană, Referatul I al tezei de doctorat, Universitatea „Transilvania“ din Braşov, Braşov, 2005.

[4] BÂLC, N., Tehnologii neconvenţionale, Editura Dacia Cluj-Napoca,2001.

[5] Bâlc, N., Gyenge, CS., Berce, P., Proiectare pentru fabricaţia competitivă. Teorie, aplicaţii şi studii de caz. Cluj-Napoca, Editura Alma Mater, 2006.

[6] Borzea, D., Ceramica în stomatologie, Cluj-Napoca, Editura Dacia, 2000.

[7] Brad, S., Radiologie şi imagistică medicală generală: lucrări practice pentru studenţii la medicină dentară, Editura Eurobit, Timişoara, 2008.

[8] Bratu, D., Nussbaum, R., Bazele clinice şi tehnice ale protezării fixe, Bucureşti, Editura Medicală, 2006.

[9] Bratu, D. s.a., Coroana Mixtă, Timişoara, Editura Signata, 1998.

[10] Bratu, D., Sistemele integral ceramice, Timişoara, Editura Signata, 2000.

[11] Chicoş, L.A. – Utilizarea conceptului de inginerie simultană în dezvoltarea de produse, Teză de doctorat, Universitatea „Transilvania“ din Braşov, Braşov, 2007.

[12] Chiru, A., Anca, H. R., Cofaru, C., Materiale compozite:Plastomeri, elastomeri şi adezivi, vol.1, Editura Universităţii „Transilvania“ din Braşov, Braşov, 2000.

[13] Craig, R.G., Materiale dentare restaurative, Editura All Educational, Bucureşti, 2001.

[14] Doroga, O., Buta, A., Prodan, D., Terapia edentaţiei parţiale prin proteze mobilizabile, Cluj-Napoca, Institutul de Medicină şi Farmacie, 1977.

[15] Dumitrescu, D., Radiologie şi imagistică în medicina dentară, Craiova, Editura Medicală Universitară, 2006.

[16] Găucan, C., Danielo, L., Enescu, E., Cartea tehnicianului dentar, vol.1, Bucureşti, Editura Medicală, 1999.

[17] Groover, M. P., Zimmers, E. W., CAD/CAM Computer-Aided Design and Manufacturing, Prentice-Hall, Englewood Clifs, NJ, 1984.

[18] Haba, D.,Tehnici uzuale folosite în radiologia dentară, Iaşi, Editura Junimea, 2005.

[19] Huţu, E., Păuna, M., Bodnar, V. Ş.A., Edentaţia totală, Editura Didactică şi Pedagogică, Craiova, 1998.

[20] Ivan, V., Metalo-ceramica în stomatologie, Bucureşti, Editura Medicală, 1977.

[21] Lancea, C., Concepţie şi fabricaţie asistate de calculator, Braşov, Editura Universităţii „Transilvania“ din Braşov, 2005.

[22] Lee, K., Principles of CAD/CAM/CAE Systems, Addison Wesley Longman, Inc., U. S. A., 1999.

[23] Lăduncă, O., Utilizarea metodelor moderne de explorării imagistice în ortodonţie, Teză de doctorat, Iași 2014.

[24] Login, S., Elefterescu, A., Tonea, M., Radiodiagnosticul afecţiunilor odonto-parodontale, Bucureşti, Editura Didactică şi Pedagogică, 1998.

[25] Mihai, A., Carabela, M., Olteanu, I., Implantele endoosoase osteointegrate în stomatologie, Bucureşti, Editura Sylvie, 1995.

[26] Pașa, A., Contribuţii privind îmbunătăţirea concepţiei şi fabricaţiei implanturilor dentare, Teză de doctorat, Universitatea “Lucian Blaga”din Sibiu, Sibiu 2011.

[27] Pătraşcu, I., Bradu, D. Ciocan, L.T., Erori de sinterizare a maselor ceramice pe substratul metalic, Tehnica dentară, nr.24, 2007, p.28.

[28] Pătraşcu, I., Materiale Dentare, Editura Horanda Press, Bucureşti, 2002.

[29] Popovici, M.M., Fenomene electromagnetice, Bucuresti, Editura Nemira, 1996.

[30] Popşor, S.C., Biriş, C.I., Coman,L.M., Tehnologii ceramice şi metalo-ceramice: note de curs pentru studenţii specializării de tehnică dentară, Târgu-Mureş, Universitatea de Medicină şi Farmacie, 2006.

[31] Popşor, S.C., Coman, L.M., Biriş, C.I., Diagnostic şi tratament în edentaţia totală, Târgu-Mureş, Universitatea de Medicină şi Farmacie, 2006.

[32] Rândaşu, C., Tehnica protezelor dentare fixe, Bucureşti, Editura Medicală, 1993.

[33] Romînu, M., Bratu, D. Ş.A., Polimerizarea în stomatologie, Timişoara, Editura Brumar, 2000.

[34] Stamate, V.M., Contribuţii privind tehnologii şi dispozitive utilizate în tehnica dentară; Aparat cu inducţie pentru barotermopolimerizare, Referatul nr. 2 al tezei de doctorat, Universitatea „Transilvania“ din Braşov, 2008.

[35] Stamate, V.M., Utilizarea tehnicii CAD/CAM în tehnica dentară, Referatul nr.3 al tezei de doctorat, Universitatea „Transilvania“ din Braşov, 2008.

[36] Stamate, V., Chicoş, L.A., Oancea, Gh., Lancea, C., Barothermopolymerization Apparatus with Electromagnetic Induction, Annals of DAAAM for 2008 & Proceedings of the 19th International DAAAM Symposium Intelligent Manufacturing & Automation: Focus on Next Generation of Intelligent Systems and Solutions”, 22-25th October 2008, Trnava, Slovakia, pp. 1285-1286 (ISSN 1726-9679 – ISI Proceedings)

[37] Stamate, V.M., Tehnologii şi dispozitive utilizate în tehnica dentară, Teză de doctorat, Universitatea „Transilvania“ din Braşov, Brașov, 2009.

[38] Stamate, V., Lancea, C., Chicoş, L.A., Vasiloni, A.M., Oancea, Gh., Device for Prosthetic Dental Works, Proceedings of the 1st International Conference an Manufacturing engineering, Quality and Production Systems (MEQAPS 09), 24-26th September, Brasov, Romania, Volume II, pp.436-439, Editor D. Lepadatescu, N. Mastorakis, Published by WSEAS Press, ISBN 978-960-474-122-9, ISSN 1790-2769, 2009.

[39] Surcel, V., Cercetări privind utilizarea unor biomateriale în realizarea de sisteme biotehnice, Teză de doctorat, Univ. Politehnică din Bucureşti, Bucureşti, 2007.

[40] Udroiu, R., Materiale compozite,tehnologii şi aplicaţii în aviaţie, Braşov, Editura Universităţii „Transilvania“ din Braşov, Braşov, 2006.

[41] Vlase, S., Teodorescu, H., s.a, Materiale compozite : metode de calcul, Braşov, Universitatea „Transilvania”, 2007.

[42] http://www.sirona.com. [43] http://www.cerec.com. [44] http://www.dental-cad-cam-shop.com. [45] http://www.3dsystems.com. [46] http://www.digital-dental-cadcam.com. [47] http://www.dentalzirconia.com. [48] http://www.dentalimplantschicagoloop.com. [49] http://www.bing.com/images/ Cone-Beam Computed

Tomography.

49


AN EXTENSION OF THE ELECTROMECHANICAL ANALOGY

IN THE DOMAIN OF HYDROSTATIC TRANSMISSIONS

Part II. THE ELECTROHYDRAULIC ANALOGY AND ITS EXTENSION

Mircea Rădulescu University of Craiova, e-mail: [email protected]

ABSTRACT. This paper represents the part II of a research: “The Transmission Coefficient of Hydrostatic Drives”, which is published in Power Transmissions, Proc. Of the 4th International Conference, June 20 – 23, Sinaia, 2012, pp.399 – 415. The paper aims to expand the electromechanical analogy in other domains of technology: hydraulic, pneumatic, acoustic, sonic, and even in thermodynamics. In addition to the similarity of the equations and mathematical models, in the domain of fluidic systems we have highlighted the analogy of the circuit elements and some basic structures, for which the equivalent schemes are given. Analogy tables are presented, including the important sizes, units, symbols and generalized mathematical models applicable in all domains above and the advantages of the analogy and its limits of application are highlighted. KEYWORDS. electromechanic / hydraulic analogy, generalized parameters, electric / mechanical / hydraulic resistance / inductance / capacity / impedance, analogy of quantities / equations, limits of the analogy. 1. THE ELECTROHYDRAULIC ANALOGY The analogy between the phenomena belonging to these domains aims different sections (kinematics, dynamics etc.) and has a high degree of generality compared to other areas of physics, given the formal identity of some mathematical models in these chapters, [8].

1.1. THE ELECTRO-HYDRODYNAMIC ANALOGY

The electro-hydro-dynamic analogy (E.H.D.A.) aims at the electric field in a homogeneous conductor, respectively, corresponding hydrodynamic field of potential movement. Considering the flat potential stationary movement of an ideal incompressible homogeneous fluid, without discontinuities of the velocity field, respectively, the potential movement of charge carriers in a electroconductive, flat, homogeneous (free from internal sources) medium with unitary thickness, one can highlight the analogy between the two phenomena, comparing the quantities and equations in Tables 1 and 2.

Given the way the potential fields E and

v were

expressed, the following types of analogies are possible:

• type I (direct analogy): σ −↔ ⋅ = 1v J E ;

ϕ ϕ↔h e ; ψ σ ψ−↔ 1h e , in which case, the

equipotential lines ϕ = .h ct of the hydrodynamic field correspond to the lines of equal electric potential ϕ = .e ct while the lines of hydrodynamic current ψ = .h ct correspond to the lines of equal electric current ψ = .e ct .

• type II (indirect analogy): ↔

v J ; ϕ ψ↔h e ; ϕ σψ= −e e in which case, to the equipotential curves ϕ = .h ct , correspond lines of equal electric current .e ctψ = , and to the hydro-dynamic current lines ψ = .e ct correspond to the curves of same electrical potential .e ctϕ = . Other analogy tables can also be made, targeting certain sections of electrodynamics, respectively, hydrodynamics. By means of the E.H.D.A. we can study various hydrodynamics problems using electric circuits analogue to hydrodynamic networks of pipes or canals, such as:

1. the study of liquid infiltration through bases of hydrotechnic structures and terrains, using theoretical and experimental methods based on the analogy between the liquid infiltrations (as potential spatial stationary flows) and stationary electrokinetics circuits;

50

2. the calculus of networks of thermal energy distribution using the analogy to the binary electric networks, considering the frequent case of the quadratic turbulent hydraulic regime. The flow of the thermal agent through hydraulic circuits of district heating networks can be studied using a reduced-scale experimental model, which contains a source of direct current connected to an electric circuit with variable resistors. Unlike the experimental hydraulic models, where the possibilities of variation of the parameter values are limited, the analogue electrical model is equipped with continuously variable resistors which allow experimentally determining a range of values with good enough precision and sensibility, offering unlimited possibilities when choosing the values for the parameters;

3. the plane stationary flow of an ideal liquid can be studied on an analogue electric circuit made of a plane-plate-type electric conductor connected to a source of direct current;

4. representing the hydrodynamic field around profiles or profile networks with or without circulation, using electrolytic tanks adequate to this purpose.

For high-precision modeling of nonlinear characteristics specific to hydraulic circuit networks or thermal networks, it is necessary to introduce correction coefficients or using a large number of electric circuit elements (resistors, potentiometers, diodes, etc.), which must have a high implementing precision. On the other hand, physical and mechanical properties of fluids depend on the state parameters (pressure, temperature, contained air or contaminants) and the conditions of use (mechanical or thermal degradation of liquid).

Table 1. The analogy between electromagnetics and hydrodynamics

Electromagnetics Quantity or law Hydrodynamics

enT n T⇒

= ⋅

Maxwell’s stress hnT n T⇒

= ⋅

0E∇× =

; 0B =

Irotational field 0v∇× =

= −∇

eE V ; ( )=;e eV V r t

ϕ σ= −e eV (reduced potential) Scalar potential

ϕ= ∇

hv ; ( )ϕ ϕ=;h h r t

Circulation of the irotational field

( )0 0

CE dr⋅ =∫

Along a closed path ( )

0C

v dr⋅ =∫

= −1 2e e eu V V Between two points ϕ ϕΓ = −

1 2v h h

( )ψ ψ=;e e r t Stream function ( )ψ ψ=

;h h r t

( ); .e r t ctϕ =

;

( ); .e r t ctψ =

Equipotential surface Stream surface

( ); .h r t ctϕ =

;

( ); .h r t ctψ =

Plane irrotational field: ( );x yϕ ϕ= ; ( );x yψ ψ= ; = −1j

Stat

iona

ry e

lect

roki

netic

s

ϕ= ∇

eJ ; ( )ϕ ϕ= ,e e x y Potential field

Stat

iona

ry h

ydro

dyna

mic

s

hv ϕ= ∇

; ( )ϕ ϕ= ,h h x y

e e kϕ ψ∆ = ∇ ×

Cauchy-Riemann monogenic conditions h h kϕ ψ∇ = ∇ ×

ϕ ϕ∇ = ∆ =2 0e e ;

ψ ψ∇ = ∆ =2 0e e Laplace equations (harmonic functions)

ϕ ϕ∇ = ∆ =2 0h h ;

ψ ψ∇ = ∆ =2 0h h

( )ϕ =; .e x y ct ;

( )ψ =; .e x y ct Equipotential line Stream line

( )ϕ =; .h x y ct ;

( )ψ =; .h x y ct

( )e e ef z jϕ ψ= + Complex potential of the plane field ( )h h hf z jϕ ψ= +

( )= = −e

c x ydf z

J J jJdz

Complex current density/ Complex fluid velocity

( )= = −h

c x ydf z

v v jvdz

c e

AB

J dz u jiσ= +∫ Complex circulation along an open path

c v vAB

v dz jQ= Γ +∫

2 1e ei ψ ψ= − Electric current/ Flow rate

between two stream lines 2 1h hvQ ψ ψ= −


51


0e

Cnϕ∂

=∂

; .e C ctψ = Boundary conditions on a plan curve (C) 0h

Cnϕ∂

=∂

; .h C ctψ =

Elec

trosta

tics

Plan capacitor: 1 cose ed V Rϕ σ θ−= − .eV ct= Parallel field

Uniform motion: cosh v Rϕ θ∞= ; .v ct∞ =

04e

eq

Rϕ

πe= Punctiform source

4v

hQ

Rϕ

π=

20

cos4

ee

M

R

θϕ

πe= − Spatial dipole 2

cos4h

hM

Rθ

ϕπ

= −

( )0

lime esM q s

∆ →= ⋅ ∆ Moment of dipole ( )

0limh vs

M Q s∆ →

= ⋅ ∆

Table 2. The analogy between electromagnetics and hydrokinematics

Electromagnetics Quantity or law Hydrokinematics J H= ∇×

(Maxwell) whirl vector of the field vω = ∇× (vortex)

0dr H× =

; 0dr E× =

differential equations of the field lines 0dr v× =

; 0dr ω× =

0H∇ ⋅ =

*H A= ∇×

* 0A J∆ + =

solenoidal vectorial field ( H

; v

) Vector potential ( *A

; Ω

) Poisson’s equation

0v∇ ⋅ =

v = ∇×Ω

0ω∆Ω + =

0H∇× =

mH V= −∇

0mV∆ =

irotational vectorial field ( H

; v

) Scalar potential ( mV ; hϕ ) Laplace’s equation

0v∇× =

ϕ= ∇

hv 0hϕ∆ =

( )mm

Cu H dr= ⋅∫

( )em

Cu E dr= ⋅∫

circulation on the closed curve (C) ( )

vC

v drΓ = ⋅∫

( )Cdrω ωΓ = ⋅∫

( )

*e H dσ

Σ

Φ = ⋅∫∫ ;

( )e H dµ σ

Σ

Φ = ⋅∫∫

flux through the surface (Σ) of the field tube

( )vQ v dσ

Σ

= ⋅∫∫ ;

( )mQ v dρ σ

Σ

= ⋅∫∫

( )

*e E dσ

Σ

Ψ = ⋅∫∫ ;

( )e D dσ

Σ

Ψ = ⋅∫∫

( )Q dω ω σ

Σ

= ⋅∫∫

Biot-Savart’s law

( )3

14 D

J rH dVrπ×

= ∫∫∫

general form ( )

31

4 D

rv dVr

ωπ

×= ∫∫∫

( )34 C

i rH dsr

τπ

×= ∫

for a very narrow field tube ( J

; ω )

( )34

v

C

rv dsr

τπΓ ×

= ∫

( )i J dσ

Σ

= ⋅∫∫

electric/ vorticity tube intensity ( )

v dω σΣ

Γ = ⋅∫∫

2. THE ELECTRO-

HYDROMECHANICAL ANALOGY In the field of hydraulic drives systems, the study on the analogy is of particular interest, given the “likeness” of equations, quantities, circuit elements and basic structures in this domain with the analogous ones in the electrical circuit theory.

The aim of the electro-hydraulic analogy is to establish the equivalent electrical scheme for a given hydraulic drive, so that the dynamic characteristics of the analogue scheme would be comparable with those in the domain of interest.

52

The analogy relates to the representation of circuit elements and some of their connections through proper electrical circuit elements (respectively, connections of elements), whose transfer functions are comparable. As a result, some hydraulic drives structures can be equated with complex electric circuits that allow the simulation of dynamic processes on analogue computers; in these conditions, varying the electrical network functional parameters, and processing and recording the results can be easier. Specific circuits of hydraulic drives can usually be studied by means of the electro-hydraulic analogy type I also frequently used for pneumatic actuator systems. For pneumatic circuits, an analogy (Qm ↔ i) would be preferred, but it does not respect the principle of energy conservation, so that only small variations in pressure are allowed in the circuit that satisfy the condition of fluid incompressibility (ρ = ct.).

Table 3 gives the correspondence between some important analogue quantities in the electric circuit theory and the hydraulic drives theory, analogy established by comparing the physical and mathematical models of the two covered areas.

For this type of analogy, one can establish the equivalence of quantities using the equations of motion, electricity conservation / mass continuity or energy conservation and comparing the hydraulic characteristic Δp = Δp (Q) to the electric characteristic u = u (i).

Both dependencies can be regarded as particular cases of the function e = e (f) which correlates the two base intensive parameters (e; f). The quantity or parameter analogy results from the identification of the two dependencies, [2].

Under these conditions, it became customary to use symbolic language, specific to electrical circuits, this terminology being adopted for a more concise and coherent description of complicated dynamic processes (respectively, phenomena), characteristic of these systems, [6].

The same table highlights an analogy between oscillatory processes specific to alternating current in sinusoidal regime and sonic drive systems, [3], respectively, between the equations of propagation of the electromagnetic field and equations of propagation of pressure waves (Table 5, [8] shows the corresponding mathematical model).

Table 3. The analogy of quantities and equations in electrics and hydromechanics

Electric quantities Hydraulic quantities Analogy

Electric power, eP

eP ui W= Hydraulic power, hP

hP pQ W= ∆

u p↔ ∆ i Q↔

e hP P↔

Ohmic resistance, eR R=

1duR Gdi

−= = Ω

0i eu V V= − >

1n

eP Ri W+= 1 2n≤ ≤

Resistance to motion (friction), hR R=

( ) 15h

d p NsR ZdQ m

−∆ = =

( ); ( 1)

; 1 2L

nN

R Q laminar regime np

R Q turbulent regime n

=∆ = < ≤

1 ,1 2nh hP R Q W n+= ≤ ≤

u p↔ ∆ i Q↔

e hR R↔ G Z↔

Electric inductance, eL L=

/euL H

di dt=

eP Li i W=

Hydraulic inductance, hL H= 2

15/

p NsH MdQ dt m

− ∆= =

2;hP HQQ W HKΦ

= =

e hL H L↔ =

Electric capacity, eC C=

/eiC F

du dt∆

=

Hydraulic capacity, hC C=

15/h h

Q NC Ddp dt m

− ∆= =

e hC C↔

ep ip H

Q (t) eV iV

eL

i (t)

ep ip HR

Q iV

i eV eR

TEHNOLOGIA INOVATIVĂ – Revista „Construcţia de maşini” nr. 3-4 / 2014 53


; ee e e

e

qP C uu W C

V= =

h hP C p p W=

; Lh

e

VC

B= ; 1

2e eNB

mβ −

=

Electric impedance, eZ Z=

eU Z I=

Hydraulic impedance, hZ Z=

hp Z Q∆ =

e hZ Z=

Speed of electromagnetic waves in vacuum:

0 0

1ce µ

=

Speed of sound in ideal incompressible fluids 1aβρ

=

c a↔

Telegraph equation (in vacuum) 2

2 22E c E

t∂

= ∇∂

; 2

2 22H c H

t∂

= ∇∂

Wave equation for ideal incompressible fluids 2

2 22v a v

t∂

= ∇∂

; 2

2 22p a p

t∂

= ∇∂

E v↔

H p↔

Transmission of electric power ( )max sin uu u tω ϕ= +

( )max sin ii i tω ϕ= +

Transmission of power through sonic waves

( )max sin pp p tω ϕ= + ( )max sin QQ Q tω ϕ= +

u p↔ i Q↔

max sin xe e tc

ω = −

max sin xp p t

aω ∆ = ∆ −

e p↔ ∆

Table 4. The analogy of circuit elements in hydromechanics and electrics

Symbol and stationary characteristic of an ideal element

Hydromechanics Electrics Volumic generator (GVR)

tQ Q Q= − ∆ ; .t G GQ K K ctω= =

0e ip p p∆ = − >

tM M M= + ∆

t GM K p= ∆

Direct current generator (GCC) tU U U= − ∆

0 1U C ω= Φ 0e iU V V= − >

tM M M= + ∆

2 .tM C I ct= Φ =

Hydrodynamic pump (GHD) Y gH= ;

0 .H ct= p Yρ∆ =

Constant voltage generator (GTC)

0 .e iU V V ct= − =

iV eV ip ep

eQ iQ p (t)

hC

ei ii u (t)

eC

0U

0U 0Q

0M

0H

54

Circular hydraulic pipe 0n

h i ep R Q p p∆ = = − >

421 h LC Ln R R

dρn

π= → = =

(0,25

4,75

1;2

0,242h N

N

n R R

LRdρn

∈ → =

≅

Electric conductor with linear / nonlinear resistance 0e i eu R i V V V= = ∆ = − >

eLRA

ρ=

* ; 1;2neu R i n= ∈

Check valve

Electric diode

Pressure valve

Zehner diode

Compensated flow-control valve

Transistor

4-way hydraulic distributor

Wheatstone bridge

Table 4 shows an electro-hydraulic analogy of the basic elements specific to hydraulic circuits; analogue elements

may have a linear behavior (resistances: R, L, C) or nonlinear (polarized diodes, transistors etc.), combinations between these being sometimes possible, [9], [2].

Table 5. The equivalent hydraulic scheme for various simple circuit elements

hydraulic circuit element analogue (equivalent) hydraulic scheme

.GK ct=

hydrostatic pump

;2GG

r GV

J Kφπ

= =

0e ip p p∆ = − >

( )t GQ K ϕ ω=

( )t GM K pϕ= ∆

.GK ct≠

hydrostatic motor

MHR

MHL

iV eV

eV iV R

i

i

iV eV ip ep

Q

i

u

u

i

i

u


55


;

.2

Mr

MM

J

VK ct

φ

π

=

= =

1

;.

rmK A ctφ =

= =

hydraulic pipe - with concentrated parameters

( )L λ

caTλ =

- with distributed parameters

( )L λ

' ; ' ; 'H HH H

dR dCdHR H Cdx dx dx

= = =

2 ' 0HQ S p G Qx taρ

∂ ∂+ + =

∂ ∂

' 0Hp Q R Qx S t

ρ∂ ∂+ + =

∂ ∂

( )0

t

i e H H Hp p p R Q L Q C Q u du∆ = − = + + ∫

hydraulic flow valve

eH Hp R Q L Q∆ = +

0i ep p p∆ = − >

hydraulic pressure valve

4-way hydraulic distributor

The elements covered by analogy correspond to some analogue circuits operating in steady state; for the non-

permanent regime, it is necessary to establish the electrical equivalent scheme, shown in Tables 5 and 6, [7].

56

Table 6. The equivalent hydraulic scheme for various simple hydromechanical structures

Type of hydraulic structure (connection) Analogue or equivalent hydraulic scheme Symmetric linear volumic motor, under dynamic regime

Rotary hydraulic actuator, under dynamic regime

Closed circuit hydrostatic transmission

Table 7 gives the relations for the impedance, admittance, impedance module ( Z ), admittance (Y ), impedance

modulus ( Z ) and its phase (φ), corresponding to various combinations (series, parallel, mixed, star - triangle) obtained from the generalized mathematical model in Table 5 [7], [8]. Table 8 gives the mathematical model and equivalent scheme for a section of pipe with concentrated parameters (based on the generalized model in Table 5, [7]) and with distributed parameters (based on the generalized model in Table 6, [8]).

3. THE ELECTRO-THERMO-HYDRAULIC ANALOGY

Due to the variety of types of thermic conduction circuits and their structural complexity, in the direct analysis of the components, respectively, the global analysis of these systems some difficulties occur, such as laborious mathematical calculations.

These impediments can be eliminated by using the analogy as a complementary method of study. Table 9 presents a thermoelectric analogy aiming some basic measures and also their units for the two domains which are subject to analogy.

The thermoelectric analogy allows the study of heat transfer on the basis of elementary processes, given the simple physical models such as analogue electrical networks, curves with electrolytes, electroconductive paper etc., [4]., these procedures being applied with the minimum of investment and good results.

The accurate measure of the parameters of the electrical phenomenon analogue to the heat exchange is favored by the diversity and precision of the electrical measuring instruments and the implementation of the results on the electric model in the thermic analogue phenomenon can be very easily made.

The thermo-hydraulic analogy allows the study of the heat conduction phenomenon based on some integrative hydraulic circuits.

R2

C3

C2

C4

C1

ZG

HM R1 HG RG RM

ZM

SP MHR GVR

iZ ZM

R2

R1

T4 T3

T2 T1

U0

UC

p0

UC

SDS

MiQ

pT=0

MeQ

V1

C1 C2

i2

R1 i

i1

R L C

i0

V2

pi

DR

Q0 Qi Qe

MiQ

MeQ

AC1 AC2

mT M

Pe


57


The analogy method is necessary because of the difficulties that may occur in the mathematical approach of phenomena in thermodynamics or hydropneumatics, obstacles that can be eliminated by approaching the electromechanical,

electrohydraulic, thermoelectric, or thermal-hydraulic analogies and some complementary study methods.

