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METALURŠKI INSTITUT“Kemal Kapetanovic”

ZENICA

UNIVERZITET U ZENICI

http://www.mf.unze.ba/index.php?option=com_content&view=article&id=118&Itemid=107

Godina (Volume) 12, Broj (Number) 3-4, Juli - Decembar (July - December) 2015.

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ISSN 1512-5173 http://www.mf.unze.ba/index.php?option=com_content&view=article&id=118&Itemid=107

MAŠINSTVO ČASOPIS ZA MAŠINSKO INŽENJERSTVO

JOURNAL OF MECHANICAL ENGINEERING Godina (Volume) 12, Broj (Number) 3-4, Zenica, Juli – Decembar (July – December) 2015.Uredništvo (Editorial): Fakultetska 1, 72000 Zenica Bosnia and Herzegovina Tel: +387 32 449 143; 449 145 Fax: +387 32 246 612 e-mail: [email protected] [email protected] [email protected]

Osnivač i izvršni izdavač (Founders and Executive Publisher): University of Zenica Faculty of Mechanical Engineering Fakultetska 1, 72000 Zenica Bosnia and Herzegovina Recenzioni odbor (Review committe): Dr. Aleksandar Karač, Dr. Hazim Bašić, Dr. Himzo Đukić, Dr. Jusuf Duraković, Dr. Nermina Zaimović-Uzunović, Dr. Gašper Gantar

Glavni i odgovorni urednik (Editor and Chief): Prof. Dr. Sc. Safet Brdarević

Časopis izlazi tromjesečno (Journal tree monthly Urednički odbor (Editorial Board): Dr. Safet Brdarević (B&H), Dr. Jože Duhovnik (Slovenia), Dr. Vidosav Majstorović (Serbia), Dr. Milan Jurković (Croatia), Dr. Sabahudin Ekinović (B&H), Dr. Gheorge I. Gheorge (Romania), Dr. Alojz Ivanković (Ireland), Dr. Joan Vivancos (Spain), Dr. Ivo Čala (Croatia), Dr. Slavko Arsovski (Serbia), Dr. Albert Weckenman (Germany), Dr. Ibrahim Pašić (France), Dr. Zdravko Krivokapić (Montenegro), Dr. Rainer Lotzien (Germany)

Tehnički urednik (Technical Editor): Prof. Dr. Sabahudin Jašarević Štampa (Print): Štamparija: EUROGRAFIKA d.o.o. Zvornik Uređenje zaključeno (Preparation ended): 30.12.2015.

Časopis je evidentiran u evidenciji javnih glasila pri Ministarstvu nauke, obrazovanja, kulture i sport Federacije Bosne i Hercegovine pod brojem 651. Časopis u pretežnom iznosu finansira osnivač i izdavač. Časopis MAŠINSTVO u pravilu izlazi u četiri broja godišnje. Rukopisi se ne vraćaju

The Journal is listed under No 651 in the list of public journals in the Ministry of science, education, culture and sport of the Federation of Bosnia and Herzegovina. The Journals is mostly financed by founder and publisher. Frequency of Journal MAŠINSTVO is 4 issues a year. Manuscripts are not returned

Časopis objavljuje naučne i stručne radove i informacije od interesa za stručnu i privrednu javnost iz oblasti mašinstva i srodnih grana vezanih za područje primjene i izučavanja mašinstva. Posebno se obrađuju slijedeće tematike: - tehnologija prerade metala, plastike i gume, - projektovanje i konstruisanje mašina i postrojenja, - projektovanje proizvodnih sistema, - energija, - održavanje sredstava za rad, - kvalitet, efikasnost sistema i upravljanje proizvodnim i poslovnim sistemima, - informacije o novim knjigama, - informacije o naučnim skupovima - informacije sa Univerziteta,

The journal publishes scientific and professional papers and information of interest to professional and economic releases in mechanical engineering and related fields. In particular, the following topics are treated: - Technology for processing metal, plastic and rubber, - Design and construction of machines and plants, - The design of production systems, - Energy, - Maintenance funds for the work, - Quality and efficiency of the system and the management of production and business systems, - Information about new books, - Information about scientific meetings - Information from the University,

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RIJEČ UREDNIKA Poštovane kolegice i kolege U ovom broju Vam predstavljamo pet različitih radova iz šireg područja mašinstva. Tri od njih su nastali u rezultau istraživanja izvedenih u postupku izrade doktorskih disertacija i magistarskih radova. Tu su i pozivi autorima za dva naučno-stručna skupa: - IV Konferencija „ODRŽAVANJE 2016“,

Zenica, 02-04 juna 2016 godine - 3rd International Conference "New

Technologies NT-2016, Mostar, 13-14 may 2016

U konceptu sadržaja časopisa je i predstavljanje laboratorijskih kapaciteta u Bosni i Hercegovini. U ovom broju su date kratke tehničko-komercijalne informacije o Metalurškom institutu „Kemal Kapetanović“ u Zenici. Na sličan način je predstavljena informacija i firma SINTEX d.o.o. za protektiranje guma. Očekujemo da će Vam predstavljeni sadržaj biti od koristi kao i Vaš doprinos sadržaju narednih brojeva časopisa.

Vaš glavni i odgovorni urednik Prof. dr. Safet Brdarević

EDITORIAL Dear Colleagues In this issue we present five different papers in the wider area of mechanical engineering. Three of them were created in the Results of research conducted in the drafting of doctoral dissertations and master's theses. There are also call for authors for two scientific conferences: - IV Conference "Maintenance 2016", Zenica, 02-04 June 2016 in Zenica- 3rd International Conference "New Technologies NT-2016, Mostar, 13-14 May 2016The concept of the Journal’s content and presentation of laboratory capacity in Bosnia and Herzegovina. In this issue we are given a short technical and commercial information about the Metallurgical Institute "Kemal Kapetanovic" Zenica. In a similar way the information presented and the company SINTEX doo for retreading. We expect that you presented content to be useful as well as your contribution to the contents of the next issues of the journal.

Your editor in chief Prof. dr. Safet Brdarević

SADRŽAJ

1. Analiza promjene tvrdoće pri oblikovanju cjevastih izradaka iz Al 99,5 % postupkom istosmjernog hladnog rotacionog istiskivanja I. Plančić, M. Čabaravdić, E. Begović, B. Fakić 59

2. Dodatni naponi zbog savijanja u procesu dubokog izvlačenja A. Talić-Čikmiš, S. Hasanbegović, N. Vukojević, F. Hadžikadunić 75

3. Prilog istraživanju zatezne čvrstoće dijelova dobijenih FDM procesom CUBE 3D printanja D.Tiro 83

4. Postupak kalibracije i uticaji koji se uzimaju u obzir tokom kalibracije kontaktnih termometara za mjerenje temperature čvrste površine N. Jarović-Bajramović, N. Zaimović-Uzunović, E. Terzić 89

5. Modernization and Automation of Automotive Industry Production Processes with Industrial Robots I. Karabegović, S. Isić, E.Husak 105

Uputstvo za autore .....................................110

CONTENTS

1. Analysis Hardness Changes of Tubular Workpieces Made of Al 99.5% Forward Cold Flow Forming Process I. Plančić, M. Čabaravdić, E. Begović, B. Fakić 59

2. The Extra Stress Because of the Bending in the Process the Deep Drawing A. Talić-Čikmiš, S. Hasanbegović, N. Vukojević, F. Hadžikadunić 75

3. Contribution to the Tensile Strength Research for Parts Obtained by CUBE 3D Print FDM Process D.Tiro 83

4. Calibration Process and Impacts Taken into Account During the Calibration of Contact Thermometers for Temperature Measurement of Solid Surface N. Jarović-Bajramović, N. Zaimović-Uzunović, E. Terzić 89

5. Modernization and Automation of Automotive Industry Production Processes with Industrial Robots I. Karabegović, S. Isić, E.Husak 105

Instruction for authors ...............................110

Mašinstvo 3-4(12), 59 – 74, (2015) I.Plančić: ANALIZA PROMJENE TVRDOĆE….

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ANALIZA PROMJENE TVRDOĆE PRI OBLIKOVANJU CJEVASTIH IZRADAKA IZ AL 99,5 % POSTUPKOM ISTOSMJERNOG HLADNOG

ROTACIONOG ISTISKIVANJA

ANALYSIS HARDNESS CHANGES OF TUBULAR WORKPIECES MADE OF AL 99.5% FORWARD COLD FLOW FORMING PROCESS

Plančić Ibrahim, Čabaravdić Malik, Begović Edin, *Fakić Belma University of Zenica, Bosnia &Herzegovina Ključne riječi: tvrdoća, ojačavanje materijala, istosmjerno hladno rotaciono istiskivanje, Al 99,5 Keywords: hardness of material, material strengthening, forward cold flow forming, Al 99,5 Paper received: 30.10.2015. Paper accepted: 15.12.2015.

Originalni naučni rad REZIME Pojava ojačavanja materijala tokom hladnog oblikovanja deformisanjem ključni je razlog koji ovu obradu čini superiornijom u odnosu na druge metode. Efekti ojačavanja se ogledaju u poboljšanju mehaničkih osobina izradaka. Upravo zbog efekata ojačavanja, a kao jedan od specifičnih postupaka oblikovanja rotaciono simetričnih dijelova u zahtjevnijim industrijskim granama sve više se primjenjuje istosmjerno hladno rotaciono istiskivanje (IHRI). U radu se na primjeru izrade cjevastih izradaka iz Al 99,5 % ovim postupkom analiziraju efekti ojačavanja materijala mjerenjem njegove tvrdoće poslije oblikovanja.

Original scientific paper

SUMMARY Final product of the cold forming process gain many advantages that are mostly produced by strengthening of the material in the process. Those advantages are primarily explained as improving mechanical characteristic of the work material. Because of the effects of strengthening and as one of the specific methods of forming rotationally symmetrical parts in demanding industries increasingly applied forward cold flow forming (FCFF). In this paper is shown an example of forward cold flow forming application process in production of 99,5% Al workpieces with focus on analysis of a strengthening effect of the processed material by the change in its hardness like HB.

1. UVOD Izrada dijelova zadovoljavajuće preciznosti u pogledu oblika i dimenzija, sa što manjom težinom i što boljim mehaničkim karakteristikama uz povoljne ekonomske efekte njihove izrade neprestano se postavlja kao zahtjev savremenih proizvodnih tehnologija. U širokoj lepezi tehnoloških postupaka izrade dijelova rotaciono simetričnog oblika kojima se ovo postiže značajno mjesto zauzimaju postupci obrade deformisanjem u hladnom stanju koji se nazivaju rotacionim oblikovanjem. Istosmjerno hladno rotaciono istiskivanje kao jedan specifičan postupak rotacionog oblikovanja omogućava pored dobijanja dijelova različitih dimenzija i redukciju debljine stijenke. Usljed redukcije debljine u hladnom stanju dolazi do efekta ojačavanja materijala koji je praćen poboljšanjem mehaničkih osobina i tačnosti finalnih izradaka.

1. INTRODUCTION Production of parts with satisfactory accuracy in terms of shape and size, with the smallest weight and the best possible mechanical properties with favorable economic effects of their production is constantly a requirement of modern production technologies. In the wide range of technological processes for making parts with rotationally symmetric shape that achieves this, of significant importance are the processes of cold deformation, which are also known as rotational forming. Forward cold flow forming as a special method of rotational forming allows, in addition to the obtaining parts with different dimensions, also wall thickness reduction. The reduction of thickness in the cold state leads to the hardening effect of material which is accompanied by improving of the mechanical properties and the accuracy of the finished workpieces.


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Stoga se njegovom primjenom stvaraju preduslovi za primjenu ekonomičnijih materijala i dijelova sa tanjim stijenkama. To je jako značajno za složene uslove eksploatacije dijelova gasnih turbina, artiljerijske municije, kućišta raketnih motora, hidrauličnih cilindara, posuda za skladištenje plina pod pritiskom i drugih dijelova u raznim industrijskim granama. Kao atraktivni materijal sadašnjosti i budućnosti, aluminijum zadovoljava većinu postavljenih zahtjeva, a posebno kada je u pitanju zahtijev za smanjenjem mase dijelova i komponenata u različitim industrijskim granama. Niža čvrstoćna svojstva aluminijskih dijelova moguće je poboljšati hladnim oblikovanjem. Na taj način se rotacioni dijelovi izrađeni iz Al, pored specifične kombinacije osobina (gustoće, korozione otpornosti, sposobnosti oblikovanja, cijene, karakterističnog metalnog sjaja, atraktivnosti, mogućnosti recikliranja i sl.) odlikuju i zadovoljavajućim čvrstoćnim osobinama. Tako se se oblast primjene Al pored proizvoda opšte upotrebe sve više širi na izradu dijelova u vojnoj, vazduhoplovoj i nuklearnoj industriji. Upravo iz tih razloga, a zbog nepostojanja dovoljno pouzdanih informacija i literaturnih podataka o ponašanju i efektima ojačavanja aluminijuma pri hladnom deformisanju, predmet istraživanja u ovom radu je oblikovanje cjevastih izradaka iz tehnički čistog Al (99,5%) postupkom rotacionog oblikovanja. Predmetno istraživanje je provedeno s ciljem utvrđivanja efekata ojačavanja kroz analizu promjene tvrdoće po debljini i dužini stijenke oblikovanog materijala.

Therefore, its application creates preconditions for the application of cost-effective materials and parts with thin walls. It is very important for complex operating conditions of gas turbine parts, artillery ammunition, rocket motor housings, hydraulic cylinders, containers for storing gas under pressure and other parts in various industries. As attractive material of the present and the future, aluminum meets most of the requirements imposed, especially when it comes to the requirement to reduce the weight of parts and components in different industries. Lower strength properties of aluminum parts can be improved by the cold forming. In this way, the rotary parts made of Al, in addition to the specific combination of properties (density, corrosion resistance, formability, cost, characteristic metallic luster, attractiveness, possibility of recycling and similar) are also characterized by satisfactory strength properties. Thus, the field of application of Al, in addition to the consumer products, is expanded to the production of parts in the military, aviation and the nuclear industry. For these reasons, and because of the lack of sufficiently reliable information and the data about the behavior and effects of the strengthening of aluminum during cold deformation, the subject of research in this paper is the design of tubular workpieces from technically pure Al (99.5%) by rotational forming process. The research was conducted to determine the effect of strengthening through the analysis of changes in hardness along the thickness and the length of the wall of the deformed material.

2. SPECIFIČNOSTI ROTACIONOG

OBLIKOVANJA DIJELOVA Rotaciono oblikovanje je proces oblikovanja metala obradom deformisanjem pri kome se ravna ploča ili cilindrični pripremak postavljen između trna i jedne ili više rolnica oblikuje u šuplji cilindar, konus ili drugi osnosimetrični dio sa pravolinijskom ili krivolinijskom izvodnicom. Postupak se odvija primjenom sile pritiska mašine koja se preko alata i složenog mehanizma rotacionog kretanja obratka i alata prenosi na obradak. Razvoj tehnologije rotacionog oblikovanja je počeo razvojem procesa koji se danas najčešće naziva konvencionalno rotaciono oblikovanje. Pri ovom procesu ravna ploča se oblikuje u proizvod željenog oblika pri čemu se polazna debljina ploče vrlo malo ili nikako ne mjenja.

2. CHARACTERISTICS OF THE ROTATIONAL FORMING OF PARTS Rotational forming is a process of shaping metal in which the flat plate or cylindrical part placed between the mandrel and one or more rolls is formed in a hollow cylinder, cone or other axisymmetric part with the straight or curved generatrices. The process is performed by applying of pressure force by the machine, which is over tool and complex rotary movement of the workpiece and the tool transferred to the workpiece. The development of technology of rotational forming began by the development of process, which is nowadays mostly known as conventional rotational forming. In this process a flat plate is formed into the desired product shape wherein the initial thickness of the plate is very little or not changed.


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Nasuprot toga, procesi pri kojima se debljina stijenke pri oblikovanju smanjuje, predstavljeni su sa dva karakteristična procesa koji su opšte prihvaćeni kao: - rotaciono oblikovanje elemenata konusnog,

konveksnog ili konkavnog oblika i - rotaciono oblikovanje elemenata cilindričnog

oblika. Postupkom rotacionog oblikovanja konusa izrađuju se osnosimetrični šuplji elementi sa pravolinijskom ili krivolinijskom izvodicom. Redukcija debljine zida je u strogoj funkcionalnoj zavisnosti i određena je odnosom između početne debljine ploče ili pripremka i ugla konusnog trna. Ovaj postupak kao i postupak konvencionalnog rotacionog oblikovanja u literaturi se sreće pod nazivom rotaciono izvlačenje. Rotaciono oblikovanje elemenata cilindričnog oblika u praktičnoj primjeni i dostupnim literaturnim izvorima se najčešće susreće pod terminom rotaciono istiskivanje, iako se često u proizvodnim uslovima karakteriše i terminom rotaciono valjanje. U ovom radu će se koristiti termin rotaciono istiskivanje, a podrazumjeva postupak oblikovanja pri kome se cilindrični pripremak oblikuje u cilindar sa unaprijed određenom redukcijom debljine zida. Shodno navedenom, osnovna razlika između ovih postupaka je da se kod rotacionog izvlačenja dobijaju dijelovi konstantne debljine oblikovanjem ravne ploče (platine) na šablonu koji rotira pomoću alata u obliku rolnice, dok se kod rotacionog istiskivanja vrši redukcija debljine stijenke cjevastog pripremka na račun povećanja dužine izratka. 2.1. Tehnologija hladnog rotacionog

istiskivanja Suština postupka rotacionog istiskivanja je da se pod dejstvom pritiska rolnica (jedna ili više) materijal prevede u područje plastičnog tečenja i istiskuje u aksijalnom pravcu uz smanjenje prečnika i povećanje dužine izratka, kako je prikazano na slici 1. Na račun redukcije debljine stijenke dobija se veća dužina izratka, te se iz uslova konstantnosti zapremine radnog komada, dužina izratka može izračunati prema:

L1 = L0 s0 (di+ s0) /[s1 (di +s1)] (1)

Pri tome se ukupna logaritamska deformacija po debljini zida može izraziti kao:

1

0lnss

s =φ (2)

In contrast, the processes during which the wall thickness is decreased are represented by the two typical processes which are generally known as: - rotational forming of elements with conical,

convex and concave shape and - rotational forming of elements with

cylindrical shape. By the process of rotational forming of the cone, axisymmetric hollow elements with a flat or curved generatrices are made. The reduction of the wall thickness is in strict functional dependence and is determined by the relationship between the initial thickness of the plate or workpiece and the angle of the conical mandrel. This process and the process of the conventional rotational forming are known in the literature as the rotational drawing processes. Rotational forming of cylindrical elements in the practice and in the available literature sources is most often known as rotational forward flow forming, although often under production conditions is characterized by the term rotational rolling. In this paper we will use the term rotational forward flow forming, implying forming process whereby a cylindrical workpiece is transformed into the cylinder with a predetermined reduction of the wall thickness. Accordingly, the main difference between these methods is that in the rotational drawing, parts with constant thickness are made by processing of flat panels (platinum) in a pattern that is rotated using a tool in the form of rolls, while by the rotational forward flow forming the reduction of the wall thickness of the tubular workpiece is performed causing the increase of the length of the workpiece. 2.1. Technology of the forward cold flow

forming The core of this procedure is to bring the material to the state of plastic flow and extrude it in the axial direction under the pressure of the rolls (one or more), resulting in the reduction of the diameter and increasing of the length of work piece, as shown in Figure 1. Because of the reduction of wall thickness, bigger length of the workpiece is obtained, and based on the conditions of the constancy of the volume of the work piece, the length of the workpiece can be calculated by:

L1 = L0 s0 (di+ s0) /[s1 (di +s1)] (1)

Thereby, the overall logarithmic strain through the thickness of the wall can be expressed as:

1

0lnss

s =φ (2)


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gdje je: L1-dužina gotovog dijela, L0-dužina početnog komada, s0-početna debljina stijenke, s1-konačna debljina stijenke, di-unutrašnji prečnik obratka/izratka

Deformisanje se odvija u uskoj dodirnoj zoni kontakta između rolnica (jedna ili više) i materijala.

where is: L1-final length of the part, L0-length of the preform, s0-thickness of the preform, s1-final thickness of the wall, di-inner diameter of the preform/final part

The deformation occurs in a narrow contact zone between the contact rolls (one or more) and the material.