Table 7. Impedances and admittances obtained for some combinations of resistances

tipe of

combi-

nation

impedance( ) 5/Z j Ns mω

admitance ( ) 5 /Y j m Nsω

modulus of impedance ( )Z j Zω = impedance angle radϕ

s e

r i

al

RH

H HR j Lω+ 2 2 2H H

H H

R j LR L

ωω

−

+ ( )

12 2 2 2H HR Lω+ ( )H

H

Larctg

Rω

RD

1H HR j Cω −−

( )( )

1

22H H

H H

R j C

R C

ω

ω

−

−

+

+ ( )

12 2 2 2H HR Cω− −+

1( )H H

arctgR Cω

−

HD

( )1 1H Hj L Cω ω− −− 21

H

H H

Cj

L Cωω−

1 1H HL Cω ω− −−

2π

+

RH

D

( )1 1H H HR j L Cω ω− −+ −

1 1

2 1 1 2( )

( )H H H

H H H

R j L CR L C

ω ωω ω

− −

− −

− −

+ −

1/22 1 1 2( )H H HR L Cω ω− − + − 1 1

( )H H

H

L Carctg

Rω ω− −−

para

lell

(der

ivat

ive)

RH

H H

H H

j R LR j Lω

ω+ H H

H H

R j Lj R L

ωω+

( ) 11 1 1H HR Lω

−− − −+ ( )H

H

Rarctg

Lω

RD

1

1H H

H H

R CC j Rω

−

− +

1

1H H

H H

C j RR C

ω−

−

+ ( ) 12 2 2

H HR Cω−− − −+ ( )H Harctg R Cω

HD

2/ (1 )H H Hj L L Cω ω− 1 1( )H Hj C Lω ω− −− 1 1 1( )H HL Cω ω− − −− / 2π±

RH

D 1 1

2 1 1 2( )( )

H H H

H H H

R j C LR C L

ω ωω ω

− −

− − −

− −

+ − ( )1 1 1

H H HR j C Lω ω− − −+ − 1/22 1 1 2( )H H HR C Lω ω−− − − + − ( )1 1

H H HarctgR L Cω ω− − −

mix

ed (c

ompo

unde

d)

R H

R1

1 1

1

2 2

2 2 2( )

( )H H H H H H

H H H

R R R L j L R

R R L

ω ω

ω

+ + +

+ + 1

1

2 2

2 2 2 2

( )

( )H H H H H

H H H

R R R L j L

R R L

ω ω

ω

+ + −

+

( )1

1

1/22 2 2

2 2 2H H

H

H H H

R LR

R R L

ω

ω

+

+ +

1

12 2[ ]

( )H H

H H H H

L Rarctg

R R R L

ω

ω+ +

DR

H

2 2

2 2 2 2 2[ (1 ) ]

(1 )H H H H H

H H H H

R j L L C C R

L C C R

ω ω

ω ω

+ − −

− +

2 2

2 2[ (1 ) ]H H H H H H

H H

R j L L C C RR L

ω ωω

− − −

+

2 2 2

2 2 2 2 2(1 )H H

H H H H

R LL C C R

ωω ω

+

− +

2 21L L C C RH H H H H

arctgRH

ωω

− −

RH

R1D

( ) 1 1 1

1

2 2 2 2

2 1 1 2

( )

( ) ( )H H H H H H H H

H H H H

R R R R L R R CZ j

R R L C

ω ωω

ω ω

− −

− −

+ + += +

+ + −

( )1

1

2 1 2 1 1 1 11

2 1 1 2

[ ( )]( ) ( )

H H H H H H H H

H H H H

j L R R C L C L CY j

R R L Cω ω ω ω

ωω ω

− − − − −−

− −

− − −+ →

+ + −

1

1

1/22 2 2 2 2 2

2 2 1 1 2

( )

( ) ( )H H H H

H H H H

R L R C

R R L C

ω ω

ω ω

− −

− −

+ + + + −

2

1 1

2

2 1 1

2 2

1 1( )2 2 2 2 2

L R R CH H HH

R R R RH HH HarctgL C L CH H H H

L R R CHH HH

ω ω

ω ω

ω ω

− −− − →

+ + − −− − → − − + +

RH

1D1 H

2D2 2 2

1 1 2 21 2 2

1 2

( )( )

H H

H

X R j R X X XX

R X X+ + +

+ +

2 21 1 2 2

2 21 2

( )( )

H H

H

R X j R X X XX R X− + +

+

1/22 22

1 2 21 2( )

H

H

R XX

R X X

+

+ +

2 21 2 2

1

H

H

R X X Xarctg

R X + +

1 1; 1;2i ii H HX L C iω ω− −= − =

R1H

1D1

R2H

2D2 1 2 1 2

1 2

1 2 2 1

1 2

( )( )

H H H H

H H

R R X X j R X R X

R R j X X

− + +

+ + +

R1H1D1 1 21 2

1 1H HR jX R jX

++ +

( )( )( ) ( )

1 2

1 2

1/22 2 2 2

1 22 2

1 2

H H

H H

R X R X

R R X X

+ +

+ + +

1 2

1 2

1 2

1 2

( ) ( )

( )

H H

H H

X Xarctg arctgR R

X XarctgR R

+ −

+−

+

58

1 1; 1;2i ii H HX L C iω ω− −= − =

s t

a r

R1

R2

C

1 2 1 2H H H H HR R j R R Cω+ +

1 2 1 2

1 2 1 2

2 2 2 2 2 1/2[( ) ]H H H H H

H H HH H

R R j R R C

R R R R C

ω

ω

+ −

+ +

1 2 1 2

1/22 2 2 2 2( )H H H H HR R R R Cω + + 1 2

1 2

H H H

H H

R R Carctg

R Rω

+

R C

1

C2

1 2

1 2

2

1 ( )H H H

H H H

j R C C

R C C

ω

ω

+ +−

1 2

1 2

2

2 2 21 ( )H H H

H H H

R C C

R C C

ω

ω

− ++

+ +

1 2 1 2

1 2

3 2

2 2 2

( )

1 ( )H H H H H

H H H

j R C C C C

R C C

ω

ω

++

+ +

1 2

1 2

2 2 2

2

1 ( )H H H

H H H

R C C

R C C

ω

ω

+ + 1 2

[ ( )]H H Harctg R C Cω +

Table 8. The mathematical models and equivalent schemes of the hydraulic pipe with concentrated/ distributed parameters

hydr

auli

c li

ne w

ith

conc

entr

ated

par

amet

ers

equi

vale

nt sc

hem

e

mat

hem

atic

al m

odel

( ) ( ) ( ) ( )0

1 1 t

h hh h

L Q t + R + Q t + Q t d p t iG C

τ

⋅ = ∆

∫ ( )maxsin aQ Qωt + ϕ=

( )1 1sin sin2h Q h Q

h h

πp = R + Qωt + + ωL Q t +GωC

ϕ ω ϕ ∆ − −

hp = Z Q;∆ 1 1h h h hh

h hZ = R + jX = R + + jωL

GωC

−

20( / ) 1 ;1

h h hh

= arctgR + L C

G

ω ωϕ

−

01

h h

ω = ;L C

0h

hh

LQ =ω

R

equi

vale

nt sc

hem

e

' hdRR

dx= ; ' hdG

Gdx

= ; ' dHHdx

= ; ' hdCC

dx=

R’dx H’dx R’dx H’dx d

R’dx

G’dx C’dx G’dx C’dx

Gh/3

Rh/2 Lh/2 Rh/2 Lh/2

Ch/3 Ch/3 Ch/3 Gh/3 Gh/3

59


lini

e hi

drau

lică

(co

nduc

tă)

cdis

trib

uted

par

amet

ers

mat

hem

atic

al m

odel

0(Δp) (ΔQ)+ R'ΔQ+H' =x t

∂ ∂∂ ∂

; 0h(ΔQ) (Δp)+ G'Δp+C' =

x t∂ ∂

⋅∂ ∂

;

22 02

d (Δp) γ (s)Δp =dx

− ; 2

2 02d (ΔQ) γ (s)ΔQ =

dx− ; γ(s) = (R' + H's)(G' +C's) ;

11

1

c

c

ch(γx) Z sh(γx) ppQ QZ sh(γx) ch(γx)−

∆∆ = ∆ ∆

; cR' + H'sZ =G' + C's

;

1

1

pp MQ Q

∆∆ = ∆ ∆ ;

1c

c

ch[γ(jω)x] Z sh γ(jω)xM

Z shγ(jω)x ch γ(jω)x−

= ; γ(jω) = δ + jε

Table 9. The thermal-electric analogy of various basic quantities and equations

Thermal field (t) Physical quantity; law Electric field (e)

[ ]tQ J ; [ ]tQ W

Heat; thermal flow ↔ electric charge; current intensity [ ]eQ C ; [ ]ei Q A= −

2/ [ / ]ttq Q d W md σ=

Thermal flow density ↔ current intensity density 2/ [ / ]ej di d A mσ=

[ ]T K Temperature ↔ electric potential [ ]eV V

[ ]1 /t t W m Kλ ρ−= ⋅ Conductivity / resistivity 1 1 1[ ]e e mσ ρ− − −= Ω 2[ / ]c W m Kα Heat release coefficient ↔ specific electric conductivity 1 1 2[ ]e e el mα σ − − −= Ω

[ ]1 /tt t

dlR K WdSλ

= ∫ Forward resistance [ ]e ee

dlRdS

ρ= Ω∫

[ ]1 /t tR G K W−= Contact resistance / conductance [ ]1e eR G−= Ω

[ ]1 /t tC Q T J K−= Caloric capacity ↔ electric capacity [ ]1e e eC Q V F−=

[ ]/tK W K Overall thermal transfer coefficient ↔ electric admittance 1[ ]eY −Ω

1 2[ / ]t t tk K S W m K−= Specific Overall thermal transfer coefficient ↔ specific electric admittance

1 1 2[ ]e e ey Y S m− − −= Ω

Local form: tq Tλ= − ∇

Fourier’s law

Ohm’s law

Local form: e e ej Vσ= ∇

Global form: 1 2 ttT T R Q− =

Global form: e eu R i=

11 2 ( )c tT T S Qα −− =

Newton’s law

Table 10. The electro-thermal-hydraulic analogy of various basic quantities and laws

Domain Laws/quantities Electric conduction (e) Thermal conduction (t) Laminar flow (l)

Local form of the law: J ρ= ∇Φ ↔

Ohm’s law: 2/e eJ u A mσ = ∇

Fourier’s law: 2/tq T W mλ = − ∇

Newton’s law: 2/l l v N mτ µ = ∇

Density of the quantity J ↔

Current density: 2/e

diJ A mdσ

=

Flow density:

2/tt

Qq W m

ddσ

=

Tangential tension: 2/l

ldF

N md

τσ

=

Flow f ↔ Current intensity:

[ ]( )

ei J d AσΣ

= ⋅∫∫

Thermal flow: [ ]

( )t tQ q d Wσ

Σ

= ⋅∫∫

Friction force: [ ]

( )l lF d Nτ σ

Σ

= ∫∫

Potential function Φ ↔ Electric potential (voltage): Temperature: Velocity:

60

[ ]1 2e eu V V V= − T [K] v [m/s]

Density ρ ↔

El. conductivity/resistivity 1 1 1

e e mσ ρ− − − = Ω Coefficient of thermal

conduction: [ ]/t W m Kλ ⋅ Dynamic fluidity / viscosity:

[ ]1 /l l m s kgϕ µ−= ⋅

Plan area of transfer: S ↔

Plan area of the electric conductor: 2[ ]eS m

Plan area of thermal transfer: 2[ ]tS m

Plan area of friction: 2[ ]lS m

Resistance R ↔

Electric forward resist.:

[ ]1e

e e

dsRdSσ

= Ω

Thermal forward resist.:

[ ]1 /tt

dsR K WdSλ

=

Hydraulic viscous resist.:

[ ]1 /vl l

dnR m NsdSµ

=

Equiv. series resist.:

1s

n

ech kk

R R=

= ↔∑

Equivalent resistance:

1s

nk

ek kk

LR

Sσ== ∑

Overall forward resistance:

1e

nk

tk kk

RSdλ=

= ∑

Overall viscous resistance:

1s

nk

vk kk

lR

Sµ== ∑

Ohm’s law: e Rf= ↔ [ ]1 2 eu V V R i V= − = [ ]1 2 t tT T R Q K− = [ ]1 2 /v lv v R F m s− = Impulse:

( )0

tf dτ τℑ = ↔∫

Electric charge:

( ) [ ]0

t

eQ i d Cτ τ= −∫ Heat: ( ) [ ]0

t

t tQ Q Jd τ= ∫

Force impulse:

( ) [ ]0

t

lH F d Nsτ τ= ∫

Table 11. The extended analogy - nomenclature

Dom

ain

Ana

logy

Type I analogy - direct (with apparent

resistance)

Type II analogy - inversed (with

admittance)

Elec

trics

(E)

stress (e) ↔ voltage: [ ]eu u V=

flow (f) ↔ amperage: [ ]i A

resistance: [ ]eR R= Ω

inductance: [ ]cL L H=

isolating conductance: 1[ ]eG G −= Ω capacitance: [ ]eC C F=

impedance/admittance: [ ]1eZ Z Y −= = Ω

Mec

hani

cs (M

)

[ ]u F N↔

[ ]/i v m s↔

1m m

NsR R Gm

− ↔ = [ ]L M kg↔

1[ / ]m mC C K m N−↔ =

[ ]m mZ Z Q↔

[ ]/u v m s↔

[ ]i F N↔ 1

m mR G − ↔ Ω

[ ]/mL C m N↔

[ ]C M kg↔ 1

m mZ Y − ↔ Ω

Aco

ustic

s (M

) Sp

ecifi

c

2u p Nm ↔

[ ]/i v m s↔ 3/

smR R Ns m ↔

2/sL M kg m ↔

3 /mC C m N ↔

2/sm mZ Z m ↔ Ω

[ ]/u v m s↔ 2/ai p N m ↔

2 /sm mR G m ↔ Ω

3 /smL C m N ↔

2/sC M kg m ↔

2 /sm mZ Y m ↔ Ω

Glo

bal

2/au p p N m ↔ = 3 /vi q m s ↔

5/aR R Ns m ↔

2 5/aL M Ns m ↔

5 /aC C m N ↔

[ ]a aZ Z↔ Ω

3 /vu q m s ↔

2/ai p N m ↔

1 1a aR R− − ↔ Ω

5 /aL C m N ↔

2 5/aC M Nm m ↔ 1

a aZ Y − ↔ Ω

Hyd

raul

ic (H

)

2/u p N m ↔ ∆ 3 /i Q m s ↔

5/hR R Ns m ↔

2 5/hL L Ns m ↔ 5 /hC C m N ↔ 5 /hG G m Ns ↔

[ ]1h h hZ Z Y −↔ = Ω

3 /u Q m s ↔

2/i p N m ↔ ∆

1 1h hR R− − ↔ Ω

5 /hL C m N ↔

2 5/hC L Ns m ↔ 1 5/hG G Ns m− ↔

1h hZ Y − ↔ Ω

The thermo-electric or thermo-hydraulic analogy method is widely used for integrating the thermic-conduction equation, having into consideration that the phenomena in these domains are in the same class of analogy. An extension of the analogy for the three domains simultaneously concerned here is possible in the case of fenomena from the conduction domain.

Table 10 shows the analogy of some basic laws in these domains, given the linearity assumption, which is experimentally confirmed for specific domains of values of state parameters and for small deviations of these values compared to the steady state of the system.


61


This table gives a limited electro-thermo-hydraulic analogy targeting certain measures or basic laws of the three domains, each measure being compared to a series of parameters for which general notations were adopted, similar to those used to define generalized parameters / quantities in chapter 3, table 1, [8].

4. THE EXTENDED ELECTRO-HYDRO-MECHANICAL ANALOGY The electrohydraulic analogy reflects the interdependency and the biunique character of the two fields, which are complementary and sustain each other because of the similarity of their mathematical models. Therefore, the extension of this study method in other domains is possible and also indicated.

The tendency to extend the electromechanical analogy to other technical areas should be regarded with some reservations on the following:

for non-electrical systems some connections / couplings between some subsystems appear, these have different sections each, so it is necessary to adopt an analogy for which the physical sizes keep their continuity while the transition from one subsystem to another.

The basic generalized variables are q and ℑ , and their derivatives in relation to time are called generalized flow or speed (f) and respectively effort (generalized force - e) so, to establish the analogies it is necessary to take into account the classification specific to physical variables in the electric circuits domain. The dissipative elements (R, G) are determined using a functional dependence between the generalized velocity and the generalized force, and the reactive elements (L, C) are determined using a functional dependence between a basic variable and the flow associated with the other basic variable; the constraints associated to the two streams are Kirchhoff’s theorems, [8].

Tables 11 gives, in a synoptic manner, the various examples covering the definitions of physical measures of the areas discussed above, compared with those in the electric domain. The analogy can also be extended to the symbols of circuit elements, given in table 12. Table 13 gives an example of an application of the extended analogy, where various scalar or vector harmonic non-stationary fields are described by the same partial differential equation (P.D.E.), obtained from the first order equations (O.D.E.) specific to each field. Beside these, there is to mention the electrooptical analogy, which allows the experimental study of some armonic fields (satisfying Laplace’s equation). Table 14 shows a comparative study regarding the possible extension of the I - type electromechanical analogy to the modeling of phenomena from other technical domains (acoustics, thermodynamics, electrochemistry etc.), which need the description of quadripoles compounding conversion systems, [1], [10].

5. LIMITS OF APPLICATION OF THE

ELECTRO / HYDRAULIC ANALOGY

Any analogy must respect the principle of conservation of energy; this is why an analogy between the electric power and the corresponding expression of power in the concerned domain is required. The analogy method is useful for the qualitative study of phenomena, but the accuracy of the results is reduced. Using the analogy as a complementary study method leads to good results in the case of linear models.

Due to the complexity of the hydraulic automation technology, there is sometimes a tendency to misuse the electro-hydraulic analogy, so we recommend a precautionary approach to this method of study. The fundamental differences between the electrical and hydraulic circuits are related to the nature of the energy and information carrier medium; the fluid mass is considerable (it can not be neglected), and its flow regime is usually turbulent, so nonlinearities appear in the equations indicating the mathematical model.

Major difficulties appear when the medium presents non-linearities caused by the inhomogeneity of the material or the saturations (e.g. in magnetism, [5]), and, respectively, by the leakage or hydraulic losses the in turbulent regime (e.g. in hydraulics, [2]). Major difficulties appear frequently also when a linear mechanic characteristic is adopted although the phenomena regarding frictions are nonlinear.

For these reasons, the development (extension) of the electro-hydraulic analogy in the dynamic regime still has some difficulties when using the simplifying assumptions in the study of phenomena in hydraulics, this affecting the accuracy of the results obtained on the electric model when returning to the hydraulic original. For hydraulic systems, it is recommended to avoid abuse of this method of study. This can lead to a superficial electrohydraulic analogy based exclusively on exploiting a correspondence between the specific terms of the two fields.

The theoretical results obtained from the study on an analogue model must be experimentally verified, in order to correct them. The values of the correction factors or the coefficients of right proportion are determined regarding the structure and characteristics of the experimental model. In the context of an analogy, the mathematical models of the two physical phenomena have the same general form, except for the notations affecting the quantities interfering in the description of the phenomena.

62

Table 12. The symbols of circuit elements in the extended analogy

domain type electrics mechanics Hydraulics Pneumatics Sonics translation Rotation

Resistance u Ri= i Gu=

nu Ri=

F kv=

M kω=

linear resistance: Lp R Q∆ =

non-linear resist.: n

Np R Q∆ =

Inductance

u L i=

F mv=

( )rM J tω= ⋅

( ) ( )p t HQ t∆ =

Capacity i Cu=

mF k x= ∆

mM k ϕ= ∆

Voltage source

( )u u t=

-

Current source

( )i i t=

Table 13. The extended analogy of some scalar or vector harmonic non-stationary fields

Dom

ain First order (coupled)

equations (ODE)

Basis of

design

Nomenclature of notations in second order (uncoupled) equations

(PDE): 2 2

2 22 2;e fe v f v

t t− −∗ ∗

∂ ∂∆ = ∆ =

∂ ∂

e f v∗ Remarks; significance of notations

Q.S

.E.M

.

HxEt

µ ∂∇ = −

∂

ExH Jt

e ∂∇ = +∂

ExH S=

.ctσ =

.ctµ =

0E∇ ⋅ =

0H∇ ⋅ =

E

H

1

emveµ

=

Q.S.E.M. - quasistationary electromagnetics

emv - propagation speed of EMQS in the material medium

Long

line

s of t

rans

miss

ion El

ectri

cs e

e eu iL R ix t

∂ ∂′ ′+ =∂ ∂

ee e e

ui C G ux t

∂∂ ′ ′+ =∂ ∂

0eR′ =0eG′ = eu i

1e

e ev

L C=

′ ′

ev - velocity of the electric current

Hyd

raul

ics /

so

nics

( ) vh h v

Qp L R Qt t

∂∂ ∆ ′ ′+ =∂ ∂

( )vh h

Q pC G px t

∂ ∂ ∆′ ′+ = ∆∂ ∂

0hR′ =0hG′ =

p∆

( )sp vQ

( )sQ 1

hh H

vL C

=′ ′

hv - speed of sound in a hydraulic line

Pneu

mat

ics m

p p mQp L R Q

x t∂∂ ′ ′+ =

∂ ∂

mp p

Q pC G px t

∂ ∂′ ′+ =∂ ∂

0pR′ =

0pG′ = p mQ

1p

p pv

L C=

′ ′ pv - speed of sound in a pneumatic

line

GS GPV

( )mQ t

GHV

( )vQ t

EG

( )tΦ

CG

( )i t

GHD

( )p t

WG

( )w t

VG

( )u t

p (t)

sC

p (t) iQ eQ

( )hC D

( )m mK C

2ϕ ( )m mK C

1x 2x

u (t) 1i 2i

eC

Q (t)

sL

( )i t

mM M=

( )v t

ω J

Q (t) ip ep

( )hL H m=

sR

Q ip ep

LR

Q

Q

NR ip ep

1ϕ 2ϕ

( )m mR G 1v 2v

( )m mR G

i 1v 2v

eR


63


Mec

hani

cs

Ster

eo-

mec

hani

cs

sm s

qA R qx tσ

ρ∂∂ ′+ =

∂ ∂

2 sm

qc G

A x tρ σ σ∗∂ ∂ ′+ =∂ ∂

0mR′ =0mG′ =

σ sq 1cρβ∗ =

ρ - mass density of the material (substance)

1;E Eβ −= - Young's modulus of elasticity σ - mechanical stress density

Vib

ratin

g str

ing

along vibration

1v f Tt

ρ⇒

−∂= + ∇ ⋅

∂

across vibration

0f =

N T

u w

lEvρ

=

tv σρ

=

u - longitudinal displacement in the string

lv - propagation speed of the longitudinal waves w - cross deviation of the string

tv - propagation speed of the transversal waves

Aco

ustic

s a aa a a

p qM R q

x t∂ ∂

′ ′+ =∂ ∂

a aa a a

q pC G p

x t∂ ∂

′ ′+ =∂ ∂

0aR′ =0aG′ =

pa qa 1

aa a

cM C

=′ ′

ca - acoustic velocity

Diff

usio

n Ther

mal

( )p

dT Ma Tdt cρ

= ∇ ⋅ ∇ +

( ) 0d vdtρ ρ+ ∇ ⋅ =

.a ct= 0M =

T Tq

pavτ

= pc - the constant - pressure heat

a - coefficient of thermal diffusivity τ - relaxation time

Mas

s ( )* *T cdC D C Pdt

= ∇ ⋅ ∇ +

*; *m Tj D C C Cρ= − ∇ =

TD ct=0eP =

C mj

Tp

Dv

τ=

DT - mass spreading coefficient τ - relaxation time

Table 14. The extended analogy of some basic quantities

Domain Flux Stress Resistance Admittance Specific constant

Elec

tro-m

agne

tics Electro-

statics ( )tΨ

1 2e e eu V V= −

1e

dlCSe

− = ∫

ee

IYU

= 0 re e e=

Electro-kinetics ( )i t e

dlRSσ

= ∫ 1eσ ρ−=

Magnetics ( )tΦ 1 2m m mu V V= − mdlRSµ

= ∫ /m m mY Uφ= 0 rµ µ µ=

Mec

han

ics Linear ( )v t ( )F t l vR k= /lY V F=

mρ Rotary ( )tω ( )M t rR kω= /rY Mω=

Hyd

ro-

pneu

mat

ics

Hydro-dynamics ( )vQ t

head drop: 1 2H H H∆ = −

42 /HM C L gdn π= /h vY Q H= ∆

1Fϕ µ−= Hydro-

mechanics pressure drop: 1 2p p p∆ = −

42 /HR C L dµ π= /h vY Q p= ∆

Pneumatics ( )mQ t 42 /pR C L dn π= /p mY Q p= ∆

Acoustics ( )aq t 1 2a a ap p p∆ = − /a a aR p dq= ∆ /p a aY q p= ∆ ρ

Thermodynamics ( )t tΦ 1 2T T T∆ = − 1t

dlRSλ

= ∫ /t tK T= Φ ∆ 1t tλ ρ−=

Electrochemistry ( )d tΦ 1 2c c c∆ = − 1 1c DR K S− −= /d dZ c= Φ ∆ DK

64

CONCLUSIONS Applying the analogy between quantities, phenomena and laws (respectively equations) of electrics and quantities, phenomena and laws from other domains is of particular interest and concerns only certain aspects of general interest.

This method of study is based on some results of reference set out in the theory of electrical circuits. Considering these results, the phenomena of non-electric fields can be described, under certain conditions, with equivalent (analogue) electrical circuits having regard to the correspondence between the characteristic quantities (respectively, parameters) and the equations used in the mathematical models describing the (analogue) phenomena in those areas.