Slika 1. Šematski prikaz IHRI [2]

Figure 1. Schematic representation of the forward cold flow forming [2]

Početni oblik - cjevasti pripremci (toplo valjane cijevi, otkovci, puni profili i sl.) pritiskivačem se čeono pritisnu uz trn da bi se obrtaji sa trna prenijeli na pripremak. Cjevasti pripremak se dodatno preko unutrašnjeg prečnika koji je jednak prečniku trna navuče na trn na kome se obavlja deformisanje. Pripremak se prethodno izrađuje kovanjem ili dubokim izvlačenjem zavisno od debljine i oblika. Rolnice obično nemaju sopstveni pogon, već se obrtanje ostvaruje dejstvom kontaktnog trenja nastalog pri dodiru rolnice sa pripremkom. Pod dejstvom sile pritiska sa suporta mašine rolnice prodiru u metal uz obrtno kretanje trna i rolnica, te uz aksijalni posmak ostvaruju plastično tečenje - istiskivanje metala u aksijalnom smjeru. To dovodi do stanjenja stijenke i povećanja dužine izratka. Mala površina kontakta između alata (rolnica) i radnog komada, zahtijeva i malu silu oblikovanja, pa se zbog toga i mogu ostvariti veliki stepeni redukcije na mašinama male snage.

The initial forms - tubular preforms (hot-rolled pipes, forgings, rod systems, etc.) are frontal pressed against the mandrel by the pressing device, causing the transfer of the rotation from the mandrel to the preform. Further, the tubular preform with the inner diameter equal to the diameter of the mandrel is pulled over the mandrel where the deformation is performed. Preforms are previously prepared by forging or deep drawing, depending on the thickness and shape. Rolls usually do not have their own actuator, and their rotation is achieved through the effect of the friction generated by the contact between rolls and the work piece. Under the force of the pressure from the apron of machine, rolls penetrate the metal causing the rotary motion of the mandrel and rolls, and with axial feed realize flowing - extruding of metal in the axial direction. This leads to a thinning of the walls and increase the length of the work piece. A small contact zone between the tool (rolls) and the work piece, requires small force for processing, achieving a great degree of reduction in low-power machines.


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Pod uticajem tako visokih pritisaka zrno materijala se drobi i razvlači u pravcu toka materijala, te se intenzivno mijenja struktura i mehaničke osobine.Obilnim hlađenjem zone zahvata materijala, najčešće uljnom emulzijom koja se pod pritiskom, putem odgovarajućih mlaznica raspršava u zoni deformisanja, spriječava se zagrijavanje materijala i zadržavaju efekti hladnog deformisanja. Po završetku obrade, skidanje izratka se obavlja primjenom izbijača smještenog u unutrašnjosti trna ili svlačenjem izratka sa trna primjenom neke vanjske sile. Postoji nekoliko metoda HRI cjevastih dijelova, a dvije osnovne vrste tehnološkog postupka HRI su: - Istosmjerno (I) ili direktno i - Suprotnosmjerno (S), odnosno indirektno. Varijante se uglavnom razlikuju prema načinu tečenja materijala u odnosu na pravac kretanja rolnica, dok je deformisanje metala u obje varijante lokalizovano na usku dodirnu zonu kontakta alata-rolnice i materijala obradka. Na slici 2. je šematskim prikazom predstavljen princip oblikovanja predmetnim varijantama HRI sa prikazom radnih elemenata alata.

Under the influence of such a high pressure grain of material is crushed and extends in the direction of material flow, causing the intensive change in structure and mechanical properties. By intensive cooling of the contact zone, usually with an oil emulsion which is under pressure, through the appropriate nozzle sprayed into the zone of deformation, the heating of material is prevented and the effects of cold deformation are retained. Upon completion of processing, the removal of the work piece is performed using the punches located in the interior of the mandrel or stripping of the work piece from the mandrel by applying some external force. There are several methods FCFF of tubular parts, and two basic types of technological process of FCFF are: - direct and - oppositional. Variants differ mainly in the direction of material flow in relation to the direction of the rotation of rolls, while the deformation of metal in both variants is localized in a narrow contact zone between tool-roll and the work piece material. In Figure 2 is given a schematic representation of the principle of forming by the mentioned FCFF variants showing the operational elements of the tool.

Slika 2. Šematski prikaz postupka istosmjernog (lijevo) i suprotnosmjernog (desno) HRI [1] Figure 2. Scheme of procedure of direct (left) and oppositional (right) CFF [1]

Pri istosmjernom (direktnom) HRI (slika 1, lijevo) tečenje nedeformisanog materijala pripremka/predoblika i kretanje rolnica (alata) je u istom smjeru, dok je kod suprotnosmjernog (indirektnog) HRI (slika 1, desno) tečenje materijala u suprotnom smjeru u odnosu na smjer kretanja rolnica.

In direct CFF (Figure 1, left) the flow of unformed material of preparation/preform and the rotation of rolls (tool) is in the same direction, while in the indirect CFF (Figure 1, right) material flow is in the opposite direction compared to the direction of the roll´s rotation.


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Na taj način se mogu oblikovati otvoreni cilindrični dijelovi veće dužine, dok se kod IHRI primjenom alata najčešće u obliku rolnica na specijalnim trnovima dobijaju šuplji cilindrični dijelovi stalne ili promjenjive debljine stijenke sa jednom zatvorenom stranom cilindra.

In this way, open cylindrical parts with larger length can be formed, while in FCFF using tools, most commonly in the form of rolls on special mandrels, special hollow cylindrical parts with constant or variable wall thickness with one closed side of the cylinder can be produced.

2.2. Ojačavanje materijala postupcima

obrade deformisanjem u hladnom stanju Najvažnija promjena koja se dešava kao posljedica hladne plastične deformacije je ojačavanja materijala. Iako još uvijek nije do kraja razjašnjena, prema većini teorija koje objašnjavaju ovu pojavu, ona je uzrokovano gomilanjem dislokacija i njihovim otežanim kretanjem. Usljed dejstva spoljašnjih sila određenim stepenom deformacije dolazi do ravnomjernog izravnavanja kristalografskih zrna u aksijalnom smjeru paralelno sa pravcima tečenja metala i formiranja homogene kristalografske orijentacije zrna koja se naziva tekstura deformacije (slika 3).

2.2. Strengthening of material using the procedures of cold deformation

The most important change that occurs as a result of cold plastic deformation is the strengthening of material. Although not yet fully clarified, according to most theories that explain this phenomenon, it is caused by the accumulation of dislocations and their mobility limitations. Due to the effects of external forces some degree of deformation leads to a uniform leveling of the crystallographic grains in the axial direction, parallel to the direction of metal flowing and forming of a homogeneous crystallographic orientation of grains, which is called texture of deformation (Figure 3).

Slika 3. Ilustracija nastanka deformacione teksture pri hladnoj obradi deformisanjem Figure 3. The emergence texture of deformation in the cold metal forming

Pojava deformacione teksture je praćena značajnim promjenama fizičko mehaničkih svojstava metala. Te promjene se odnose na znatno povećanje mehaničkih osobina, kvaliteta površine i povećanje dimenzijske tačnosti izradaka uz istovremeno smanjenje plastičnosti. Pored toga, nastupaju i druge promjene koje su povezane sa povećanjem elektrootpornosti, smanjenjem magnetnih karakteristika, toplotne provodnosti i drugih fizičko hemijskih svojstava oblikovanih dijelova.

The occurrence of deformation texture is accompanied by significant changes in physical and mechanical properties of metals. These changes are related to an extensive increase in mechanical properties, surface quality and dimensional accuracy of work pieces while the plasticity is reduced. In addition, other changes occur which are associated with an increase in electrical resistance, decrease of magnetic characteristics, thermal conductivity and other physical and chemical properties of formed parts.


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Ilustrativan prikaz promjene fizičko-mehaničkih osobina u zavisnosti od stepena deformacije pri plastičnom deformisanju u hladnom stanju prikazan je na slici 4.

U nastavku je na primjeru oblikovanja cilindričnih izradaka iz tehnički čistog aluminijuma analiziran porast tvrdoće materijala kao jednog od najznačajnijih mjerljivih parametara kojim se pojava deformacionog ojačavanja može identificirati.

Illustrative representation of changes in physical and mechanical characteristics in dependence of the degree of deformation by the cold plastic deformation is shown in Figure 4.

The analysis of the increase in the hardness of the material as one of the most important measurable parameters, by which the strain hardening phenomenon can be identified, on the example of forming of cylindrical work pieces which are made of technically pure aluminum is given below.

3. EKSPERIMENTALNI RAD 3.1. Tehnologija oblikovanja izradaka S ciljem analize ponašanja tehnički čistog aluminijuma i efekata njegovog ojačavanja tokom hladne obrade deformisanjem izvršeno je oblikovanje Al 99,5 komore u dvije faze IHRI. U tabeli 1. su predstavljene karakteristike pripremaka koji su korišteni za IHRI. Vrijednosti predstavljaju prosječne veličine parametara dobijenih ispitivanjem epruveta iz deset slučajno odabranih pripremaka.

3. EXPERIMENTAL WORK 3.1. Technology of the forming of work pieces For the purposes of the analysis of the behavior of technically pure aluminum and its effects strengthening during the cold metal forming, processing of Al 99.5 chamber in two phases of FCFF was carried out. Table 1 presents the characteristics of preforms which are used for FCFF. Values represent the mean values of the parameters obtained from specimens from ten randomly selected preforms.

Tabela 1. Mehaničke karakteristike pripremaka za IHRI Table 1. Mechanical characteristics of the preforms for FCFF

Materijal Material

Prosječne vrijednosti parametara - Mean values of parameters

mpr [gr] Rp0,2

[N/mm2] Rm [N/mm2] A [%] Z [%]

Al 99,5 % 2268 80 98 28,0 86 Tokom oblikovanja su korištene ranije utvrđene optimalne vrijednosti geometrijskih karakteristika alata i tehnoloških parametara procesa, a odnose se na sljedeće:

- Tehnološki proces oblikovanja se odvija alatom u obliku rolnica prečnika D1=D2=D3=250 mm, radijusom R1=R2=4 mm, R3=2 mm, napadnim uglom α=20° i aksijalnim podešenjem rolnica u tri ravnine na udaljenosti a1=7 mm, a2=4 mm i a3=3 mm,

- Pritisak na rolnice: p1=p2= p3= 6 [N/mm2], - Intenzivno hlađenje vanjske površine

izradaka emulzijom 1:10 (voda/ulje), - Podmazivanje trna (unutrašnja površina

izratka) mješavinom masti i grafitnog praha u omjeru: 1 kg masti na 100 gr. grafita.

Na slici 5. su predstavljene dimenzije pripremka i izradaka po fazama IHRI.

During the forming have been used previously determined optimal values of geometric characteristics of tool and technological para-meters of the process, that refer to the following: - Technological process of the forming is

performed by the tool in the form of rolls with the diameters D1=D2=D3=250 mm, radii R1=R2=4 mm, R3=2 mm, incidence angle α=20° and axial adjustment of the rolls in the three planes at the distances a1=7 mm, a2=4 mm i a3=3 mm,

- Pressure to the rolls: p1=p2= p3= 6 [N/mm2], - Intensive cooling of the outer surface of work

piece by emulsion 1:10 (water/oil), - Lubrication of the mandrel (inner surface of

work piece) by the mixture of grease and graphite powder with the ratio: 1 kg grease to 100 gr. graphite.

In Figure 5 are presented dimensions of preforms and work pieces in the different stages of the FCFF.


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Slika 4. Promjene fizičko-mehaničkih svojstava u zavisnosti od stepena deformacije pri plastičnom

deformisanju u hladnom stanju [4, 5] Figure 4. Changes physical and mechanical properties depending on the degree of deformation in

cold metal forming Prilikom provođenja eksperimenta, a u svrhu istraživanja uticaja tehnoloških parametara na pojavu ojačavanja materijala tokom hladne plastične deformacije vršena su preliminarna i glavna istraživanja. Preliminarnim istraživanjima su utvrđene optimalne vrijednosti tehnoloških parametara oblikovanja: broj obrtaja trna n [o/min], minutni posmak rolnica sv [mm/min] i ukupna dubina prodiranja rolnica: ∆s= ∆s1+∆s2+∆s3 [mm] sa aspekta efikasnosti oblikovanja i dobijanja potrebnih dimenzija izradaka. Glavnim istraživanjem kroz primjenu metodologije planiranog eksperimenta utvrđene su ključne zakonitosti izbora tehnoloških parametara oblikovanja za dobijanje izradaka određenih karakteristika.

By the experiment, in order to research the impact of technological parameters on the occurrence of the strengthening of material during the cold plastic deformation, preliminary and main investigation were carried out. Preliminary investigations have determined optimal technological parameters of forming: speed of mandrel n [o/min], minute in-feed of rolls sv [mm/min] and total depth of the penetration of rolls: ∆s= ∆s1+∆s2+∆s3 [mm] in terms of the efficiency of forming and obtaining of the required dimensions of work pieces. Through the application of the methodology of planned experiment in the main investigation are identified key rules for the choice of technological parameters of forming for obtaining work pieces with certain characteristics.


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U ovom radu predstavljeni su dobijeni rezultati i izvedene zakonitosti promjene tvrdoće izradaka nakon prve operacije IHRI tokom preliminarnih i glavnih istraživanja koja su vršena u Laboratoriji za obradu rezanje i alatne mašine- LORAM na Mašinskom fakultetu i Laboratorijama Metalurškog instituta Univerziteta u Zenici. Tvrdoća izradaka nakon druge faze kod preliminarnih i glavnih istraživanja zbog žarenja i oporavljanja strukture ne odražava efekte hladne obrade deformisanjem zbog čega ovi rezultati nisu ni analizirani.

This paper presents obtained results and derived principles for the change in hardness of work pieces after the first operation by FCFF during the preliminary and the main research conducted in the Laboratory for cutting and cutting tool machines - LORAM at the Faculty of Mechanical Engineering and in the laboratories of the Institute of Metallurgy at the University of Zenica. The hardness of work pieces after the second stage of forming in the preliminary and main research does not reflect the effects of cold metal forming because of tempering and the recovery of structure and that is the reason why these results have not been analyzed.

Slika 5. Izgled i dimenzije pripremka i izradaka po fazama IHRI a) Pripremak b) Izradak poslije I faze

c) Izradak poslije II faze [2] Figure 5. The workpiece in the different stages of processing a) Preform; b) Workpiece after the phase

I; c) Workpiece after the phase II [2]


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3.2. Mjerenje i analiza tvrdoće oblikovanih uzoraka

U cilju izvođenja zaključaka u vezi sa ojačavanjem materijala tokom hladne obrade deformisanjem tehnologijom IHRI ispitivanje tvrdoće je vršeno po debljini stijenke pri vrhu cilindričnog dijela izradaka (zona intenzivne deformacije) i po njihovoj dužini. Za ispitivanje tvrdoće korišteni su uzorci dužine 60 mm sa debljinom koja odgovara debljini izradaka. Mjerenje tvrdoće kod preliminarnih istraživanja (izradci oblikovani sa međufaznim žarenjem) je vršeno Vikersovom metodom ispitivanja, dok je Brinelova metoda mjerenja tvrdoće korištena kod glavnih istraživanja (oblikovanje izradaka bez međufaznog žarenja). U oba slučaja su na svakom uzorku definisana mjerna mjesta i to na unutrašnjoj (površina prema trnu tokom oblikovanja) i vanjskoj (površina ispod rolnica tokom oblikovanja) strani izratka. Na slici 6. su predstavljene lokacije mjernih mjesta.

3.2. Measurement and analysis of the hardness of processed specimens

In order to draw conclusions with regard to strengthening of the material during the cold metal forming technology FCFF, hardness measurement was performed along the wall thickness at the top of the cylindrical section of work pieces (zone of intense deformation) and along their length. For hardness measurement are used specimens with the length of 60 mm with a thickness corresponding to the thickness of the work piece. Hardness measurement in preliminary studies (the specimens formed with interphase tempering) was performed using Vickers test method, while the Brinell hardness measurement methods were used in the main study (forming of work pieces without interphase tempering). In both cases were defined measuring points on each sample on the inner (the surface facing mandrel during forming) and the outer (the area under the rolls during the forming) side of the workpiece. In Figure 6 are presented locations of measurement points.

Slika 6. Mjesto uzorkovanja (gore) i lokacije mjernih mjesta po debljini stijenke (dolje)

Figure 6. Sampling location (up) and the location of measurement points per the wall thickness of the workpiece (down)

U tabeli 2. su predstavljene prosječne vrijednosti tvrdoće izradaka na lociranim mjernim mjestima u funkciji tehnoloških režima oblikovanja i izvršenog stepena deformacije.

In Table 2 are presented mean values of the hardness of work pieces at the located measuring points in dependence on the technological regimes of forming and the obtained degree of deformation.


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Tabela 2. Rezultati mjerenja tvrdoće nakon prve faze IHRI Table 2. Results of the hardness measurement after the first stage of FCFF

No.

Režimi oblikovanja Regimes of forming

ϕ [%]

HB uzorka na* HB of specimen on*

Prosječna Mean [HB]

Porast tvrdoće Increase

in hardness

[%]

n [o/min]

sv [mm/o]

∆s [mm] a b c

0 - - - - 32,42 32,52 33,1 32,68 - 1 140 60 2 18,1 33,78 34,92 39,36 36,02 10 2 240 60 2 17,6 31,02 35,46 33,24 2 3 140 100 2 15,3 32,08 32,2 37,9 34,06 4 4 240 100 2 21,0 33,78 38,28 36,03 10 5 140 60 3,5 35,4 36,44 34,4 34,44 35,09 7 6 240 60 3,5 35,2 36,9 33,94 34,24 35,03 7 7 140 100 3,5 32,9 32,4 36,3 34,35 5 8 240 100 3,5 33,6 33,04 32,16 34,5 33,23 2 9 190 80 2,75 23,15 34,04 37,64 35,84 10 10 190 80 2,75 22,9 35,7 34,92 36,96 35,86 10 11 190 80 2,75 23,5 35,04 36,98 36,01 10 12 190 80 2,75 25,1 33,56 36,64 35,10 7

*a-unutrašnja strana/inner surface; b-polovina debljine/half thickness; c- vanjska strana/ outer surface

Dobijeni rezultati mjerenja tvrdoće nakon prve faze oblikovanja i kod preliminarnih i kod glavnih istraživanja ukazuju na sljedeće zaključke: - Rezultati mjerenja tvrdoće nakon prve

operacije IHRI su u granicama očekivanih jer je na svim uzorcima došlo do povećanja tvrdoće u odnosu na tvrdoću pripremka. Prosječne vrijednosti tvrdoće na izradcima koji su dobijeni tehnologijom IHRI su u rasponu od 33,23 do 36,03 HB. S obzirom da je srednja vrijednost izmjerene tvrdoće na pripremcima bila 32,68 HB to je maximalni porast tvrdoće u rasponu od 2 do 10 %.

- Pošto je Al 99,5 materijal koji, pored niza izuzetno dobrih karakteristika, ima dobra plastična svojstva, a male čvrstoćne karakteristike (Rp0,2, Rm i HB) u odnosu na druge materijale (npr. čelike) očekivano se kod oblikovanja tehnički čistog Al 99,5 nemogu dobiti njihove značajno veće vrijednosti obradom deformisanjem u hladnom stanju. Dobijeni rezultati su u skladu sa dosadašnjim objavljenim rezultatima u vezi sa porastim tvrdoće tehnički čistog aluminijuma deformisanjem na hladno [5,7].