To avoid significant errors, when using the analogy method it is necessary to define with sufficient precision in the range studied the concept of impedance. In these circumstances the analogy may be a basic process for the synthesis of non-electric complex circuits / systems, if one takes into account the synthesis algorithms specific to electrical or electronic circuits. In this case, the analogy allows a simplification of the study and a better understanding of the phenomena, because some results can be transposed from a domain (e.g. electrics) to another domain (the investigated domain) by simply changing the notations of the quantities and coefficients of the mathematical model. A remarkable aspect is that, in general, the equivalence or / and the analogy as a method of study is of particular interest from a practical and pedagogical point of view, with great educational advantages in science, so it is necessary to deepen the studies in this domain. REFERENCES [1]. ANTROPOV, L. Electrochemie theoretique. Mir Moscow, 1979. [2]. BUCULEI, M., RADULESCU, M. Hydraulic Drives and Automations. University of Craiova, 1993. [3]. CONSTANTINESCU, G. Sonic Theory. The Acad. Publishing House, Bucharest, 1985. [4]. LEONĂCHESCU, N. Thermodynamics. E.D.P., Bucharest, 1981. [5]. MOCANU, C.I. Electromagnetics Theory. E.D.P. Bucharest, 1981. [6]. PROKES, J. Hydraulic mechanisms in Automation. Elsevrier Publishing Company, Amsterdam, 1977. [7]. RADULESCU, M. A Systematization of the Resistance Theory in Hydraulic Drives. Mecatronica, 1/2010. [8]. RADULESCU, M. An Extension of the Electromechanical Analogy in the Domain of Hydrostatic transmissions, Part I. BJMT, vol. 1 (2012), issue 1. [9]. ŞORA, C. Basic Electrotechnics. E.D.P., Bucharest, 1982. [10]. VASIU, M. - Theoretical Physics, E.D.P., Bucharest, 1970.

Quick Info Top Prizes Awarded in the Create the Future Design Contest On November 7, the top prizes in the 2014 Create the Future Design Contest were presented in New York City. Winners in seven categories, as well as the Grand Prize winner, received awards for their innovations in the annual contest. The Create the Future Design Contest – sponsored by COMSOL and Mouser Electronics, and presented by Tech Briefs Media Group, an SAE International company – stimulates and rewards innovation, and has attracted more than 9,000 product design ideas from engineers, entrepreneurs, and students since 2002. Keynote speaker Monika Weber, Grand Prize winner of the 2011 Create the Future contest, talked about how far her technology has progressed since her win. The Fluid-Screen silicon biosensor chip technology she co-invented at Yale University brings the power of an entire lab into the palm of your hand to detect bacteria in blood and water in 30 minutes or less. Her spinoff company, Integrated Microfluidic Devices (IMD), is based in Boston, MA and New Haven, CT. What if you could 3D-print emergency shelters for tens of millions of victims of war and natural disasters? And what if those shelters could be built automatically in just a day? Behrokh Khoshnevis of the University of Southern California (center) won the $20,000 Grand Prize for his answer to those questions: Contour Crafting, a computerized construction method that 3D-prints entire buildings automatically. Here, Bernt Nilsson (left) of COMSOL (contest sponsor) joins Khoshnevis and Coby Kleinjan (right) of Mouser Electronics (contest sponsor). Each of the seven category winners received a workstation from prize sponsor Hewlett-Packard. John Bickel, Corporate Account Manager, Workstation Sales, represented HP at the event. 2014 Create the Future Design Contest winner sand sponsors. Standing from left: Bernt Nilsson of contest sponsor COMSOL; Rikki Razdan, Machinery/Automation/Robotics category winner; Marilyn Cooper of contest sponsor Mouser Electronics; E. Hunt Bergen of contest supporting sponsor Analog Devices; Sumit Awasthi of Analog Devices; and Coby Kleinjan of contest sponsor Mouser Electronics. Seated from left: Jim Hester, Electronics category winner; Dipul Patel, Sustainable Technologies category winner; Steve Arnold, Automotive/Transportation category winner; Alan Kielar, Machinery/Automation/Robotics category-winning team member; Grand Prize winner Behrokh Khoshnevis; Frederick Moxley, Aerospace & Defense category winner; Yunus Alapan, Medical category winner; and Jonathan Moritz, Consumer Products category winner. (http://www.techbriefs.com/component/content/article/23-ntb/features/feature-articles/21098-top-prizes-awarded-in-the-create-the-future-design-contest)

TEHNOLOGIA INOVATIVĂ – Revista „Construcţia de maşini” nr. 3-4 / 2014 65


OVERVIEW ON FEATURE-BASED DESIGN

Chicoş Lucia Antoneta

Transilvania University of Braşov, Braşov, ROMANIA, e-mail: [email protected]

REZUMAT Ingineria concurentă /simultană admite că activităţile de proiectare şi fabricaţie sunt puternic interdependente. Aceasta susţine că problemele de fabricaţie esenţiale trebuie luate în considerare încă din faza de proiectare constructivă în scopul reducerii numărului iteraţiilor în proiectare. În consecinţă, informaţiile furnizate de un sistem CAD trebuie să conţină, pe lângă informaţiile geometrice, informaţii suplimentare destinate proiectării tehnologice, programării NC etc. Proiectarea bazată pe entităţi - Feature-Based Design - a primit multă atenţie în ultimele decenii tocmai pentru faptul că entităţile sunt considerate elemente de legătură între sistemele CAD, CAPP şi CAM. Lucrarea prezintă rezultatul cercetărilor efectuate asupra utilizării proiectării bazate pe entităţi/trăsături, definiţii, moduri de abordare, precum şi rolul lor în proiectare şi fabricaţie. ABSTRACT Concurrent/simultaneous engineering admits that the design and manufacturing are strongly interdependent. Concurrent engineering argues that critical manufacturing issues should be considered early in design stage in order to reduce the number of design iterations. Therefore the information provided by a CAD system must contain, in addition to the geometric information, information for process planning, manufacturing, NC programming etc. Feature-based design has received much attention in last decade because the features are considered the connection elements among CAD, CAPP and CAM systems. This paper presents an overview of the research carried out in feature-based design (FBD), the evolution of their definitions, representation techniques as well as their role in design and manufacturing.

KEYWORDS: feature-based design, manufacturing features, concurrent engineering, features recognition, design by features, CAD/CAPP/CAM CUVINTE CHEIE: proiectare bazată pe entităţi, entităţi de fabricaţie, inginerie simultană, recunoaşterea entităţilor, proiectare prin entităţi, CAD/CAPP/CAM

1. INTRODUCTION

One of the first target of the simultaneous/concurrent engineering is the simultaneous approach of product design and its related processes in order to reduce the launching time on the market, improvement of quality and costs reduction of development cycle of the product [3], [4].

Modelling of the product is essential within the effort of successful integration of CAD/CAPP/CAM systems and for creating a simultaneous engineering environment. CAD systems used in the present involve at least one solid modelling technique for

product definition. Most of them provide a combination of wireframe, B-rep, and/or CSG techniques. These techniques define the product mainly by using its geometric features at various levels [2].

An efficient mechanism should allow on the one hand the modelling of the product in the shortest time and the other hand integration of the constructive designing data with the technological data.

Currently, features are widely used for product modelling [3], [4], [2], [1]. They play an important role for integrating CAD to CAM. Moreover, the constructive-technological features or manufacturing

66


features are the medium of transmission the information in CAD/CAPP/CAM integration because besides the geometrical design information they carry non-geometrical design information too (like tolerance, roughness etc.).

Since the CAD phase, they allow taking into account the technological and manufacturing aspects thus facilitating Concurrent Engineering [3], [2]. This information is very useful for process planning and manufacturing at the conceptual or early design stage.

This paper presents an overview of the research carried out in feature-based design (FBD). Current methods, definitions, types of features and procedures are reviewed and analyzed so that to determine their importance in modelling and to emphasize the need for development of new modelling techniques. 2. FEATURES DEFINITION

Currently, the term of feature is widely used in engineering language. The first using of it was, however, in the context of process planning at the beginning of 80s. One of the first entity definitions can be found in the CAM-I (in 1981): a specific geometric configuration, consisting of surface, edge or corner of the work piece designed to modify the external appearance or to help in obtaining a given function [5], [6].

Over time the entity term has received many and different interpretations/definitions. In [7] have been proposed the following definitions:

a syntactic means to group data that define the relationship to other elements of design; a computer representable data relating to functional requirements, manufacturing process or physical properties of design; attributes of the work piece whose presence or absence affect any part of the manufacturing process starting with process planning to packaging; region of the part with some manufacturing significance.

Pratt and Wilson (in 1985) defined the feature as a region of interest on the surface of a part. Shah (1991) defined features as elements used in generation, analysis or evaluation of the design. Pratt (in 1992) defined the form feature as set of elements attached to product model, with links between them, which have some significance in the life cycle of the product.

Henderson (1990) considers the feature as geometric and topological patterns of interest in a part model and which represent high level entities useful in part analysis [8], [9], [1], [10].

Hummel defined them as objects to which problem-solving knowledge such as process planning will refer. They serve to classify geometric and topological patterns as being manufacturable by one process or another.

According to Hirschtick, a feature is a geometrical form which is used in CAD. Luby described feature as a part of a work piece which has some manufacturing specification [3], [5], [9], [1], [2], [10].

According to Tsang and Brissaud [10], [11], [3] a feature is a geometrical form and a set of specifications for which a process planning process exists and this process is almost independent of the other features of the part.

In [11] features are described as any geometrical form which is used in design or manufacturing activities. They are significant parts of an object.

According to Cunningham [10], [3] a feature is any geometric form or entity that is used in reasoning in one or more design or manufacturing activities.

According to Claassen [12], [13], [3] a feature is described as follows: feature = form feature + semantics (Fig.1). In this context form feature is a group of elements that describes the geometry of the feature. Semantics refer to: attributes (technological aspects), rules or methods that determine the behaviour of an entity, links for establish the connections among features.

Figure 1. Pocket feature

In [3] constructive-technological feature is defined as a feature obtained from combination of a form/constructive feature, a precision feature and a set of machining processes, machine-tools and cutting tools for which can be generated a technological sequence independent of the technological sequences of the other features. These features are named simple constructive-technological feature (ECTs).

Complex constructive-technological feature (ECTc) is a feature consists of several simple constructive-technological features of the same or different types which can be grouped so that to allow establish of precedence relations among ECTS. These features have the main role to group the processing procedure in operations [3].

It is obvious that there is no consensus among researchers concerning the definition of the feature. Its definition is definitely dependent on the application specific.

3. TYPES OF FEATURES

In design and manufacture engineering there are

different ways of using the feature concept. Although

Form feature: geometry, geometrical constraints Semantics: attributes, rules, methods, connections

67


there were a number of attempts to create rules for the classification of entities (CAM-I in 1986), no standard has been adopted in this regard by the research community.

Pratt and Wilson have developed a scheme for the CAM-I [5], [3] which was then adopted by the Form Informational Feature Model - FFIM of Product Data Exchange Specification (PDES).

In PDES features are classified as following: passages, depressions, protrusions, transitions, areas and deformations.

Cunningham and Dixon (1988) classified entities, depending on their role in the design, in static and dynamic features [5], [3].

Pratt (1991) classified features in: manufacturing features, design features, analysis features, tolerance and control features, assembly features and features of general form [3].

Shah and Mantyla (1995) classified the features as follows [5], [15]:

1. Form features - describe regions of nominal geometry;

2. Tolerance features - describe deviations from the nominal shape / size / position;

3. Assembly features - describe assembly connections, kinematic relations, surfaces interaction;

4. Functional features - describe sets of characteristics related to a specific function;

5. Material features - describe the material structure, heat treatment etc.

In IPDM system [16] features are classified in two categories:

a. Micro features: they are form features to which is added a wide range of geometric feature, from the simple (cylinder, cone etc.) to the complex;

b. Macro features: functional entities (keyways, shoulders, fillets etc.).

According to [9] features class contains three subclasses, namely:

1. Functional feature; 2. Design feature: form features, material features,

tolerance features; 3. Manufacturing feature: machining features,

casting features, welding features, laminating features etc.

In [3] features are classified in: a. form features: contain only elements for

describing the nominal shape and relative position to a reference point. It is called geometric/constructive feature;

b. precision features: refers to deviation from the nominal dimension, geometric deviation, surface roughness etc.

c. constructive-technological features: contain a form feature, a precision feature and a set of processing procedure, machine tools, cutting tools specific to the entity type.

It can be seen from the literature that have been developed various classification systems of the features and still there are different opinions regarding their classification and definition.

In the literature, the features considered to be the most used are defined as follows: Form feature

- is defined on the basis of their geometry not on their function. Examples of form features: holes, slots, steps / shoulders and pockets [6];

- groups the geometric shapes mathematically defined: point, line, area, volume;

- they did not to contain any semantic meaning apart from the ability to identify themselves through the corresponding shape (ISO 10303-48) [18].

Manufacturing feature - is significant in the manufacturing [6]; - explicitly expressed the manufacturing method of

the entity. One of the most used manufacturing features is the machining feature. Machining feature

- is a feature which is generated by a machining process [6];

- is used for all surfaces that have a certain relation to processing operations (turning, drilling, milling etc.)

Precision features, including tolerances and surface roughness

- describe additional geometric characteristics of an existing geometric model or form features [19];

- reflect deviations in relation to the nominal shape /dimension [6].

Material features - describe characteristics of the material

(mechanical, electrical, chemical, thermal etc.) for defining the behaviour of parts [19]. It can be seen in literature that depending on the

application and the functions of the developed product there are different semantics that can be connected to the geometry. If the designer focuses on the function of the feature, the engineer is interested in how, with what tools and processes can produce that geometry. It can be said that the features must customized depending on the application and the functions of the developed product.

4. FEATURES REPRESENTATION TECHNIQUES

The models based on features facilitate the

integration of CAD, CAPP and CAM by following approaches [5], [6], [20], [17]:

1. Human Assisted Feature Recognition; 2. Automatic Features Recognition; 3. Design by Features.

68


In the Human Assisted Feature Recognition approach, the designer interacts with the CAD model to define a feature by picking up entities from the part drawing. Examples of such systems are: TIPPS system, developed by Chang and Wysk and KAPPS system create by Iwata and Fukuda [5], [10], [16].

In the Automatic Features Recognition systems, the features are recognized from a part designed in a CAD system. Generally, these systems use geometric and/or topological information to detect the presence of a specific type of feature. For this are used algorithms for recognition the geometries and their association with the features [5], [6], [20], [10].

In Design by Features, the designer creates the model of the part using both Boolean operations and inserting the feature in the desired position [17]. Design by features involves first creating a library of features.

Both in automatic feature recognition and in design by feature, the data attached of a feature are defined in the design phase. This information can be used both in the geometric design and in the process planning. 4.1. DESIGN BY FEATURES

In design by feature, the model of the part is directly built with features already defined in a library. The libraries can be predefined or user defined. This method provides to computer aided design more relevant and also facilitates the integration of CAD and CAM [21], [13], [9], [10].

Design by feature uses two methods: Synthesis by features (Fig.2) and Destructive modelling with features (Fig.3).

With synthesis by features (Fig.2) each feature is defined by a number of individual parameters. Synthesis method generates a model by adding the protrusion feature and subtracting the depressions feature [21].

Figure 2. Synthesis by features

In destructive modelling with features (Fig.3) method one single operation is available namely the subtraction. The features are subtracting in order they will be machined in reality. Therefore, the design model is built by subtracting depression feature from the row stock and the machining features are derived simultaneously [1], [21], 10].

Various systems of design by features have begun to be developed since 80s. Shah and Rogers (1988) developed an expert system for modelling the form features and which supports the user in defining of this type of features. Chang (1989) proposed a feature-based design and process planning system using a solid modeller [1], [21], [10].

De Martino [22], [21] introduced a method of recognition and update of the features after each feature-based design operation.

Figure 3. Destructive modelling

Lee and Kim [21] used an incremental approach to extract the machining features from a feature-based design.

Schulz and Schuster [13], [21], [1] developed and implement the FINDES (Feature INtegrated DEsign System) system to design the prismatic parts using the design by feature methodology. The system has two modules one for constructive design and the other for process planning.

Tseng (1999) presented a modular modelling approach by strengthening the technical support provided to the designer.

Bidarra and Bronsvoort (2000) proposed a semantic feature modelling system to defining and maintaining the semantics of the feature during all the modelling operations [1], [21].

In [3], [14] is proposed a system, named SIIRoD, which allows simultaneous and integrated approach the processes of geometric design, process planning and manufacturing. The system is totally developed using the 3D constructive-technological features and builds the parts using the design by features method.

Base feature

Feature to be added

Part

Stock

Features to be extracted

Part

69


The advantage of this method, besides the fact it eliminates the need of recognizing the features of the part, is that, subsequently, are available all feature data for its machining.

The part model which is design by feature contains geometrical and technological data that facilitates the integration with CAPP and CAM systems. Also, the geometry of the parts is described at high level and the libraries with features can help to fast building the parts [13], [5], [23], [3], [14].

Therefore, should be set what features to be included in the library. A solution to this problem is the definition of a limited set of features in a library and the designer to have the possibility to create their own features. 4.2. AUTOMATIC FEATURES RECOGNITION

Most systems of automatic features recognition are dependent of the representing scheme of solid modelling. Depending on the CAD representation scheme used systems for automatic recognition can be classified as follows [5], [6], [7], [23], [10], [7], [24]:

systems based on the CSG representation; systems based on the B-Rep representation; systems based on the cellular decomposition; systems based on the wireframe representation (or

graphs recognition); knowledge based features recognition systems; hybrid recognition systems; syntactic recognition systems etc.

The most used CAD representation schemes to the feature recognize are B-Rep representation, CSG representation, syntactic recognition and knowledge based features recognition [6], [7], [10].

Both in case of design by features and in automatic features recognition, features are more powerful design tools than low level geometric primitives. CAD systems based on features are more intuitive as regards their use and time to create a part/project is much shorter. CONCLUSIONS

Feature based design systems puts inevitably some restrictions on designers. On the one hand designing in this way restrict, to some extent, the creativity of the designer and on the other hand, because of infinite number of entities, is not possible to create a library to include all features.

Therefore must be established which entities should be included in the library. A solution to this problem is the existence of a limited set of entities in a library (indicated would be entities frequently used) and the designer should be able to create their own entities.

Feature based design enhance the integration of conception (the design) with downstream activities (manufacture, assembly, inspection etc.) and falls in the direction of DFM (Design For Manufacturing), DFA (Design For Assembly) etc. Using feature based design in a CAD/CAM system results in its integration into the concept of simultaneous engineering.

REFERENCES [1]. Shahin, T., Feature-Based Design – An Overview, Computer-

Aided Design & Applications, 5(5), 2008, http://www.cadanda.com.

[2]. Salomons, O. W., Van Houten, F.J.A.M., Kals, H.J.J., Review of Research in Feature-Based Design, Journal of Manufacturing Systems, Volume 12/No. 2, 1995.

[3]. Chicoş, L. A., Using of Simultaneous Engineering Concept in Products Development, Doctoral thesis, Transilvania Universitatea of Braşov, Braşov, 2007.

[4]. Nahm, Y. E., Ishikawa, H., A new 3D-CAD system for set-based parametric design, International Journal of Advanced Manufacturing Technology, 2006, www.springerlink.com.

[5]. Allada,V., Computer-aided design, engineering, and manufacturing. Systems techniques and applications, vol.V, cap. 2, Feature-Based Design in Integrated Manufacturing, Elsevier, 2001 www.springerlink.com.

[6]. Yip-Hoi, D., The mechanical systems design handbook, Chapter2. Computer-Aided Process Planning for Machining, 2002, www.springerlink.com

[7]. Joshi, S., Chang, T. C., Feature extraction and feature based design approaches in the development of design interface for process planning, Journal of Intelligent Manufacturing,1990, vol. 1, pp. 1-15, http://download.springer.com/ static/pdf/11/art%253A10.1007%252FBF01471338.pdf?auth66=1405066728_e767e2cd718ef2a313117edbf3cd39a8&ex.pdf

[8]. Başak, H., Gülesin, M., A feature based parametric design program and expert system for design, Mathematical and Computational Applications, Vol. 9, No. 3, pp. 359-370, 2004. http://mcajournal.cbu.edu.tr/volume9/vol9no3p359.pdf

[9]. Parry-Barwick, S., Bowyer A., Feature Technology, 1998, http://homepages.inf.ed.ac.uk/rbf/CVonline/ LOCAL_COPIES/BOWYER1/ft/ft.htm

[10]. Singh, A., Manufacturing Feature Recognition From Solid Models. A Survey Report, 2002, http://dspace.thapar.edu:8080/dspace/bitstream/123456789/307/1/91898.PDF

[11]. Dereli, T., Baykasoglu, A., Concurrent engineering utilizes for controlling interactions in process planning, Journal of Intelligent Manufacturing,15, 471-479, 2004, www.springerlink.com.

[12]. Claassen, E.,s.a., Support of the CAD/CAM-process chain by manufacturing features, 2000.

http://whitepapers.zdnet.co.uk/......artigo. Pdf [13]. Schützer, K., Claassen, E., Gyldenfeldt, C., Support for the

Product Development Chain Through Manufacturing Features, Revista De Ciência & Tecnologia, V. 11, no. 21,pp. 19-27, 2004, http://www.unimep.br/phpg/editora/revistaspdf/ rct21art02.pdf

[14]. Chicoş, L. A., Oancea, Gh., Lancea, C., Bancila, D., Software System of Integrated and Simultaneous Engineering, Proceedings of the 10th WSEAS International Conference on Applied Computer Science (ACS'10), Iwate Prefectural University, pp. 238-241, (ISSN: 1792-4863, ISBN: 978-960-474-231-8), Iwate, Japonia, 2010.

[15]. Zhou, F., s.a., Form Feature and Tolerance Transfer from a 3D Model to a Setup Planning System, The International Journal of Advanced Manufacturing Technology, Springer-Verlag London Limited, 2002, www.springerlink.com.

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http://www.cadanda.com/

http://www.springerlink.com/


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[16]. El Maragy, H.A., Intelligent Product Development and Manufacturing, Artificial Intelligence in Design, Springer-Verlag London Limited, 1991.

[17]. Manić, M., Miltenović, V., Stojković, M., Banić, M., Feature Models in Virtual Product Development, Strojniški vestnik - Journal of Mechanical Engineering 56,vol. 3, 2010.

[18]. Baumann, R. A., Structure-Oriented Exchange of Product http://opus4.kobv.de/opus4-tuberlin/ files/788/baumann_richard.pdf

[19]. Zhou, F.,s.a., Form Feature and Tolerance Transfer from a 3D Model to a Setup Planning System, The International Journal of Advanced Manufacturing Technology, Springer-Verlag London Limited, 2002, www.springerlink.com.

[20]. Tseng, J., Jiang, B. C., Evaluating multiple feature-based machining methods using an Activity-based cost analysis model, The International Journal of Advanced Manufacturing Technology, Springer-Verlag London Limited, 2000, www.springerlink.com.

[21]. Ding, L., Yue, Y., An intelligent hybrid approach for Design by-features, 2000, www.luton.ac.uk.

[22]. De Martino, T., Falcidieno, B., Giannini, F., Hassinger, S., Ovtcharova, J., Feature-based modeling by integrating design and recognition approaches, Computer-aided Design, Vol 26, No 8, pp 646-653, 1994, http://www.sciencedirect.com

[23]. Chen,Y., Huang, Z., Chen, L., Parametric process planning based on feature parameters of parts, International Journal of Advanced Manufacturing Technology, 28: 727–736, DOI 10.1007/s00170-004-2428-5, Springer-Verlag London Limited, 2005, www.springerlink.com.

[24].Tan, C. F., Kher, V. K., Ismail, N., Design of a Feature Recognition System for CAD/CAM Integration, World Applied Sciences Journal 21 (8): 1162-1166, 2013.

Quick Info Tech Talk Alert News from Proto labs Real Parts. Really Fast.

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(https://event.webcasts.com/starthere.jsp?ei=1049200)

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http://opus4.kobv.de/opus4-tuberlin/%0bfiles/788/baumann_richard.pdf

http://opus4.kobv.de/opus4-tuberlin/%0bfiles/788/baumann_richard.pdf



COMPORTAREA ÎN FUNCŢIONARE A GRUPURILOR DE REZEMARE ALE CUPTOARELOR ROTATIVE

Gheorghe Ene, Teodor Sima

University Politehnica of Bucharest, Bucharest, ROMANIA, e-mail [email protected] University Politehnica of Bucharest, Bucharest, ROMANIA, e-mail [email protected]

REZUMAT În lucrarea de faţă se prezintă modul cum se comportă în funcţionare bandajele şi rolele din componenţa grupurilor de rezemare ale cuptoarelor cu tambur rotativ. Se are în vedere influenţa asupra funcţionării grupurilor de rezemare a preciziei execuţiei, montajului şi reglării lor.

ABSTRACT In the present work is presented the functional behavior of bindings and roles as parts in the bearing groups of rotational ovens. The influence of manufacturing precision, installation and adjustment of bearing groups is considered.

KEYWORDS: rotary kilns, live-rings, tyres, supporting rollers, rotary kilns supports CUVINTE CHEIE: cuptoare rotative, inele de rulare, bandaje, role de rezemare, reazemele cuptoarelor rotative.

1. GENERALITĂŢI Cuptoarele rotative constau dintr-un tambur cilindric (prevăzut cu amenajările interioare corespunzătoare), înclinat cu un unghi mic (1…40) faţă de planul orizontal, rezemat pe două sau mai multe grupuri de rezemare şi care se roteşte cu o turaţie redusă (0,75…4,0 rot/min) în jurul axei longitudinale. Rezemarea tamburului cuptoarelor rotative este specifică acestor utilaje, fiecare grup de reazem constând dintr-un bandaj (inel de rulare) montat pe tambur şi două role de rezemare plasate simetric, la un unghi de 300, în raport cu planul diametral vertical al bandajului. Axele rolelor de rezemare sunt paralele cu axa tamburului. La funcţionarea normală a cuptorului rotativ, în timpul rotirii tamburului, acesta are şi o mişcare în lungul axei lui, alternativ, când spre capătul inferior, când spre cel superior, în anumite limite. Această mişcare longitudinală alternativă a tamburului pe reazeme contribuie la buna funcţionare a tuturor subansamblurilor componente ale cuptorului rotativ: grupuri de rezemare, angrenajul pinion-coroană dinţată al sistemului de acţionare, etanşări de capăt. Pentru a preveni căderea cuptorului de pe reazeme, unul dintre grupurile de rezemare este prevăzut, pe lângă rolele obişnuite, şi cu role de gardă. Acestea nu pot prelua decât temporar încărcări axiale relativ reduse, ele având numai rolul de a semnala dacă tamburul are tendinţa de a se deplasa în lungul lui, sub

acţiunea componentei axiale a propriei greutăţi. Pentru preluarea componentei axiale a greutăţii tamburului, se impune reglarea corespunzătoare a rolelor de rezemare ale grupului prevăzut cu role de gardă. La cuptoarele rotative de dimensiuni şi capacităţi mari există pericolul ca, în urma dereglării rezemării, tamburul să se deplaseze preponderent spre unul din capete şi, avariind rolele de gardă, să cadă de pe reazeme. Pentru a evita un asemenea grav incident de exploatare, grupul de rezemare prevăzut cu role de gardă este prevăzut cu opritoare fixe de siguranţă, jocul dintre bandaj şi opritor fiind mai mare decât cel dintre bandaj şi rolele de gardă. Calculul şi construcţia grupurilor de rezemare ale cuptoarelor rotative au fost tratate într-o serie de monografii [1-4] şi de alte lucrări [5-8] în lucrarea de faţă abordându-se chestiuni privind montarea, reglarea şi comportarea în funcţionare a inelelor de rulare şi a rolelor de rezemare. 2. DEPLASAREA TAMBURULUI CUPTORULUI ROTATIV PE ROLELE DE REAZEM, SPRE CAPĂTUL LUI INFERIOR Tamburul cuptorului rotativ, montat înclinat faţă de planul orizontal cu unghiul α, transmite sistemului de rezemare forţele (fig. 1):

72


- după direcţia normală la axa tamburului:

ψα

coscos

1⋅

=GG ; (1)

- după direcţia axei tamburului:

ψα

cossin

2⋅

=GG (2)

unde G este greutatea totală a tamburului în condiţii de exploatare, MN; α – unghiul de înclinare al axei tamburului în raport cu orizontala, grade; ψ – unghiul sub care sunt plasate rolele de reazem în raport cu axa verticală care trece prin centrul secţiunii tamburului, grade.