The results of measurement of hardness after the first phase of forming in both studies (preliminary and main) suggest the following conclusions: - Results of measurement of hardness after the

first stage of FCFF were expected because in all samples, hardness was increased compared to the hardness of the preform. Mean values of hardness of the work pieces obtained by FCFF technology are in the range from 33.23 to 36.03 HB. Since the mean value of the hardness of preforms was 32.68 HB, the maximum increase of hardness was in the range from 2 to 10%.

- Since the Al 99,5 is a material, which, besides a number of extremely good properties, compared to other materials (e.g., steel) has good forming properties and low strangth characteristics (Rp0,2, Rm and HB), their significantly higher levels, as expected, can not be obtained by cold forming of technically pure Al 99,5. The results are comparable with previous published results regarding the increase in the hardness of technically pure aluminum by cold forming [5,7].


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- Procentualni porast tvrdoće je maximalan na uzorcima koji su oblikovani sa srednjim vrijednostima tehnoloških režima rada (n=190 [o/min]; sv=80 [mm/o] i ∆s=2,75 [mm]) kako je prikazano i dijagramima na slici 7.

Na osnovu približnog obrasca ruskih istraživača H.V.Tretjakova i V.J. Zjuzina do kojih su došli ispitujući oko 133 vrste metala i legura moguće je izvesti i zakonitost promjene tvrdoće ovisno o stepenu deformacije drugog reda (Ψ) sljedećim izrazom:

J=J0 + a xn (za HB) (3)

Uvrštavajući eksperimentalno dobijene vrijednosti tvrdoće, u sklopu predmetnih istraživanja izračunati su koeficijenti a i n, te se promjena tvrdoće pri oblikovanju Al 99,5 postupkom IHRI može predstaviti sljedećim izrazom:

HB=32,68 + 1,0977 ψ - 0,37472 (4)

Ono što se takođe može izvesti kao zaključak provedenih istraživanja, a na osnovu mjerenja tvrdoće izradaka odnosi se na činjenicu da postoji razlika u tvrdoći kako po debljini stijenke tako i po dužini izradaka. Očigledno je da se kod dijelova oblikovanih IHRI javlja anizotropija mehaničkih osobina, kao posljedica obrazovanja teksture deformacije. S tim u vezi, mehaničke osobine izradaka se mjenjaju od spoljašnjeg ka unutrašnjem zidu oblikovanog elementa. To je potvrđeno mjerenjem tvrdoće na uzdužnom presjeku deformisanog cilindričnog izratka. Položaj i broj mjernih mjesta na specifičnim dijelovima oblikovanog cilindričnog izratka prikazan je na slici 8 (0-dno izratka sa tri mjerna mjesta na unutrašnjoj i vanjskoj površini i dijelovi oblikovanog cilindra 1, 2, 3, 4 sa po tri mjerna mjesta na unutrašnjoj i spoljnoj površini).

Sistematizovani rezultati ovih mjerenja sa prosječnim vrijednostima tvrdoće na unutrašnjoj i vanjskoj strani izradaka predstavljeni su u tabeli 3 i dijagramom na slici 9. Isti pokazuju da je tvrdoća na vanjskoj strani (ispod rolnica) veća nego na unutrašnjoj strani uzoraka (površina prema trnu tokom izrade). Do istog zaključka došlo se i u istraživanjima [6] tokom oblikovanja konusa od Cu.

- The percentage increase in hardness has its maximum by the samples which are formed with medium values of technological parameters (n=190 [o/min]; sv=80 [mm/o] and ∆s=2,75 [mm]) as shown in the diagrams in Figure 7.

Based on the approximate equation of Russian researchers H.V. Tretjakov and V.J. Zjuzin which was obtained by examining of about 133 kinds of metals and alloys, the law of the change in hardness depending on the degree of deformation of the second order (Ψ) can be described by the following expression:

J=J0 + a xn (za HB) (3)

Incorporating the experimentally obtained values of hardness, as part of the underlying research, coefficients a and n were determined, and changes in hardness by the forming of Al 99.5 by FCFF procedure can be presented by the following expression:

HB=32,68 + 1,0977 ψ - 0,37472 (4)

The point that can also be defined as a conclusion of the research based on measuring the hardness of workpiece, refers to the fact that there is a difference in the hardness both in the wall thickness and the length of the work piece. It is obvious that in parts formed by FCFF occurs anisotropy of mechanical properties, as a result of forming of deformation texture. According to that, the mechanical properties of work pieces are changed from the outer to the inner wall of the formed element. It was confirmed by the measuring of hardness of the longitudinal section of a deformed cylindrical work piece. The position and number of measuring points on the specific parts of the formed cylindrical work piece is shown in Figure 8 (0-bottom of the work piece with three measuring points on the inner and outer surface and the parts of formed cylinder 1, 2, 3, 4 with three measuring points on the inner and outer surface). Systematized results of these measurements with mean values of hardness on the inside and outside of work pieces are presented in Table 3 and Figure 9. These results show that the hardness on the outside (below rolls) is higher than on the inner side of samples (surface toward the mandrel during the processing). The same was concluded also in research [6] during the forming of the cone of Cu.


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Slika 7. Tvrdoća izradaka u funkciji n, ∆s i sv nakon prve faze IHRI

Figure 7. Hardness of workpieces in the function n, Δs and sv after the first phase FCFF Tabela 3 Rezultati mjerenja tvrdoće po dužini izratka Table 3 Results of the measurement of hardness along the length of work piece

Uzorak

Sample

Tvrdoća HV 1 - Hardness HV 1

Mjerna mjesta na unutrašnjoj strain

Measurement points on the inner surface

Mjerna mjesta na vanjskoj strain

Measurement points on the outer surface

1 2 3 HV1 sr 1 2 3 HV1sr

0-Dno/Bottom 27,4 27,4 27,0 27,3 28,3 28,3 29,2 28,6

1 35,1 34,5 35,1 34,9 35,1 35,1 35,1 35,1

2 33,9 33,9 34,8 34,2 37,0 37,0 36,3 36,7

3 35,1 35,1 35,1 35,1 37,0 37,0 37,6 37,2

4 32,7 32,7 32,7 32,7 35,1 34,8 35,1 35,0

33

34

22200

175150

25200

35

36

9075

60

90105

HB

sv n


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Slika 8. Položaj mjernih mjesta za mjerenje tvrdoće po dužini izradaka

Figure 8. Location of measurement points for measuring the hardness lengthwise of workpieces

Slika 9. Promjena tvrdoće po dužini izratka Figure 9. Change of hardness along the length of the workpiece

Navedeni zaključak ukazuje na nehomogenost deformacije po presjeku komada, tj. na nehomogeno tečenje materijala. Nehomogeno tečenje materijala može prouzrokovati pojavu ljuspi, prevaljanosti, pa čak i mikropukotina na površini [6]. Pojava ljuspičenja i odvajanje sitnih čestica na površini izradaka po cijeloj dužini izradaka izuzev na 30-40 mm dužine od početka zahvata rolnica, potvrđena je i kod provođenja vlastitog eksperimenta.

This conclusion indicates the inhomogeneity of deformation in cross-section of work pieces, i.e. the inhomogeneous material flow. Inhomogeneous material flow can cause the appearance of flakes, over-rolling and even microcracks on the surface [6]. The appearance of flakes and separation of fine particles on the surface of work pieces along the entire length of work pieces except on the first 30-40 mm from the starting point of procedure, has been confirmed by own experiment.


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Slika 10. prikazuje pojavu ljuspičenja Al 99,5 pri oblikovanju svih eksperimentalnih uzoraka.

Generalno se, sa aspekta ovog tehnološkog postupka oblikovanja može konstatirati da se najviše vrijednosti mehaničkih karakteristika, zbog tečenja metala u aksijalnom i tangencijalnom pravcu, dobijaju na strani do rolni, dok je jačina materijala na unutrašnjem sloju - do trna manja.

Figure 10 shows the appearance of flakes on Al 99,5 by the forming of all experimental samples.

Generally, in terms of the technological process of forming can be concluded that the highest values of mechanical properties, due to the flow of metal in the axial and tangential direction, are obtained on the side of the roll, while the strength of the material in the inner layer (mandrel side) is lower.

Slika 10. Odvajanje sitnih čestica od izradaka iz Al 99,5 pri IHRI

Slika 10. Separation of small particles of workpieces from Al 99.5 during the FCFF 4. ZAKLJUČAK Tehnologijom IHRI uz adekvatne geometrijske karakteristike alata (prečnik, radijus, napadni ugao, radijalno i aksijalno podešavanje i dr.), tehnološke (n i s) i druge procesne parametre (pritisak rolnica, sredstvo za hlađenje i podmazivanje i sl.), te ostvarene stepene deformacije tokom oblikovanja u rasponu 51 do 58 % efikasno se mogu oblikovati osnosimetrični izradci zadovoljavajuće tačnosti oblika, dimenzija, kvaliteta (glatkosti) unutrašnje i vanjske površine izratka i sa poboljšanim čvrstoćnim karakteristikama u odnosu na materijal pripremka. Iako su efekti ojačavanja kroz povećanje tvrdoće za Al 99,5 koji su identificirani u ovom radu dosta manji u odnosu na oblikovanje različitih vrsta čelika i legura obojenih metala na isti način ipak su, s obzirom na druge pozitivne aspekte primjene aluminijuma oni jako značajni. Nivo povećanja tvrdoće na primjeru oblikovanja cjevastih izradaka od Al 99,5 u ovom radu se kreće u rasponu 2 do 10 % što zajedno sa porastom zatezne čvrstoće može značajno povećati čvrstoćna svojstva rotaciono simetričnihi zradaka. Time se postiže efekat ojačavanja tehnološkim postupkom oblikovanja, a ne nekom naknadnom termičkom ili drugom vrstom obrade.

4. CONCLUSION Using FCFF technology with adequate geometric characteristics of the tool (diameter, radius, angle of attack, radial and axial adjustment, etc.), technological (n and s) and other process parameters (pressure of rolls, means for cooling and lubrication and so on) and achieved degrees of deformation during the forming in the range 51 to 58%, can be efficiently formed axisymmetric work pieces with satisfactory accuracy in shape, dimensions, the quality (smoothness) and the inner and outer surface of a work piece with improved strength characteristics compared to the preform material. Although the effects of strengthening through the increase of hardness of Al 99,5 identified in this study are much lower compared to the effects by the forming of different types of steel and non-ferrous alloys in the same way, thea are, however, very important because of the other positive aspects of the use of aluminum. The level of increase in hardness in the case of forming of tubular work pieces of Al 99,5 in this study ranges from 2 to 10%, which together with the increase in tensile strength can significantly increase strength properties of rotationally symmetrical work pieces. This allows the effect of strengthening by the technological process of forming itself, and not by an additional thermal or other type of treatment.


74

Ovo su razlozi primjene navedene tehnologije oblikovanja za izradu dijelova visoke tačnosti, kvaliteta obrađene površine i dobrih čvrstoćnih karakteristika u najzahtjevnijim privrednim granama poput nuklearne, vazduhoplovne i vojne industrije. U tom smislu provedena metodologija i dobijeni rezultati u ovom radu mogu da posluže kao dobra osnova za nastavak istraživanja usmjerenih na proizvodnju uređaja i konstrukcija manje težine, a iste ili povećane čvrstoće primjenom tehnički čistog aluminijuma.

These are the reasons for application of this forming technology for producing parts with high accuracy, high surface quality and good strength characteristics in the most demanding industries such as nuclear, aviation and defense industries. In that sense, the methodology and the results obtained in this study can serve as a good basis for the further research work focused on the production of equipment and constructions of less weight, and the same or increased strength by using technically pure aluminum.

5. LITERATURA - REFERENCES [1] I. Plančić, M. Čabaravdić, E. Begović, S.

Härtel, S. Kleditzsch: Simulation Of The Heat Distribution By The Forward Cold Flow Forming, Journal of Trends in the Development of Machinery and Associated Technology Vol. 18, No. 1, 2014, ISSN 2303-4009 (online), p.p. 71-74, 2014.

[2] S. Ekinovic, H. Đukic, I. Plancic, E. Begovic: Assessment of the surface topography of Al 99.5% tubular products formed by cold flow forming technology, Proceedings of the 6th Manufacturing Engineering Society International Conference – MESIC Conference 2015 Topic 2 Forming Processes, 127-133, ISBN: 978-84-1568863-1, Barcelona, 22nd to 24th July 2015.

[3] I. Plančić, D. Petković, S. Lemeš, H. Bašić: Research on impact factors influencing roundness of products made of Al 99.5 % formed by flow forming technology, ANNALS of Faculty Engineering Hunedoara, – International Journal of Engineering, Tome XIII [2015] UNIVERSITY Politehnica Timisoara, Faculty Of Engineering Hunedoara, 5, Revolutiei, 331128, Hunedoara, Romania, http://annals.fih.upt.ro

[4] S. Ekinović, I. Plančić, E. Begović, H. Đukić, B. Muminović: Očvršćavanje materijala pri oblikovanju cjevastih izradaka iz Al 99,5 % kod istosmjernog hladnog rotacionog istiskivanja, X Naučno/stručni simpozij sa međunarodnim

učešćem, ''Metalni i nemetalni materijali'' Bugojno, BiH, 21-22. april 2014.

[5] V. Pavelić: Specifične tehnologije u proizvodnji oružja, Novi Travnik-Zagreb, MORH-TP-4/95 1995.

[6] M. Nikačević, Lj. Radović: Rotaciono valjanje: specifična tehnologija za izradu delova raketa, - kumulativna naučnotehnička informacija-, Vojnotehnički institut - Beograd, Naučno tehničke informacije, ISSN 1820-3418, Volume XLIV Broj 2, 2010.

[7] C.C. Wong, T.A. Dean, J. Lin: Incremental forming of solid cylindrical components using flow forming principles, Journal of Materials Processing Technology 153–154, 60–66, 2004.

Coresponding author: Plančić Ibrahim University of Zenica Faculty of Mechanical Engineering Email: [email protected] Phone: +387 32 449 120

Mašinstvo 3-4(12), 75 – 81, (2015) A. Talić-Čikmiš,…: DODATNI NAPONI ZBOG SAVIJANJA …

75

DODATNI NAPONI ZBOG SAVIJANJA U PROCESU DUBOKOG IZVLAČENJA

THE EXTRA STRESS BECAUSE OF THE BENDING IN THE PROCESS THE DEEP DRAWING

Amra Talić-Čikmiš1 Suad Hasanbegović2 Nedeljko Vukojević1 Fuad Hadžikadunić1 1University of Zenica 2University of Sarajevo Ključne riječi: duboko izvlačenje, dodatni naponi savijanja, plastično područje Keywords: deep drawing, extra bending stress, plastic region Paper received: 04.09.2015. Paper accepted: 21.12.2015.

Prethodno saopštenje REZIME Opšte rješenje, problema u uslovima ravninskog stanja deformacije za plastično područje, dato je u radu[3]. Ovo rješenje ograničeno je na polarne koordinate i neočvršćavajuće materijale. U radu [4] data su neka pojedinačna rješenja ovakvih ravninskih problema u plastičnom području na bazi opšteg rješenja. Na osnovu prethodno pomenuta dva rada nastao je ovaj rad. Rezultat ovog rada jeste analitički izraz za izračunavanje dodatnog napona koje se pojavljuje u procesu dubokog izvlačenja zbog savijanja i ispravljanja lima preko radijusa prstena za izvlačenje. Po ovom izrazu, dodatno naprezanje zbog savijanja, u procesu dubokog izvlačenja, direktno je proporcionalno pomjeraju neutralne linije u procesu savijanja lima prema centru savijanja. U stvari, to je vrijednost srednjeg radijalnog napona po debljini lima u procesu savijanja momentima.

Preliminary notes

SUMMARY The general solution of the plane problem in plastic region was given in the paper [3]. This solution is limited to polar coordinates and the non-hardening material. In the paper [4] are given same individual solutions of problems in the plastics region on the basis of the general solution. In this paper, on the basis of results of two papers earlier mentioned, the principal normal stresses are calculated in the ideal conditions and polar coordinates, which are the effect of a bending a sheet metal in the process of the deep drawing of rotation caps with a bottom. In this way, the directly calculation of the additional stress because of the bending and the correction of a sheet across a radius of a die for drawing is enabled in mentioned process, which increased stresses in a wall of the cap and a force of drawing.

1. UVOD Nalaženje sile i deformacionog rada u procesu dubokog izvlačenja rotacionih posuda s dnom vezano je za određivanje ukupnog radnog naprezanja. Kao što je poznato, ovo radno naprezanje dobiva se tako što se na teorijsku vrijednost radijalnog naprezanja dodaju preostala naprezanja koja se pojavljuju u realnim uvjetima. 2. OSNOVNI KOMPONENTNI NAPONI U uvjetima ravninske deformacije εz = 0, za plastično područje je ν = 0,5, treće normalno

naprezanje σz = 2

yx σσ +=

2yx σσ +

= σ3 jest i

glavno normalno naprezanje.

1. INTRODUCTION Calculation of the force and deformation work in the process of deep drawing of rotational caps with a bottom is engaged for a determination of the total working stress. As it is known, this working stress is obtained in way that on the theoretical value of radial stress remaining stresses which appears in the real conditions are added. 2. ELEMENTARY COMPONENT STRESS Under conditions of plane strain εz = 0, for plasticity region is ν = 0, 5, the third normal

stress 321

22σ

σσσσσ =

+=

+= yx

z is principal

normal stress.


76

Komponentna naprezanja σx, σy i τ (τ = τxy = τyx) mogu se izraziti posredstvom glavnih normalnih naprezanja σ1, σ2 i ugla nagiba ϕ prvog glavnog normalnog naprezanja σ1 u odnosu na osu x u vidu [1]

The components stress σx, σy and τ (τ = τxy = τyx) can be expressed through the principal normal stresses σ1, σ2 and the angle of inclination φ of the first principal normal stress σ1 in respect to axis x as [1]

σx = 2

21 σσ + + 2

21 σσ − cos 2ϕ

σy = 2

21 σσ + - 2

21 σσ − cos 2ϕ (1)

τ = 2

21 σσ − sin 2ϕ.

U ravnini x-y sa In x-y plane with

σ = 2

yx σσ + =

221 σσ + , τmax =

221 σσ − (2)

određeno je srednje normalno naprezanje σ, koje je invarijantna veličina, i maksimalno tangencijalno (smičuće) naprezanje τmax. Naprezanja σ i τmax djejstvuju na trajektorijama linija klizanja.

the middle normal stress σ, as invariant value and maximal shear stress τmax are defined. The stresses σ, τmax effect on a slide line trajectory.

Po hipotezi najveće deformacione energije utrošene na promjenu oblika (kriterij von Misesa), uvjet početka plastičnog tečenja za ravninsko stanje deformacije izražava se u vidu [2]

According to the hypothesis of the largest deformation energy consumed to the change a shape (criterion of von Mises), the condition of the plasticity flow beginning for plain state of deformation is expressed by [2]

τmax = 2

21 σσ − = 22 4)(21 τσσ +− yx = ks, (3)

gdje je zbog jednostavnijeg izražavanja uvedena reducirana vrijednost ks specifičnog

deformacionog otpora k (2 ks = k3

2 ).

Iz (1), uzimajući u obzir (2) i (3), dobiva se

where for the purpose of simple expression reduced value ks of specific deformation resistance k ( kks 3

22 = ) is introduced. From

(1), with the using (2) and (3), system of the differential equations is obtained

σx = σ + ks cos 2ϕ σy = σ - ks cos 2ϕ (4) τ = ks sin 2ϕ

sistem jednadžbi koje zadovoljavaju uvjet plastičnog tečenja. Radi toga kod daljnjeg razmatranja problema i operiranja sa sistemom (4) nije potrebno uzimati u obzir i uvjet plastičnog tečenja, jer će ovaj uvjet biti zadovoljen za proizvoljne vrijednosti ugla ϕ.