Figure 1. Schemă pentru determinarea încărcării

grupurilor de reazem ale tamburului. Componenta axială G2 a greutăţii tamburului tinde să-l deplaseze pe acesta în lungul axei lui, spre capătul inferior, existând pericolul ca tamburul să cadă de pe reazeme. Acestei forţe i se opune forţa totală de frecare dintre bandaje şi rolele de reazem, determinată de relaţia:

1, GfF tf ⋅= (3) unde f este coeficientul de frecare dintre bandaje şi role. Pentru ca tamburul să nu cadă de pe reazeme, trebuie îndeplinită condiţia :

2, GF tf ≥ . (4) Ţinând seama de relaţiile (1), (2) şi (3), condiţia (4) poate fi pusă sub forma :

αϕ ≥ (5) unde φ este unghiul de frecare corespunzător coeficientului de frecare f. Deoarece atât bandajele cât şi rolele de reazem se realizează din oţel şi, în condiţii normale de funcţionare a cuptorului, între suprafeţele în contact ale acestora nu există lubrifiant, coeficientul de frecare are valorile f = 0,15…0,20. De asemenea, de regulă, unghiul de înclinare al tamburului cuptoarelor rotative faţă de orizontală nu depăşeşte valoarea α = 20 20’ = 2,30 (corespunzătoare pantei i = 4 %). În această situaţie, condiţia (5) este satisfăcută:

( ).3,23,115,8

20,015,0arctgfarctg00 =≥⋅⋅⋅=

=⋅⋅⋅==

α

ϕ

Dacă se consideră ( )%4202 '0=α , 030=ψ , din relaţiile (1), (2) şi (3) rezultă:

GGGG ⋅=⋅

=⋅

= 16,130cos

202coscos

cos0

'0

1 ψα ; (6)

GGG ⋅=⋅

= 047,030cos

202sin0

'0

2 ; (7)

GfGfF tf ⋅⋅=⋅= 16,11, . (8)

Considerând f =0,15, din relaţia (8) rezultă, pentru forţa totală de frecare dintre bandaje şi rolele de reazem, valoarea:

GGGfF tf ⋅=⋅⋅=⋅= 174,015,016,11, . (9)

Comparând relaţiile (9) şi (7), rezultă că forţa de frecare depăşeşte componenta axială a greutăţii tamburului de 0,134/0.047 = 3,7 ori. Prin urmare, dacă nu intervin alte forţe suplimentare, tamburul înclinat al cuptorului nu se poate deplasa în lungul lui, spre capătul inferior. În timpul rotirii însă, asupra tamburului intervine şi forţa periferică produsă de mecanismul de acţionare al acestuia. Sub acţiunea rezultantei dintre forţa periferică produsă de mecanismul de acţionare al tamburului şi componenta axială a greutăţii lui, acesta se va deplasa spre capătul inferior. Cuplul bandaj-role se comportă ca o transmisie prin fricţiune, bandajul fiind roata motoare, iar rola cea condusă. La transmisia prin roţi de fricţiune are loc o lunecare a roţii motoare faţă de cea condusă atât datorită aderenţei insuficiente dintre roţi, cât şi datorită elasticităţii materialelor din care roţile sunt realizate. În cazul cuptoarelor rotative, forţa periferică transmisă bandajului de către mecanismul de acţionare al tamburului este de 3…4 ori mai mică decât forţa frecării de alunecare dintre bandaj şi rolele de reazem [9]. Prin urmare, lunecarea (patinarea) bandajului pe role din cauza aderenţei insuficiente este exclusă, aceasta având loc numai datorită deformaţilor elastice ale materialelor din care acestea sunt realizate. Datorită acestei lunecări elastice, viteza periferică a bandajului va fi mai mică decât cea a rolei. Lunecării elastice pe role a bandajului i se opune forţa periferică de frecare Ff,p = f·G1. Deplasării produse de componenta axială a greutăţii tamburului (orientată spre capătul lui inferior) şi de lunecarea elastică a bandajului pe role i se opune forţa frecării de alunecare dintre suprafeţele în contact ale acestora.

73


Viteza axială va de deplasare a tamburului spre capătul lui inferior şi viteza lunecării elastice vl,e a bandajului în raport cu rola sunt proporţionale cu forţele corespunzătoare care produc aceste mişcări [9]:

pf

ela

Fv

Gv

,

,

2=

sau:

1

2,

,

2, Gf

GvFGvv bp

pfela ⋅

⋅⋅=⋅= ξ (10)

unde:

bp

el

vv

,

,=ξ (11)

este un coeficient care exprimă viteza de lunecare a bandajului în raport cu rola, în funcţie de viteza lui periferică v p,b . În comparaţie cu transmisiile prin fricţiune, se poate adopta pentru acest coeficient valorile ξ=0,02…0,05, în funcţie de materialele utilizate pentru realizarea bandajului şi rolelor şi de coeficientul de frecare din lagărele acestora [9]. Viteza lunecării elastice a bandajului în raport cu rolele de reazem depinde de proprietăţile elastice ale oţelului din care sunt realizate elementele în contact şi de rezistenţa care se opune rotiri rolelor (frecarea din lagărele acestora). Dacă frecările din lagărele rolelor sunt reduse şi dacă bandajul şi rolele de reazem au rigidităţi ridicate (sunt realizate din oţeluri de duritate mare), lunecarea elastică a bandajului pe role este foarte mică şi, prin urmare, tamburul nu va avea tendinţa să se deplaseze pe reazeme către capătul lui inferior. Deoarece oţelurile din care se realizează bandajul şi rolele sunt materiale deformabile, soluţia posibilă pentru a preveni deplasarea tamburului pe reazeme (către capătul lui inferior) este să se reducă frecarea în lagărele rolelor. În general, pentru învingerea frecărilor din lagărele rolelor de reazem se utilizează până la 30% din puterea motorului electric folosit pentru acţionarea tamburului. De aceea este necesar să se acorde atenţia cuvenită construcţiei lagărelor, ungerii şi etanşării acestora. 3. DISPUNEREA AXELOR ROLELOR DE REAZEM ÎN RAPORT CU AXA TAMBURULUI Rolele de reazem se montează astfel încât axele lor să fie paralele cu axa tamburului cuptorului rotativ. Pentru a preveni alunecarea tamburului pe reazeme spre capătul inferior al lui, rolele unor grupuri de reazem se dezaxează în acelaşi sens, cu un unghi mic β = 20…30’ în raport cu axa tamburului (fig. 2) [1-4].

Figure 2. Dezaxarea rolelor de reazem

Prin această dezaxare, viteza periferică a fiecăreia dintre role se descompune în două componente: v1 - dirijată în lungul axei tamburului şi v2 - viteza periferică a bandajului, perpendiculară pe aceasta, între cele două componente existând corelaţia:

βtg21 ⋅= vv . (12)

Este necesar ca viteze v1 să fie egală cu cea de deplasare a tamburului spre capătul inferior şi orientată în sens contrar acesteia. Modalitatea de dezaxare a rolelor, prezentată în figura 2, este singura acceptată pentru a preveni deplasarea tamburului spre capătul inferior sub acţiunea componentei axiale a greutăţii lui. Pentru a preveni deplasarea tamburului pe role spre capătul inferior al acestuia, trebuie îndeplinită condiţia:

2GTfnr ≥⋅⋅ (13)

unde nr este numărul de role care urmează a fi dezaxate; f –coeficientul frecării de alunecare dintre bandaj şi role (fără ca între suprafeţele acestora să existe lubrifiant) f = 0,15…0,20; T – forţa pe care tamburul cuptorului rotativ o exercită asupra unei role (reacţiunea rolei), MN; G2 – componenta axială a greutăţii tamburului, MN. Utilizând relaţia (13) se determină numărul de role care trebuie dezaxate pentru a preveni deplasarea tamburului spre capătul lui inferior. Exemplu de calcul Se consideră cazul cuptorului rotativ pentru clincher de ciment care lucrează după procedeul uscat, Φ 4,6 x 78 m, cu următoarele caracteristici [1]: - greutatea totală a tamburului : G = 12,0 MN (1200 t) ; - unghiul de înclinare al tamburului faţă de orizontală: α = 20 (i = 3,5 %); - numărul grupurilor de rezemare: ng = 3. Pentru acest cuptor, încărcarea unei role are valoarea:

MN3,230cos6

12cos2 0 =

⋅=

⋅⋅=

ψgnGT (230 t)

74


Pentru a prelua componenta axială G2 a greutăţii tamburului care tinde să-l deplaseze spre capătul inferior, este necesar să se dezaxeze un număr de role dat de relaţia:

2,13,215,0

2sin12sin 02 =

⋅⋅

=⋅

⋅=

⋅=

TfG

TfGnr

α (14)

Prin urmare, trebuie să se dezaxeze rolele unui singur grup de rezemare (cel care este prevăzut cu role de gardă şi care se află în imediata apropiere a coroanei dinţate pentru acţionarea tamburului). Unghiul cu care trebuie să se încline axele rolelor faţă de axa tamburului se determină cu relaţia (10) pusă sub forma:

1

221 G

Gf

vv ⋅⋅=ξ

din care, ţinând seama că βtgvv ⋅= 21 , rezultă:

tgαcossin

cossintgβ

1

2 ⋅=⋅=⋅⋅

⋅=⋅=ffG

GfG

Gf

ξααξ

ααξξ

(15)

În cazul exemplului de faţă, considerând ξ = 0,04, rezultă:

0093,0tg20,150,04tgα

fξtgβ 0 =⋅=⋅= ,

adică unghiul este: β =0,5330 = 32’. Pentru a realiza echilibrul dintre componenta axială a greutăţii tamburului, care tinde să-l deplaseze spre capătul inferior, şi forţa de frecare de alunecare, direcţionată în sens invers acesteia, trebuie ca suprafeţele în contact ale bandajului şi rolelor de reazem să fie uscate (între ele să nu existe lubrifiant). Apariţia accidentală a lubrifiantului între role şi bandaj perturbă funcţionarea normală a cuptorului rotativ deoarece, reducându-se forţa de frecare dintre acestea, tamburul începe să se deplaseze către capătul lui inferior. Numai în cazul în care tamburul are tendinţa de a se deplasa spre capătul superior se introduce lubrifiant între bandaj şi role. După stabilirea regimului de funcţionare normală a tamburului pe reazeme, prin reglarea corespunzătoare, la rece, a rolelor unui grup de rezemare, la funcţionarea la cald, în regim staţionar, tamburul trebuie să aibă o mişcare atât spre capătul superior, cât şi spre cel inferior, în limitele jocului dintre bandaj şi rolele de gardă, fără ca acestea să fie încărcate excesiv. Această funcţionare stabilă a cuptoarele rotative depinde atât execuţia, montajul, cât şi exploatarea corectă a lor (alinierea corectă a tamburului, poziţionarea corectă a grupurilor de reazem; execuţia

îngrijită bandajelor şi rolelor, asigurând precizia dimensională şi de formă a acestora; păstrarea regimului de temperatură al cuptorului, cu evitarea încălzirilor neuniforme sau a supraîncălzirilor tamburului care să conducă la deformarea (curbarea) acestuia etc.). Pentru diminuarea lunecării tamburului pe reazeme, spre capătul inferior al acestuia, trebuie redusă valoarea coeficientului de frecare în lagărele rolelor de reazem. În acest scop, rolele de reazem sunt prevăzute cu lagăre de rostogolire (rulmenţi), în locul celor de alunecare. 3. TENSIUNI ÎN ZONELE DE CONTACT DINTRE BANDAJ ŞI ROLELE DE REZEMARE Rolele grupurilor de reazem trebuie să aibă toate acelaşi diametru, iar axele lor trebuie să fie plasate în acelaşi plan orizontal (centrul fiecărei role trebuie să se afle la aceiaşi distanţă, pe verticală, faţă de axa tamburului) (v. fig. 3) pentru a fi toate în contact cu bandajele. “Lăsarea” rolelor unui reazem conduce la supraîncărcarea celorlalte reazeme şi la solicitări suplimentare mari ale tamburului. Dacă rolele se plasează sub unghiul ψ =300, în raport cu planul diametral vertical al tamburului, atunci distanţa dintre centrele lor, în planul orizontal, este egală cu suma razelor bandajului şi rolei (RB+RR). La valoarea unghiului ψ=300 nu există pericolul ca tamburul cuptorului să se răstoarne de pe rezeme, iar apăsarea exercitată de role asupra bandajului este minimă. Apăsarea (reacţiunea) fiecăreia dintre role asupra bandajului are expresia:

QQQT ⋅=⋅

=⋅

= 578,030cos2cos2 0ψ

. (17)

unde Q este sarcina care încarcă grupul de rezemare respectiv.

Fig. 3. Schema încărcării reazemului.

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Cuplul rolă-bandaj este supus la strivire în zona de contact. De mărimea tensiunilor de contact depinde, în principal, durata de viată a bandajului. Bandajul şi rola de reazem sunt corpuri cilindrice circulare supuse acţiunii efortului de contact:

bTp /= N/m (18)

unde b este lăţimea bandajului. Efortul de contact produce deformarea elastică a elementelor formându-se o zonă (pată) de contact dreptunghiulară cu lăţimea 02 bbc ⋅= şi lungimea b (lăţimea bandajului). Presiunea maximă de contact p0 şi lăţimea zonei de contact bc = 2·b0 (v. fig. 4) se determină pe baza teoriei lui Hertz pentru cilindri de lungime mare, când se pot neglija influenţele zonelor de capăt. În cazul în care materialul de construcţie al corpurilor în contact (bandaj şi role) este oţel (coeficientul contracţiei transversale (Poisson) µ = 0,3, modulul de elasticitate longitudinal (Young) E = 2⋅101 N/m2) presiunea maximă de contact şi lăţimea zonei de contact are expresiile [1-4]: • presiunea maximă de contact:

2

0

mN, 591,0

418,0

RB

RB

RB

RB

DDDDEp

RRRREpp

⋅+

⋅⋅=

=⋅+

⋅⋅=

, N/m2 (19)

• lăţimea petei de contact:

m,158,2

044,32 0

RB

RB

RB

RB

DDDD

Ep

RRRR

Epb

+⋅

⋅=

=+⋅

⋅=⋅ (20)

în care DB este diametrul exterior al bandajului (RR – raza acestuia), DR, cel al rolei de reazem (RR – raza acesteia). La bandajele de dimensiuni mari, lăţimea zonei de contact 2b0 este de ordinul a 1,0 mm [2]. În zona de contact apare o stare spaţială de tensiuni. Tensiunile normale după cele trei direcţii având valori maxime în centrul petei de contact (fig. 4), sunt: • 00 2 px ⋅−== µσ , după direcţia axială ; • 00 py −==σ , după direcţia inelară ;

(21) • 00 pz −==σ , după direcţia radială.

Se observă că toate cele trei tensiuni sunt de

compresiune (solicitare hidrostatică). În consecinţă mărimea fiecăreia dintre ele, în parte, poate depăşi

limita de curgere a materialului, tensiunile remanente de compresiune nefiind dezavantajoase, deci valorile admisibile p0 pot fi relativ mari.

Figure 4. Schema zonei de contact dintre bandaj şi

rolă

Tensiunea tangenţială maximă apare dincolo de suprafaţa de contact, în profunzimea materialului, la adâncimea:

079,0 bz ⋅= , (22) unde b0 este lăţimea petei de contact dintre bandaj şi rolă. Tensiunea tangenţială maximă are mărimea:

0max 60,0 p⋅=τ . (23)

Deoarece: 2max echστ = , rezultă că:

0max 60,02 pech == στ din care se obţine:

raapp σσ 83,083,0,00 ==≤ . (24)

Întrucât, tensiunile sunt de compresiune, rezistenţa admisibilă σa se poate considera egală cu cea de rupere a materialului. Practic, pata de contact dintre bandaj şi rolă este o elipsă care are axa mare egală cu lăţime b a bandajului, iar axa mică: bc = 2·b0. Lăţimea bandajului se determină cu relaţia (18) în care efortul de contact p are valorile [2]: - mMN4,2≤p , pentru tambure cu turaţii reduse (3…4 rot/min); - mMN0,1=p , pentru tambure cu turaţii mai mari.

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Dacă condiţia (24) nu este îndeplinită, se măreşte fie lăţimea bandajului, fie valoarea raportului BR RR , fie se utilizează un material cu limita de curgere mai ridicată. În cele expuse nu s-a ţinut seama de frecarea dintre bandaj şi rolă care are ca efect o sporire cu aproximativ 10% a tensiunii echivalente [2].

4. UZAREA SUPRAFEŢEI BANDAJULUI AFLATĂ ÎN CONTACT CU ROLELE DE REZEMARE Uzarea suprafeţei exterioare a bandajului se datorează, în special, creşterii presiunii de contact dintre bandaj şi rolele de rezemare, care apare ca urmare fie a reducerii ariei suprafeţei de contact, fie a creşterii apăsării pe reazem. Reducerea ariei suprafeţei de contact se datorează neparalelismului dintre axa geometrică a bandajului şi axele rolelor de rezemare (apăsare pe muchie (v. fig. 6 a)). Bandajul se uzează neuniform, căpătând treptat, în timpul funcţionării, o formă tronconică, ceea ce conduce la accentuarea neuniformizării apăsării pe lăţimea lui şi, prin urmare, la accentuarea uzării. Creşterea apăsării pe reazem (supraîncărcarea acestuia), apare ca urmare a «lăsării», din diferite cauze, a unora dintre reazeme, în raport cu celelalte, sau din cauza alinierii incorecte a acestora la montare. În practica exploatării cuptoarelor rotative din industria cimentului, se întâlnesc frecvent creşteri ale încărcărilor pe reazeme de 1,5…..2,0 ori faţă de situaţia normală fie din motivele expuse, fie din cauza suprasarcinilor la care este supus cuptorul în timpul exploatării [9]. Acestea conduc la exfolierea materialului suprafeţei exterioare a bandajului însoţită de o serie de aspecte negative specifice (creşterea rezistenţei la rotire a tamburului cuptorului pe reazeme, accentuarea uzurii etc.). La uzarea suprafeţei exterioare a bandajului contribuie şi alţi factori: pătrunderea în zona de contact dintre bandaj şi role a unor impurităţi abrazive (particule solide, praf etc.), răcirea incorectă a bandajului, lipsa ungerii suprafeţelor în contact ale bandajului şi rolelor etc. Mărimea şi uniformitatea presiunii de strivire şi a petei de contact influenţează puternic asupra durabilităţii în funcţionare a ansamblului bandaj-role de rezemare. Aceste influenţe depind în măsură importantă de o serie de factori: materialul utilizat pentru construcţia elementelor în contact, precizia dimensională şi de formă a acestora, precizia montajului (abaterile de la poziţia lor corectă) etc. În cazul în care rolele sunt înclinate faţă de bandaj, fie în planul orizontal, fie în cel vertical, apăsare rolelor pe bandaj şi, prin urmare, presiunea de contact dintre bandaj şi role cresc foarte mult.

Dacă axele rolelor sunt riguros paralele cu cea a bandajului, pata de contact dintre rolă şi bandaj va avea forma dreptunghiulară, iar presiunea de contact se va distribui după o semielipsă (v. fig. 5 a) [10].

Figure 5. Variaţia presiunii de contact dintre rola de

rezemare şi bandaj În această situaţie, forţa cu care rola apasă pe bandaj este determinată de relaţia [10]:

bbpT ⋅⋅⋅= 002p (25)

unde presiunea de contact p0 şi lăţimea petei de contact b0 sunt definite de relaţiile (19) respectiv (20), iar b este lungimea petei de contact (lăţimea bandajului). Dacă bandajul este mult înclinat faţă de rolă atunci pata de contact are forma triunghiulară (v. fig. 5 b) şi forţa cu care rola apasă pe bandaj este determinată de relaţia [10]:

32 0101bbpT ⋅⋅⋅=

p (26)

unde 0001 73,13 ppp ⋅=⋅= . Se observă că în acest caz presiunea de contact este mai mare decât cea din cazul anterior cu 73 %. Dacă lungimea petei de contact este de numai 80 % din lăţimea bandajului atunci presiunea de contact va creşte de 94,18,03 = ori, adică cu 94 %. Trebuie să se evite ca lungimea contactului dintre bandaj şi rolă să scadă sub 70 % din lăţimea bandajului deoarece, în aceste situaţii, apare pericolul ca suprafeţele de lucru ale rolelor şi bandajului să se uzeze prin sudare locală sau pitting. Dacă axele rolelor sunt înclinate faţă de cea a cuptorului (bandajului) în planul orizontal atunci, rola fiind oblică în raport cu bandajul, apare o forţă axială care încarcă suportul rolelor. De asemenea, între suprafeţele de lucru ale bandajului şi rolelor apare o oarecare alunecare care conduce la creşterea uzurii acestora. În situaţia când înclinarea rolelor este suficient de redusă astfel încât să se păstreze contactul dintre acestea şi bandaj, pata de contact are formă eliptică, iar presiunea de contact se distribuie după un

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semielipsoid (v. fig. 5 c). În acest caz, forţa cu care rola apasă pe bandaj este determinată de relaţia [10]:

232

0202bbpT ⋅⋅⋅

⋅=

p (27)

unde 0002 22,123 ppp ⋅=⋅= . Dacă înclinarea rolei faţă de bandaj determină o lungime a contactului egală cu 80 % din lăţimea bandajului, atunci presiunea de contact dintre bandaj şi role creşte de ( ) 37,18,023 =⋅ ori, adică cu 37 %. Înclinarea rolelor faţă de bandaj determină suprasolicitări ale acestora care conduc la deteriorarea şi la reducerea duratei lor de serviciu. Suprasarcinile din grupurile de rezemare conduc, de asemenea, la deformaţii ale tamburului cuptorului, cu efecte negative aspra durabilităţii căptuşeli refractare a acestuia. Utilizarea grupurilor de rezemare cu role autoreglabile conduce la evitarea acestor neajunsuri (v. fig. 6).

Figure 6. Grup de rezemare cu reglare hidraulică a

poziţiei rolelor de reazem [11]. 1 - bandaj; 2 – rolă de reazem;

3 – lagăr oscilant; 4 – cilindri hidraulici. Datorită greutăţii mari a bandajelor cuptoarelor rotative, care ating valori de 35…40 t, din motive economice, acestea nu se realizează din oţeluri de calitate superioară cum sunt cele pentru şine de cale ferată, de exemplu. De regulă bandajele se realizează prin turnare din oţeluri OT 40…OT 50, a căror duritate este limitată la circa 220 HB (unităţi Brinell). Deoarece aceste oţeluri suportă presiuni de contact de valori relativ ridicate, suprafeţele de lucru ale bandajelor nu se uzează prea repede, uzura lor având loc treptat, în timp.

Uzura bandajelor reprezintă un fenomen negativ important de care trebuie să se ţină seama, repararea sau înlocuirea lor necesitând oprirea cuptorului pentru un interval de timp destul de mare. Ruperea bandajelor, aşa cum arată practica exploatării cuptoarelor rotative pentru clincher de ciment (care au răspândirea cea mai mare din toate industriile) are loc foarte rar şi numai în acele cazuri când bandajele au defecte de turnare sau când sunt suprasolicitate excesiv. Uzura bandajele se amplifică dacă acestea, aşa cum s-a amintit, se reazemă pe role montate necorespunzător (cu abateri de la paralelism). În aceste situaţii apăsarea bandajelor pe role se măreşte, iar suprafaţă (pata) de contact dintre aceste se reduce, amplificând uzura. Uzura bandajului are loc neuniform şi pe lăţimea acestuia, bandajele care rulează pe role cu abateri de la paralelism căpătând treptat o formă tronconică care constituie, de asemenea, o cauză a repartiţiei neuniforme a presiunii dintre bandaj şi role care, prin urmare, amplifică uzura acestora. Uzura bandajelor sporeşte şi datorită apăsării neuniforme a tamburului pe reazeme (”lăsării” reazemelor) , unele dintre acestea fiind mai mult sau mai puţin încărcate faţă de celelalte. Creşterea încărcării unui reazem de 1,5…2,0 ori faţă de cea normală (teoretică) se întâlneşte frecvent în practica exploatării cuptoarelor rotative pentru clincher de ciment. În aceste cazuri tensiunile de strivire a bandajului în zonele de contact cu rolele de rezemare ating valori de 400…600 MN/m2 [9]. La asemenea valori ridicate ale presiunii de contact, rostogolirea bandajului pe rolele de rezemare are loc în alte condiţii, în funcţie de durităţile oţelurilor utilizate pentru realizarea bandajului şi rolelor, suprasolicitările acestora, durata de funcţionare etc., putând să apară lipituri între suprafeţele bandajului şi rolelor, modificarea structurii oţelurilor acestora, tensiuni remanente etc. Un alt fenomen negativ privind funcţionarea bandajului îl reprezintă încălzirea neuniformă a acestuia, temperatura fiind mult mai mare în interiorul bandajului şi mai mică la suprafaţa lui. Din cauza încălzirii neuniforme în bandaj apar tensiuni termice (din temperatură) care pot avea valori importante, îndeosebi în cazul bandajelor în formă de cheson (cu goluri interioare). Uzura bandajelor se datorează şi faptului că, după fabricare, ele se abat de la forma cilindrică corectă, prelucrarea mecanică bandajelor cu diametre de 4,5…5,5 m realizându-se cu dificultate. În condiţiile în care bandajele sunt fabricate şi realizate corect ele trebuie să aibă o durată de serviciu, fără reparaţii, de circa 15…20 ani. Această durată de viaţă este cu atât mai necesară cu cât bandajele cuptoarelor rotative actuale, fiind de dimensiuni şi greutăţi din ce în ce mai mari prezintă dificultăţi de execuţie şi se realizează întru-un timp mai îndelungat.