This system satisfies the condition of the plastic flow. In order to a further consideration of the problem and an operation with system (4) the condition of the plastic flow is not needed to take into consideration, because this condition will be satisfied for an arbitrarily value of an angle φ.


77

3. TRANSFORMACIJA JEDNAČINA RAVNOTEŽE

Polarni sistem koordinata (O; r, ϕ) postavlja se tako da se podudara (poklapa) s glavnim pravcima normalnih naprezanja σ1, σ2. Drugim riječima, polarne koordinate r, ϕ su i glavni pravci normalnih naprezanja σ1 = σr, σ2 = σϕ. Tada je veza osnovnih x, y i polarnih koordinata r, ϕ dana sa

x = r cos ϕ, y = r sin ϕ. (5)

Diferencijalne jednadžbe ravnoteže elementa koji se nalazi u uvjetima ravninskog stanja, uz zanemarivanje inercionih (zapreminskih) sila može biti predstavljena u vidu

0=∂∂

+∂∂

yxx τσ , .0=

∂

∂+

∂∂

yxyστ (6)

U idealnim uvjetima plastičnog tečenja (bez očvršćavanja) ks = const., jednadžbe (6), u polarnom koordinatnom sistemu r, ϕ, transformiraju se u jednadžbu [3]

.2sincossincos

skxr

r −=∂∂

+−

+∂∂ σ

ϕϕϕϕσ (7)

Jednadžba (7) je linearna, nehomogene i prvog reda.

3. TRANSVORMATION OF EQUATIONS Polar system coordinates (O; r, φ) are arranged that coincide to the principal directions of normal stresses σ1, σ2. In other words, polar coordinates r, φ are also principal directions of the normal stresses σ1 = σr, σ2 = σϕ. Then, the connection between elementary x, y and polar coordinates r, φ are given by x = r cosϕ, y = r sinϕ. (5) Differential equations of equilibrium of an element which is situated under plane state conditions, ignoring the inertia (volume) force can be presented by

0=∂∂

+∂∂

yxx τσ , .0=

∂

∂+

∂∂

yxyστ (6)

In ideal conditions of plastic flow (without hardening) ks= const., in polar system of coordinates r, φ, equation (6) are transformed to equation [3]

.2sincossincos

skxr

r −=∂∂

+−

+∂∂ σ

ϕϕϕϕσ (7)

The equation (7) is linear, non homogenous and first order.

4. OPĆE RJEŠENJE Za jednadžbu

skxr

r 2sincossincos

−=∂∂

+−

+∂∂ σ

ϕϕϕϕσ (σr > σϕ)

prvi nezavisni integrali dani su sa [3] ln r + ln(cos ϕ - sin ϕ) = C1 (8) σ - 2ks ln(cos ϕ - sin ϕ) = C2. Za jednadžbu

skxr

r 2sincoscossin

−=∂∂

+−

−∂∂ σ

ϕϕϕσ (σr < σϕ)

prvi nezavisni integrali dani su sa [4] ln r + ln(sin ϕ - cos ϕ) = C1 (9) - σ - 2ks ln(sin ϕ - cos ϕ) = C2.

4. GENERAL SOLUTOIN For equation

skxr

r 2sincossincos

−=∂∂

+−

+∂∂ σ

ϕϕϕϕσ (σr >σϕ),

the first independent integrals is given by [3] ln r + ln(cos ϕ - sin ϕ) = C1 (8) σ - 2ks ln(cos ϕ - sin ϕ) = C2. For equation

skxr

r 2sincoscossin

−=∂∂

+−

−∂∂ σ

ϕϕϕσ (σr < σϕ),

the first independent integrals is given by [4] ln r + ln(sin ϕ - cos ϕ) = C1 (9) - σ - 2ks ln(sin ϕ - cos ϕ) = C2.


78

5. SAVIJANJE MOMENTIMA U procesu dubokog izvlačenja preko zaobljene ivice prstena za izvlačenje polumjera rm (slika 1) lim se savija. Ako se pretpostavi da se u procesu ne koristi držač lima, zanemari trenje između alata i radnog dijela može se uzeti da se savija momentima u plastičnom području.

5. BENDING WITH MOMENTS In the deep drawing process over a round rim of the drawing die with radius rm (Figure 1) a sheet is bent. If it is supposed that in the process of drawing the blank holder does not use, the friction between a tool and a piece of work is neglected, then can be suppose that it is buckled with moments in the plastic region.

Slika 1. Savijanje momentima Figure 1. Bending and correcting with the moments

Glavno radijalno naprezanje σr po čitavom presjeku je tlačno. Glavno obimno naprezanje σϕ tlačno je u zoni r < ρn i vlačno za r > ρn ≤ rm + s = R1, gdje je ρn polumjer neutralnog vlakna. Treće glavno normalno naprezanje

σθ = 2

ϕσσ +r , pod uvjetom da se proces odvija

u uvjetima ravninskog deformiranja. Uz pretpostavku da nema očvršćavanja, postavljanje pravouglog koordinatnog sistema u centar polumjera rm, tačaka O, prstena za izvlačenje omogućava korištene općih rješenja danih u radovima [3,4]. U zoni r > ρn prvo glavno normalno naprezanje je obimno naprezanje σϕ (σr < σϕ). Srednje normalno naprezanje σ = σθ, za plastično deformiranu oblast, dano je sa [4]

.ln21 1 ⎟⎠

⎞⎜⎝

⎛ −=rRksσ (10)

Koristeći uvjet plastičnog tečenja i definiciju srednjeg normalnog naprezanja σ

,22σσσ

σσ

ϕ

ϕ

=+

=−

r

sr k (11)

dobivaju se vrijednosti druga dva glavna normalna naprezanja

The principal radial stress σr around a complete cross-section is compressive stress. The principal circumferential stress σφ in the zone r<ρn is compressive stress and tensile stress for r > ρn ≤ rm + s = R1, where the ρn is radius of the neutral surface. The third principal normal

stress is given by σθ = 2

ϕσσ +r , under the

condition the process is evolved in the condition of plane deformation state. Under the suppose that the process is evolved in non hardening condition, putting the rectangular coordinate systems in the center of the radius rm, the point O of the drawing die, enable the application of the solutions given in the papers [3, 4]. In the zone r > ρn the first principal stress is circumferential stress σφ (σr < σφ). The middle normal stress σ = σθ, in the plastic region, is given by [4]

.ln21 1 ⎟⎠

⎞⎜⎝

⎛ −=rRksσ (10)

Using the condition of plastic flow (3) and definition of the middle principal normal stress σ

,22σσσ

σσ

ϕ

ϕ

=+

=−

r

sr k (11)

the values of other normal stresses are obtained as

y

ϕ

O x

rm

s

ρ n

M

M


79

.ln12

ln2

1

1

⎟⎠

⎞⎜⎝

⎛ −=

−=

rRk

rRk

s

sr

ϕσ

σ (12)

U zoni r < ρn sva tri glavna normalna naprezanja su naprezanja pritiska. Prvo glavno normalno naprezanje je radijalno naprezanje σr

(σr > σϕ). Srednje normalno naprezanje σ = σθ, za plastično deformiranu oblast, dano je sa [4]

.ln21 ⎟⎟⎠

⎞⎜⎜⎝

⎛+−=

ms r

rkσ (13)

Koristeći uvjet plastičnog tečenja i definiciju srednjeg normalnog naprezanja

,22σσσ

σσ

ϕ

ϕ

=+

=−

r

sr k (14)

dobivaju se vrijednosti druga dva glavna normalna naprezanja koja djejstvuju u uzdužnim ravninama

.ln12

ln2

⎟⎟⎠

⎞⎜⎜⎝

⎛+−=

−=

ms

msr

rrk

rrk

ϕσ

σ

(15)

.ln12

ln2

1

1

⎟⎠

⎞⎜⎝

⎛ −=

−=

rRk

rRk

s

sr

ϕσ

σ (12)

In the zone r < ρn every three the principal normal stresses are compressive stress. The first principal normal stress is radial stress σr (σr > σφ). The middle normal stress σ = σθ, in the plastic region, is given by [4]

.ln21 ⎟⎟⎠

⎞⎜⎜⎝

⎛+−=

ms r

rkσ (13)

Using the condition of plastic flow (3) and definition of the middle principal normal stress

,22σσσ

σσ

ϕ

ϕ

=+

=−

r

sr k (14)

values of other two principal normal stresses acting in longitudinal planes are obtained as

.ln12

ln2

⎟⎟⎠

⎞⎜⎜⎝

⎛+−=

−=

ms

msr

rrk

rrk

ϕσ

σ

(15)

6. DODATNO NAPREZANJE ZBOG

SAVIJANJA Ukupno naprezanje, pri proračunu sile u procesu dubokog izvlačenja, sadrži i naprezanje zbog savijanja i ispravljanja lima preko zaobljene ivice prstena za izvlačenje. Prema slici 2 srednja vrijednost obimnog naprezanja σφs po debljini lima na mjestu savijanja i također na mjestu ispravljanja lima (slika 1) može se izraziti sa

6. THE EXTRA CIRCUMFERENTIAL STRESS

Total strain, when calculating the forces in the process of deep drawing, includes a strain due to bending and straightening the sheet over the rounded edges of the pull ring. According to Figure 2, the mean value of extensive stress σφs by the thickness of the sheet at the point of bending and also at the point of correcting plate (Figure 1) can be expressed with.

σφs = s1∫

1R

rm

drϕσ = drrr

rR

ks

n

mn r m

R

s ⎟⎟⎠

⎞⎜⎜⎝

⎛+−− ∫∫

ρ

ρ

)ln1()ln1(21 1

1 .

Nakon integracije dobiva se After integration an expression can be given by

∫11 R

rm

drs ϕσ = )ln2(21

21

1n

MnMns

rRrRks ρ

ρρ ++− .

Ako se za polumjer neutralne linije uzme vrijednost [ ] Mn rR1=ρ dobiva se

If the radius of the neutral axis takes the value [6] Mn rR1=ρ a relation is given as

σφs = sk s2

)2( 11 MM rrRR +− = sk s4

)2

( 1n

MrRρ−

+ . (16)


80

U izrazu (16) na lijevoj strani u zagradi pojavljuje se razlika između vrijednosti

srednjeg polumjera ρs = 2

1 mrR + i neutralnog

polumjera ρn = mrR1 savijenog lima. Prema tome, kod savijanja lima momentima pojavljuje se i obimna sila, što je suprotno od dosadašnjih shvaćanja da kod savijanja lima momentima ova sila ne postoji. Prema slici 1 u prvoj operaciji procesa dubokog izvlačenja pojavljuje se dodatno naprezanje Δσρ zbog savijanja i ispravljanja lima s vrijednošću dva puta većom od σφs iz (16), tj. Δσρ =

sk s2 )

2( 1

1m

m rRrR−

+, odnosno

Δσρ =2ks s

ns ρρ − . (17)

In the expression (16) on the left in parentheses appears the difference between the value of the

middle radius ρs = 2

1 mrR + and neutral radius

ρn = mrR1 of bended sheet. Thus, in the case of the sheet bending with moments appear circumferential forces also, what is opposed to the current understanding that in the case of the sheet bending with moments this force does not exist. Referring to Figure 1 in the first operation of deep drawing process occurs additional stress Δσρ due to bending and correction of sheet with a value greater twice than σφs from

(16), i.e Δσρ = sk s2 )

2( 1

1m

m rRrR−

+,

Δσρ =2ks s

ns ρρ − . (17)

7. ZAKLJUČAK Rezultat ovog rada jest analitički izraz (17) za izračunavanje dodatnog naprezanja Δσρ koje se pojavljuje u procesu dubokog izvlačenja zbog savijanja i ispravljanja lima preko polumjera rM prstena za izvlačenje. Po ovom izrazu, dodatno naprezanje zbog savijanja Δσρ direktno je proporcionalno pomjeraju neutralne linije, ρs – ρn, u procesu savijanja lima prema centru savijanja. Ustvari, to je vrijednost srednjeg obimnog naprezanja σφs (16) po debljini lima u procesu savijanja momentima. Ovo je suprotno od dosadašnjih shvaćanja da u procesu savijanja momentima srednje obimno naprezanje σφs je jednako nuli kod ne očvršćavajućih materijala [5].

7. CONCLUSION The result of this paper is the analytical expression (17) for the calculation of additional stress Δσρ which is appeared in the process of deep drawing because of the bending and correcting a sheet across the rim of the draw-die. According to this expression, the additional stress because of the bending Δσρ, in the process of deep drawing, is directly proportional to the neutral line shift, ρs – ρn, to center of bending a sheet. In fact, it is the value of the mean circumference stress σφs (16) by the thickness of the sheet in the process of bending with moments. This is contrary to previous understanding that in the process of bending with moments mean circumference stress σφs is equal to zero for no-hardening materials [5].

O

Slika 2. Dijagrami naprezanja Figure 2. Diagram of the stresses

2ks

2ks rm

R1

ρ n

σφ

σρ


81

U dosadašnjoj praksi smatralo se da dodatno naprezanje, u procesu dubokog izvlačenja zbog savijanja lima, nastaje na dijelu trase prstena gdje se pojavljuje skokovita izmjena njegovog polumjera. Na toj ideji dolazilo se do ovog dodatnog naprezanja posredstvom izjednačavanja radova obimne sile i momenta savijanja [6]. Pri tome se kod izračunavanja momenta M za polumjer neutralne linije koristio izraz mn rR1=ρ , a kod izračunavanja dodatnog naprezanja Δσρ koristio se izraz ρn = rm + 0,5 s.

In the to date practice it is supposed that the additional stress, in the process of deep drawing because of the bending a sheet, rises on the part of die where exists a significant change of its curvature. On this idea, the calculation of this additional stress was done through the process of equalization the works of the forces and moment of the bending on the neutral line. In the same time, for the calculation of the moment M for radius of neutral line the expression ρn = mrR1 is used and for the calculation of additional stress Δσp an expression ρn = rm + 0,5 s is used.

8. LITERATURA - REFERENCES [1] Musafia, B.: Primijenjena teorija

plastičnosti I i II dio, Univerzitet u Sarajevu, Sarajevo, 1974.

[2] Sokolovskij, V.V.,. Teorija plastičnosti, Visšaja škola, Moskva, 1969.

[3] Hasanbegović, S.: Opće rješenje ravninskog problema u polarnim koordinatama za plastično područje, Časopis Mašinstvo 1(1), Zenica, 1997., p.23-27.,

[4] Hasanbegović, S.: Neka rješenja ravninskih problema u polarnim koordinatama za plastično područje, Časopis Mašinstvo 1(2), Zenica, 1998., p. 15-21

[5] Storožev, M. V., Popov, E. A.: Teorija obrabotki metallov davieniem, Mašinostroenie, Moskva, 1977.

[6] Talić-Čikmiš, A.: Prilog analizi napona i deformacija u procesu izvlačenja pravouglih tijela, Doktorska disertacija, Mašinski fakultet Univerziteta u Zenici, Zenica, 2009.

Coresponding author: Amra Talić-Čikmiš University of Zenica, Faculty of Mechanical Engineering, B & H Tel: +387 32 449 120 e-mail: [email protected]

CONFERENCE DATE AND VENUEThe conference will be held from 02 to 04 2016 in

Zenica, B HZenica is a town in the Zenica-Doboj Canton, in the central part ofBosnia and Herzegovina. Area of the city is 500 km ², population isabout 130 thousand. Economic center of the geographic region ofcentral Bosnia and near Travnik and Jajce, the most important cityin that part of the state.

nd th June HotelZenica, osnia and erzegovina.

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Conference objectives are:- Gathering of people engaged in maintenance funds for theoperation of various aspects and their structural organization,- Communication of the results of research in the field ofmaintenance, as theoretical and practical,- Exchange of experiences from practical maintenanceactivities,- Transfer of knowledge in the field of maintenance.

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UDRUŽENJEDRUŠTVO ODRŽAVALACAU BOSNI I HERCEGOVINI

UNIVERSITY OF ZENICA(Bosnia and Herzegovina)

FACULTY OF MECHANICALENGINEERING

DRUŠTVO ODRŽAVALACAU BOSNI I HERCEGOVINIASSOCIATION „SOCIETYOF MAINTAINERS INBOSNIA AND HERZEGOVINA“

Mašinstvo 3-4(12), 83 – 88, (2015) D.Tiro: PRILOG ISTRAŽIVANJU ZATEZNE….

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PRILOG ISTRAŽIVANJU ZATEZNE ČVRSTOĆE DIJELOVA DOBIJENIH FDM PROCESOM CUBE 3D PRINTANJA

CONTRIBUTION TO THE TENSILE STRENGTH RESEARCH FOR

PARTS OBTAINED BY CUBE 3D PRINT FDM PROCESS

Dragi Tiro University „Džemal Bijedić“ Mostar, Bosnia &Herzegovina Ključne riječi: brza izrada prototipova, 3D printanje, zatezna čvrstoća, Cube 3D printer Keywords: Rapid Prototyping, 3D Printing, Tensile Strength, Cube 3D Printer Paper received: 01.07.2015. Paper accepted: 08.09.2015.

Stručni rad REZIME U ovom radu vršena su ispitivanja zatezne čvrstoće dijelova dobivenih postupkom Cube 3D printanja od PLA plastične mase. U sprovedenom istraživanju kroz statističku obradu rezultata provjeravalo se da li je zatezna čvrstoća standardnih epruveta izrađenih ovim postupkom jednaka zateznoj čvrstoći materijala. Eksperimentalna istraživanja su se sastojala od izrade standardnih epruveta od PLA plastične mase i ispitivanja njihove zatezne čvrstoće. Cube 3D proces je proces koji omogućava jednostavno i brzo dobijanje prototipova, direktno iz 3D CAD modela. Pored niza prednosti ovog postupka, istraživanje u ovom radu je pokazalo da zatezna čvrstoća dijelova nastalih postupkom Cube 3D printanja je nešto manja od čvrstoće samog materijala. Razlog je način printanja, koji produkuje poprečne presjeke dijela u kojim ima vrlo malih šupljina.

Professional paper

SUMMARY The tensile strength of parts obtained by Cube 3D printing is described in this paper. The material of the parts are PLA. In the research through the statistical analysis of results we checked whether the tensile strength of standard test specimens made by this method is equal to the tensile strength of the material. Experimental research has consisted of making parts of PLA plastics and testing the tensile strength of standard specimens obtained by Cube 3D printing process. Cube 3D process allows to easily and quickly obtain the prototype directly from 3D CAD models. Besides a number of advantages of this process, the research in this paper has shown that the tensile strength of parts produced by Cube 3D printing is somewhat less than the strength of the material. The reason is the way of printing that produces cross-sectional of part in which there are a very small cavities.

1. UVOD Svi FDM postupci rade na principu predstavljenom na slici 1. Materijal u vidu žice se dovodi u ekstruder, gdje se topi i deponuje sloj po sloj, pri čemu očvršćava, tako da se dobija radni komad zadatog oblika i dimenzija. Cube 3D printer može izrađivati dijelove veličine do 140 mm u sva tri pravca. Kompanija 3D Systems uz Cube 3D printer daje i jednostavan softver, koji STL fajl pretvara u CUBE fajl. U ovom istraživanju korišten je materijal PLA – Polylactic Acid, koji je biorazgradiv materijal i dobija se iz biomaterijala. Ovaj materijal nema mirisa, pa se može koristiit za printanje u uredu [5, 6]. Neke negativne karakteristike Cube 3D printera su: printer je prilično glasan i dugo se „priprema za posao“, a dimenzije na isprintanom modelu nisu vrlo precizne [11].

1. INTRODUCTION All FDM methods operate on the principle presented in Figure 1. The material in the form of wire is brought into the extruder, where it melts and is deposited layer by layer. Each layer solidifies and the workpiece receives a specified shape and dimensions. Cube 3D printer is one of many that use FDM technology. The company 3D Systems with Cube 3D printer provides a simple software, which converts STL file into CUBE file. In this study we have used material PLA - Polylactic Acid, which is a biodegradable material and obtained from biomaterials. This material is odourless, so it can be used for printing in the office [5, 6]. Some negative characteristics of Cube 3D printer are: printer is quite loud and it need long time to "prepare for the job". The dimensions of printed models aren’t very accurate [11].


84

očvrsli plastični material (prema konturi modela)

ekstruziona brizgalica

dotur plastične žice

plastična žica sa namotaja

topionik

Slika 1. FDM postupak [1] Slika 2. Cube 3D printer [11] Figure 1. FDM process [1] Figure 2. Cube 3D printer [11] 2. ISTRAŽIVANJE U literaturi je data zatezna čvrstoća PLA materijala između 48 i 53 MPa. Eksperimentalnim ispitivanjem u ovom radu nastojalo se utvrditi da li je zatezna čvrstoća dijelova dobivenih postupkom Cube 3D printanja jednaka toj vrijednosti. Ispitivanje modela dobivenih postupkom Cube 3D printanja je izvršeno na kidalici maksimalne sile od 50 kN (Slika 3. i 4.). Prilikom ispitivanja modela na kidalici pomoću odgovarajućeg softvera na osnovu zadatih vrijednosti za debljinu i širinu modela dobijene su vrijednosti za maksimalnu silu i izduženje. 2.1. Statistička obrada podataka U eksperimentu je izvršeno mjerenja maksimalne sile zatezanja. Aritmetička sredina primijenjena na rezultate eksperimenta daje srednju ocjenu zatezne čvrstoće materijala PLA:

36,32=Rmx MPa. Standardna devijacija:

3,065)(11

2 =−= ∑=

n

iRmiRm xx

nσ

Procjena standardne devijacije osnovnog skupa:

3,431=

−=

nnS RmRm σ

2. RESEARCH Tensile strength of PLA material in the literature is between 48 and 53 MPa. We sought to determine whether the tensile strength of parts obtained by the method Cube 3D printing is equal to that value or not by experimental research. We conducted our test of models obtained by the Cube 3D printing on the testing machine with maximum force of 50 kN (Figure 3. and 4.). When testing the model on the testing machine we get a value of maximum force and elongation with the appropriate software based on the given value for the thickness and width of the model. 2.1. Statistical analysis We measured the maximum tension force in the experiment. We get a tensile strength on the basis of that. The arithmetic mean gives evaluation of tensile strength for material PLA:

36,32=Rmx MPa. Standard deviation:

3,065)(11

2 =−= ∑=

n

iRmiRm xx

nσ

Estimate the standard deviation of the basic set:

3,431=

−=

nnS RmRm σ


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Slika 3. Ispitivanje na zatezanje Figure 4. Epruvete nakon ispitivanja na kidalici Slika 3. Testing Machine Figure 4. The specimens after tests on the testing machine

Provjera hipoteze o aritmetičkoj sredini osnovnog skupa na osnovu malog uzorka (Studentov t – test):

17,61436559

53,43

4832,36=

−=

−=

nS

Xxt

Rm

RmRmRm

Iz tabele za broj stepeni slobode k=n-1=5-1=4 i tRm=7,614365591 nalazi se:

01,0)(001,0 1 <≥< ttP Na osnovu toga može se konstatovati da je:

05,0)( 1 <≥ ttP . Tada razlika između aritmetičke sredine osnovnog skupa i aritmetičke

sredine uzorka Rmx i RmX nije slučajna već signifikantna, odnosno visoko signifikantna, to znači da se ne može pretpostaviti da je aritmetička sredina osnovnog skupa jednaka traženoj vrijednosti, tj. 48.

10,8739399

53,43

5332,36=

−=

−=

nS

Xxt

Rm

RmRmRm

Testing the hypothesis about arithmetic mean of the basic set based on a small sample (Student t - test):

17,61436559

53,43

4832,36=

−=

−=

nS

Xxt

Rm

RmRmRm

We can find from a table for the number of freedom degrees k=n-1=5-1=4 and tRm= 7,614365591:

01,0)(001,0 1 <≥< ttP On this basis, we can conclude that:

05,0)( 1 <≥ ttP . So, the difference between the arithmetic mean of the basic set and of the sample ( Rmx and RmX ) is not random but significant, or highly significant, this means that we cannot assume that the mean of basic set equal to the requested value, i.e. 48MPa.

10,8739399

53,43

5332,36=

−=

−=

nS

Xxt

Rm

RmRmRm


86

Iz tabele za broj stepeni slobode k = n-1 = 5-1 = 4 i tRm= 10,8739399 nalazi se:

001,0)( 1 <≥ ttP Na osnovu toga možemo konstatovati da je sigurno: 05,0)( 1 <≥ ttP Dakle, razlika između aritmetičke sredine osnovnog skupa i aritmetičke sredine uzorka je visoko signifikantna, to znači da se ne može pretpostaviti da je aritmetička sredina osnovnog skupa jednaka traženoj vrijednosti, tj. 53MPa. Pošto je P(|t|≥t1) < 0,05 u oba slučaja na osnovu t – testa može se zaključiti da je zatezna čvrstoća materijala dijelova dobivenih postupkom Cube 3D printanja različita od vrijednosti zatezne čvrstoće materijala, tj. manja je.

From the table for the number of freedom degrees k=n-1 = 5-1 = 4 and tRm= 10,8739399:

001,0)( 1 <≥ ttP From this we can conclude for sure:

05,0)( 1 <≥ ttP . So, the difference between the arithmetic mean of the basic set and of the sample is highly significant for value 53MPa, too. Since in both cases based on the "t - test" P(|t|≥t1) < 0,05, we can conclude that the tensile strength of the parts obtained by the method Cube 3D printing is different from the materials’ tensile strength, i.e. it is less.

Tabela 1. Statistička obrada rezultata dobivenih ispitivanjem na zatezanje

Table 1. The results of statistical data processing Rm (MPa)

Zatezna ćvrstoća PLA the tensile strength of PLA 48 - 53

= 36,31888859

= − 3,065052312

− √ (nivo pouzdanosti 95%) (confidence level 95%)

32,06459599 + √ (nivo pouzdanosti 95%) (confidence level 95%)

40,5731812

nSC = (mjera nepouzdanosti)

(measure of uncertainty) 4,254292609

%100⋅=xCc (relativna nepouzdanost)

(relative unreliability) 11,71371915 %

Potvrda ovog izvršiti će se i pomoću ocjene tačnosti aritmetičke sredine osnovnog skupa na osnovu uzorka. Provjeriti će se tačnost aritmetičke sredine dobivene eksperimentom.

Confirmation of this will be done also by evaluation accuracy of the arithmetic mean of the basic set based on a sample. We will check the accuracy of the arithmetic mean obtained by experiment.

− √ < < + √ = 2 , = 95%


87

Za P = 95% = 0,95 i k = n–1 = 5-1 = 4, iz tabele očita se vrijednost t = 2,776. Tada je aritmetička sredina osnovnog skupa za Rm:

53,43776,232,36

53,432,776-36,32 +<< Rmμ

57,0406,23 << Rmμ

Na osnovu rezultata, može se zaključiti da se zatezna čvrstoća materijala ne nalazi u intervalu pouzdanosti 32,06 ÷ 40,57. Time je potvrđeno da je zatezna čvrstoća materijala dijelova dobivenih postupkom Cube 3D printanja različita od vrijednosti zatezne čvrstoće materijala, tj. manja je. U Tabeli 1. dati su rezultati statističke obrade podataka. Iz Tabele 1. se vidi da zatezna čvrstoća materijala PLA (48 ÷ 53)MPa ne ulazi u interval pouzdanosti (32,06 ÷ 40,57)MPa.

For P=95% = 0,95 and k=n–1=5-1= 4, we obtain the value t from a table: t=2,776. Then the arithmetic mean of the basic set of Rm:

53,43776,232,36

53,432,776-36,32 +<< Rmμ

57,0406,23 << Rmμ

Based on this, we can conclude that the tensile strength of the material is not in the confidence interval 32,06 ÷ 40,57. This confirmed that the tensile strength of the parts obtained by the method Cube 3D printing is different from the materials’ tensile strength, i.e. it is less. Table 1. shows the results of statistical data processing. The tensile strength of the material PLA (48 ÷ 53)MPa does not fall within the confidence interval (32,06 ÷ 40,57)MPa as we can see from Table 1.

3. ZAKLJUČAK Na osnovu Studentovog t – testa i ocjenom tačnosti aritmetičke sredine osnovnog skupa pokazano je da razlika aritmetičkih sredina Rmx

i RmX nije slučajna već signifikantna, odnosno visoko signifikantna. Zatezna čvrstoća materijala dijelova dobivenih postupkom Cube 3D printanja je različita od vrijednosti zatezne čvrstoće materijala, tj. manja je. Cube 3D printer prilikom printanja, nastoji da uštedi materijal, te cijeli prototip nije od punog materijala. Vanjske stjenke modela su od punog materijala, a unutrašnje presjeke Cube 3D printa pod uglom od 45o. Zbog toga postoje vrlo sitne šupljine u poprečnim presjecima modela i zatezna čvrstoća dijelova je malo niža od zatezne čvrstoće materijala. Na to treba računati kada se izrađuju dijelovi ovim postupkom.

3. CONCLUSION According to the Student t - test and evaluation of the accuracy of the arithmetic means has been proved that the difference between the arithmetic means ( Rmx and RmX ) is not random but significant, or highly significant. So, the tensile strength of the parts obtained by the method Cube 3D printing is different from the materials’ tensile strength, i.e. it is less. Cube 3D printer is trying to save material during printing process, and the whole prototype is not made of solid material. External model’s walls are made of solid material, and the inner sections Cube 3D prints at angle of 45o. Therefore, there is a very small cavity in the cross sections of the model and the tensile strength of parts is slightly lower than the tensile strength of the material. It should be borne in mind when we make the parts by this process.

4. LITERATURA - REFERENCES [1] Tiro D., Fajić A.: Trodimenzionalno

printanje i ostali postupci brze izrade, Univerzitet „Džemal Bijedić“ Mašinski fakultet u Mostaru, ISBN: 996860433, Mostar 2008.

[2] Vrbanec D.: Analiza dostupnih postupaka brze izrade prototipova, Sveučilište u Osjeku, Strojarski fakultet Slavonski Brod, 2011.

[3] Stanić, J.: Upravljanje kvalitetom proizvoda – Metode I, Mašinski fakultet Beograd, 1995.

[4] Stanić, J.: Upravljanje kvalitetom proizvoda – Metode II, Mašinski fakultet Beograd, 1991.

[5] http://www.3d-tisk.si/S7500/Materiali [6] http://www.utwente.nl/ctw/opm/research/d

esign_engineering/rm/RM%20processes/ [7] http://www.cnet.com/products/3d-systems-

cube-2013/


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[8] Manish S., Kumar S. et al.: Influence of Process Parameters on Product Characteristics in Direct Metal Deposition: A Review“, Conference: Recent Advancements in Manufacturing and its Management, India, February, 2014.

[9] http://www.explainingthefuture.com/3dprinting.html

[10] http://www.3dsystems.com/ [11] Tiro D., Brdarević S.: Prilog istraživanju

dimenzione tačnosti dijelova dobijenih FDM procesom Cube 3D printanja, 9th Research/Expert Conference with International Participations ”QUALITY 2015“, Neum, B&H, June 10 – 13, 2015., p.

Coresponding author: Dragi Tiro University of „Džemal Bijedić“ Mostar Faculty of Mechanical Engineering Email: [email protected] Phone: +387 61 285 347

Mašinstvo 3-4(12), 89 – 103, (2015) N.Jarović-Bajramović,…: POSTUPAK KALIBRACIJE I UTICAJI….

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POSTUPAK KALIBRACIJE I UTICAJI KOJI SE UZIMAJU U OBZIR TOKOM KALIBRACIJE KONTAKTNIH TERMOMETARA ZA

MJERENJE TEMPERATURE ČVRSTE POVRŠINE

CALIBRATION PROCESS AND IMPACTS TAKEN INTO ACCOUNT DURING THE CALIBRATION OF CONTACT THERMOMETERS FOR

TEMPERATURE MEASUREMENT OF SOLID SURFACE

Narcisa Jarović-Bajramović1, Nermina Zaimović-Uzunović2, Edin Terzić1 1Metallurgical Institute „Kemal Kapetanović“ 2University of Zenica, Bosnia &Herzegovina Ključne riječi: Kalibracija, kontaktni termometri, mjerna nesigurnost Keywords: calibration, contact thermometers, measurement uncertainty Paper received: 21.09.2015 Paper accepted: 04.11.2015.

Originalan naučni rad REZIME Na prototipu/etalonu – aparatura za kalibraciju kontaktnih termometara na čvrstoj površini (u nastavku teksta prototip), izvršena su mjerenja odnosno kalibracija kontaktnog termometra. Kako bi dobijeni rezultat kalibracije bio potpun izvršena je procjena mjerne nesigurnosti. Iskorištena je mogućnost variranja parametra uticaja ambijentne temperature tik iznad referentne površine. Ovaj parametar je direktno proistekao iz konstrukcije samog protitpa.

Original scientific paper

SUMMARY Measurements, calibrations of contact thermometer have been conducted on prototype/standard – apparatus for calibration of contact thermometers on solid surface (in following text just prototype). In order to make the calibration obtained result whole an estimation of measurement uncertainty is done. The possibility to vary parameter of influence of ambient temperature just above the reference surface is used. This parameter is directly derived from the construction of the prototype.

1. UVOD Kako bi bili sigurni u rezultate mjerenja kontaktnim termometrom svako mjerilo odonosno senzor mora biti provjeren, kalibrisan. Kalibracija je operacija koja, pod određenim uvjetima, u prvom koraku, određuje odnos između vrijednosti veličine sa mjernom nesigurnošću od etalona mjerenja i odgovarajućih pokazivanja sa pridruženim mjernim nesigurnostima, a u drugom koraku, koristi ovu informaciju da uspostaviti odnos za dobijanje mjernog rezultata iz očitanja. [1] Kontaktni termometri za mjerenja na čvrstoj površini su predmet kalibracije na prototipu i imaju svoj udio u doprinosima pri procjeni mjerne nesigurnosti.

1. INTRODUCTION To be sure in measurement results of contact thermometer every measure or sensor must be checked, calibrated. Calibration is the operation that, under certain conditions, in a first step, define the relationship between the value of the size of the uncertainty of measurement standards and corresponding indications with associated measurement uncertainty, and in the second step, uses this information to establish a relation for obtaining a measurement result of the reading. [1] Contact thermometers for measuring the solid surface are subject to calibration on a prototype and have their share of contributions to the assessment of measurement uncertainty.


90

Naime, široka je primjena kontaktnih termometara u prehrambenoj industriji, kulinarstvu, te raznim granama industrije, gdje se javlja potreba za mjerenje temperature čvrste površine. Na primjer premazi na bazi recijskih smola se ne smiju primjenjivati na temperaturama ispod tačke rosišta ili na temperaturi ispod 5°C te se u te svrhe koristi kontaktni termometar kao i u auto industriji i drugim lakirerskim granama, gdje se premazi odnosno slojevi nanose tek nakon provjere temperature koristeći kontaktne termometre. Isti također imaju primjenu kod praćenja temperature toplotnih vodova, građevinarstvu i u mnoge druge svrhe. 2. POSTUPAK KALIBRACIJE

KONTAKTNIH TERMOMETARA ZA MJERENJE TEMPERATURE ČVRSTE POVRŠINE I KORIŠTENA OPREMA

Postoje različite izvedbe kontaktnih termometara za mjerenja na čvrstoj površini čiji senzori su obično termoelementi ili otporni termometri. Na Slici 1. su dati samo neki primjeri izvedbi ove vrste kontaktnih termometara.

Namelly, there is wide application of contact thermometers in the food industry, culinary, and various industries, where there is a need to measure the temperature of the solid surface. For example coatings based secretion resin should not be used at temperatures below the dew point or at a temperature below 5°C. So contact thermometers are used for this purpose as well as in the auto industry and other branches of the paint, where the coatings or layers are applied only after checking the temperature using a contact thermometer. The same also have application in the monitoring of temperature heat pipes, construction and many other purposes. 2. THE METHOD OF CALIBRATION OF

CONTACT THERMOMETERS FOR TEMPERATURE MEASUREMENT OF SOLID SURFACE AND USED EQUIPMENT

There are different versions of contact thermometers for measuring temperarture of solid surface whose sensors are typically thermocouples or resistance thermometers. The Figure 1 shows only some exemples of these types of contact thermometers.

a) b)

c) d)

Slika 1. Kontaktni termometri za mjerenja temperature na čvrstoj površini Figure 1. Contact thermometers for measuring temperature at solid surface

Uporedna metoda kalibracije senzora temperature je metoda, gdje se do rezultata kalibracije dolazi na bazi uporednog očitavanja etalona poznatih karakteristika i mjerila koje se podvrgava kalibraciji i to na temperaturnim tačkama ostvarenim uz pomoć korištenja odgovorajuće aparature.

The comparison method of calibration of temperature sensor is a method where the calibration results are obtained on the basis of comparative readings of standard of known characteristics and measure that is calibrated at certain temperature points achieved by using appropriate apparatus.