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Una dintre măsurile pentru sporirea duratei de serviciu a bandajelor constă în reducerea uzurii acestora prin mărirea durităţii suprafeţei lor de lucru, ceea ce prezintă însă serioase dificultăţi tehnice. 5. CONCLUZII La funcţionarea normală a cuptorului rotativ, în timpul rotirii tamburului, acesta are şi o mişcare în lungul axei lui, în anumite limite, alternativ, când spre capătul inferior, când spre cel superior. Această mişcare longitudinală alternativă a tamburului pe reazeme contribuie la buna funcţionare a tuturor subansamblurilor componente ale cuptorului rotativ: grupuri de rezemare, angrenajul coroană dinţată-pinion al sistemului de acţionare, etanşări de capăt. Funcţionare în condiţii normale a cuptorului rotativ necesită ca elementele componente ale grupului de rezemare să fie realizate, montate şi reglate corect. Lipsa paralelismului dintre axele bandajului şi rolelor de rezemare conduce, datorită apăsării pe muchie, la reducerea ariei petei de contact şi, prin aceasta, la creşterea tensiunii de contact dintre bandaj şi rolele de reazem. Din această cauză, în timp, bandajul se uzează neuniform, căpătând treptat o formă tronconică, ceea ce conduce la accentuarea neuniformizării apăsării pe lăţimea lui şi, prin urmare, la accentuarea uzării. Creşterea apăsării pe reazeme de 1,5…..2,0 ori faţă de situaţia normală apare frecvent exploatarea cuptoarelor rotative fie ca urmare a « lăsării » accidentale a unora dintre reazeme, fie din cauza alinierii incorecte a acestora la montare. Acestea supraîncărcări conduc la exfolierea materialului suprafeţei exterioare a bandajului însoţită de o serie de aspecte negative specifice (creşterea rezistenţei la rotire a cuptorului pe reazeme, accentuarea uzurii etc.). Pe lângă cauzele amintite, uzarea suprafeţelor exterioare ale inelelor de rulare se datorează şi altor factori: pătrunderea în zona de contact dintre bandaj şi role a unor impurităţi abrazive (particule solide, praf etc.), răcirea neuniformă a bandajului, lipsa lubrifiantului din zona de contact dintre bandaje şi role etc.

BIBLIOGRAFIE [1] Ene, Gh., „Instalaţii termotehnologice pentru industria cimentului”, Editura Printech, Bucureşti, 2010. [2] Jinescu, V. V., „Utilaj tehnologic pentru industrii de proces”, IV, Editura Tehnică, Bucureşti, 1989. [3] Iordache, Gh., Ene, Gh., Rasidescu, M., „Utilaje pentru industria materialelor de construcţii”, Editura Tehnică, Bucureşti, 1987. [4] Renert, M., „Calculul şi construcţia utilajului chimic”, vol.II, Editura Didactică şi Pedagogică, Bucureşti, 1971. [5] Ene, Gh., „Inelele de reazem ale agregatelor cu tambur rotativ. Aspecte privind calculul de rezistenţă”, în Revista de Chimie, 52, nr. 1-2, 2001, p. 28 – 33. [6] Ene, Gh., „Calculul inelelor de reazem ale agregatelor cu tambur rotativ”, II. Aspecte privind calculul de rigiditate, Revista de Chimie, 53, nr. 6, 2002, p. 456-459. [7] Ene, Gh., „Inele de reazem ale agregatelor cu tambur rotativ III. Aspecte privind montarea şi comportarea în funcţionare”, Revista de Chimie, 54, Nr. 2, 2003, p. 140 – 141. [8] K. Swartzentruber, „Analytical and finite element modeling of rotary kiln riding rings”, Thesis presented to the Faculty of Bucknell University, U.S.A., december, 2004. [9] Boganov, A. I., „Vraşciaiusciesia peci ţementnoi promîşlenosti”, Izd. Maşinostroenie, Moskva, 1965. [10] Andersen, K. T., „Belasten und Überlasten von Ofenunterstützungen”, Zement – Kalk - Ghips International, Nr. 4, 1961. [11] Jensen, F.E., „Self-aligning support rotary kilns”, VDZ Kongress 1977, Verfahrenstechnik der Zementherstellung Bauverlag GMBH.

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INFLUENCE OF THE FEED ON THE PRINCIPLE QUALITY AND ACCURACY INDICATORS

AT THE SPD PROCESSING OF THE INVOLUTES TOOTH

Gheorghe Mareş

TRANSILVANIA Univesity of Braşov, ROMANIA, e-mail: [email protected]

REZUMAT Procesul de prelucrare prin deformare plastică superficială a flancurilor active ale danturilor evolventice ale angrenajelor cilindrice se aplică în scopul îmbunătăţirii microdurităţii şi a rugozităţii acestora. Performanţele procesului sunt influenţate de: parametri regimului de deformare, forţa de deormare, de proprietăţile fizico-mecanice ale piesei de prelucrat,etc. În lucrare autorul prezintă influenţa vitezei de avans asupra microduritaţii HV, rugozităţii Ra şi indicilor de precizie ai danturii: lungimea peste dinţiW, grosimea dintelui Sc, eroarea de profil Ffr şi toleraţa la bătaia radial Fk.

ABSTRACT: The processing trough Superficial Plastic Deforming (SPD) of the spur gear is a final cold-work hardening and finishing process of the superficial stratum. Quality and accuracy of the processing are influenced by the deforming parameters regime, deforming force, physical and mechanical properties of the work piece and by the cooling and lubricating regime. In this paper the author presents the influence of the feed over the roughness Ra, micro hardness HV of the tooth flank and over the processing accuracy. This influence is given by the next terms: length over the tooth W, teeth thickness Sc, profile error Ffr and tolerance from teeth striker Fk.

KEY-WORDS: feed, tool-life, involute worm, hardness, roughness, teeth.

CUVINTE CHEIE: viteză de avans, durabilitate, melc evolventic, duritate, rugozitate, dantură.

1. INTRODUCTION

The final manufacturing processing of the spur gears, using the special involute worms, is characterized by the next high performances: a good quality and accuracy, a more productivity and high life of the deformation tool. The cinematic of the process is

simple (figure 1), the machine-tool used can be a universal milling-machine. The deformation tool used is a special involute worm, which process the spur gear through superficial plastic deformation.

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mailto:[email protected]


Figure 1. The cinematic of the process.

2. EXPERIMENTAL EQUIPMENT

• Machine-tool – gear-cutting machine, type FD400;

• Working spur gears was fabricated from steel OLC45 with: the hardness 195-210HB, tooth number- 26, 29, 33, 36, the module – 3mm, 3,5mm, the spur gear wide – 12mm, 25mm.

• Special involute worms used are: ZE 1*3,5*25/dr. STAS 6845-82 with: D0=88mm and f1=2mm, f1=4mm, f1=6mm; ZE 1*3*28/dr. STAS 6845-82 with D0=84mm and f1=3mm; ZE 1*3*26/dr. STAS 6845-82 with D0=78mm and f1=mm.

• The special involute worms was fabricated from steel C120 heat treatment at 62-63HRC.

• The process passes in the cooling and lubricating regime.

• The measurement apparatus used are: 1. For the profile error Ffr and tolerance from

teeth striker Fk measurement it was used PFS 600 apparatus, made by KLINGELNBERG Company;

2. For the roughness measurement it was used FORM TALYSURF apparatus, made by TAYLOR HOBSON Company;

3. For the microhardness measurement it was used AKASY apparatus, with 1daN load, made in Japan.

3. EXPERIMENTAL RESULTS AND CONCLUSION The experimental results are presented in the table 1. Table 1.

N0.

test

v

minm

va

minmm

f1

[mm]

Ra

[m]

Hv

2mmdaN

cS

[mm]

W3

[mm]

ffr

[m]

Fk

[m]

1 46,53 11,2 3,0 0,92 224 5,042 27,610 0,011 0,012

2 56,33 11,2 3,0 0,65 229 4,911 27,150 0,010 0,013

3 73,48 11,2 3,0 0,47 238 4,880 27,042 0,010 0,012

4 56,33 8 3,0 0,91 217 4,923 27,149 0,012 0,012

5 56,33 14,5 3,0 0,97 223 4,859 26,968 0,013 0,013

6 56,33 22,5 3,0 1,23 234 4,862 26,979 0,011 0,013

7 56,33 11,2 2,0 0,80 214 4,903 27,122 0,011 0,012

This image cannot currently be displayed.

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3.1 The influence of the feed va upon the roughness Ra

Va RaVa=8 910Va=14,5 970Va=22,5 1230Scara: *1000

The roughness Ra

0200400600800

100012001400

Va=8 Va=14,5 Va=22,5

Va

Ra

Ra

The exponential equation of the roughness

y = 760.4e0.1507x

0

500

1000

1500

Va=8 Va=14,5 Va=22,5

Va

Ra

RaExpon. (Ra)

0200400600800

100012001400Ra

Va=8 Va=14,5 Va=22,5Va

The roughness Ra

Ra

Figure 2. The influence of the feed va upon the roughness Ra

The conclusion: at the increase of the feed with 81.12%, the roughness increases with 35.1%.

82


3.2 The influence of feed va upon of the microhardness Hv

Va HvVa=8 217Va=14,5 223Va=22,5 234

The Microhardness

205

210

215

220

225

230

235

240

Va=8 Va=14,5 Va=22,5

Va

Hv

Hv

The exponential equation of the Microhardness

y = 208.24e0.0377x

205210215220225230235240

Va=8 Va=14,5 Va=22,5Va

Hv

HvExpon. (Hv)

205

210

215

220

225

230

235Hv

Va=8 Va=14,5 Va=22,5Va

The Microhardness

Hv

Figure 3. The influence of feed va upon of the microhardness Hv

At increase of feed with 81.12%, the microhardness increases with ~7.8%.

83


3.3 The influence of feed v upon the “Sc’, “W3”, Ffr” şi “Fk” accuracy index Va Sc W3 Ffr FkVa=8 492,3 271,94 120 120Va=14,5 485,9 269,68 130 130Va=22,5 486,2 269,78 110 130Scara: *100 *10 *10000 *10000

0

50

100

150

200

250

300

350

400

450

500

Va=8 Va=14,5 Va=22,5Va

ScW3FfrFk

ScW3FfrFk

y = 3,35x2 - 16,45x + 505,4

y = -5x2 + 25x + 100

y = -15x2 + 55x + 80

y = 1,18x2 - 5,8x + 276,56

0

50

100

150

200

250

300

350

400

450

500

Va=8 Va=14,5 Va=22,5

Va

ScW3FfrFk

ScW3FfrFkPoly. (Sc)Poly. (Fk)Poly. (Ffr)Poly. (W3)

84


Va Sc W3 Ffr FkVa=8 492,3 271,94 120 120Va=14,5 485,9 269,68 130 130Va=22,5 486,2 269,78 110 130Scara: *100 *10 *10000 *10000

Sc W3 Ffr Fk0

50100150200250300350400450500Sc

W3FfrFk

Sc W3 Ffr FkVa

Va=8Va=14,5Va=22,5

Figure 4. The influence of feed va upon the “Sc’, “W3”, Ffr” şi “Fk” accuracy index

Those results it can be see the slight influence of the feed upon the accuracy index. These indexes improve only with 0.012-0.015%. :

REFERENCES [1]. Gh. Mareş, “Contributions at the tools geometry optimization used to levelness of the active teeth areas”. Master’s degrees,“TRANSILVANIA” University of Braşov, 1998. [2]. Gh. Mareş, “Reasearches with reference to final processing of involute form tooth using the special worm with involute profile”. Sofia, Bulgaria, 2004, pp 103-109. [3]. Mil’Stein M.Z. “The fashioning of the spur gears”. Technical Publisher, Kиеv, 1978

85


PRINCIPALELE PROBLEME ALE TEHNOLOGIEI PRELUCRĂRII METALELOR PRIN DEFORMARE

PLASTICĂ LA RECE

Teodor Sima

University Politehnica of Bucharest, Bucharest, ROMANIA, e-mail: [email protected]

REZUMAT În lucrarea de faţă se prezintă principalii parametrii tehnologici la prelucrarea prin deformare plastică la rece şi determinarea acestora în cazul curbării pe maşini cu cilindri rotativi. ABSTRACT In this paper the main technological parameters of manufacturing through plastic cold deformation are reviewed and their calculation in the specific case of bending on machines with rotational cylinders is considered. KEYWORDS: Deformation load, deformation degree, deformation precision, stresses, deformations, curvature radius. CUVINTE CHEIE: Efort de deformare, grad de deformare, precizia deformării, tensiuni, deformaţii, rază de curbură.

La elaborarea proceselor tehnologice, la proiectarea sculelor şi a echipamentelor de prelucrare prin deformare plastică la rece, atât tehnologii cât şi proiectanţii întâmpină dificultăţi la determinarea unora dintre parametrii tehnologici. 1. PRINCIPALII PARAMETRII

TEHNOLOGICI 1.1. Efortul necesar pentru deformare. Pentru calculul de rezistenţă al echipamentului şi a sculelor, în majoritatea cazurilor este suficientă cunoaşterea efortului maxim necesar deformării. Pentru alegerea corectă a echipamentului şi mai cu seamă la proiectarea echipamentelor mari, este necesar să fie cunoscută legea variaţiei efortului consumat în timpul deformării. 1.2. Formele şi dimensiunile cele mai raţionale ale semifabricatului iniţial. Alegerea corectă a formei şi dimensiunilor semifabricatului permite obţinerea pieselor cu deşeuri minime, iar în unele cazuri (ştanţarea), prin alegerea unui semifabricat de precizie, se poate renunţa la unele prelucrări manuale (debavurarea) sau să fie redus volumul de muncă pentru astfel de prelucrări.

1.3. Gradul maxim de deformare care poate fi suportat de material în condiţii concrete de deformare, fără ca în materialul semifabricatului să se producă distrugeri superficiale sau interioare (microfisuri). Cunoaşterea limitei începutului distrugerii este necesară pentru a se evita distrugerea materialului piesei în timpul prelucrării sau în timpul exploatării acesteia. 1.4. Gradul de deformare necesar transformării semifabricatului în piesă finită de o formă dată. După determinarea acestuia şi cunoscând gradul admisibil de deformare al materialului în timpul unei faze de prelucrare, tehnologul va putea să determine numărul fazelor necesare precum şi forma semifabricatului astfel încât să poată fi obţinută piesa cu volum minim de muncă şi cu cheltuieli minime. 1.5. Precizia pe care o poate asigura procesul tehnologic elaborat (adică, gradul de corespondenţă dintre forma şi dimensiunile piesei obţinute şi forma şi dimensiunile din desenul acesteia). Precizia trebuie să fie stabilită dinainte, pentru a avea posibilitatea de a alege varianta procesului tehnologic care să asigure obţinerea piesei cu volum de muncă minim şi la precizia prescrisă.

86


Pentru determinarea efortului necesar deformării la un moment dat, trebuie aflată legea repartiţiei tensiunilor pe suprafaţa de contact dintre piesa de prelucrat şi sculă. Prin însumarea acestora se poate determina mărimea efortului necesar. Pentru a stabili cea mai convenabilă formă a semifabricatului trebuie determinată poziţia pe care o ocupă punctele de pe semifabricat la începutul şi la sfârşitul procesului de deformare, adică deplasările acestor puncte. Gradul maxim admisibil de deformare depinde de proprietăţile fizico-mecanice ale materialului şi de schema stării de tensiune şi deformare în care acesta se află. Gradul de deformare poate fi determinat pe baza încercărilor mecanice ale materialului, efectuate la o stare de tensiune apropiată de condiţiile reale de deformare. Pentru alegerea numărului necesar de faze şi forma semifabricatului, cu condiţia ca deformaţiile la fiecare fază să nu atingă în nici unul din puncte valori periculoase din punctul de vedere al rezistenţei materialului, trebuie stabilită legea repartiţiei tensiunilor şi deformaţiilor în orice moment al deformării. Problema cea mai complicată o reprezintă calculul preciziei ce poate fi asigurată de procesul tehnologic proiectat. Pentru acest calcul, pe baza legii deformaţiei pasive, trebuie determinate deplasările punctelor semifabricatului supus deformării, la sfârşitul deformării, sub sarcină şi deplasările aceloraşi puncte, sub aceeaşi sarcină, pentru cazul când semifabricatul ar fi fost din material ideal elastic şi determinarea diferenţelor dintre aceste deplasări reziduale (remanente) ale punctelor materialului supus deformării. Cunoscând poziţia iniţială a acestor puncte şi deplasările reziduale, se poate afla poziţia punctelor după anurelarea sarcinii, adică forma şi dimensiunile piesei obţinute după deformare. Ca atare, pentru rezolvarea problemelor de mai sus, trebuie stabilite în momentele de deformare care interesează, fie legea repartiţiei tensiunilor sau deformaţiilor, fie deplasările punctelor semifabricatului sau şi una şi cealaltă. La rezolvarea problemelor practice ale deformaţiilor plastice, se recurge la unele ipoteze şi supoziţii. Cu cât aceste ipoteze şi supoziţii corespund mai mult cu realitatea, cu atât mai precise vor fi rezultatele calculelor, sau cu cât se impune un rezultat mai precis, cu atât premisele şi supoziţiile ce vor fi luate în considerare trebuie să fie mai aproape de realitate. Cele mai utilizate premise sunt următoarele: 1. În toate punctele corpului supus deformării, lipsesc deformaţiile în una dintre direcţii (starea de deformare plană). Ca exemplu la starea de deformare plană sau apropiată de aceasta îl poate constitui încovoierea unei table late, când deformaţiile în direcţia muchiei de încovoiere practic lipsesc.

2. În toate punctele corpului (piesei) supus deformării lipseşte tensiunea în una dintre direcţii (starea de tensiune plană). Cu oarecare aproximaţie, se poate considera că starea de tensiune plană poate fi considerată la curbarea unei table pe maşini cu cilindri de rotaţie, când tensiunea în direcţia grosimii tablei poate fi neglijată în raport cu valoarea tensiunilor în alte direcţii. 3. Axele principale ale tensiunilor şi deformaţiilor se consideră cunoscute. În aceste caz, axele de coordonate se aleg astfel încât direcţiile lor să coincidă cu direcţiile presupuse ale axelor principale. În acest caz tensiunile tangenţiale şi alunecările vor fi nule ceea ce simplifică mult calculele. 4. Deformaţiile şi tensiunile într–o anumită direcţie sunt repartizate uniform. 5. Toate punctele care au aparţinut unui plan sau unei drepte înainte de deformare, vor fi situate după deformare în acelaşi plan sau pe o singură dreaptă. Din această premisă face parte ipoteza secţiunilor plane, ipoteză admisă la încovoierea într–un singur plan şi ipoteza normalelor plane la formarea din tablă a unor piese cu curbură dublă. 6. Materialul semifabricatului nu ecruisează în procesul de deformare. Această ipoteză poate fi valabilă numai în cazul deformărilor la cald când deformarea plastică este urmată instantaneu de procesul de recristalizare. 7. Tensiunile tangenţiale pe suprafeţele de contact lipsesc, adică se neglijează forţele de frecare pe suprafeţele de contact dintre semifabricat şi sculele de lucru. 8. Repartizarea tensiunilor tangenţiale pe suprafeţele de contact urmează o anumită lege. În anumite cazuri se introduce ipoteza repartiţiei uniforme a forţelor de frecare pe suprafaţă. La rezolvarea problemelor prelucrării prin deformare plastică se pot lua în considerare una sau mai multe dintre ipotezele de mai sus care nu se contrazic una pe cealaltă. 2. DETERMINAREA PARAMETRILOR TEHNOLOGICI LA CURBAREA PRIN DEFORMARE PLASTIC LA RECE PE

MAŞINI CU CILINDRI ROTATIVI Principalii parametrii tehnologici la curbarea prin deformare plastică la rece pe maşini cu cilindri rotativi sunt: - efortul necesar deformării, consumat în timpul

procesului de deformare; - gradul maxim de deformare pe care îl poate suporta

materialul semifabricatului; - raza minimă de curbare; - precizia pe care o poate asigura prelucrarea.

87


2.1. EFORTUL NECESAR DEFORMĂRII

În majoritatea cazurilor, pentru calculul de rezistenţă al elementelor componente ale echipamentului de lucru, este suficientă cunoaşterea efortului maxim de deformare. Pentru alegerea corectă a echipamentului şi, mai ales, la proiectarea unor echipamente noi, este necesar să fie cunoscută legea de variaţie a efortului consumat în timpul procesului de deformare. Solicitările (eforturile) pe cilindri se determină pe baza unei scheme simplificate de curbare la o maşină cu dispoziţia simetrică a acestora (fig. 2.1). Raza de curbură a virolei între cilindri se consideră la fibra neutră.

Figura 2.1: Solicitări în cilindri la maşina de curbat

cu trei cilindri dispuşi simetric.

Din condiţia egalităţii momentului de încovoiere Mi , la cilindrul central (de presare) cu suma momentelor componentelor verticală şi orizontală a solicitărilor (eforturilor) pe cilindri laterali (Fl), se obţine:

,αsin

2

+

=sR

MF îl

(2.1)

sau, neglijând mărimea 0,5 s, mică în raport cu raza R:

,sinαRMF î

l = (2.2)

Din paralelogramul forţelor se poate determina solicitarea pe cilindrul central

αcos2 lc FF = (2.3) Prin înlocuire se obţine:

,

2

2

αtgsR

MF îc

+

= (2.4)

sau ,2αRtg

MF îc = (2.5)

Valoarea unghiului α (a cărui semnificaţie rezultă din figură), se determină cu relaţia:

lDRa+

=2

sinα . (2.6)

Pentru simplificarea calculelor se neglijează influenţa revenirii elastice (arcuirii) a materialului semifabricatului. Din compararea schemei cu dispoziţie simetrică a cilindrilor (fig. 2.1, a) cu schema în care dispoziţia cilindrilor este asimetrică (fig. 2.1, b) se constată că, pentru aceasta din urmă, solicitarea în cilindrul central (superior) este mai mare. În felul acesta se explică greutatea mai mare şi puterea mai mare a maşinilor cu cilindri dispuşi asimetric decât a celor cu cilindri dispuşi simetric. Momentul necesar rotirii cilindrilor în timpul curbării va fi:

'rîr MMM += (2.7)

în care: Mî reprezintă momentul de încovoiere a tablei (ce se consumă pentru deformare); '

rM — momentul ce se consumă prin frecarea de rostogolire a cilindrilor pe semifabricat şi prin frecarea de alunecare a acestora în lagăre. Mărimea momentului de încovoiere Mî poate fi determinată din condiţia de echilibru între forţele exterioare şi interioare. Momentul dat de tensiunile interioare care acţionează asupra unui element al semifabricatului de înălţime infinit mică dy (fig. 2.2.) este:

dybydFydM xx ⋅⋅⋅=⋅⋅= σσ (2.8)

Figura 2.2.

88


Momentul de încovoiere va fi egal cu momentul tensiunilor interne, care acţionează în înteaga secţiune şi va fi determinat de suma tensiunilor interne faţă de fibrele întinse şi, respectiv, comprimate ale secţiunii semifabricatului:

dyybdyybM xy

yxys

yîc ⋅⋅⋅+⋅⋅⋅= ∫∫

−σσ 0

00 (2.9)

în care: b reprezintă lăţimea grinzii (variabila by într-un caz general); σx – tensiunea nominală în direcţia tangenţială (funcţie de y). În cazul grinzii cu secţiunea dreptunghiulară (fig. 2.2, b):

dyybM xs

î ⋅⋅⋅= ∫ σ2/

0 2 (2.10)

În modul acesta, pentru determinarea momentului de încovoiere al semifabricatului, trebuie găsită legea variaţiei tensiunilor normale pe înălţimea (grosimea) semifabricatului. Dacă se consideră că direcţiile x, y şi z sunt direcţii principale, atunci:

0=== zxyzxy τττ (2.11) Se neglijează presiunea exercitată de fibre una asupra celeilalte, adică:

0=yσ . Deoarece la curbarea unei grinzi, deformaţiile în direcţie axială, practic lipsesc, se poate considera:

0=zε . În aceste condiţii se obţin relaţiile:

xi εε ⋅=3

2 (2.12)

şi

xi σσ ⋅=3

2 (2.13)

unde: εi este intensitatea deformaţiilor; iσ - intensitatea tensiunilor. Având în vedre relaţia σi=f(εi) şi considerând că stratul neutru trece prin mijlocul grosimii semifabricatului, momentul încovoietor va fi:

( ) dyyfbM i

s

î ⋅⋅⋅⋅⋅= ∫ ε2

0 322 . (2.14)

Cum: ( ) m

iiii kf εεσ ⋅== (2.15) adică:

m

xii k

⋅⋅= εσ

32 (2.16)

unde: k şi m sunt constante de material, înlocuind în relaţia (2.14), după transformări, se obţine:

dyykbMs

mmi

m

î ⋅⋅⋅⋅⋅

= ∫+

+ 2/

0

2

21

2

3

2 ε . (2.17)

În cazul deformaţiilor plastice mici, εx=y/R , atunci:

∫ ⋅⋅⋅

⋅⋅= +

+

+ 2/

0

1

21

2

3

2 s m

mm

im

î dyyR

kbM . (2.18)

Prin integrare se obţine:

( ) mm

mi

î

Rm

sbkM⋅+

⋅⋅= +

+

21

2

32. (2.19)

Dacă se admite că diametrele fusurilor celor trei cilindri sunt identice şi egale cu d, atunci, momentul consumat prin frecare va fi:

( )

++=

22 1

' dfFFM cr µ (2.20)

unde: f reprezintă coeficientul de frecare de rostogolire a cilindrilor pe tabla de curbat (f=0,8 mm); μ — coeficientul de frecare de alunecare a fusurilor cilindrilor în lagăre (μ=0,06 ... 0,1 în cazul cuzineţilor din bronz); d — diametrul fusurilor cilindrilor. Puterea necesară mecanismului de acţionare a cilindrilor, în cazul unei viteze tangenţiale v (viteza de avans a tablei) este dată de relaţia:

( )kW,2η⋅

=l

r

DvMN (2.21)

în care η reprezintă randamentul maşinii (η =0,7.... 0,8), iar v — viteza de avans a tablei (m/s). 2.2. GRADUL MAXIM DE DEFORMARE Prin grad maxim de deformare se înţelege gradul de deformare pe care îl poate suporta materialul semifabricatului fără ca în acesta să se producă distrugeri superficiale sau interioare (microfisuri). Cunoaşterea limitei de început a distrugerii este necesară pentru a evita distrugerea materialului, fie în timpul prelucrării, fie în timpul exploatării piesei. 2.3. RAZA MINIMĂ DE CURBARE Curbarea tablelor se poate face la rece sau la cald. Curbarea la rece are cea mai largă răspîndire. În timpul curbării la rece, materialul semifabricatului este deformat. Procesul curbării la rece poate fi aplicat atunci când materialul semifabricatului este deformat la un grad de deformare mai mic decît gradul critic. În cazul când deformarea depăşeşte gradul critic sau când puterea necesară deformării este mai mare decît puterea maşinii de curbat, se aplică curbarea la cald. Una din premisele ce stau la baza teoriei încovoierii plastice este ipoteza secţiunilor plane. Conform acestei ipoteze, secţiunile transversale ale tablei încovoiate rămân plane şi dirijate spre centrul de curbură în cursul întregului proces de încovoiere chiar dacă acesta s-ar termina prin distrugerea tablei.