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Očitana razlika predstavlja odstupanje kalibri-sanog mjerila od vrijednosti zadate kalibracione tačke. Jedan od načina mjerenja temperature na čvrstoj površini je mjerenje kontaktnim termometrima. Mjerenje temperature na ovaj način je proisteklo iz mnogih aspekata života i rada, te otud i potreba za “pravilnom” provjerom odnosno kalibracijom te vrste termometara. Većina termometara pravljena tako da se koriste, a i kalibrišu uporednom metodom odnosno da se uranjaju u mjerni medij, bez da ambijentni uvjeti imaju značajan utjecaj na konačan rezultat. Ali kada je riječ o kontaktnim senzorima za mjerenje temperature (čvrste) površine i kalibraciji istih oni u potpunosti odstupaju od ovog pravila. Oni su koncipirani za direktnu primjenu odnosno mjerenje na čvrstoj površini. [2, 3]. Slijedom navedenog nekoliko nacionalnih metroloških laboratorija je razvilo uređaje koji generišu temperaturu površine pod uvjetima koji najviše nalikuju onima koji se susreću tokom uobičajenog korištenja površinskih senzora. [4]. A slijedeći primjer prototip ove vrste aparature je razvijen i na Metalurškom institute “Kemal Kapetanović” Zenica. Kontaktni termometri se općenito kalibrišu uz korištenje kontrolirane temperature vruće ploče. Na ovakvom uređaju referentna temperatura je ona na gornjoj površini metalnog tijela, a ista se određuje linearnom ekstrapolacijom iz očitanja kalibriranih senzora (sondi) koji su uvučeni u tijelo na različitim dubinama odnosno udaljenostima od referentne površine. Stvarna temperatura referentne površine u mnogome zavisi od interakcije senzora na površinu. [5, 6] Princip kalibriranja senzora za mjerenja na površini je poređenje standardne temperature površine (dobijenom ekstrapoliranjem) sa temperaturom senzora određenom kad se senzor za mjerenje na površini direktno prisloni na jedan od materijala (referentnih površina). Prema Michaelsky-om [2] metod ekstrapoliranja predstavlja jedan od najpreciznijih načina određivanja temperature površine čvrstih tijela, a bazira se na principima datim na slici 2. Za određivanje temperature referentnih tijela koja su deblja, a koja se mogu posmatrati kao polu-beskonačna tijela, također se može koristiti metod Yarisheva i Minina (1969) koji se pokazao kao veoma precizan. Ovaj metod se zasniva na mjerenju temperature q1 i q2 sa dva senzora, na određenim rastojanjima x1 i x2 od referentne površine, pri čemu se temperatura površine računa iz izraza:

The difference that is read out represents the deviation of calibrated measure from the value of set calibration point. One way to measure the temperature of the solid surface is a measurement by using contact thermometers. Temperature measurement in this way is derived from the many aspects of life and work, and hence the need for a „proper " checking and calibration of this type of thermometer. Most thermometers are created so that it is used and calibrated by comparison method meaning to be immersed in the measuring medium, where ambient conditions have no significant impact on the final score. But when it comes to contact sensors for measuring temperature of (solid) surface and calibrating them they completely deviate from this rule. They are designed for direct application or measurement on a solid surface. [2, 3]. Consequently, several national metrology laboratories have developed devices that generate a surface temperature under conditions that most closely resemble those encountered during normal use of the surface sensors. [4]. And following example of the prototype of this kind of apparatus has been developed and the Metallurgical Institute "Kemal Kapetanovic" Zenica. Contact thermometers are generally calibrated using temperature-controlled hot plate. For such a device reference temperature it is on the upper surface of the metal body, and it is determined by linear extrapolation from the readings of calibrated sensors (probes) that are pulled into the body at different depths and distances from the reference surface. The actual temperature of the reference surface depends largely on the interaction of the sensor to the surface. [5, 6] The principle of calibration of sensors for measuring the surface is comparison of standard surface temperature (obtained by extrapolating) with temperature from sensor specified when the sensor for measuring the surface is directly pressed on one of the materials (the reference surface). According to Michaelsky [2] the extrapolation method represents one of the most precise ways to determine temperature of solid body and is based on principles shown at figure 2. To determine the temperature of the reference bodies that are thicker and which can be seen as a semi-infinite body, can also be used method Yarisheva and Min's (1969) which proved to be very precise. This method is based on measuring the temperature of q1 and q2 from the two sensors, the specified distance x1 and x2 of the reference surface, wherein the surface temperature is calculated according the expression:


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Č sto tijelovrEkstrapoliranavrijednost ( )t

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Slika 2. Shematski prikaz metoda mjerenja temperature ekstrapoliranjem Figure 2. Schematic representation of the method of temperature measurement by extrapolating

ϑ ( ) = ϑ ( ) − ϑ ( )ϑ ( ) (1)

Sa malim područjem variranja temperature i malim temperaturnim razlikama u referentnom tijelu, kao što su ploče konačno male debljine, moguće je obezbijediti konstantnu ili približno konstantnu termičku provodnost λb, što znači da je pad temperature u tijelu vrlo blizak linearnom. U ovom slučaju se radi o veoma jednostavnoj linearnoj ekstrapolaciji, zasnovanoj na dvije mjerne vrijednosti što se može izraziti slijedećom jednadžbom:

ϑ ( ) = ϑ ( ) ϑ ( ) (2) Metoda ekstrapolacije se u principu koristi za mjerenje temperature referentnih površina gdje su kontrolirani uvjeti i obezbjeđeno stacionarno stanje sistema. Obično se koriste tanki termolementi koji su postavljeni uzduž izotermi unutar čvrstog tijela. Samo se takvi termolementi sa mjernim krajevima izoliranim vatrostalnim izolacionim materijalima koriste u metalima i poluprovodnicima. Metoda ekstrapoliranja je zasnovana na pokazivanju temperature svakog pojedinog termolementa te se tako može odrediti temperatura površine bez da se deformiše temperaturno polje odnosno naruši originalna raspodjela temperature površine. [2, 7] Glavni izvori greški kod ekstrapolacione metode su vezani za nehomogenost i anizotropiju materijala od kojeg je izrađeno referentno tijelo i zbog deformacije temperaturnog polja do kojeg dolazi uvođenjem senzora unutar referentnog tijela.

ϑ ( ) = ϑ ( ) − ϑ ( )ϑ ( ) (1)

With a little variation of temperature and low temperature differences in the reference body, such as the board of ultimately small thickness, it is possible to provide a constant or nearly constant thermal conductivity λb, which means that the temperature fall in body very close to linear. In this case it is a very simple linear extrapolation, based on two measured values that can be expressed in the following equation:

ϑ ( ) = ϑ ( ) ϑ ( ) (2) Extrapolation method is generally used to measure the temperature of the reference surface where conditions are controlled and secured stationary state. Commonly are used thin thermocouples which are placed along the isotherms within a solid base. Only such thermocouples with measuring ends isolated refractory insulation materials used in metals and semiconductors. The method of extrapolating is based on the temperatures of each thermo’couples and thus can determine the surface temperature without deforming temperature field and distort the original distribution of the surface temperature. [2, 7]. The main sources of errors in extrapolation methods are related to the inhomogeneity and anisotropy of the material from which a reference body is made and due to the deformation of temperature field that occurs by introducing the sensor within the reference body.


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Za otklanjanje ili minimziranje ovih izvora greški preporučuje se primjena termoelemenata koji su što je moguće tanji, te njihovo uvođenje u tijelo uzduž izotermi.

To eliminate or minimase these sources of errors is recommended to use a thermocouple which is as thin as possible, and their introduction into the body along the isotherms.

2.1. Prototip – aparatura za kalibraciju

kontaktnih senzora za mjerenje temperature čvrste površine

Na slici 3. dat je izgled prototipa i referentnog tijela/ ploče i drugi podaci vezani za iste. Sa prototipom - aparaturom za kalibraciju kontaktnih termometara se nastojalo postići da ima temperaturni omjer: od ambijentne do 600 °C. To je moguće ostvariti primjenom izmjenjive referentne ploče. Jedna od bakra za opseg od ambijentne do cca 250 °C i druga od „procrona“ – Č.4171 po JUS-u za opseg temperature do 600 °C. Na slici 4. je predstavljena referentna površina izrađena od čelika.

2.1. Prototype - apparatus for calibrating contact sensors for measuring the temperature of the solid surface

Figure 3 gives an appearance of a prototype and reference bodies / boards and other data related to the same. With the prototype - apparatus for calibrating contact thermometers has sought to achieve a ratio of temperature: from ambient to 600 ° C. This can be achieved by using removable reference board. One of the copper for a range of ambient to about 250 ° C and the other of "procron" - Č.4171 by JUS for the temperature range up to 600 ° C. Figure 4 presents the reference surface made of steel.

Slika 3. Prototip aparature za Slika 4. Referentna ploča/blok (tijelo izrađeno od čelika) Figure 3. Figure 4. The reference plate / block (body made of steel) U radu je vršeno variranje i mjerenje parametra koji se ne može zanemariti, a koji je proistekao iz karakteristika izvedbe prototipa. Parametar vezan za uticaj na ambijentnu temperaturu tik iznad površine, a nastao kao posljedica broja, rasporeda i pozicije grijača u prototipu.

The research focused on measuring the variation of the parameter that cannot be ignored, and that came out of the performance characteristics of the prototype. Parameters related to the impact on the ambient temperature just above the surface, and came as result of the number, arrangement and position of the heater in the prototype.

2.2. Opis prototipa Kalibrirani termoelementi tipa K, sa slike 5. su smješteni na različitim udaljenostima, paralelno sa površinom referentnog tijela/ ploče. Isti termoelementi su prikopčani na digitalni termometar sa četiri kanala Chub-E4 (Slika 6), u svrhu praćenja vrijednosti temperatura unutar referentnog tijela, te korištenja tih podataka za ekstrapoliranje temperature referentne površine.

2.2. Description of the prototype Calibrated thermocouples type K, presented on Figure 5 are located at different distances parallel to the surface of the reference body / board. The same thermocouples are connected to a digital thermometer with four channels Chub-E4 (Figure 6), in order to monitor the value of the temperature inside the reference body, and use this data to extrapolate the temperature of the reference surface.

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94

Ovakvo pozicioniranje senzora karakteristično i kod drugih aparatura koje su ranije razvijene, s tim da nisu na svim aparaturama korišteni termoelementi tip K kao senzori.

This positioning of the sensors is characteristic in the other apparatuses that have previously been developed. But, type K thermocouples as sensors where not used at all the apparatus.

Slika 5. Termoelmenti, grijači i regulator koji su u sastavu aparature

Figure 5. Thermocouples, heaters and regulator that are part of the apparatus

Slika 6. Digitalni termometar Chub-E4 na koji

su prikopčani termoelementi za praćenje temperature unutar referentnog tijela za

ekstrapoliranje Figure 6. Digital thermometer Chub-E4 to Which the thermocouples are connected to

monitor the temperature within the reference body and to extrapolate

Slika 7. Slika tiristorskih sklopki za regulacija temperatura grijača

Figure 7. Thyristor switches to control temperature heaters

Termoelemenati tip K (prikazani na slici 5), su također korišteni i za regulaciju temperatura grijača i uvezani sa regulatorom Imago 500 (slika 5) i tiristorskim sklopkama proizvođača JUMO, tip B 70.9040.0 (slika 7.). Sve zajedno čini jedan sistem za reguliranje temperature referentnog tijela. Svi termoelementi i digitalni termometar su prethodno kalibrisani u svrhu provjere i sljedivosti istih.

Thermocouple type K (shown in Figure 5), were also used for regulating the temperature of the heater and connectd with other regulator Imago 500 (Figure 5) and thyristor switches manufacturer JUMO, type B 70.9040.0 (Figure 7). All together makes a system to regulate the temperature of the reference body. All thermocouples and a digital thermometer are pre-calibrated for the purpose of verification and traceability of the same.

Prstenasti grijači Ring heaters

regulator

termoelementi thermocouples

Grijač u keramici Heater in ceramic


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Ispod referentnog tijela je jedan grijač u keramici, a dva u obliku prstena (slika 5.) su oko i iznad ili ispod i oko referentnog tijela/ ploče. Jedan položaj referentne ploče je kada se ista nalazi u „gornjem“ položaju i tada je praktično referentna ploča u visini (poravnata) sa gornjim obodom gornjeg (prestenastog) grijača koji u tom slučaju grije referentnu ploču okolo. (Slika 8).

Below the reference body is a heater in ceramics, and two ring (Figure 5) around and above or below and around the reference body / board. One position of the reference board is when the same is in the "top" position and then practically the reference board is in height (aligned) with the upper rim of the upper (ring) heater, which in this case heated the reference sheet around. (Figure 8).

Slika 8. Gornji položaj referentnog tijela/ ploče Figure 8. Upper position of reference of body/

plate

Slika 9. Donji položaj referentnog tijela/ ploče Figure 9. Lower position of reference of body/

plate

Drugi položaj je kada je referentna ploča u „donjem“ položaju i tada donji (prstenasti, a srednji od tri) grijač grije referentnu ploču okolo, a gornji grijač je u višem položaju u odnosu na referentnu ploču i na taj način ima uticaja na ambijentnu temperaturu tik iznad same površine referentne ploče. (slika 9). Ovo je značajan podatak jer je ovo novina na prototipu odnosno jedno od unapređenja ove aparature. Ovaj podatak je važan i utoliko jer će isti biti iskorišten za poređenje rezultata dobijenih u jednom i u drugom položaju aparature na istim temperaturnim kalibracionim tačkama.

The second situation is when the reference plate in the "lower" position and then the lower (the ring, and the mean of three) heater heats the reference plate around, and the upper heater is in a higher position relative to the reference plate and in this way influences the ambient temperature just above the surface of the reference board. (Figure 9). This is an important fact because this is a novelty on the prototype that one of the improvements of the apparatus. This information is important in so far as they will be used to compare the results obtained in one and in the second position of the apparatus at the same temperature calibration points.

2.3. Postupak kalibracije kontaktnih

termometara 2.3.1. Metodologija rada i koraci izvođenja kalibracije kontaktnog termometra Ne postoji definirana metoda odnosno standard za kalibraciju kontaktnih termometara na prototipu odnosno aparaturi ove vrste. Moguće je generalno dati ideju kako sortirati operacije koje se izvode tokom kalibracije.

2.3. Contact thermoemetars calibration procedure

2.3.1. Methodology and steps performing calibration of contact thermometer There is no defined method or norm for calibration of contact thermometers on a prototype or apparatus of this type. It is possible to give a general idea of how to sort operations performed during calibration.


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Iz navedenih razloga veliki dio procedure izvođenja kalibracije kontaktnog termometra je preuzet iz Projekta Termometrija 635, a dijelom po uzoru na bilateralno poređenje između BNM-LNE (Francuska) i OMH (Mađarska). Procedura za kalibraciju:

1. Uključuje prvo i konačno, određivanje površinske temperature ekstrapoliranjem prije primjene senzora (tp-prije) na određenoj kalibracionoj tački.

Temperature površine mjerene ekstrapoliranjem bi trebalo da ostanu unutar ±2 °C od nominalne temperature, a u svrhu da se izbjegne korekcija koja nastaje uslijed razlike između nominalne tačke i temperature površine.

2. Slijedeći korak je prislanjanje kontaktnog termometra na površinu referentnog bloka u svrhu mjerenja i dobijanja podataka očitanih sa termometra.

Kontaktni termometar se potom primijeni ručno. Po uzoru na projekat Termometrija 635[4] i bilateralno poređenje BNM-LNE i OMH [9] trebalo bi da su zabilježena tri mjerenja izvedena na kalibracionoj tački, a srednja vrijednost bi definirala temperaturu (tk). Ili se može vršiti više mjerenja: „Procedura ipak može biti prilagođena imajući u vidu da neki senzori zahtjevaju više mjerenja; mjerenja sa površinskim senzorom ponavlja operater dok se ne utvrdi da je mjerena vrijednost stabilna“. [8]

3. Nakon uklanjanja kontaktnog termometra (senzora), površinska temperatura se još jednom određuje ekstrapoliranjem (tp-poslije). Prosječna temperatura površine određena ekstrapoliranjem definira referentnu temperaturu (tp), što je i osnovna vrijednost između (tp-prije) i (tp-poslije).

4. Dakle mjerenja temperature referentne površine i predmeta kalibracije – kontaktnog termometra (senzora) se vrše kako je opisano i to jedan ciklus kada je referentno tijelo u „donjem“ položaju (Slika 8.), a potom mjerenje na istoj kalibracionoj tački kada je referentna površina u „gornjem“ položaju (Slika 9.).

Na taj način, kada je referentna površina u „donjem“ položaju, se temperatura ambijenta tik iznad referentne površine praktično zagrijava na zadatu temperaturu, a i kontaktni termometar koji se postavi tik iznad referentne površine se na taj način „predgrijava“ te nakon prislanjanja istog na referentnu ploču „oduzima“ manje toplote sa referentne ploče.

For these reasons, a large part of the procedure performing calibration of contact thermometer is taken from Project Thermometry 635, and partly modeled on a bilateral comparison between BNM-LNE (France) and the OMH (Hungary). Calibration procedure:

1. Includes the first and finally, to determine the surface temperature by extrapolating before applying the sensor (tp-before) at a certain point calibration.

Surface temperature measured by extrapolating should remain within ±2 ° C of the nominal temperature, in order to avoid the correction that occurs due to the difference between the nominal point and surface temperature.

2. The following step is leaning contact thermometer on the surface of the reference blocks for purpose of measuring and obtaining data read from the thermometer.

Contact thermometer is then applied manually. Following the example of the project Thermometry 635 [4] and a bilateral comparison BNM-LNE and OMH [9] should have recorded three measurements performed at the calibration point, and the mean to define the temperature (tk). Or may be several measurements: "The procedure can still be adjusted taking into account that some sensors require more measurements; measurement with surface sensor operator repeated until it is determined that the measured value is stable“. [8]

3. After removing the contact thermometer (sensor), the surface temperature is once again determined by extrapolating (tp-after). The average surface temperature determined by extrapolating is defining reference temperature (tp), which is the basic value between (tp-before) and (tp-after).

4. Thus measurement of the temperature of the reference surface and of the calibration object - contact thermometer (sensor) is performed as described, and one cycle when reference body is in the "lower" position (Figure 8.), and then measuring at the same calibration point when the reference surface is in "upper" position (Figure 9.).

In this way, when the reference surface is in the "lower" position, the ambient temperature just above the reference surface is practically heated to a given temperature, and also contact thermometer which placed just above the reference surface is "preheated" in this way. In this way after leaning thermometer to the reference board it "takes" less heat from the reference board.


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Time se željelo postići smanjenje razlike izmjerenih rezultata vrijednosti temperature referentne površine i vrijednosti temperature očitane sa kontaktnog termometra, te na taj način potvrditi hipotezu o postizanju boljih približnijih rezultata mjerenja. Razlika temperatura se javlja kod prislanjanja kontaktnog termometra i na taj način narušavanja temperaturnog polja na samoj referentnoj površini. Pretpostavka je bila da će razlika temperatura očitanih vrijednosti sa termometra i referentne ploče (dobijeno ekstrapoliranjem) i izmjerenih na višim kalibracionim tačkama biti znatno veća. Pretpostavka je bila i da će razlika temperatura posebno biti izražena u slučaju kada nema uticaja ambijentne temperature tik iznad površine referentnog bloka odnosno kada nema „predgrijavanja“ referentne površine i kontaktnog termometra.

The aim was to achieve a reduction of diference measured results of the reference surface temperature and temperature values read out of with contact thermometer, thus confirm the hypothesis of achieving better or closer measurement results. Temperature difference occurs when leaning contact thermometer and thus distortion of the temperature field on the reference surface. The assumption was that the temperature difference in readings from a thermometer and the reference board (obtained by extrapolating) that are measured at the higher calibration point will be much higher. The assumption was also that the temperature difference will be particularly obvious in the case when there is no influence of ambient temperature just above the surface of the reference block or when there is no "preheat" of the reference surface and the contact thermometer.