89


Această ipoteză este perfect valabilă în cazul încovoierii pure, caracterizată prin aceea că momentul încovoietor este constant pe întreaga lungime a piesei ce se curbează. Încovoierea pură nu se întâlneşte în practică, însă ipoteza secţiunilor plane este acceptabilă în cazul când piesa capătă forma unei curbe fără variaţii bruşte ale curburii pe lungime. Deoarece la virolele ce se obţin prin curbarea tablelor pe maşini cu cilindri rotativi, curbura variază foarte puţin în lungul piesei, ipoteza secţiunilor plane poate fi considerată ca aproximativ justă. Adoptarea ipotezei secţiunilor plane permite exprimarea deformaţiei la întindere (sau compresiune) pe direcţie tangenţială, în orice punct, prin raza de curbură a piesei şi distanţa de la punctul considerat până la fibra neutră (fig. 2.3):

( )Ry

Ry

RyR

RddyR

x ≅

+=

+=

+= 1lnlnln

ϕϕε

(2.22)

Figura 2.3. Element de tablă curbată

Gradul de deformare se apreciază prin raza relativă de curbură r=R/s. Conform prescripţiilor ISCIR C4-78, dacă R/s>10, fibra neutră se consideră chiar fibra medie a grosimii. În acest caz, pentru fibra exterioară (y=0,5 s):

Rs5,0=ε (2.23)

Dacă R/s<5, gradul de deformare trebuie determinat ţinând seama de poziţia reală a fibrei neutre, iar relaţia (2.23) se corectează. Gradul critic de deformare corespunde unei anumite valori a lui ε, valoare ce depinde de calitatea oţelului, ca de exemplu:

%5,2...2=crε la oţeluri nealiate cu 0,10 ... 0,25% C;

%5,4...3=crε la oţeluri de construcţii;

%3=crε la oţeluri aliate cu Mn şi Mo. Rezultă că, pentru oţelurile carbon, poate fi aplicată curbarea la rece dacă:

sR )25...20(≥ . (2.24) Dacă R<(20 ... 25) s, curbarea se face la cald sau dacă se face la rece, se aplică un tratament termic de recristalizare fazică.

Intervalul temperaturilor de începutul şi sfîrşitul deformării se stabileşte după aceleaşi criterii ca şi pentru alte prelucrări la cald (forjare, matriţare etc). 2.4. PRECIZIA CURBĂRII Una din problemele tehnologice de bază şi cu consecinţe economice importante, o constituie determinarea preciziei pe care o poate asigura procesul tehnologic. Unul din factorii principali care influenţează precizia pieselor obţinute prin curbare pe maşini cu cilindri rotativi, îl constituie reculul (revenirea) elastic al materialului semifabricatului după ieşirea dinre cilindri maşinii. Determinarea revenirii elastice a materialului semifabricatului permite reglarea maşinii de curbat, astfel încât, cu un număr minim de faze acesta să capete forma şi raza de curbură prescrisă (necesară). Pentru determinarea valorii razei remanente de curbură Rr, după revenirea elastică a materialului, se porneşte de la egalitatea cunoscută:

IEM

RRî

r ⋅−=

11 (2.25)

în care: Rr reprezintă raza remanentă de curbură; R – raza sub sarcină, între cilindrii maşinii; Mî – momentul de încovoiere; E – modulul de elasticitate al materialului; I – momentul de inerţie al semifabricatului. Din relaţia (2.25), rezultă în cazul încovoierii elastice (Rr=∞)

IEM

Rî

⋅=

1 (2.26)

adică nu va exista niciun fel de curbură remanentă. Folosind ecuaţia (2.19) şi ştiind că momentul de inerţie al unei benzi de secţiune dreptunghiulară, este:

12

3sbI ⋅=

în care: b reprezintă lăţimea benzii; s – grosimea benzii. Din relaţia (2.25) rezultă:

mr

sR

Ek

m

RR−

−⋅⋅

+−

= 13

241

. (2.27)

Valoarea razei de curbură sub sarcină (R), poate fi determinată din considerente geometrice (fig. 2.4) şi are expresia:

( )( )hsD

asshDhR

l

i

−+⋅

+−+⋅−=

24

222

, (2.28)

90


în care: h, a, Dl au semnificaţiile din figura 2.4.

Figura 2.4.

3. CONCLUZII 1. Mărimea deformaţiilor, la solicitare dată, depinde de comportarea materialului semifabricatului. 2. La curbarea tablelor, pe maşina de curbat cu cilindri (fig. 2.4), raza de curbură sub sarcină, se poate determina, funcţie de geometria dispunerii rolelor, diametrul lor şi grosimea tablei, conform relaţiei (2.28). 3. Cunoaşterea valorii razei curburii remanente permite reglarea corectă a poziţiei cilindrilor maşinii de curbat. În acest scop, pentru o anumită valoare a razei curburii remanente ( )rR , trebuie calculată raza curburii sub sarcină R (între cilindrii maşinii de curbat) şi în funcţie de aceasta stabilită poziţia reciprocă dintre cilindri presori (de încovoiere) şi cilindrul central pentru fiecare tip de maşină de curbat.

BIBLIOGRAFIE [1] Raşeev, D.D., Oprean, I.D., „Tehnologia fabricării şi

reparării utilajului tehnologic”, Editura Didactică şi Pedagogică, Bucureşti, 1983.

[2] Drăgan, I., ş.a., „Tehnologia deformărilor plastice”, Editura Didactică şi Pedagogică, Bucureşti, 1979.

[3] Buzdugan, Gh., „Rezistenţa materialelor”, Editura Tehnică, Bucureşti, 1979.

91


REZEMAREA CIURURILOR VIBRATOARE PE ELEMENTE ELASTICE DIN CAUCIUC /

THE VIBRATING SCREENS BEARING SYSTEM WITH ELASTIC RUBBER ELEMENTS

Ene I. Gheorghe1, Prodea Iuliana-Marlena2

1 Universitatea POLITEHNICA din Bucureşti, e-mail: [email protected] 2 Universitatea POLITEHNICA din Bucureşti, e-mail: [email protected]

REZUMAT Lucrarea se concentrează asupra problemelor de proiectare referitoare la rezemarea ciururilor vibratoare pe elemente elastice din cauciuc. Este prezentată o metodă de calcul a acestor sisteme elastice de rezemare, iar în final, pentru a ilustra aplicarea metodei, este folosit un exemplu numeric.

ABSTRACT The paper focuses on design issues related to the vibrating screens bearing system with elastic rubber elements. A calculation method for this elastic support systems is presented. Finally, a numerical example is used to illustrate the application of this methodology.

KEYWORDS: vibrating screens; elastic bearing systems; elastic rubber elements CUVINTE CHEIE: ciururi vibratoare; sistem elastic de rezemare; elemente elastice din cauciuc

1. GENERALITĂŢI

Ciururile vibratoare inerţiale se utilizează pe scară largă pentru clasarea prin cernere a diferitelor tipuri de materiale granuloase, în numeroase procese tehnologice. Construcţia tipică a ciururilor vibratoare inerţiale (cu vibraţii circulare) cuprinde carcasa oscilantă 1 (în care sunt plasate 1÷4 site), rezemată prin intermediul elementelor elastice din cauciuc 2, pe cadrul fix 4 (fig. 1).

Figure 1. Ciur vibrator inerţial [10]:

1 - carcasa sitei; 2 – sistem elastic de rezemare;

3 – generator de vibraţii inerţial; 4 – cadru fix (batiu)

Vibraţiile carcasei sunt produse de către forţa centrifugă de inerţie a unor mase excentrice neechilibrate (contragreutăţi) (fig. 2) ale generatorului inerţial de vibraţii 3, antrenat în mişcare de rotaţie de către un motor electric.

Figure 2. Schema generatorului de vibraţii inerţial

Elementele din cauciuc 2, care intră în componenţa rezemării elastice a carcasei 1, pot fi înlocuite cu alte tipuri de elemente elastice: baloane din cauciuc umflate cu aer sub presiune (fig. 3); elemente din cauciuc, masive sau cu goluri (fig. 4); arcuri elicoidale din oţel etc.

92


Figure 3. Rezemare elastică cu baloane din

cauciuc [5]

Pentru a înlesni înaintarea materialului pe site, acestea se montează înclinate cu un unghi de 15…300 faţă de orizontală. Sub acţiunea generatorului de vibraţii, carcasa ciurului realizează oscilaţii după traiectorii circulare. În funcţie de raportul rigidităţilor axială şi transversală ale elementelor elastice de rezemare, punctele de pe carcasa ciurului din vecinătatea axei generatorului de vibraţii (vibratorului) descriu traiectorii mult apropiate de cerc, iar cele mai depărtate pot să aibă traiectorii eliptice sau liniare. Pentru a înlesni înaintarea materialului pe site, acestea se montează înclinate cu un unghi de 15…300 faţă de orizontală. Sub acţiunea generatorului de vibraţii, carcasa ciurului realizează oscilaţii după traiectorii circulare. În funcţie de raportul rigidităţilor axială şi transversală ale elementelor elastice de rezemare, punctele de pe carcasa ciurului din vecinătatea axei generatorului de vibraţii (vibratorului) descriu traiectorii mult apropiate de cerc, iar cele mai depărtate pot să aibă traiectorii eliptice sau liniare. Raza traiectoriei oscilaţiei depinde de raportul dintre masa carcasei sitei şi masa contragreutăţilor. Pentru domeniul de funcţionare supracritic (postrezonanţă), suficient de depărtat de rezonanţă, în care ω = (6…10)⋅p (p - pulsaţia proprie a sistemului vibrator), se poate scrie:

200

2 ωω ⋅⋅=⋅⋅ mrmA (1) unde A este amplitudinea oscilaţiei carcasei ciurului (raza traiectoriei circulare a vibraţiilor ciurului); m - masa totală a carcasei ciurului (inclusiv masa generatorului de vibraţii şi masa materialului supus cernerii, aflat pe sită); m0 - masa contragreutăţilor; r0 – excentricitatea acestora (distanţa de la axa de rotaţie la centrul de masă al contragreutăţii) (fig. 2). Analizând relaţia (1) se observă că amplitudinea oscilaţiilor nu este constantă, ea depinzând, pentru o construcţie de ciur dată (r0 şi m0 impuse), de cantitatea de material care se alimentează pe sită. La supraîncărcarea ciurului cu material, amplitudinea vibraţiilor scăzând, acestea tind să se amortizeze, conducând la reducerea eficienţei cernerii. La scăderea încărcării ciurului, eficienţa cernerii scade de asemenea, deoarece, ca urmare a creşterii amplitudinii oscilaţiilor, viteza materialului pe sită se măreşte, granulele materialului sărind peste ochiurile sitei. Prin

urmare aceste ciururi necesită o alimentare corectă şi uniformă cu material. Pentru ca ciurul vibrator să realizeze o cernere de calitate, trebuie ca amplitudinile vibraţiei Ax şi Ay, după direcţiile orizontală şi verticală, ale carcasei sitelor să se stabilească în funcţie de caracteristicile materialului supus cernerii şi de factorii tehnologici care influenţează asupra acesteia. Ciurul va vibra cu amplitudinile Ax şi Ay, dacă se determină în mod corespunzător atât momentul static m0∙r0 al maselor excentrice ale generatorului de vibraţii, cât şi constantele kx şi ky după direcţiile Ox şi Oy ale rezemării elastice a carcasei sitelor. Valorile constantelor elastice kx şi ky, necesare realizării vibraţiei ciurului cu amplitudinile Ax şi Ay, se asigură prin proiectarea adecvată a elementelor componente ale rezemării elastice. 2. CONSTRUCŢIA REAZEMULUI CU ELEMENTE ELASTICE DIN CAUCIUC Elementele elastice din cauciuc, datorită proprietăţilor şi caracteristicilor mecanice ale acestuia, prezintă o serie de avantaje în comparaţie cu arcurile elicoidale [2]: a. Valori reduse ale modulului de elasticitate la compresiune (E = 1,0...10,0 MPa), ceea ce face ca elementele elastice din cauciuc să se deformeze mult, putând să preia prin şoc un lucru mecanic de peste patru ori mai mare decât arcurile din oţel; b. Rigiditatea (constanta elastică) având valori foarte mici, sistemele de rezemare formate din elementele din cauciuc se caracterizează prin valori reduse ale pulsaţiei proprii ale ciurului; c. Factorul de amortizare este mult mai mare la cauciuc decât la oţel. Aceasta permite elementelor elastice din cauciuc să disipeze până la 30...35% din energia totală a vibraţiilor. De asemenea, datorită valorilor mari ale amortizării, amplitudinile vibraţiilor la rezonanţă ale maşinilor rezemate pe elemente elastice din cauciuc au valori de numai 10...20% din valorile amplitudinilor maşinilor rezemate pe arcuri din oţel. Din aceste motive, maşinile rezemate pe elemente din cauciuc, care funcţionează în postrezonanţă (şi trec atât la pornire, cât şi la oprire prin zona de rezonanţă), nu mai necesită şi elemente de amortizare aşa cum necesită aceleaşi maşini rezemate pe arcuri de oţel; d. În comparaţie cu alte materiale, viteza de propagare a sunetului prin cauciuc este foarte redusă şi anume de numai 0,9 % din viteza de propagare a acestuia prin oţel şi de numai 14 % din viteza de propagare prin aer (viteza de propagare a sunetului are valoarea de 45 m/s în cauciuc, de 340 m/s în aer şi de 5100 m/s în oţel). Datorită vitezei reduse de propagare a sunetului prin cauciuc, acesta are o capacitate mare de amortizare a zgomotelor. Folosirea elementelor elastice de cauciuc, în locul arcurilor de oţel, pentru rezemarea maşinilor cu turaţii mari conduce la

93


atenuarea semnificativă a zgomotelor produse în timpul funcţionării; e. La aceeaşi eficienţă a izolării vibraţiilor, elementele elastice din cauciuc au, în comparaţie cu arcurile metalice, gabarit şi greutate mai reduse; f. Cauciucul are rezilienţă mare în raport cu oţelul; g. Sistemele elastice de rezemare realizate din elemente de cauciuc au o stabilitate mai mare decât cele realizate din arcuri de oţel; h. Elementele elastice din cauciuc nu necesită întreţinere în exploatare; i. Elementele elastice din cauciuc sunt capabile să suporte solicitări ridicate de scurtă durată (suprasarcini accidentale); j. Rezemările elastice realizate din elemente de cauciuc se caracterizează prin simplitate constructivă şi greutate redusă. Elementele elastice din cauciuc prezintă însă şi unele dezavantaje: a. Elementele din cauciuc se degradează şi îşi pierd proprietăţile elastice sub influenţa agenţilor atmosferici sau a agenţi chimici agresivi (uleiuri, solvenţi, acizi etc.). Pentru a evita acţiunea nocivă a acestor agenţi agresivi sunt necesare măsuri adecvate de protecţie; b. Cauciucul "îmbătrâneşte" pe măsura trecerii timpului (după 5...20 de ani) şi se degradează pierzând proprietăţile elastice. Din acest motiv, la maşinile cu durată mare de serviciu trebuie prevăzute posibilităţi constructive pentru înlocuirea elementelor elastice din cauciuc degradate; c. La elementele elastice din cauciuc (natural sau sintetic) relaţia dintre tensiuni şi deformaţii este neliniară, iar valorile constantelor elastice variază mult în funcţie de compoziţia cauciucului; d. Temperatura de utilizare a elementelor elastice din cauciuc este limitată. De regulă, elementele elastice din cauciuc natural îşi păstrează caracteristicile elastice în intervalul de temperatură -40 0C…+200 0C, cele din cauciuc sintetic în intervalul -20 0C…+70...80 0C, iar cele din cauciuc siliconic în intervalul -75 0C…+200 0C. Pentru calculul de proiectare a rezemărilor diferitelor tipuri de maşini vibratoare care utilizează elemente elastice de cauciuc de diferite tipuri şi forme (cilidrice, prismatice) se pot consulta lucrările [2, 6, 7-9]. În cele ce urmează se prezintă construcţia unui tip deosebit de reazem pentru ciururile vibratoare (fig. 4), care utilizează elemente elastice din cauciuc de formă cilindrică, cu goluri (fig. 5).

Figure 4. Reazem elastic, pentru un ciur vibrator greu, format din elemente de cauciuc, cu goluri [4]. 1 – placa de reazem (fundaţia); 2 – placa superioară; 3 – elemente elastice cilindrice din cauciuc; 4 – elemente de distanţare ale acestora; 5 – element cilindric prin care ciurul se sprijină pe reazemul elastic.

La reazemul elastic din figura 4, între fundaţie şi placa de reazem a carcasei ciurului sunt plasate liber elementele elastice cilindrice din cauciuc 3, cu goluri interioare, ale căror axe de simetrie sunt orizontale. Pentru a-şi menţine poziţia în cadrul ansamblului acestea sunt distanţate prin utilizarea elementelor profilate 4. Elementele elastice au posibilitatea să se deplaseze în direcţia orizontală rotindu-se în cavităţile elementelor profilate 4, aceasta având ca efect reducerea încărcărilor dinamice, după orizontală, a fundaţiei ciurului. Cea mai mare deplasare are loc în timpul regimului tranzitoriu când amplitudinea vibraţiilor creşte brusc.

Figure 5. Element elastic cilindric din cauciuc,

cu gol interior Existenţa golului central din elementele elastice, pe lângă faptul că le sporeşte acestora elasticitatea, contribuie şi la răcirea mai bună a lor (arie mare a suprafeţei de transfer termic). Utilizarea acestor elemente în locul arcurilor elicoidale a permis reducerea amplitudinii la rezonanţă de aproximativ 3 ori (de la 45…50 mm în cazul arcurilor, la 16 mm), reducerea perioadei de trecere prin rezonanţă la 2…3 s, scăderea importantă a nivelului de zgomot [4]. 3. CALCULUL SISTEMULUI ELASTIC DE REZEMARE Ciururile vibratoare inerţiale sunt sisteme dinamice monomasice, excitate cu forţe perturbatoare armonice produse de generatoare de vibraţii cu mase excentrice în mişcare de rotaţie.

94


Generatorul de vibraţii, plasat în centrul de masă al maşinii, produce o forţă perturbatoare armonică al cărei modul este (fig. 2):

2000 ω⋅⋅= rmF (2)

unde m0 reprezintă valoarea masei excentrice sau, în cazul în care se utilizează mai multe mase excentrice care rotesc în jurul aceleiaşi axe, valoarea totală a lor; r0 - excentricitatea acestora (distanţa dintre axa de rotaţie şi centrul de masă al masei neechilibrate); ω - pulsaţia forţei perturbatoare (viteza unghiulară a arborelui generatorului de vibraţii). Excitat fiind de către generatorul de vibraţii, ciurul realizează vibraţii armonice după traiectorii circulare, cu amplitudinea Ax = Ay şi pulsaţia ω , egală cu cea a forţei perturbatoare. Pentru proiectarea sistemului elastic de rezemare al carcasei sitelor ciurului, care trebuie să realizeze vibraţii cu o anumită valoare a amplitudinii, este necesar să se cunoască: - amplitudinea vibraţiei după direcţiile orizontală şi verticală Ax = Ay; - pulsaţia forţei perturbatoare (viteza unghiulară a generatorului de vibraţii): ω; - masa sistemului vibrator (inclusiv masa generatorului de vibraţii şi masa materialului supus cernerii aflat pe sită): m; - raportul corespunzător regimului de funcţionare în postrezonanţă cu kω/p =ω/py (py – pulsaţia proprie a sistemului elastic după direcţia verticală); - factorul de amortizare după direcţia verticală: 2⋅ny /py. În vederea proiectării, se adoptă pentru sistemul de rezemare: - numărul total de elemente elastice: u; - caracteristicile mecanice ale cauciucului din care sunt realizate elementele elastice. Calculul se desfăşoară în următoarea succesiune: - se adoptă excentricitatea masei: r0 (fig. 2); - se determină masa excentrică a vibratorului [1, 3]:

y

y

ArA

mm−

⋅=0

0 ; (3)

- se corectează valoarea masei excentrice a vibratorului:

yy

y

AArA

mm−⋅

⋅=00

0 . (4)

unde A0y este factorul de amplificare [1, 3]:

21222

2

2

2

0

21

⋅+

−

=

yy

y

y

yy

ppn

p

pA

ωω

ω

(5)

- pulsaţia proprie a sistemului elastic, după direcţia verticală:

py k

p/ω

ω= ; (6)

- constanta elastică a sistemului de arcuri, după direcţia verticală [1 - 3]:

mpk yy ⋅= 2 ; (7) Amplitudinea la rezonanţă se determină cu relaţia:

yyr AAA 0⋅= (8) unde factorul de amplificare A0y este definit de expresia (5) în care 1/ =ypω . În această situaţie, relaţia (5) devine:

y

yy

pnA⋅

= 21

0 (9)

Pentru sistemul de rezemare de tipul celui prezentat în figura 4, se consideră un element cilindric din cauciuc, cu gol interior (fig. 5) comprimat între două plăci metalice (fig. 6). Parametrii solicitării la compresiune a acestui element elastic sunt definiţi de relaţiile [4]:

Rf

=α ; (10)

3

212δ

β⋅⋅⋅

=E

RPc (11)

unde f este săgeata elementului elastic sub acţiunea încărcării statice Pc, R - raza exterioară a elementului elastic, δ - grosimea peretului acestuia (fig. 6).

Figure 6. Stări de deformare ale elementului elastic

Interdependenţa parametrilor α şi β este reprezentată grafic în figura 7. Stării de deformare II din figura 6 îi corespunde curba 1 din figura 7, iar stării de deformare III, curba 2.

Figure 7. Interdependenţa parametrilor α şi β [4].

95


Cunoscând încărcarea statică Pc şi parametrii constructivi ai elementului elastic, cu relaţia (11) se determină parametrul β, iar cu valoarea acestuia, din figura 7, se determină parametrul α. În continuare, utilizând relaţia (10) se determină săgeata f corespunzătoare încărcării statice Pc şi apoi elasticitatea elementului:

fPk cy /= . (12)

Pentru 285,0==Rfα , starea de deformare II trece în

III, iar interdependenţa ( )αβ f= este dată de curba trasată cu linie continuă în figura 7. 4. EXEMPLU DE CALCUL Pentru exemplificare se consideră un ciur vibrator excitat de către un generator de vibraţii inerţial cu mase excentrice în mişcare de rotaţie. Sistemul elastic folosit pentru rezemarea carcasei sitelor este de tipul celui prezentat în figura 4. Se cunosc: - amplitudinea vibraţiei după direcţiile verticală şi orizontală: Ay=Ax =2,5 mm; - pulsaţia forţei perturbatoare: ω =100,55 s-1 (n=960 rot/min); - masa sistemului vibrator: m =650 kg; - regim de funcţionare în postrezonanţă cu kω =ω/py = 5; - factorul de amortizare după direcţia verticală: 2⋅ny /py = 0,3. Se adoptă pentru sistemul de elastic de rezemare: - numărul total de elemente elastice de rezemare: u=4 (patru reazeme, fiecare constând din câte un singur element elastic). Calculele se desfăşoară în următoarea succesiune: * Dimensionarea generatorului de vibraţii Ţinând seama de valorile date (impuse) pentru masa m a sistemului vibrator şi pentru amplitudinea Ay după direcţia verticală, calculul se realizează adoptând o valoare convenabilă din punct de vedere constructiv pentru excentricitatea r0, astfel încât să rezulte o valoare convenabilă m0 pentru masa excentrică: - se adoptă constructiv excentricitatea masei: r0 = 120 mm; - se determină masa excentrică a generatorului de

vibraţii: kgAr

Amm

y

y 16,140025,0120,0

0025,06500

0 =−

⋅=−

⋅= ;

- se determină factorul de amplificare:

( )[ ] 04,153,051

5

21

212222

2

21222

2

2

2

0

=⋅+−

=

=

⋅+

−

=

yy

y

y

yy

ppn

p

pA

ωω

ω

- se corectează valoarea masei excentrice a generatorului de vibraţii:

kg

AArA

mmyy

y

140025,0033,1120,0

0025,0650

000

=−⋅

⋅=

=−⋅

⋅=

Pentru generatorul de vibraţii se alege soluţia constructivă cu două mase excentrice plasate la capetele aceluiaşi arbore, fiecare având valoarea m0/2 = 7 kg. * Dimensionarea sistemului elastic de rezemare Pulsaţia proprie a sistemului, pentru regimul de funcţionare în postrezonanţă cu 5== yp pk ωω , are valoarea:

11,20555,100 === py kp ωω s -1. Constanta elastică a sistemului de rezemare, după direcţia verticală (relaţia (7)), este:

mNmpk yy /107,265011,20 522 ⋅=⋅=⋅= . Se adoptă pentru sistemul de rezemare un număr u = 4 elemente elastice, cu secţiunea transversală inelară, aşezate pe generatoare (fig. 3). Elementele elastice au coeficientul de formă Φ = 0,25 şi se realizează din cauciuc cu duritatea de 40 0Sh A. Caracteristicile mecanice ale acestui tip de cauciuc sunt prezentate în tabelul 1. Tabelul 1. Caracteristicile mecanice ale cauciucului

cu duritatea de 40 0Sh A [6] Caracteristica Valoarea

Modulul de elasticitate longitudinală static (pentru coeficientul de formă Φ = 0,25)

Est=1,6 MN/m2

Coeficientul de amplificare dinamic

φd = 1.05

Factorul de pierderi interne δ = 0,035 Factorul de formă al acestui tip de element elastic (fig.5) are expresia [2, 6]:

( )( ) h

dDhdD

dD

⋅−

=⋅+⋅

−⋅=Φ

44

22

π

π (13)

în care D este diametrul exterior; d – diametrul interior; h - lungimea.