3. MATEMATIČKI MODEL PRORAČUNA

MJERNE NESIGURNOSTI • Zavisnost senzora temperature (Tc) o

temperaturi površine (Ts) i ambijentnoj temperaturi (Tamb)

E = ts –tp (3)

gdje je: tp - temperatura površine određena ekstrapolacijom i ts – očitana temperatura senzora. Nesigurnost vezana za odstupanje E je:

u2(E) = u2(tp) + u2(ts) (4)

• Uticaj referentne temperature površine (tp) Temperatura tp se određuje metodom ekstrapolacije prema formuli:

= ( )∙ + (5)

gdje je: , - Temperature u tijelu (dalja i bliža od referentne površine) ℎ , ℎ - Vertikalne pozicije otvora u osi cilindrične referentne površine e - Debljina referentne ploče (tijela) Ako: tinf =ti+ci-cal+ci-stab+ci-hom+ci-drift i tsup=tj+ cj-cal+cj-stab+cj-hom+cj-drift

3. MATEMATIČKI MODEL PRORAČUNA MJERNE NESIGURNOSTI

• Zavisnost senzora temperature (Tc) o temperaturi površine (Ts) i ambijentnoj temperaturi (Tamb)

E = ts –tp (3)

where: tp – temperature of surface obtained by extrapolation and ts – Temperature of sensor Uncertainty related to deviation E:

u2(E) = u2(tp) + u2(ts) (4)

• Influence of temeperature of reference

surface (tp) Temperature tp is determined by extrapolation metod according to equation:

= ( )∙ + (5) where: , - Temperature within body (further and closer of reference surface) ℎ , ℎ - Vertical position of openings in axis of cylindrical reference surface e - The thickness of the reference plate (body) If: tinf =ti+ci-cal+ci-stab+ci-hom+ci-drift and tsup=tj+ cj-cal+cj-stab+cj-hom+cj-drift


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Onda je: tx - Srednja izmjerena temperatura sa senzorom x u referentnoj ploči(tijelu), x može biti x = i ili j (senzor koji je bliže ili dalje od referente površine cx-stab. - Korekcija u odnosu na kalibraciju senzora x cx-hom. - Korekcija u odnosu na nehomogenost temperature u okolini senzora x cx-drift. - Korekcija u odnosu na drift senzora x ℎ , ℎ - Vertikalna pozicija otvora u osi cilindrične referentne površine U odnosu na specificirane doprinose mjerna nesigurnost, vezana za temperaturu referentne površine (specimena) prema [6], iznosi:

Than: tx - Mean temperature measured by sensor x in reference plate (body), x may be x = i or j (sensor that is closer or further of referece surface cx-stab. - Correction due to calibration of sensor x cx-hom. - Correction related to inhomogenity of temperature around sensor x cx-drift. - Correction related to drift of senzor x ℎ , ℎ - Vertical position of openings in axis of cylindrical reference surface In relation to specified contributions the measurement uncertainty related to reference surface (specimen) temperature according to [6], is:

= ∙ ( ) + ∙ ( ) + ∙ ( ) + ∙( ) + ∙ + ∙ + ∙ +∙ + ∙ + ∙ + ∙( ) + ∙ ℎ + ∙ ℎ (6)

sa: with: = = = = = (7) = = = = = (8) = ( )∙( ) ; = ( )∙( ) ; = (9)

Pripadajući doprinosi mjernoj nesigurnosti za procjene vrijednosti pojedinih uticaja, su specificirani za kalibracionu aparaturu, a izražavaju se prema datim formulama. • Uticaj temperature instrumenta (ts) Temperatura senzora ts se određuje prema jednačini: = č . + . + . ++ . + . + . +. (10) gdje su: ts-očit. - Srednja očitana temperatura kontaktnog senzora crezol. - Korekcija u odnosu na rezoluciju instrumenta camb. - Korekcija u odnosu na uticaj ambijentne temperature na mjerenje u toku kalibracije

The corresponding contributions to the measurement uncertainty for the valuation of individual impact, are specified for the calibration apparatus, and expressed according to the formulas. • Influence of the instrument temperature (ts) Temperature of sensor ts is defined according to: = č . + . + . ++ . + . + . +. (10) where: ts-očit. - Mean measured temperature of contact sensor crezol. - Correction in relation to the resolution of the instrument camb. - Correction with regard to the impact of ambient temperature on measurement during calibration


99

cmaterijal - Korekcija u odnosu na termičku provodnost vezanu za vrstu materijala od kojeg je napravljena referentna ploča (tijelo) [27] ctp-nazad - Korekcija u odnosu na promjene u temperaturi referentne površine kod stacionarnog stanja nakon izvlačenja senzora koji se kalibrira cdeb. - Korekcija uslijed razlike u debljini materijala u odnosu na referentne uvjete cpov. - Korekcija uslijed razlike kontaktnog otpora u odnosu na referentne uvjete coperat. - Korekcija u odnosu na efekat operatera (*) Nesigurnosti cdeb., cpov., coperat. trenutno nisu uzete u obzir. Na osnovu specificiranih doprinosa u odnosu na E dobije se:

cmaterijal - Correction in respect of thermal conductivity of type of material from which the reference plate (body) is made [27] ctp-nazad - Correction in relation to changes in the temperature of the reference surface at steady state after the draw sensor that is calibrated cdeb. - Correction due to differences in the thickness of the material in relation to the reference conditions cpov. - Correction due to differences of the contact resistance in comparison to the reference conditions coperat. - Correction in relation to the effect of the operator (*) Uncertainties cdeb., cpov., coperat. currently not taken into account. Based on the specified contributions in relation to E is:

( ) = ( č .) + ( .) + ( .) + . + . +( .) + . + . (11) Specificirani doprinosi, procjenjene vrijednosti, vrste distribucije vjerovatnoće, standardne nesigurnosti, koeficijenti osjetljivosti prema jednačinama od (3) do (11) će biti tabelarno prikazane u poglavlju 4 u četiri kalibracione tačke, da bi se dobile i predstavile pojedinačne vrijednosti doprinosa nesigurnosti. Njihovim uvrštavanjem u jednačinu (6) dobija se mjerna nesigurnost metode. Na ovom principu su izvedeni svi proračuni potrebni za izračunavanje proširene (ukupne) mjerne nesigurnosti što je i predmet ovog rada.

The specified contributions, estimated value, types of probability distributions, standard uncertainties, sensitivity coefficients of the equations of (3) to (11) will be given in tables of results. Their inclusion in the equation (6) gives the uncertainty methods. On this principle are done all calculations required to calculate the extended (overall) measurement uncertainty which is needed to be add to results and is the subject of this paper.


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4. REZULTATI KALIBRACIJE I PROCJENA UKUPNE MJERNE NESIGURNOSTI NA KALIBRACIONOJ TAČKI 300 °C

A) Kada je referentna površina u „donjem“ položaju

4. CALIBRATION RESULTS AND ESTIMATION OF MEASUREMENT UNCERTRAINTY AT CALIBRATION POINT 300 °C

A) When reference surface is in the „lower“ position

Tabela 1. Doprinosi mjernoj nesigurnosti referentne površine kada je referentno tijelo/površina u „donjem“ položaju na kalibracionoj tački 300 °C Table 1. Contributions to measurement uncertainty of reference surface when reference body/surface is in the „lower“ position at calibration point 300 °C

Xi Procjena xi

Estimation xi Raspodjela Distribution

St.nes u(xi) St.uncert.

u(xi)

Koef.osjet. Sensitivity coef. │ci│

Dopr. Contributions │ci⋅u(xi)│

ti 300,57 °C N 0,04 °C 0,391 0,02 Ci-cal 1,67 °C N 0,42 °C 0,391 0,17 Ci-stab 0 °C P 0,05 °C 0,391 0,02 Ci-hom 0 °C P 0,05 °C 0,391 0,02 Ci-drift 0 °C P - 0,391 - tj 299,65 °C N 0,03 °C 1,391 0,04 Cj-cal 1,67 °C N 0,42 °C 1,391 0,59 Cj-stab 0 °C P 0,05 °C 1,391 0,07 Cj-hom 0 °C P 0,05 °C 1,391 0,07 Cj-drift 0 °C P - 1,391 - e 50,0 mm N 0,10 mm 0,027 °C/mm 0,01 hinf 2,0 mm N 0,10 mm 0,028 °C/mm 0,01 hsup 36,5 mm N 0,10 mm 0,037 °C/mm 0,01 tp 300,96 °C / / / 0,63 °C

Tabela 2. Doprinosi mjernoj nesigurnosti kontaktnog senzora na kalibracionoj tački 300 °C kada je referentno tijelo/ površina u „donjem“ položaju Table 2. Contributions to measurement uncertainty of contact sensor at calibration point 300 °C when the reference body/ surface in the „lower“ position

Xi Procjena xi


St.nes u(xi) St.uncert.

u(xi)



ts-očit 299,88 °C N 0,23 °C 1 0,23 °C crezol. 0 °C P 0,33 °C 1 0,33 °C camb. 0 °C P 0,11 °C 1 0,11 °C cmaterijal. 0 °C P 0,05 °C 1 0,05 °C ctp-nazad 0 °C P 0,07 °C 1 0,07 °C ts 299,88 °C / / / 0,43 °C ( ) = 2( ) + 2

u (E) = ( ) = 2( ) + 2 = 0,76


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B) Kada je referentna površina u „gornjem“ položaju

B) When reference surface is in the „upper“ position

Tabela 3. Doprinosi mjernoj nesigurnosti referentne površine kada je referentno tijelo/

površina u „gornjem“ položaju na kalibracionoj tački 300 °C Table 3. Contributions to measurement uncertainty of reference surface when reference body/surface is in the „upper“ position at calibration point 300 °C

Xi Procjena xi


St.nes u(xi) St.uncert. u(xi)



ti 295,71 °C N 0,05 °C 0,391 0,02 Ci-cal 1,67 °C N 0,42 °C 0,391 0,17 Ci-stab 0 °C P 0,05 °C 0,391 0,02 Ci-hom 0 °C P 0,05 °C 0,391 0,02 Ci-drift 0 °C P - 0,391 - tj 291,28 °C N 0,03 °C 1,391 0,04 Cj-cal 1,67 °C N 0,42 °C 1,391 0,59 Cj-stab 0 °C P 0,05 °C 1,391 0,07 Cj-hom 0 °C P 0,05 °C 1,391 0,07 Cj-drift 0 °C P - 1,391 - e 50,0 mm N 0,10 mm 0,129 °C/mm 0,02 hinf 2,0 mm N 0,10 mm 0,136 °C/mm 0,02 hsup 36,5 mm N 0,10 mm 0,179 °C/mm 0,02 tp 291,22 °C / / / 0,63 °C

Tabela 4: Doprinosi mjernoj nesigurnosti kontaktnog senzora na kalibracionoj tački 300 °C kada je referentno tijelo/ površina u „gornjem“ položaju Table 4: Contributions to measurement uncertainty of contact sensor at calibration point 300 °C when the reference body/ surface in the „upper“ position

Xi Procjena xi


St.nes u(xi) St.uncert. u(xi)



ts-očit 289,87 °C N 0,16 °C 1 0,16 °C crezol. 0 °C P 0,33 °C 1 0,33 °C camb. 0 °C P 0,11 °C 1 0,11 °C cmaterijal. 0 °C P 0,24 °C 1 0,24 °C ctp-nazad 0 °C P 0,13 °C 1 0,13 °C ts 289,87 °C / / / 0,41 °C ( ) = 2( ) + 2

u (E) = ( ) = 2( ) + 2 = 0,75


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Dijagram 1. Prikaz razlika srednjih izmjerenih vrijednosti temperatura (tprije i tposlije) za Ti -

termoelement bliži ref.površini mjereno u donjem i gornjem položaju referentne površine. (300 °C) Chart 1. Display of differences in mean values of measured temperature (tbefore and tposlije) for Ti -

thermocouple closer to reference surface, measured in the lower and upper position of the reference surface. (300 ° C)

Dijagram 2. Prikaz razlika srednjih izmjerenih vrijednosti temperatura (tprije i tposlije) za Tj - termoelement dalji od ref.površine mjereno u donjem i gornjem položaju referentne površine (300 °C).

Chart 2. Display of differences in mean values of measured temperature (tbefore and tposlije) for Tj - thermocouple further from reference surface, measured in the lower and upper position of the

reference surface (300 ° C).

Dijagram 3. Prikaz rezultata srednjih vrijednosti temperature za Ti i Tj (termoelementi dalji i bliži referentnoj površini) korišteni za ekstrapoliranje temperature površine kada se referentna površina

nalazi u donjem pa u gornjem položaju. (300 °C) Chart 3. Results of mean values for temperature Ti and Tj (thermocouples further and closer to the reference surface) are used to extrapolate the surface temperature when the reference area is in the

lower and in the upper position (300 ° C).


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5. ZAKLJUČCI a) Istraživanje je provedeno u cilju

uspostavljanja vlastite procedure za kalibraciju kontaktnih termometara za mjerenje temperature čvrste površine.

b) Da se jasno definiraju i kvantifikuju doprinosi mjernoj nesigurnosti pri kalibraciji kontaktnih termometara za mjerenje temperature čvrste površine.

c) Da su sprovedene prve kalibracije na prototipu aparature-etalona za kalibraciju kontaktnih termometara za mjerenje temperature čvrste površine, a u smislu pripreme za validaciju same aparature.

5. CONCLUSIONS a) The survey was conducted in order to

establish own procedures for the calibration of contact thermometers for temperature measurement on solid surface.

b) In order to clearly define and quantify the contributions to measurement uncertainty during the calibration of contact thermometers for temperature measurement of solid surface.

c) To carried out the first calibration on the prototype apparatus-standard for calibration of contact thermometers for solid surface temperature measurement, and in terms of preparation for the validation of the apparatus.

6. LITERATURA - REFERENCES [1] JCGM 200-2012, “International

Vocabulary of Metrology – Basic and General Concepts and Associated Terms“ (VIM) 3rd Edition (2008 with minor corrections), također objavljen kao ISO/IEC Guide 99-12:2007 International Vocabulary of Metrology - Basic and General Concepts and Associated Terms, VIM.

[2] Michaelski, L., Eckersdorf, K., McGhee, J.: Temperature measurement; John Wiley & Sons; Chichester; New York; Brisbane 1991.

[3] Thomas Donald McGhee: Principles and methods of temperature measurements, 1988

[4] EUROMET Project No 635 (Thermometry) – Comparison of the reference surface temperature apparatus at NMIs by comparison of transfer surface temperature standards, Final Report, Emese Andras; OMH, national Office of Measures, Hungary, November, 2003.

[5] Arpino, F., Fernicola, V., Frattolillo, A., Rosso, L.: – A CFD Study on a Calibration System for Contact Temperature Probes, Inter. Journal Thermophys (2009) 30:306–315, DOI 10.1007/s10765-008-0451-8

[6] Rosso, L., Koneva N.,·Fernicola, V.: Development of a Heat-Pipe-Based Hot Plate for Surface-Temperature Measurements, International Journal Thermophys, (2009) 30:257–264, DOI 10.1007/s10765-008-0495-9

[7] Kovacs, T.: Qualification of Temperature Field by Temperature Gradient, VDI Berichte, 1998, pp. 275..279

[8] N. Zaimović-Uzunović, S. Lemeš, D. Daut, A. Softić: Proizvodna mjerenja, Mašinski fakultet, Univerzitet u Zenici, Zenica, 2009.

[9] Report of collaboration on surface temperature sensors calibration: Bilateral comparison of measurement between BNM-LNE (F) and OMH (HG); Morice Ronan, Andras Emese, April 2001

[10] Jarović-Bajramović, N.: Određivanje ukupne mjerne nesigurnosti etalona-prototip aparature za kalibraciju kontaktnih senzora za mjerenje temperature na površini, Magistarski rad, Mašinski fakultet u Zenici, 2014

Coresponding author: Narcisa Jarović-Bajramović University of Zenica Metallurgical Institute „Kemal Kapetanović“ Email: [email protected] Phone: +387 32 247 999/ local 172

Main topics: • MECHANICAL ENGINEERING • ELECTRICAL ENGINEERING • ELECTRONICS • INFORMATICS • CONSTRUCTION

ENGINEERING • WOOD INDUSTRY • TEXTILE INDUSTRY • FIELD OF ENERGY

• METALLURGY • ROBOTICS • MECHATRONICS • RENEWABLE ENERGY • BIOENGINEERING • AGRICULTURE • LIVESTOCK BREEDING • FRUIT PROCESSING • LOGISTICS • ENVIRONMENTAL SYSTEMS • ECOLOGY

Conference deadlines: Dec. 31, 2015 Submission of abstracts. Jan. 15, 2016 Notification of abstract acceptance. Jan. 30, 2016

Submission of manuscripts. Feb. 27, 2016 Notification of manuscript acceptance. Apr. 15, 2016 Fee payment, registration. May 13-14, 2016 .

For further questions contact us by e-mail [email protected] [email protected]. Mostar,13-14 May 2016 Bosnia and Hezegovina

Sincerely !

ICNT-2016 3rd International Conference "New Technologies NT-2016"

* Please kindly forward to those who may be interested. Dear Colleagues, It is my pleasure to invite you to attend 3rd International Conference "New Technologies NT-2016". Conference hosts are Academy of Sciences and Arts of Bosnia and Herzegovina, Society for Robotics of Bosnia and Herzegovina, Faculty of Mechanical Engineering, University of Mostar, and Technology park INTERA. Conference will be held in Mostar on 13th and 14th May 2016. Conference will gather scientists and entrepreneurs to exchange knowledge and to implement new technologies in practice. All information about conference, including topics, deadlines, manuscript templates, etc could be found at conference webpage www.icnt.robotika.ba. Submitted paper should be written in four to six (4 - 6) pages.

Mašinstvo 3-4(12), 105 – 109, (2015) I. Karabegović; ….: MODERNIZATION AND…

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MODERNIZATION AND AUTOMATION OF AUTOMOTIVE INDUSTRY PRODUCTION PROCESSES WITH INDUSTRIAL

ROBOTS

Subject review Isak Karabegović* Safet Isić** Ermin Husak* *University of Bihać, Faculty of Technical Engineering, Irfana Ljubijankića bb., 77 000, Bihać ** „Džemal Bijedić“ University of Mostar Faculty of Mechanical Engineering, 88 104 Mostar Keywords: industrial robots, production process, automation, automotive industry, vehicle. Paper received: 17.11.2015. Paper accepted: 20.12.2015.

SUMMARY The paper aims to answer if the industrial robot is a motif of accelerated trend of automation and modernisation of production processes in automotive industry in the world. It describes the application of industrial robots in the World for the period from 2009 – 2014. It offers analysis of the application of industrial robots in the automotive industry, as well as metal industry, which is also related to the automotive industry. Based on this analysis, conclusions were made about the role of industrial robots in the growing trend of modernisation and automation of production processes in the automotive industry. The role of industrial robots is interesting when it comes to energy efficiency, as well as the role of new materials from the aspect of weight reduction, as well as innovation when it comes to IT technology. Information technologies provide new softwares whereby we get a far greater utilization of industrial robots from the point of performing a large number of operations, and therefore improves the automation of production processes in the automotive industry. The materials and their combinations are always demanding both in the metal as well as in automotive industries, and require new skills with applications such as sewing, weaving and knitting all types of fiber (for the car industry) that represent a challenge and are introduced in robotics. Changes, such as integration of engineering disciplines, bring improvement in production processes. The paper gives an overview of the increase in the production of vehicles in the world through the use of industrial robots. The stated example is China, which is the first in the world by the application of industrial robots, and the first in the world for producing automobiles. Industrial robots are essentially a reason for the accelerated trend of modernization and automation of production processes in the automotive industry.

1. INTRODUCTION For successful and efficient automation of the production process, it is fundamental to know the production process and its technology, but also the means to implement automation. Nowadays, the means for the implementation of automation are far more advanced than those in the last 10 years. When one mentioned automation 30 years ago, it was meant only electronics, but those times changed. From a contemporary aspect, a technical progress– when it comes to the modernization and automation of production processes– is conditioned not only with a continuous improvement, but also with a continuous development and improvement of technologies such as robotic, sensor, computer, pneumatic, hydraulic, etc., as well as their interaction.

The development of mathematics itself contributed to the development of automation of production processes, because every production process can be mathematically analyzed, processed, systematized, and then the technology that will automate the production process is selected. The goal of any modernization and automation of the production process is to stabilize that process, even though it goes through a lot of changes, as well as to improve its efficiency. The future of industrial robots application in production processes is in the potential for multi innovation, but mechatronics is so-to-speak a bridge which opens technological possibilities provided there is a growing and more secure cooperation between an industrial robot and a worker


106

[1,6,7,8,9,12,13,18]. If we analyze the proportion of value, mechanical components in the past amounted to approximately 80% of the industrial robots, but now the software components have an increasing share of the value of industrial robots.

2. IMPLEMENTATION OF INDUSTRIAL ROBOTS IN AUTOMOTIVE AND METAL INDUSTRIES IN THE WORLD Implementation of industrial robots in the world in the period from 2009 to 2014 is shown in Figure 1. Statistical data are retrieved from the International Federation of Robotics (IFR), United Nations Economic Commission for Europe (UNECE), the Organization for Economic Cooperation and Development (OECD), as well as the literature [1, 2, 3, 4, 5].

Figure 1. Implementation of industrial robots in the World from 2009 – 2014 The trend of industrial robots application in the World for the period from 2009–2014 at the annual level is shown in Figure 1., based on which we can conclude that it has an increase in applications from 58 000 robot units to 178 000 units since 2009. The minimum application of industrial robots was in 2009 due to economic and industrial crisis in the world, which had effect on the application of industrial robots. The total stock of industrial robots is constantly on the rise since 2009, with around 1 000 000 up to 1 400 000 units of robots in 2014. It has been estimated that the number of applications of industrial robots will increase every year. The reason for this trend is the application of industrial robots lies in a fact that there is a development, modernization and automation of production processes of the automotive industry. The trend of industrial robots installation in the automotive and metal industry is shown in Figure 2.

In chart we can see the representation of industrial robots application on an annual basis in automotive industry and metal industry. The use of robots in the automotive industry has a growing trend from year to year so that it reached 68 000 units in 2013. The reason for this trend of increasing applications of industrial robots is the fact that the process of welding of automotive body is fully automated, as well as painting and assembly of carrosserie, where industrial robots are mostly applicable. Also, when it comes to the process of manufacturing vehicles, we can conclude that the modernization and automation are carried out almost every day, which requires the application of industrial robots. The consequence of such trend and investment in the modernization is the competition of companies at the market. Examples of industrial robots application in the automotive industry are presented in Figure 3.

u

nits

Total

Annual


107

Figure 2. Annual installation of industrial robots in automotive and metal industries in the period 2010 – 2013 [2,17]

Figure 3. Application of industrial robots in the automotive industry [19,20] In the production process of welding and painting in automotive industry, the application of industrial robots is inevitable for two reasons, the first being the exclusion of workers from these processes due to the negative effects of these processes on workers’ health, and the other is high-quality assurance.

3. APPLICATION OF INDUSTRIAL ROBOTS IN AUTOMOTIVE INDUSTRY IN CHINA The trend of total vehicle production in the world is shown in the Figure 4, according to the data by the OECD (Organization for Economical Co-operation and Development).

Figure 4. Production of vehicles in the world in period

2009 – 2014 [10, 11, 25]

units

Automotive industry

Metal industry

Production of vehicles

Production of cars

Production of comm. vehicles

un

its


108

From the chart can be concluded that the number of produced vehicles increases every year, and this can be attributed to the application of new technologies, as well as application of industrial robots in automotive production processes. Annual production of vehicles in the world has reached a level of about 89 million units of vehicles. Figure 5 presents the production of automobiles in 2014 in 10 countries in the world in which the most vehicles is produced.

China

Figure 5. Production of automobiles in China in period 2009 – 2014 and other 10 countries in the world in 2014 [25, 26] Based on Figure 5, we can conclude that China comes first when it comes to the production of automobiles in the world, and it reached production of about 20 million units of vehicles in 2014. As we can see from the Figure 6, annual application of industrial robots in China is increasing from year to year, reaching application of about 48 000 units in 2014, which resulted in a total production of vehicles that also increases from year to

a) Annual installation of robots

b) Total stock of robots

Figure 6. Annual supply and total stock of industrial robots in China in the period 2009 – 2014 [2,3,4,10,27] year and it reached the value of about 24 million units (automobiles and commercial vehicles). Since most industrial robots are used in manufacturing processes of welding, painting, varnishing and control in the automotive industry, the trend of vehicle production in China is logical. China is the world’s first when it comes to the application of industrial robots, and it can be said that 90% of those robots is installed in a production process of the automotive industry to the aforementioned activities, which resulted in an increase in vehicle production and China has become a leading country in the world for the production of vehicles. 4. CONCLUSION Analyzing the application of industrial robots in the world, then their implementation in the production processes of the automotive industry, it can be concluded that each year installation of new industrial robots increases. Rapid development of new technologies which include information technology, robotic technologies, new materials, intelligent systems, has resulted in the development of the automotive industry, through


109

modernization and automation of production processes of the automotive industry using industrial robots. Industrial robots are the most represented in the processes of: welding, painting, assembly and control when it comes to automotive industry. The increase in the industrial robots application in the production processes of the automotive industry has resulted in an increase in the number of production vehicles, and we can take China as an example. In the last six years (from 2009 to 2014) in China, the number of industrial robots increased by seven times. In the same period, total vehicle production doubled which suggests that the application of industrial robots in the automotive industry leads to the modernization and automation of production processes of the automotive industry. 5. REFERENCES [1] Doleček V., Karabegović I.: Roboti u

industriji, Tehnički fakultet Bihać, Bihać, 2008.

[2] World Robotics 2014, United Nations, New York and Geneva, 2014.




[6] Bakšys B., Fedaravičius A.: Robotu Technika, Kaunas Technologija, Kaunas, 2004.

[7] Rogić M.: Industrijski roboti, Mašinski fakultet Banjaluka, Banjaluka, 2001.

[8] Wolka, D.W.: Roboter sisteme, Technishe Universität des Saarlandes im Stadtwald, 1992.

[9] Freund, E., Stern, O.: Robotertechnologie I, Institut für Roboterforschung, Dortmund, 1999.

[10] VDA: „AutoJahresbericht 2013“, 2013. [11] VDA: „AutoJahresbericht 2014“, 2014. [12] Karabegović I., E. Karabegović, M.

Mahmić, E. Husak: Comparative Analysis of Robot Application in Welding Process at Continents Europe and Asia/Australia, Dan varilne tehnike, industrijske robotike in transporta v industriji, DVTIRT 2013, Lendava, Slovenia, 2013. pp. 157-164.

[13] Karabegović I., Karabegović E., Pašić S., Isić S.: World wide Trend of the Industrial Robot Applications in the Welding Processes , International Journal of Engineering & Technology, vol: 12 N0 : 01, IJENS, Pakistan, pp 69-74.

[14] Karabegović I., Karabegović E., Husak E.: Comparative analysis of the industrial robot application in Europe and Asia, International Journal of Engineering & Technology, Vol: 11 No:01, 2011.

[15] Karabegović I., Karabegović E., Husak E.: Application analyses of industrial robot in world automobile industry in 2010, Journal of International Scientific Publications: Materials, Methods & Technologies, Vol 5 (2), December 2011.

[16] Karabegović E., Karabegović I., Hadžalić E.: Industrial robots application trend in world metal industry, Journal Engineering Economics, Vol.23.No.4, Lithvania, 2012, pp.368-378.

[17] Karabegović I., Doleček V., Husak E.: Analysis of the Industrial Robots in Various Production Processes in the World, International Review of Mechanical Engineering, Vol.5., No.7., 2011, Napoli, Italy, pp. 1272-1277.

[18] www.westermans.com/roboticwelding.aspx;16.05.2015.

[19] www.wardsauto.com/ar/hyundai_boosts_alabama_111006;16.05.2015.

[20] www.ifr.org./industrial-robots/,18.05.2015.

[21] www.kuka-robotics.com/en/products/industrial_robots/;18.05.2015.

[22] www.robots.com;12.06.2015. [23] www.sciencedaily.com;12.06.2015. [24] www.vda.de;14.06.2015. [25] www.unsere-autos.de,14.06.2015 [26] www.made-in-china.com;18.06.2015. [27] www.reuters.com;18.06.2015. Coresponding author: Isak Karabegović Univeristy of Bihać Faculty of Technical Engineering Email: [email protected]. Phone: +037 226 273


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Mašinstvo 3-4(12), 111 – 116, (2015) N. Surname 1 et al.: TITLE OF PAPER….

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INSTRUKCIJE ZA AUTORE (Style: Times New Roman, 14pt, Bold)

INSTRUCTIONS FOR AUTHORS (Style: Times New Roman, 14pt, Bold)

Name Surname 1, Name Surname 2, Name Surname X (Author's name, Co-author's name - Style: Times New Roman, 11pt, Bold) Authors’Institution (Style: Times New Roman, 11pt) Ključne riječi: abecedni popis ključnih riječi na bosanskom, hrvatskom ili srpskom jeziku (Style: Times New Roman, 10pt) Keywords: Alphabetic list of keywords in English (Style: Times New Roman, 10pt) Paper received: xx.xx.xxxx. Paper accepted: xx.xx.xxxx.

Kategorizacija članka (Style: Times New Roman, 10pt, Bold, Italic) REZIME (Style: Times New Roman, 10pt, Bold) Naslov rada (do 15 riječi). Puna imena i prezimena autora (bez navođenja zvanja i akademskih titula). Rezime rada (do 150 riječi). Rezime treba što vjernije odražavati sadržaj rada. U njemu se navode upotrebljene metode i ističu ostvareni rezultati kao i doprinos rada. Naslov, rezime rada i ključne riječi autori sa ex-YU prostora pišu i na bosanskom, hrvatskom ili sprskom jeziku. Ključne riječi u pravilu su iz naslova rada, a samo eventualno iz sažetka rada. Ovaj dio rada se ne lektoriše i autori su odgovorni za njegovu jezičnu i gramatičku ispravnost. Nakon završetka recenzentskog postupka autori mogu biti zamoljeni da naprave određene popravke ili dopune svoj rad. (Style: Times New Roman, 10pt, Italic)

Categorization of paper (Style: Times New Roman, 10pt, Bold, Italic)

SUMMARY (Style: Times New Roman, 10pt, Bold) Title of the paper (up to 15 words). The full list of authors (without specifying grades and ranks). Summary (up to 150 words). Summary should be as faithfully reflect the content of the paper. It outlines the methods used and highlight the results achieved as well as the contribution of the paper. Title, summary of paper and keywords, authors from ex-Yugoslavia area, write to the Bosnian, Croatian or Serbian languages. Keywords are generally from the title of paper, and just possibly from the summary. This part of the paper is not proofread and authors are responsible for the linguistic and grammatical correctness. After completion of the review process, authors may be asked to make certain repairs or additions to their paper. (Style: Times New Roman, 10pt, Italic)

1. INTRODUCTION (Style: Times New Roman, 11pt, Bold)

Upon its acceptance the article is categorized as follows: original scientific paper, preliminary notes, subject review, professional paper and conference paper. Original scientific papers should report original theoretical or practical research results. The given data must be sufficient in order to enable the experiment to be repeated with all effects described by the author, measurement results or theoretical calculations. Preliminary notes present one or more new scientific results but without details that allow the reported data to be checked. The papers of this category inform about experimental research, small research projects or progress reports that are of interest.

Subject reviews cover the state of art and tendencies in the development of the specific theory, technology and application with given remarks by the author. Such a paper ends with a list of reference literature with all the necessary items in the related field. Professional papers report on the original design of an instrument, device or equipment not necessarily resulting from the original research. The paper contributes to the application of well-known scientific results and to their adaptation for practical use. Papers presented at scientific conferences can also be published in the journal upon the agreement of the conference organizer and the author. (Style: Times New Roman, 11pt, Normal) Papers to be published in the journal Tehnički vjesnik/Technical Gazette, should be written in


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English. The metrology and terminology used in the paper have to meet legal regulations, standards and International System of Units (SI) 1.1. Subtitle 1 (Writing Instructions)

(Style: Times New Roman, 11pt, Bold) The text of the paper is arranged in sections and when necessary into subsections. Sections are marked with one Arabic numeral and subsections with two Arabic numerals, e.g. 1.1., 1.2., 1.3., ... When a subsection is arranged in smaller parts, each of them is marked with three Arabic numerals, e.g. 1.1.1., 1.1.2., ... Further divisions are not allowed. The text has to be organized in the following order: Title of the paper (up to 15 words). Papers should be headed by a concise but informative title that clearly reflects the subject of the paper. Authors' full names (without grades and ranks). Summary-Abstract (up to 150 words) should present a brief and factual account of content and conclusions of the paper, and an indication of the relevance of the new material presented. Title and abstract in Bosnian/Croatian/Serbian (BCS). Only for authors from ex-Yugoslavian area. Alphabetic list of keywords in English and in (BCS). Keywords normally originate from the title and from the abstract. Introduction should state the reason for the work, with brief reference to previous work on the subject. It informs about the applied method and its advantages. Central part of the paper may be arranged in sections. Complete mathematical procedures for formula derivations should be avoided. The necessary mathematical descriptions may be given in an appendix. Authors are advised to use examples to illustrate the experimental procedure, applications or algorithms. In general all the theoretical statements have to be experimentally verified. In Conclusions all the results are stated, and all the advantages of the used method are pointed out. The limitations of the method should be clearly described as well as the application areas. List of references should be brought together at the end of the article and numbered in square brackets in order of their appearance in the text followed by other literature. Coressponding authors' full names followed by the name and address of the institution in which the work was carried on. A List of used symbols and theirs SI units is optional after list of references.

1.1.1. Subtitle 2 (Preparation of Manuscript) (Style: Times New Roman, 11pt, Bold)

The paper should be written using Latin characters. Greek letters may be used for symbols. The volume of the article is limited to 10 pages (A4 format). That includes blanks and equivalent number of characters covered by figures and tables. Number of pages must be even. The text should be sent to the Editorial Board using e-mail. For the text preparing may be used only MS Word for Windows respectively *.doc, *.docx (Word Document) or *.rtf (Rich Text Format) format of records. The text has to be prepared in accordance with this template. The Editorial Board may exceptionally request the CD-ROM with recorded articles and figures and tables. In that case the figures (drawings, diagrams and photographs) should be submitted stored on the CD-ROM in JPG/JPEG, PNG, TIF (TIFF Bitmap) or BMP (Windows Bitmap) format, min. resolution of 300 dpi. Each figure is labelled the same as it is in the paper and recorded format (e.g. fig-1.JPG). If figures inserted into text they must be also with min. resolution of 300 dpi. Latin or Greek characters in italics are used for physical symbols and normal characters for measuring units and numerical values. Text in figures is also written with normal letters. Character size is to be chosen on the basis of the following criteria: after expected figure size reduction a capital Latin character should be about 2 mm high (no less than 6pt). All figures in the Journal will be printed in black and white technique. Coloured figures will be seen only in the PDF format on the Web address http://www.mf.unze.ba/index.php?option=com_content&view=article&id=118&Itemid=107 Tables are created with the word processing program. Each table is positioned in the desired place in the text. In the case of decimal numbers use comas (e.g. 0,253); use a small gap separating the thousands (e.g. 25.000, but not in the case of 1500). The texts under figures and table titles are in English language and in BCS for authors from ex-YU area. Section titles and titles of subsections are typed in small letters only in English language. Equations are numbered with Arabic numerals in parenthesis at the right margin of the text. In the text an equation is referenced by its number in parenthesis like "... from Eq. (3) follows ...".


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(Notice: If you convert and save your document as a MS Word 2010 file and then add equations to it, you will not be able to use previous versions of MS Word to change any of the new equations.). Figures and tables are numbered with Arabic numerals (1 ÷ n). In the text in figure or table is referenced by its number (e.g. in Fig. 1, in Tab. 1, etc.).

Slika 1. Tekst unutar formula (samo za autore sa ex-YU prostora)

Figure 1 The texts under figures (Style: Times New Roman, 11pt, Italic)

Figure 2. Simplified musculoskeletal model of an arm

(Style: Times New Roman, 11pt, Italic)

When reference to literature is made the publication number from the list of references in square brackets is used like "... in [7] the authors showed ...". In the list of references literature is cited in accordance with examples in Section. 2 COPYRIGHT TRANSFER AGREEMENT Copyright assignment. The author hereby assigns to the journal "Mašinstvo" the copyright in the above article (for U. S. government employees: to the extent transferable), throughout the world, in any form,

in any language, for the full term of copyright, effective upon acceptance for publication. Author's warranties. The author warrants that the article is original, written by stated author/s, has not been published before and it will not be submitted anywhere else for publication prior to acceptance/rejection by "Mašinstvo", contains no unlawful statements, does not infringe the rights of others, and that any necessary written permissions to quote from other sources have been obtained by the author/s. Rights of authors. Authors retain the following rights: - all proprietary rights relating to the article,

other than copyright, such as patent rights, - the right to use the substance of the article in

future own works, including lectures and books,

- the right to reproduce this article for own purposes, provided the copies are not offered for sale.

Co-authorship. If the article was prepared jointly with other authors, the signatory of this form warrants that he/she has been authorized by all co-authors to sign this agreement on their behalf, and agrees to inform his/her co-authors of the terms of this agreement.


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Figure 3. Page setup (Style: Times New Roman, 11pt, Italic)

Figure X. Photography resolution of 300 dpi (min) (Style: Times New Roman, 11pt, Italic) 3. PUBLICATION ETHICS AND PUBLICATION MALPRACTICE STATEMENT The publication of an article in a peer reviewed journal is an essential model for our journal "Mašinstvo". It is necessary to agree upon standards of expected ethical behaviour for all parties involved in the act of publishing: the author, the journal editor, the peer reviewer and the publisher. Publication decisions. The editor of the "Mašinstvo" is responsible for deciding which of the articles submitted to the Journal should be published. The editor may be guided by the policies of the Journal's editorial board and constrained by such legal requirements as shall then be in force

regarding libel, copyright infringement and plagiarism. The editor may confer with other editors or reviewers in making this decision. Fair play. An editor at any time evaluate manuscripts for their intellectual content without regard to race, gender, sexual orientation, religious belief, ethnic origin, citizenship, or political philosophy of the authors. Confidentiality. The editor and any editorial staff must not disclose any information about a submitted manuscript to anyone other than the corresponding author, reviewers, potential reviewers, other editorial advisers, and the publisher, as appropriate. Disclosure and conflicts of interest. Unpublished materials disclosed in a submitted manuscript must not be used in an editor's own research without the express written consent of the author. Contribution to editorial decisions. Peer review assists the editor in making editorial decisions and through the editorial communications with the author may also assist the author in improving the paper. Acknowledgement of sources. Reviewers should identify relevant published work that has not been cited by the authors. Any statement that an observation, derivation, or argument had been previously reported should be accompanied by the relevant citation. A reviewer should also call to the editor's attention any substantial similarity or overlap between the manuscript under consideration and any other published paper of which they have personal knowledge.


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Table 1. Table titles (Style: Times New Roman, 11pt, Normal)

Engineering stress σe / MPa

Engineeringplastic strain εe,pl / %

True stress σt / MPa

True plastic strain εt,pl / %

250,0 0,00 250,8 0,00 250,0 0,21 250,8 0,21 285,7 1,35 290,0 1,34 322,7 2,13 330,1 2,10 358,4 3,06 370,0 3,00 393,1 4,35 411,0 4,24 423,6 6,05 450,1 5,85 449,7 8,76 490,1 8,36 457,0 15,79 530,1 14,59 467,9 21,58 570,0 19,45 475,0 29,77 617,5 25,94

(Style in table: Times New Roman, 11pt, Normal) X. CONCLUSION Paper manuscripts, prepared in accordance with these Instructions for Authors, are to be submitted to the Editorial Board of the "Mašinstvo" journal. Manuscripts and the CD-ROM are not returned to authors. When being prepared for printing the text may undergo small alternations by the Editorial Board. Papers not prepared in accordance with these Instructions shall be returned to the first author. When there are several authors the first author is to be contacted. The Editorial Board shall accept the statements made by the first author. The author warrants that the article is original, written by stated author/s, has not been published before and it will not be submitted anywhere else for publication prior to acceptance/rejection by "Mašinstvo", contains no unlawful statements, does not infringe the rights of others, and that any necessary written permissions to quote from other sources have been obtained by the author/s.

XX. REFERENCES (Style: Times New Roman, 11pt, Normal) [1] P.E. Nikravesh, Computer-Aided Analysis

of Mechanical Systems, Prantice Hall Inc.,Englewood Cliff,NJ,1988.

[2] Gordon Robertson, Graham Caldwell, Joseph Hamill, Gary Kamen, Saunders Whittlesey: Research Methods in Biomechanics, Human Kinetics; 2nd edition, 2014.

[3] Imai, M.: KAIZEN: the key to Japan’s competitive success, Editorial CECSA, Mexico. In Spanish, 1996.

[4] Nemoto, M.: Total quality control for management. Strategies and techniques from Toyota and Toyoda Gosei, Prentice-Hall, Englewood Cliffs, NJ, 1987.

[5] Cheser, R.: The effect of Japanese KAIZEN on employee motivation in US manufacturing, Int J Org Anal 6(3):197–217, 1998.

[6] Aoki, K.: Transferring Japanese KAIZEN activities to overseas plants in China, Int J Oper Prod Manag 28(6):518–539, 2008.

[7] Tanner, C.; Roncarti, J.: KAIZEN leads to breakthroughs in responsiveness and the Shingo prize at Critikon, Natl Prod Rev 13(4):517–531, 1994.

[8] Rink, J.: Lean can save American manufacturing. Reliable plant. http://www.reliableplant.com/Read/330/lean-manufacturing-save. Accessed at 14 April 2014.

[9] SolidWorks, http://www.solidworks.com (12.5.2015)

Coresponding author: Name and surname Institution Email: [email protected] Phone: +xxx xx xxxxxx (Style: Times New Roman, 11pt, Bold)


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Godina (Volume) 12, Broj (Number) 3-4, Juli - Decembar ...idealab.unze.ba/Masinstvo/Masinstvo-num3-4-2015.pdf · - tehnologija prerade metala, plastike i gume, ... zahtjev savremenih