96


Constanta elastică a unui singur element:

mNuk

k yy /10675,0

4107,2 5

5

1 ⋅=⋅

==

Forţa preluată de un element elastic:

N

ukAgm

P yc

18004

107,2105,281,9650 53

1,

=⋅⋅⋅+⋅

=

=⋅+⋅

=

−

Deformaţia (săgeata) elementului elastic:

mmmkPf c 26026,0

10675,01800

51

11 ==

⋅== .

Amplitudinea vibraţiei ciurului la trecerea acestuia prin rezonanţă:

mAAA yr 325,833,35,20 =⋅=⋅= unde A0y este factorul de amplificare la rezonanţă (relaţia (9)):

33,33,0

12

10 ==

⋅=

y

yy

pnA

(2∙ny/py = 0,3 – factorul de amortizare). Se constată că elementul poate prelua amplitudinea vibraţiei ciurului la trecerea acestuia prin rezonanţă (la pornirea şi la oprirea ciurului), (f1 > Ar). Adoptând diametrul elementului elastic D =200 mm (R=100 mm), mărimea parametrului α, pentru care rigiditatea elementului elastic are valoarea ky1, este determinată de relaţia (10): 26,0

100261 ===

Rfα .

Pentru α = 0,26, considerând că elementul elastic lucrează în starea de deformaţie II, din diagrama din figura 7 (curba 1) rezultă: β =2,7. Modulul de elasticitate longitudinal static al cauciucului are valoarea Est =1,6 MN/m2, iar coeficientul de multiplicare dinamic valorea φd =1, 05 (tabelul 1). Prin urmare, pentru modulul de elasticitate longitudinal dinamic rezultă valoarea Edin = Est∙φd =1,6·1,05 =1,68 MN/m2. Utilizând relaţia (11), se determină grosimea peretului elementului elastic din cauciuc:

mmmE

RP

din

c

5,360365,01068,17,2

1,0180012123

6

2

3

21

==

=⋅⋅⋅⋅

=⋅

⋅⋅=

βδ .

Celelalte dimensiuni ale elementului elastic sunt: - diametrul interior: d= D - 2∙δ= 200 - 2·36,5= 127 mm; - lungimea elementului (relaţia (13)):

mmdDh 7325,04127200

4=

⋅−

=Φ⋅−

= .

Transmisibilitatea vibraţiilor către fundaţie are valoarea [2]:

[ ]0416,0

035,051

035,01

1

1

222

2

2

22

2

=+−

+=

=

+

−

+=

p

p

p

T

δω

δ

în care, pentru cauciuc cu duritatea de 40 0Sh A, factorul de pierderi interne are valoarea δ = 0,035 (tabelul 1). Gradul de izolare a vibraţiilor [2]:

( ) ( ) %84,951000416,011001 =⋅−=⋅−= TI . Forţa dinamică transmisă fundaţiei [2]:

NTrMTFFT

14080416,055,10035,3 2

2000

=⋅⋅=

=⋅⋅⋅=⋅= ω .

5. CONCLUZII

Parametrii tehnologici ai procesului de cernere (debitul, eficienţa şi precizia cernerii) pot fi realizaţi dacă sunt bine stabiliţi parametrii dinamici ai ciurului (amplitudinea, frecvenţa şi traiectoria vibraţiilor). Pentru aceasta un rol important îl are sistemul elastic de rezemare al carcasei ciurului, care influenţează parametrii dinamici ai ciurului prin constanta sa elastică.

Constanta elastică se adoptă astfel încât pulsaţia proprie a sistemului să asigure, în afara parametrilor dinamici şi funcţionali ai ciurului, trecerea rapidă prin rezonanţă (la pornirea şi oprirea acestuia) şi transmiterea redusă a forţelor dinamice către fundaţia maşinii.

BIBLIOGRAFIE [1]. Ene, Gh., Echipamente pentru clasarea şi sortarea materialelor solide polidisperse, Editura Matrix Rom, Bucureşti, 2005. [2]. Ene, Gh., Pavel, C., Introducere în tehnica izolării vibraţiilor şi a zgomotului, Editura Matrix Rom, Bucureşti, 2012. [3]. Ene, Gh., Marin, C., Calculul şi construcţia maşinilor vibratoare, Editura Printech, Bucureşti, 2009. [4]. Vaisberg, L.A., Proektirovanie i rascet vibraţionnîh grohotov, Izd. Nedra, Moskva 1986. [5]. *** Prospect, firma Allis - Chalmaers, Miwaukee, Wiscounsin, USA. [6]. Bratu, P., Sisteme elastice de rezemare pentru maşini şi utilaje, Editura Tehnică, Bucureşti, 1990. [7]. Ene, Gh., Design of the Elastic System of the Vibrating Screens, Revista de Chimie, 60, Nr. 11, 2009, p. 1123-1128. [8]. Gh. Ene, Marilena Dănuleţ, Proiectarea sistemului de rezemare elastică a transportoarelor vibratoare elicoidale, Romanian Review Precision mechanics, optics & mecatronics, Nr. 39, 2011, ISSN 1548-5982, p. 167-173. [9]. Gh. Ene, Marilena Dănuleţ, Proiectarea morilor vibratoare rezemate pe elemente elastice din cauciuc, Sinteze de Mecanică teoretică şi aplicată, ISSN 2068-6331, vol. 2, nr. 1, 2011, p. 219-236. [10].http://www.clevelandvibrator.com/Product/39/1262/ems-electromechanical-vibratory-screener.aspx The Cleveland Vibrator Co., Cleveland, OH, USA.

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CAD-CAM SOLUTIONS FOR CNC MILLING OF 3D SURFACES USING FASC-14 SOFTWARE SYSTEM

Camil Lancea, Valentin-Marian Stamate

Transilvania University of Brasov, Brasov, ROMANIA, [email protected], Transilvania University of Brasov, Brasov, ROMANIA, [email protected]

REZUMAT Indiscutabil, prelucrarea suprafeţelor complexe trebuie realizată astăzi în contextul condiţiilor tehnico-ştiinţifice actuale. Aceasta presupune ca toate prelucrările să fie realizate în conformitate cu tehnica sistemelor CAD/CAM. De aici, ca şi din noile concepte de inginerie, precum ingineria modelării și simulării, dar şi din necesitatea luării în considerare a impactului tehnologicului asupra constructivului, rezultă că este necesar ca informaţiile geometrice, generate în palierul CAD-C (CAD - constructiv), să fie utilizate şi în palierul CAD-T (CAD - Tehnologic). Lucrarea prezintă o alternativă la utilizarea sistemelor software consacrate, de tip CAD/CAM/CAE, destinate proiectării și prelucrării CNC, prin frezare, a unor suprafețe complexe spațiale, definite de 4 curbe spline, utilizând freze cilindro-frontale sau cu freze cap sferic pentru prelucrare. Pachetul software prezentat, oferă facilităţi atât in faza de proiectare a suprafețelor, cât şi în faza de fabricaţie a acestora, prin proiectarea de meniuri pull-down personalizate și de comenzi specifice fazelor CAD CAPP și CAM, în limba română. Un alt avantaj, deloc de neglijat, al acestui sistem, îl constituie şi un cost de achiziţie mult mai mic decât cel al sistemelor consacrate existente pe piaţă: CATIA, ProEngineer, Solid Works etc.

ABSTRACT Absolutely, the manufacturing of complex 3D surfaces should be performed nowadays in accordance with the newest scientific and technical conditions. This implies that the parts manufacturing should be performed according with the CAD / CAM techniques. Hence, as well as the new engineering concepts such as modelling and simulation engineering and also because of the need to consider the technological impact over the constructive phase, it is necessary that the geometric information, generated within the CAD-C (CAD - Conception) stage to be used in the CAD-T (CAD - Technology) stage. This paper proposes an alternative for using established CAD / CAM / CAE systems, for CNC processing, by milling complex shape surfaces, generated with 4 spline curves, using end mills or ball nose mills. The software package presented in this paper offers facilities both for the surfaces designing phase and also for the manufacturing process phase, through the design of customized pull-down menus and commands specific the CAD CAPP and CAM phases in Romanian language. Another advantage, far from being insignificant, of this system, is a significantly lower acquisition cost than dedicated systems existing nowadays on the market: CATIA, ProEngineer, Solid Works etc.

KEYWORDS: CAD, CAM, Software, CNC Milling, 3D Surfaces, Optimizing CUVINTE CHEIE: CAD, CAM, Software, Frezare CNC, Suprafețe 3D, Optimizare

1. INTRODUCTION Since the problems caused by the world financial crisis, which took place several years ago and still hasn’t been totally removed yet, it is important that the purchases made by the companies, to be

accomplished in accordance with their specific needs, in order to avoid unnecessary expenses. In this regard, is necessary a good cooperation between the purchasing department and beneficiary departments.

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As mentioned before, in order to obtain the desired parts as quickly as possible, it is very important to consider the technological impact over the constructive phase. This means that it is necessary that the geometric information, generated within the CAD stage to be used in the CAM stage. To put this principle successfully into practice is very important that during the CAD phase all the information that is needed for the CAM phase to be structured and stored within the CAD/CAPP/CAM system. This approach to the problem requires that the CAD phase must be developed in accordance to obtain geometrical information with technological conections. This is possible through an analysis of the 3D model [1, 2], generated by using adequate graphics processors, with respect to the manufacturing parameters. The purpose is to prepare the CAD data for manufacturing on CNC systems (eg. profile curves obtained by cutting the 3D surface with a large beam of parallel planes). In accordance with the above presented problems, the paper proposes a CAD/CAPP/CAM software for processing 3D surfaces by milling, called FASC-14

(Frezarea Asistată a Suprafețelor Complexe 2014 – NC Milling of Complex Surfaces 2014). In this way, the complex surface generation is done by driving the cutting tool along the curves obtained by sectioning the surface with a beam of parallel planes. The manufacturing of complex surfaces is made by using end mills, during the roughing phase, and ball nose mills, during the finishing phase. The diameter of these mills depends on the surfaces curvature. This system is created, as a flexible manufacturing system [3], using AutoCAD, Visual Lisp and DCL language as base software for modeling and programming. 2. SOFTWARE MODULES [4] As mentioned before, FASC-14 software was developed with AutoCAD, Visual LISP and DCL language and is structured as shown in figure 1. FASC-14 has 5 different modules (figure 1): FASC-Input, FASC- Geometry (for the CAD phase); FASC- Manufacturing, FASC- Post processing (for the CAPP/CAM phase) and FASC-Simulation.

Figure 1. FASC-14 modules 3. SOFTWARE INTERFACE [4] The FASC-14 interface (Fig. 2) presents the software menus. Each menu contains a set of commands which

can be used for solving different problems such as file operations (open, close, save etc.), CAD commands (line, circle, spline etc.), CAM procedures (manufacturing possibilities), simulations or help.

File Draw Cutting parameters Milling path Help

Figure 2. The FASC-14 interface 4. FASC-I MODULE For designing the surface, FASC-14 program [5] offers three different modalities: • surface design using only FASC-14 functions; • surface generating using a bounded set of points,

as input data;

• importing the surface from other CAD systems,

as *.dxf, files; After the generation, the surface it is checked to determine the possibility to obtain this surface using exclusively 2½ axes or 3 axes NC milling machines.

FASC -I

FASC -G

FASC -S

FASC -P

FASC -T

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For incompatible surfaces (Fig. 3) the program displays error messages and recommends geometrical modifications.

5. CURVES DIVIDING If the surface tests pass, within the next stage, all the curves which define the surface will be divided in accordance with the manufacturing precision to be obtained (Fig. 4).

Figure 3. Incompatible surface for manufacturing on a 3 axis NC milling machine

Figure 4. Curve dividing in accordance with the manufacturing precision 6. INTERMEDIATE SURFACES FASC-14 software generates three different cutting paths, in accordance with the manufacturing process (fig. 5): • for roughing process; • for half-finishing process; • for finishing process;

The finishing surface geometry is computed to obtain the half-finishing and roughing surfaces [6, 7].

Detail

Incompatibility problems

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Figure 5. The intermediate surfaces

7. THE CUTTING PATH GENERATION In concordance with the above selected path orientation (Fig. 6 and 7), it will be determined the final cutting path for roughing, half-finishing and finishing processes.

As mentioned before, these paths can be computed for 3 axes NC milling machines and also for 2½ axes NC milling machines. Better images which reflect the differences between 2½ axes and 3 axis milling can be seen in a top view of the cutting path (Fig. 8).

Figure 6. A path orientation for roughing, half-finishing and finishing processes

Figure 7. A different path orientation for roughing, half-finishing and finishing processes

Figure 8: The differences between 2 ½ and 3 axes cutting path – top view

Roughing surface

Half-finishing surface

Finishing surface

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8. THE CUTTING PARAMETERS A dedicated procedure for cutting parameters calculation, created for rapid steel tools and inserts

tools as well, runs when selected Cutting parameters menu (Fig. 2). This menu contains also a shortcut for displaying the CAPP/CAM data input dialog window, represented in figure 9.

Figure 9: The CAPP/CAM data input dialog window

The data input dialog window offers different possibilities to determine the CAM strategy by: • choosing the tool material; • accepting the recommended tool diameter or not; • inserting the mill teeth number, asperities high,

breaking strain or cutting depth; • all inserted values were verified and error

messages will be displayed when incompatibilities are detected;

When successfully finishing the data checking process, a result dialog window will be displayed (Fig. 10) with the possibility to save all this results into a text file. After finishing all the calculations, the optimal cutting parameters and tool path must be sent to the NC machine. The postprocessor bill is to convert these values into NC commands used by the machine.

All converted data will be saved into one or more text files in accordance with the selected cutting operation. For a better management of the CNC programs, the software gives the possibility to insert different comments, having maximum 123 characters, at the beginning of each CNC program. When the selected input data is only for one metal cutting operation (roughing, half-finishing or finishing), a single dialog window, with the possibility to fill in a comment, will be displayed. When the selected input data is for two or three metal cutting operations (Fig. 11) other dialog windows will be displayed, with the possibility to insert different comments for each cutting operation as well(Fig. 12). This comment will be inserted at the top of the NC program.

Tool material

Tool diameter Recommended tool

diameter

Teeth number of mill

Asperities high

Breaking strain

Cutting depth

Error message

OK – Cancel - Help

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Figure 10. The results dialog window

Figure 11. Input data for the surface precision when using two or three successive operation

Figure 12. NC program generation for roughing, half finishing and finishing operations

Crossing feed Feed per tooth for the first cutting sweep

Feed per tooth for other cutting sweep Feed rate for the first cutting sweep

Feed rate for other cutting sweep Cutting speed for the first cutting sweep

Cutting speed for other cutting sweep Speed for the first cutting sweep

Speed for other cutting sweep

Cutting diameter Chip thickness

Save to file

One metal cutting operation Two or three metal cutting operation

Comment for the roughing NC file

Comment for the

half-finishing NC file

Comment for the finishing NC file

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When finishing all the tasks, the CNC program files are saved into text files having a *.fnc extension, because the software was developed for a FANUC post processor. CONCLUSIONS The FASC-14 software can be very useful for any company interested in the design and manufacturing of complex shapes surfaces. The software was created in accordance with simultaneous engineering concepts and its advantage, comparing with other CAD/CAM/CAPP similar products is that within the CAD phase an important volume of CAM information are determined for generating the NC program. Because of its costs advantages, this software package can be very useful for supporting the development of small and medium enterprises having activities in the field of NC manufacturing of complex shape parts. Some of the software benefits for the Romanian economy are: • the user-computer dialog is in Romanian

language and the software has also a Romanian help section;

• the software can be used with a low price software (AutoCAD - $4195 [8], CATIA - $34,700.00 [9], ProEngineer - $6,000 [10]) but the software runs as well on previous versions of AutoCAD with much lower costs;

• the software has an original mathematical algorithm which automatically generates the tool diameter and paths for roughing and half finishing phases, by using as input data the geometric information of the designed surface ;

In future the researches will aim to expand this system also for manufacturing revolved parts on NC turning machines.

REFERENCES [1]. Galvez, A., Iglesias, A., “From Nonlinear Optimization to

Convex Optimization through Firefly Algorithm and Indirect Approach with Applications to CAD/CAM”, Scientific World Journal, The Scientific World Journal, vol. 2013, Article ID 283919, 10 pages, doi:10.1155/2013/283919, ISSN: 1537-744X. 2013..

[2]. Galvez, A., Iglesias, A., Avila, A. “Immunological-based approach for accurate fitting of 3D noisy data points with Bezier surfaces”, 13th Annual International Conference on Computational Science (ICCS), ISSN: 1877-0509, Volume: 18, pp. 50-59, Edited by: Alexandrov, V; et. all., Published by : Elsevier Science Bv, Amsterdam, Netherlands, 2013.

[3]. Kostal, P., Mudrikova, A. “Laboratory of Flexible Manufacturing System”, Advanced Materials Research. - - Vol. 429 (2012), p. 31-36, ISSN 1022-6680(P). - ISSN 1662-8985(E).

[4]. Lancea, C., “CNC Milling Of Closed Contours Using Faci-13 Software System”, Tehnologia Inovativa Journal, ISSN 2248 - 0420; pp. 21-26, ISSN-L 2248 – 0420, Anul 65, Nr. 3-4 / 2013.

[5]. LANCEA, C., “CAD Solutions for NC Milling - Fasc-2000 Software”, The 1st International Conference on Computing and Solutions in Manufacturing Engineering - CoSME’04, Braşov-Sinaia, Universitatea TRANSILVANIA din Braşov, p. 198-201, ISBN 973-635-373-7, 2004.

[6]. Leung Y. S, Wang C. L., Zhang Y. “Localized construction of curved surfaces from polygon meshes: A simple and practical approach on GPU”, Computer-Aided Design Journal, vol. 43, no. 6, pp. 573–585, ISSN: 0010-4485, 2011.

[7]. Zhao,X., Zhang, C., Yang, B., Li P., “Adaptive knot placement using a GMM-based continuous optimization algorithm in B-spline curve approximation”, Computer Aided Design Journal, vol. 43, no. 6, pp. 598–604, ISSN: 0010-4485, 2011.

[8]. http://www.autodesk.com/products/autocad/buy [9]. http://www.worldcadaccess.com/blog/2012/05/whats-the-price-

of-catia.html [10]. http://www.deskeng.com/de/ptc-creo-revealed/

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Quick Info

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RESTITUŢIA STEREOSCOPICĂ A ACOPERIŞURILOR

Adina Oprea, Alexandru Valentin Rădulescu

Faculty of Mechanics and Mechatronics, University POLITEHNICA of Bucharest, ROMANIA,

E-mail: [email protected]

REZUMAT

Pentru realizarea unor modele 3D este necesară utilizarea unor metode eficiente care să reducă timpului de lucru şi să uşureze munca operatorilor. În acest context se creează un flux tehnologic continuu care să aducă la uşurarea realizării unor modele virtual realistice. ABSTRACT For 3D models, it is necessary to use some effective methods to reduce working time and lighten the work of operators. In this context it creates a continuous flow technology to bring the ease of achievin g realistic virtual models. CUVINTE CHEIE: Vectorizare, SNAP KEYWORDS: Vectorization, SNAP

1. INTRODUCERE

Restituţia stereoscopică reprezintă operaţia de extragere a informaţiilor (vectorizare). Este metoda cu ajutorul căreia se generează harta digitală a zonei respective în format vectorial care poate fi editată apoi cu softuri CAD sau GIS în vederea cartografierii automate, extrăgându-se în acelaşi timp şi punctele necesare modelării 3D.

Este metoda cu ajutorul căreia se generează harta digitală a zonei respective în format vectorial care poate fi editată apoi cu softuri CAD sau GIS în vederea cartografierii automate, extrăgându-se în acelaşi timp şi punctele necesare modelării 3D.

2. PROGRAMUL SNAP ÎN ARCGIS

În ArcGIS s-a implementat funcţia „snap” într-un program de intersecţie a unei linii cu un plan şi de proiecţie a unui punct pe plan.

Fig. 1. Programul SNAP în ArcGIS

Clădirile produc cele mai mari deformaţii în ortofotograme după cât sunt de înalte datorită perspectivei diferite în fiecare imagine. Din acest motiv este important să se vectorizeze acoperişurile în modul 3D şi să se proiecteze pe modelul terenului pentru a se genera corpul construcţiei respective.

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Pentru acoperişurile clădirilor vor fi generate aplicaţii simple care să minimizeze liniile ce urmează a fi vectorizate şi a mări astfel randamentul de producţie implementându-se astfel în softul ArcGDS funcţiile: snap 2D, snap 3D şi on a plane . 3. VECTORIZAREA

Fiecare faţetă din acoperişul fiecărui corp de

clădire este vectorizat separat ca poligon. De asemenea şi diferitele elemente ce pot

apărea pe acoperiş au fost vectorizate într-un layer separat, tot de tip poligon.

O atenţie sporită a fost acordată creării de elemente corecte din punct de vedere topologic, fiecare element al acoperişurilor fiind legat de elementul vecin pentru a nu exista spaţii libere. Un alt aspect important în această etapă este reprezentat de necesitatea ca toate elementele unei feţe să fie coplanare.

Pentru atingerea acestui deziderat, în ArcGDS s-a folosit funcţia „on a plane”, funcţie conform căreia, o dată selectate 3 puncte ce definesc planul, toate celelalte elemente vectorizate până la încheierea editării obiectului respectiv se află în planul delimitat de primele 3 puncte.

Fig. 2. Modul de utilizare a funcţiei „on a plane ”

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Fig. 3. Vectorizarea acoperişurilor

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Layerele de tip linie sunt folosite pentru a ajuta utilizatorul să vectorizeze corect acoperişurile respectând condiţiile geometrice. Acestea nu sunt folosite în procesul de modelare virtuală CityGML, fiind doar ajutătoare în vectorizarea din ArcGDS. Vectorizarea propriu-zisă se face folosind layerele de tip poligon, acestea fiind necesare modelului de date CityGML.

Utilizatorul trebuie să citească corect înălţimea colţurilor acoperişurilor cu ajutorul ochelarilor 3D şi mouse-ul special care permite mişcarea pe axa Z. Pentru finalizarea vectorizării unei faţade de acoperiş, poligonul trebuie obligatoriu închis, închiderea făcându-se pe primul punct de unde s-a început vectorizarea.

Vectorizarea în plan s-a facut cu funţia snap 2D, iar în spaţiu cu funţia snap 3D.

Fig. 4. Funcţia SNAP 2D din ArcGDS

Fig. 5. Funcţia SNAP 3D din ArcGDS

Pentru a respecta condiţiile de coplanaritate s-a folosit funcţia „On a plane” (fig. 9), aceasta permiţând vectorizarea în plan prin definirea a 3 puncte, restul fiind automat în acest plan până la închiderea vectorizării. După fiecare vectorizare se verifică în ArcScene dacă aceasta respectă condţiile geometrice, prin vizualizarea planurilor în 3D.

Fig. 6. Verificarea coplanarităţii planurilor în ArcScene

Un alt aspect important al generării suprafeţelor acoperişurilor o reprezintă condiţia de coplanaritate a faţadelor acestora, dar şi orientarea poligonului de contur astfel încât normala la suprafaţă să fie generată în exteriorul construcţiei şi nu în interior.

Această condiţie este utilă standardului CityGML dar şi altor softuri de modelare pentru ca efectele de umbrire sau însorire pe aceste planuri să fie conforme expunerii.

Planurile ce compun acoperişurile clădirilor sunt frecvent deosebit de complexe şi îmbinările dintre acestea sunt greu de realizat respectând matematic condiţiile de coplanaritate.

Pentru a genera astfel de suprafeţe, operatorul trebuie să construiască planurile acoperişurilor prin construcţia de paralele şi alte construcţii ajutătoare care să asigure coplanaritatea.

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Fig.7. Construcţii cu acoperişuri complexe

Pentru a respecta condiţiile de obţinere a

modelului 3D în standardul CityGML, poligoanele de contur ale suprafeţelor au fost create în sensul de rotaţie a acelor de ceasornic, dacă presupunem că privim fiecare

suprafaţă din exteriorul clădirii (Pentru construcţii cu acoperiş complex, suprafeţele se pot genera şi prin triunghiuri sau alte poligoane elementare (fig. 7).

Fig. 8. Vedere în perspectivă a construcţiilor cu acoperişuri complexe

Aşa cum se vede în fig. 7, fiecare element de suprafaţă de pe acoperiş se vectorizează separat, devenind în modelul 3D din CityGML nodurile arborelui

ce descrie construcţia în limbajul VRML sau X3D, ansamblul fiind de fapt o scenă X3Dscene.

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Fig. 9. Implementarea funcţiei “snap” pe plan în ArcGDS

Fig. 10. Rezultatul vectorizării în mod 3D

4. CONCLUZII Acest articol, se referă la restituţiei stereoscopică (vectorizarea) ce permite modelarea 3D a construcţiilor . În prezent, pentru a crea un model 3D este nevoie de multă muncă şi timp. Un soft de restituţie fotogrammetrică este necesar pentru îndeplinirea condiţiile de coplanaritate. Pentru respectarea acestor condiţii utilizatorul trebuie să cunoască foarte bine geomatria în spaţiu astfel încât să construiască planurile acoperişurilor prin construcţia de paralele ajutătoare care să asigure coplanaritatea.

Un dezavantaj al restituţiei stereoscopice îl reprezintă timpul de execuţie, ajungându-se să fie de ordinul a 100 de ore pentru un 1ha de construcţii complexe.

BIBLIOGRAFIE

1. Balotă, O., Generarea modelelor virtuale pentru localităţi utilizând tehnici de fotogrammetrie digitală, Teză de doctorat, Universitatea Tehnică de Construcții Bucuresti, 2009.

2. Balotă, O., Aerofotografierea digitală multiplă în sprijinul modelării virtuale realistice a localităţilor, Revista de Geodezie, Cartografie şi Cadastru, Vol. 18, Nr. 1-2, 2009, pp. 27-33.

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TEHNOLOGIA INOVATIVĂ – Revista „Construcţia de maşini” nr. 3-4/ 2014

NONLINEAR FINITE ELEMENT ANALYSIS FOR ENGINEERING APPLICATIONS

OF COMPRESSIBLE METALLIC FOAMS

I. Carciog1, A. Gavrus2, A. Belhadj3, S. Cananau1, F. Bernard2

1. Dep. Machine Elements and Tribology, Polytechnic University from Bucharest, ROMANIA 2. Laboratory of Civil and Mechanical Engineering (LGCGM, EA3913), INSA Rennes, FRANCE

3. Laboratory of Materials Science and Engineering (LSGM), Univ. of Sciences & Technologies Houari Boumediene, Bab-Ezzouar, Alger, ALGERIA

e-mail:[email protected]

ABSTRACT The present article proposes the improvement of a Finite Element Analysis (FEA) applied to the study of a metallic foam material submitted to a compression loading. The purpose of the study is to achieve a compressible model using the finite element method that will reproduce the experimental conditions and physical phenomena resulted while testing the sample on a test bench. Based on identified rheological input data, the model is used for two different samples geometries. The corresponding simulation results are compared with those obtained from a test bench. Starting from the obtained numerical results, conclusions will be made concerning the used numerical mesh and its geometry morphology. KEYWORDS: Metallic Foams, FEA, Simulation

1. INTRODUCTION

The Finite Element Method is a numeric approximation method that is used in order to reveal linear or nonlinear mechanical behavior of complex structures by dividing this one in small parts called finite elements. This method of analysis helps to reduce the production costs by removing other intermediate solutions that are more expensive and accelerates different parts manufacturing for production line by finding fast solutions for different geometry modifications on the already existing pieces or for prototypes. In addition, this method helps to improve the piece performance by finding fast and optimal solutions for its geometry and material conception. The model starts from discretized thermo-mechanical balance equations using adequate behavior laws describing the true tress – true strain constitutive relationships. In order to apply the finite element method, it is necessary to know what are the external loads, boundary conditions and material properties.

After the built of model it is verified for any convergence and precisions issues of the iterative calculus. Finally, the obtained results (in the range of some approximations) help the user to determine potential risk of the model prediction. Basically, a nonlinear analysis is caused by different modifications in material stiffness properties for a defined geometry and corresponding to different external loads intensity that are applied on the material structure. There are three types of nonlinearities: Geometrical nonlinearities that has two effects, one is caused by large geometry displacements and second is caused by flexion when compression loads are applied; Physical nonlinearities (material nonlinearities) caused by different modification on the material characteristics; Boundary nonlinearities caused by contact problems, displacement dependent boundary conditions. In this study, mechanical properties of metallic foam will be analyzed by a finite element method starting from previous experimental and numerical researches [1-12].

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Metallic foams are porous, low density materials that can have good mechanical properties. This type of materials can be used for low weight structures, acoustic absorption, vibrations control, shock absorbers, mechanical damping and buoyancy. Metallic foams can be made in three different ways: liquid metal, solid metal and metallic steam. Obtaining procedures for liquid metal: foaming by injecting gas in the molten metal, foaming using reactive chemicals, mold casting using wax polymer and gas-metal eutectic solidification (constant temperature). Obtaining procedures for a solid metal: foaming by using gas embedding, foaming by using empty spheres sintering, foaming by using powder sintering. Obtaining procedures for a metallic steam: foaming by vapor deposition. 2. EXPERIMENTAL STUDY 2.1 Material In this study, a Sn50-Pb50 metallic foam material is analyzed (Tin 50% and Lead 50%). Belhadj et al. [1] obtained samples of Sn-Pb metallic foam by mold casting of the liquid metal and using the salt particles with defined dimensions in order to create cavities in the sample. After solidification, the sample was introduced in water to dissolve the salt particles It is then obtained porous metallic foam cylindrical sample with medium porous cavities of 3.15 mm. Small samples are carried out in order to have dimensions of 30 mm x 6 mm (Fig. 1).

Fig. 1. Metallic foam Sn50-Pb50 [1]

2.2 Mechanical tests

In order to identify the mechanical properties of the Sn50-Pb50 sample, compression tests were made from a test bench [1,2]. The compression load was applied with a constant speed and the characteristic material diagram was determined until the starting point of complete material densification (Chart 1).

2.3 Experimental results During the experimental test, three main phases can be distinguished: a) at low displacements under small loads the material behavior is linear elastic;

b) under high loads, the cell walls fail because of the elastic buckling, plastic flow or fragile breaking; c) cell walls begin to make contact, resulting in a suddenly tension increase. The tensile stress is rising when the material starts to increase its density till it reaches the values of a material without cavities.

Chart 1. Conventional Characteristic material

diagram [2]

In the simulation model, the true stress – true strain hardening law of the foam was introduced as input data using a point by point data file (Chart 2).

Chart 2. Material input data diagram [2]

3. FINITE ELEMENT MODEL

PREPARATION 3.1 Study purpose The study is based on a comparison of results obtained by the finite element analysis of the metallic foam sample submitted to a compression load, and the experimental results obtained from the test bench. The purpose of the study is to achieve a predictive finite element model that can be used in future studies. The used software is Abaqus and the simulation was performed using the explicit version. The reason of using this time integration type is the use of updated time-displacement equations. Abaqus explicit function works very

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well in nonlinear analysis of compressible materials.

a. Model i. Software and workstation

description

In order to achieve the best results using the finite element analysis, firstly the Pre-treatment and Post-treatment was made via the code interfaces. The calculus launched on the Abaqus solver was processed using the following workstation: Processor Intel Quad Core 3.1 GHz, RAM memory 8Gb DDR3, Hard Disk 320 Gb, SATA2 port, 7200 rpm. The workstation performance will have direct impact over the solver time to run the calculus.

ii. Geometry Mesh

Based on the input data, a cylindrical sample was made with 30 mm in diameter and 6 mm of height. The geometry was initial meshed using axisymmetric linear elements of CAX4R type [2] (Fig. 2 Mesh 1). Also, a second mesh was performed on the geometry using C3D8 elements with the maximum element length of 1 mm (Fig.3 Mesh 2). In order to reach accurate analysis results, it is important to have a homogeneous mesh without any distortions between elements or high differences in elements length. For this case, the element length of 1 mm was chosen in order to reach a good balance between the geometry approximation and the number of elements generated. The elements number will have a direct impact on the analysis time spent on the server and the allocated storage space. The mesh achievement for any part in study is directly dependent to the user experience and it will have a direct impact over the analysis results.

Fig. 2. Mesh 1 [2]

CAX4R are axisymetric elements very similar to the eight-node shell element. These are linear, reduced-integration elements and expanded into C3D8 elements.

Fig. 3. Mesh 2

C3D8 is an 8 node linear hexahedral element, fully integrated with 2x2x2 integration points. The total number of elements for Mesh 2 is 5808 with a total of 7049 nodes. Analyzing previous simulation results obtained with the Mesh 1 [Fig.2], regarding the distribution plot of the material density after a compression of 1.5 mm, the Mesh 2 seems to be well improved then previous one, and it will be considered for all the following simulations.

iii. Material Properties In order to define the material properties for the metallic foam sample, in Abaqus was declared the “Crushable Foam plasticity model“ using “Isotropic hardening“ property. The “Isotropic hardening model“ uses an elliptic flow surface type, that is centered at the p-q plan origin. The material flow evolution is defined by the true stress – true strain variation σc obtained by uniaxial compression In this case, the tridimensional flow function can be defined as : F = sqrt ( q2 + a2p2 ) – B = 0 ( where : p=-(1/3)traceσ is the hidrostatic pressure, q= sqrt[(3/2)S:S] is the equivalent von Mises stress, S=σ +pI is the deflector tension and B= apc = σc*sqrt[1+(a/3)2] is the elliptic dimension on the q axis. (Fig.4)

Fig.4. Crushable material behaviour ([13])

The material density (ρ) is calculated from the initial relative density that was measured by experiment ρ/ρ0 =0.3349 and from the basic

Mesh 1 – CAX4R

Mesh 2- C3D8

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material density ρb=8.86*10-9 t/mm3. Considering this values, the initial material density used by Abaqus analysis is ρ=ρr*ρb=2.9672*10-9 t/mm3. The Young Modulus is defined by E=80000 MPa and because the sample hasn’t changed its diameter during the experiment, the Poisson Coefficient is chosen to be close to 0 (υ = 0).

iv. Loads and boundary conditions

To make possible the results comparisons, it is necessary to use the same loading conditions as they defined during the test bench experiment. The compression effort, as for the experiment, it evolves in time. In order to run a Dynamic Explicit calculus it is essential to determine the load value/displacement, applied in a specified time period. In this type of integration method, three different time increments must be considered: 1) First it is chosen the total time needed to apply the maximum displacement of 3.05 mm. Because no data concerning the maximum time needed to deform the part was given, a default period was taken as input data Tmax = 100 seconds (ex : for a Tmax = 100 sec --> Displacement Max = 3.05 mm --> Von Mises Max ). The time increment is 2.5 sec with a 2.5 % part deformation from the maximum displacement. 2) Second it is defined the solver time increment generally setting automatically by the software in order to ensure the calculus convergence (This is the solver convergence increment time, defined as an user option but it is recommended to chose the automatically option ). 3) Third, it is necessary to define the results time increment. Because the storage memory where the results are recorded is limited, it was established to get results at each 5 sec in order to reduce the file dimension ( i.e. tmax = 100 sec --> for each 5 sec, results will be recorded). The sample was embedded on one direction (restrictions on all degrees of freedom) and the load was applied on the other one. (Fig. 5)

Fig. 5. Model: Load / Embedded Conditions

v. Run of the simulation model on the server

After the check of model and definition of all variables values and material properties, the calculus is launched on the software solver. The files containing the input data have the extension .cae ( the model ) and .inp. The output data (results) are written in the .odb file. 4. NUMERICAL RESULTS 4.1 Cylindrical sample analysis For this analysis model, the total time spent on the server was approximately 2 hours. The variable studied here are: equivalent von Mises Stress [MPa] and Displacement [ mm ]. After the sample was submitted to a compression load, was obtained a maximum stress of 17.52 MPa corresponding to a maximum displacement of 3.038mm ( Fig. 6, Fig.7 ). The value is comparable with the one reveal during the experiment i.e.17.62 MPa, consequently the maximum difference between these two values is 0.56%. Concerning the diagram von Mises stress – plastic strain, the finite element analysis model give a comparable curve with the experimental one. (Chart 3). For both Von Mises values and Displacement, the fringe bars colors shows the area of stress concentration or the maximum displacement ( depending of the variable studied ). Color intensity represents the amplitude of the values from the lowest determined to the highest.

Fig. 6. Sample Displacement

Compression Load

Encastret

Displacement [mm]

Ttotal= 100 s U = 3.04 mm

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Fig. 7. Von Mises Stress distribution corresponding

to 3.038 mm of punch displacement

Chart 3. Von Mises Stress – Displacement curve comparison

4.2 Honeycomb sample analysis Based on previous finite element analysis the study assumes a second geometry to be tested in same conditions in order to reveal its mechanical behavior. The second structure is has a honeycomb geometry made of same material as the sample. Mesh properties are as follows: 2D shell Quad elements with 1 mm in length and membrane thickness of 2 mm. For this model, at a 3.4 mm displacement, the structure wall fails resulting very high stresses in material. The high stress is generated by the contact between structure walls (Fig. 8, Fig.9, Fig. 10). In Abaqus, the structure walls collapse can be physically represented by suddenly stress rising by excessively elements distortions.

If we go back few seconds before walls collapse, it can be seen that for 90s, the maximum stress when the structure is deformed with a displacement of 3 mm is equal to 8548 MPa (Fig.11, Fig.12). The obtained high value is caused by the local structure stiffness and especially by the missing of a failure criterion.

Fig. 8. Honeycomb Displacement Distribution

Fig. 9. Honeycomb Stress distribution for a compression time = 95 s

Von Mises Stress [MPa]

Displacement [mm]

Ttotal= 100 s U = 3.4 mm


T = 95 s

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Fig. 10. Honeycomb Stress distribution for

compression time = 100 s



5. CONCLUSIONS Based on the study presented above, the following conclusions can be made: 1. Conclusions regarding the finite element

analysis: a) The meshed used for the sample model was 1mm 3D hexahedral elements and for the honeycomb structure 1 mm 2D shell element (Quad); b) The time increment is calculated from a total time (ttotal) and the number of imposed displacements; c) The total time spent by the model on the server is directly dependent of the number of elements that define the structure mesh, of the number of variables needed to be recorded and of the output time increment;

2. Conclusions regarding the results: a) Concerning the sample model, the finite element analysis results are comparable with the experimental results; b) Differences between the analysis results and experimental results are around of 0.56%; c) The honeycomb structure analysis was made in same conditions as the cylindrical sample; d) Because of structure stiffness, the stress values corresponding to a honeycomb structure are greater; e) Between 95s and 100s, the honeycomb structure walls fail resulting high tensions in the foam material.

Starting from this numerical analysis of the foam material, based on obtained results and conclusions, the finite element model can be considered for feature studies, especially during an impact compression test.


T = 100s


T = 85 s


T = 90 s

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REFERENCES

[1] A. Belhadj, S.A. Kaoua, M. Azzaz, J.D. Bartout, Y. Bienvenu – “Elaboration and characterization of metallic foams based on tin–lead”, Materials Science and Engineering A, 494 (2008) 425-428. [2] Abd-Elmouneïm BELHADJ, Adinel GAVRUS, Mohammed AZZAZ, Fabrice BERNARD - “Mechanical properties characterization of tin-lead open-cell foams using upsetting experimental tests and finite elements modeling“, The 3rd International Conference on Advanced Manufacturing Engineering and Technologies, NEWTECH 2013 - Stockholm, Sweden, 28 – 30 October 2013, pp.25-34. [3] Gibson, L.J., Ashby, M.F., 1997. Cellular Solids: Structure and Properties, 2nd ed. Cambridge University Press, Cambridge. [4] Gibson, L.J. (Ed.), 2003. Cellular solids. [5] Wen-Yea Jang, Stelios Kyriakides: On the crushing of aluminum open-cell foams: Part I. Experiments. International Journal of Solids and Structures 46 (2009) 617–634. [6] Wen-Yea Jang, Stelios Kyriakides: On the crushing of aluminum open-cell foams: Part II analysis. International Journal of Solids and Structures 46 (2009) 635–650.

[7] D.P. Kou, J.R. Li, J.L Yu and H.F. Cheng: Mechanical behavior of open-cell metallic foamswith dual-size cellular structure: Scripta Materialia 59 (2008) 483–486; [8] Kwan Moo Ryu, Jae Young An, Won-Seung Cho, Yeon-Chul Yoo and Hyoung Seop Kim : Mechanical Modeling of Al-Mg Alloy Open-Cell Foams . Materials Transactions, Vol. 46, No. 3 (2005) pp. 622 to 625. [9] Sid-Ali Kaoua, Djaffar Dahmoun, Abd-Elmouneim Belhadj, Mohammed Azzaz: Finite element simulation of mechanical behaviour of nickel-based metallic foam structures. Journal of Alloys and Compounds 471 (2009) 147–152. [10] Guilherme da Costa Machado, Marcelo Krajnc Alves, Hazin Ali Al-Qureshi, Rodrigo Rossi: Constitutive modeling of the large strain behavior of crushable foams using the element-free Galerkin method. Mechanics of Solids in Brazil 2007. [11] Liang Cui, Stephen Kiernan and Michael D. Gilchrist: Designing the energy absorption capacity of functionally graded foam materials. [12] Wiwat Tanwongwan and Julaluk Carmai, Member, IAENG : Finite Element Modelling of Titanium Foam Behaviour for Dental Application Proceedings of the World Congress on Engineering, Vol III, 2011. [13] Abaqus Documentation.

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RESEARCHES REGARDING THE ACHIEVEMENT OF AN INTERVIEW QUESTIONNAIRE

FOR BUSINESS ENVIRONMENT AGAINST AN ECO-INNOVATION HUB

Irina Rădulescu, Florica Costin

POLITEHNICA University of Bucharest, S.C. ICTCM S.A. Bucharest, ROMANIA,

e-mail: [email protected]

REZUMAT Realizarea unui chestionar pentru întreprinderile ce activează în domeniul reciclării deșeurilor de echipamente electrice și electronice din România ridică multe probleme. Este necesară creșterea competitivității organizaționale a firmelor ce activează in acest domeniu, dar și o mărire a gradului de implicare a acestor entităţi în promovarea eco-inovării pentru dezvoltarea economiei verzi. Prin realizarea unui prototip de hub de eco-inovare se va obține o infrastructură de colectare și analiză a datelor, transparentă, ușor de accesat pentru publicul larg. Se va facilita transferul de know-how în domeniul eco-inovării, cu scopul de a îmbunătăți reciclarea deșeurilor de echipamente electrice și electronice și de a promova eco-inovarea. Chestionarul realizat este trimis la firme ce activează în domeniu, a căror experiență și competență poate fi utilă și altor actori interesați din zona DEEE.

ABSTRACT Development of a questionnaire for enterprises that is working in the Romanian recycling of waste electrical and electronic equipment raises many issues. It is necessary to increase organizational competitiveness of firms operating in this area, also to increase the degree of involvement of these entities in promoting eco-innovation for green economy development. By creating an eco-innovation hub prototype will get a transparent, easy to access infrastructure for collecting and analysing data. It will be facilitated the transfer of eco-innovation know-how, in order to improve the recycling of Electrical and Electronic Equipment Wastes and promote eco-innovation. The questionnaire is sent to companies that operate operating in this field, whose experience and competence may be useful to other stakeholders in the WEEE area. KEYWORDS: hub, Electrical and Electronic Equipment Waste, eco – innovation, enterprise, questionnaire

CUVINTE CHEIE: hub, deșeuri de echipamente electrice și electronice, eco-inovare, întreprindere, chestionar

1. INTRODUCTION

At international level, Waste Electrical and Electronic Equipment (WEEE) is one of the fastest growing sources of waste in the European Union.

At national level, one of the many activities of the Ministry of Economy and Commerce and the Ministry of Environment and Water Management is to transpose and implement the EU Directives governing the management of waste electrical and electronic equipment (WEEE), [1].

The Directives have been transposed into Romanian legislation through Government Decision No. 448/2005 and No. 992/2005, that are

accompagnied by Ministerial Orders No. 1225/2005, 1223/2005 and 901/2005. Also there are given many Directives and Laws regarding waste conditions and WEEE regime (the 2008/98/CE Directive regarding wastes, totally transposed, the 211/2011 and 187/2012 Laws regarding waste conditions, the 2012/19/UE Directive – regarding WEEE), [2].

The EU Directives and EU environmental policies state clearly that the industry has to accept the responsibility for taking back and recycling WEEE.

The adopted legislation requires an active participation of industry factors for compliance and enforcement of regulations on waste and WEEE management.

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At national scale, the responsibility is needed, all the factors must be involved, not only industry: academia, business environment and authorities.

The paper is part of research undertaken to achieve a virtual hub for eco-innovation for increasing the competitiveness in the recycling of waste electrical and electronic equipment. Requirements analysis of potential users of the hub of eco-innovation involved the investigation of academic and research institutions, public authorities and Business Environment.

Considering the „Virtual eco-innovation Hub for increasing the competitiveness in the recycling of waste electrical and electronic equipment (EcoInnWaste)” project the first activity requires an analysis of user requirements for the eco-innovation hub. In the project consortium S.C. ICTCM S.A. Bucharest was the partner responsible for analyzing business requirements. 2. THE ACHIEVEMENT OF A QUESTIONNAIRE FOR BUSINESS ENVIRONMENT AGAINST AN ECO-INNOVATION HUB

Researches made in EcoInnWaste project aim to answer to a challenge with profound economic, social and environmental implications. It is about increasing organizational competitiveness of firms operating in the recycling of waste electrical and electronic equipment (e-waste, WEEE) in Romania and increasing the involvement of public and private entities in promoting eco-innovation for developing green economy. A large number of challenges in e-waste recycling is facing against business environment and authorities. It aims to eliminate hazardous components and recovering bigger quantity of recyclable materials, in safe for humans and for the environment conditions.

Entrepreneurs (particularly SMEs) often face barriers in business development for the recycling of e-waste, especially in the implementation of eco-innovative technologies. For this achievement the needs of innovators must be visible and they must find support at the authorities level and also, at the business and research levels. The complex challenges of recycling WEEE implies a carefully and detailed analysis of user requirements for the eco-innovation hub, that involves finding principal issues of business environment.

Activities have focused attention on: 1. Drawing up a list of companies (micro,

small, medium and large) - representatives for Romanian business environment, that are operating in electrical and electronic equipment field or they have related activities in this area;

2. Consultation of existing information from the identified companies websites, for an accurate determination of products and services classification in the range of activities directly or related connected to WEEE domain;

3. Development of a questionnaire addressed to companies with questions about electrical and electronic equipment waste and eco – innovation issues and performing an investigation by distributing this questionnaire;

4. Processing of the received information from the replies to sent questionnaires;

5. Completion, analysis and drawing of conclusions regarding Romanian position and business environment requirements against WEEE and eco - innovation issues.

3. BUSINESS ENVIRONMENT ISSUES

The challenge of world countries is the development of economic opportunities connected to increasing environmental pressures. The transition to a greener growth pattern is well spread and every country has its own effort to expand policies and tools for sustainability. Taking into account the business environment and especially SMEs, they have an important role because they represent a great majority of production units and employment across most OECD and non-OECD countries. The transition to a greener growth pattern is crucial for the greening of the business sector,[3].

Studies made by the Organization for Economic Co-operation and Development consider that in short term costs may be incurred in this transition, but in the long term new firms, jobs and industries will be created as eco-innovations and sustainable models of existing systems across the world economy,[3].

It is important to focus on the contribution of business environment, SMEs and entrepreneurs to the transition to green growth, at international and national levels.

Their capacity to eco – innovation and their participation in emerging green industries represent the key to sustainability.

It is important to make known sustainable practices and eco – innovations made by SMEs and business entrepreneurs, as key drivers.

It is also important to show issues and barriers against green growth and have discussions about policies that must be developed to foster entrepreneurial endeavors and support SMEs’ transition to sustainable practices, in both manufacturing and services, [3].

Romanian legislation works for: - the prevention of waste electrical and electronic equipment and reuse, recycling and other forms of recovery of such waste types to reduce the amount of waste for disposal;

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- improving the environmental performance of all operators involved in the life cycle of electrical and electronic equipment (producers, distributors and consumers) and especially the businesses staff directly involved in the treatment of electrical and electronic equipment waste, [4]. The questionnaire was developed for

manufacturers, distributors and recyclers of the following categories of electrical and electronic equipment:

Category 1. Large domestic appliances Category 2. Small domestic appliances Category 3. Informatics equipment and telecommunications Category 4. Consumer equipment Category 5. Lighting Equipment Category 6. Electrical and electronic tools Category 7. Toys, leisure and sports equipment Category 8. Medical devices (exception of all implanted and infected products) Category 9. Monitoring and control instruments Category 10. Automatic dispensers.

Starting 2008, in Romania, the goal of collecting

WEEE is at least 4 kg waste / inhabitant / year. Despite efforts by the authorities and responsible

operators so far it was not reached the annual collection target of 4 kg / capita / year.

In the 2006 – 2010 period there was collected an amount of 91,540.87 tonnes of WEEE. Its distribution by year and category is shown in Table 1, [5]. Table 1. The distribution by collected WEEE categories [5]

Provided data emphasizes the importance of

business environment awareness regarding the possibilities of improving of WEEE collection and taking action towards an improvement in this area.

Collected WEEE are treated both in Romania and in other EU Member States. The difference between the collected ones and treated WEEE, during an year is stocked at collectors / treating traders. Statistical data show that:

- In 2007 there were treated 19.7% of collected WEEE;



- In 2010 there were treated 100% of collected WEEE and a part of stocked WEEE that were in stock at the beginning of the year, [5].

Concerning the annual increase of the collected

WEEE percentage, it can be justified both by energetic action of the authorities, and also by the

awareness and interest increasing of the business environment. Considering recovery targets imposed by legislation since 2008 and those made in 2008, 2009 and 2010 - there are presented in Table 2, [5]. Table 2. Recovery Objectives [5]

Concerning recovery objectives it is obvious their annual increase for all categories, also justified by authorities action/ legislation and by the business environment awareness.

The survey is the basis for EcoInnWaste project to increase organizational competitiveness of Romanian firms operating in the recycling of electrical and electronic equipment and to increase the involvement of Research – Development – Innovation public and private entities for promoting eco-innovation for green economy.

4. THE QUESTIONNAIRE FOR BUSINESS ENVIRONMENT AGAINST AN ECO-INNOVATION HUB

By analysing the Activities Classification of National Economy (CAEN codes) there were not found WEEE or eco - innovation specific activities separately coded, so the documentation for choosing companies was done by consulting the databases of the National Institute for Small and Medium Enterprises (INIMM) and Chamber of Commerce and Industry of Bucharest (CCIB), [6]. [7].

Documentation for the companies list achievement intended that the respondents belong to all types of companies: micro, small, medium and large. They must have the activity directly related to the WEEE production, distribution and recycling or working in areas related to this field.

INIMM and CCIB database consulting was supplemented by checking the information available on the companies websites selected for investigation.

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List made to disseminate questionnaires to conduct the survey comprises 658 companies, grouped by established categories.

The questionnaire has the purpose to analyse the behaviour and business requirements against WEEE and eco - innovation issues. The questionnaire consisted of 20 questions and it included:

- general questions about the company: - details about the company, specifying the scope

and the number of employees, its position in the category of EEE producers / distributors / recyclers;

- company certification, its degree of experience in the WEEE and eco – innovation, issues and experience developed in the field;

- questions to show the degree of interest in WEEE management and usefulness of a virtual hub for eco-innovation to increase the firm competitiveness:

- company interest for a specific issue (legislation, recycling, environmental impact, waste management policies, training, user behaviour, informal sector, etc);

- expected results from accessing an eco-innovation virtual hub for competitiveness increasing in WEEE recycling and possible useful tools;

- financial willingness to use the hub. The questionnaire was sent to the email address

of each company from the list, being accessible to any education level of the respondent; the responses will be centralized by the work team of SC ICTCM SA Bucharest partner.

CONCLUSIONS

The importance to achieve a questionnaire for the business environment against the conception and the use of an eco-innovation hub translates into obtain relevant and transparent information from the current society reality.

These data will form the foundation for the realization of necessary and useful tools that can bring a fresh impetus to modernization and development companies.

REFERENCES [1]. http://www.minind.ro [2]. http://www.mmediu.ro [3]. Working Party on SMEs and Entrepreneurship (WPSMEE) -GREEN ENTREPRENEURSHIP, ECO-INNOVATION AND SMEs, Final Report. CFE/SME(2011)9/FINAL. 04-Apr-2013. CENTRE FOR ENTREPRENEURSHIP, SMEs AND LOCAL DEVELOPMENT. OECD. [4]. H.G. nr. 1037/2010. Protecţia Mediului (ANPM): http://www.anpm.ro/articole/deseuri_de_echipamente_electrice_si_electronice-28 [5].74137_Informatii privind gestionarea deseurilor de echipamente electrice si electronice (DEEE) 25.07.2012.pdf [6]. Bazele de date ale Institutului Național pentru Întreprinderi Mici și Mijlocii (INIMM) [7].Bazele de date ale Camerei de Comerț și Industrie București (CCIB).

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