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MECHANICAL CHARACTERIZATION OF HEAT RESISTANT TITANIUM ALLOYS
FOR AUTOMOTIVE APPLICATIONS Author: Dr. Eng. Silvia Gaiani
Akrapovič d.d. - Technology Supervisor
ABSTRACT
In the last five years, the use of titanium
alloys for exhaust systems manufacturing in
automotive industry has increased
significantly. Due to this reason, also the
variety of heat resistant alloys available on the
market is raised considerably. In order to
better evaluate the characteristics of this wide
range of products, Akrapovič d.d. developed a
classification method which can be used to
check incoming materials and compare
properties between different alloys. Because
of the strongly anisotropic behavior of
titanium, to obtain a comprehensive overview
of the plastic performance, a testing approach
based on biaxial tensile trials has been used.
1.0 INTRODUCTION
Actually, titanium alloys used for exhaust
system fabrication are all α alloys, which use
as addition small quantities of different
alloying elements, as aluminum, copper,
niobium, silicon and iron. Addition of these
elements has increased significantly the
oxidation resistance and mechanical
properties, if compared whit the performance
of commercially pure titanium, especially
Grade 2. For production of exhaust system
dedicated to high performance bikes and cars,
Akrapovič buys several types of titanium
alloys, from different producers worldwide;
the most common purchased raw material is
in shape of coils, with a thickness between 0,5
- 1,5 mm. These advanced alloys show
excellent properties for their target
application (high strength, elevated thermal
properties, weldability); however, their use for
realizing parts with complicated shapes is still
limited, because of problems associated with
poor formability and consequently high
manufacturing costs. Formability problems of
cold rolled titanium alloys are well known
several years ago, and basically are strictly
related to the anisotropic behavior of the
materials.
Anisotropy behavior in α titanium alloys is
strictly related to two aspects mostly:
- Type of titanium lattice, which is, until
882 °C, hexagonal closed packed (HCP).
- Crystallographic orientation (texture)
For titanium, the hexagonal unit cell of the α
phase shows values of the lattice parameters
a=0.295 nm and c=0.468 nm. The resulting c/a
ratio for pure α titanium is therefore 1.587, or
rather smaller than the ideal ratio of 1.633 for
the hexagonal close-packed crystal structure.
This condition means that the three most
densely packed lattice planes are the following
(see Pic. 1):
- Two ( 0002 ) plane, also called
basal plane,
- Four {1010 } planes, also called
prismatic planes
- Six {1011} planes, also called
pyramidal plane
Looking Picture 1, it is very easy to understand
that hexagonal unit cell don't present
symmetric slip systems.
Pic.1 - Theoretical slip planes for titanium [[[[ 1]]]]
2
Combining the three different types of slip
planes mentioned above, together with the
possible slip directions there are a total of 12
slip systems. These slip systems can be
reduced to nominally 4 independent.
However, according to Von Mises principle, to
obtain a homogeneous plastic deformation at
least five independent slip systems are
required. This means that in order to have
plastic deformation, also a system with a non-
basal Burgers vector needs to be activated; for
these type of titanium alloys this non-basal
Burgers system most commonly activated is
the type <1123> {1122}. The need to activate
two different types of dislocations (a vector
basal, c vector non basal) at the same time is
strictly related also to the direction of load.
For all these reasons, plastic deformation in α
titanium alloy is also strongly dependent from
the activation of twinning deformation modes
in addition to conventional slip by
dislocations. To be more precise, these
twinning modes are probably the most
important for the deformation behavior of the
considered α titanium alloys.
Concerning the crystallographic orientation, it
is well known that during the production
process, especially during final cold rolling,
titanium α alloys show a considerable attitude
to give rise to a preferred crystallographic
orientation. When preferred orientation
exists, the structure is said to be “textured” or
that it has a strong “texture”. The orientation
of the lattice is related to many factors, like
c/a ratio, rolling conditions, annealing
temperature, etc. Most HCP alloys show a
nearly basal texture (i.e. c-axis aligned normal
to the plane of the sheet); for titanium α
alloys obtained with standard production
processes the basal planes are inclined
approximately 30° towards the transverse
direction [2]. However, certainly alloying
agents, direction of rolling, heat treatment
temperature should play an important role in
determining the final texturing direction of the
material. For sure, texture in titanium alloys
has a big impact on the final mechanical
characteristic of the product, especially
formability, because, as previously explained,
the slip planes of HCP lattice are not
symmetrically sorted.
2.0 UNIAXIAL TENSILE TESTS
Akrapovič d.d. purchases for its exhaust
system production six diffent types of titanium
alloys from three different suppliers; four of
them are mostly used for deep drawed parts,
as endcap or rosette. Executing a practical
deep drawing test under the press, the
behavior of these materials is completely
different. However, if we compare the results
of a tensile test executed along the rolling
direction the outcome are the following:
Rp 0,2
(MPa) Rm
(MPa) A80
(%) Agt
(%) Rp/Rm
(--)
Mat. 1 300,26
425,93 30,76 14,34 0,705
Mat. 2 319,63 452,43 29,93 17,48 0,706
Mat. 3 297,74 431,44 31,60 17,35 0,691
Mat. 4 476,72* 576,43 24,38 13,32 0,827
Table 1 – Tensile test in rolling direction
The results listed in Table 1 are medium value
obtained executing n°5 tensile test for every
type of materials according to standard EN
10002-1 on a specimen with L0=80 mm. (*) For
material n°4 the measured yield limit is not
Rp0,2 but REH. Looking the tensile value
obtained in rolling direction, is clearly visible
that the first three materials show similar
behavior and characteristics; unfortunately
this results was not supported from practical
deep drawing tests. For this reason, also
tensile tests in transverse direction were
performed. The obtained results are in Tab 2.
Rp 0,2
(MPa) Rm
(MPa) A80
(%) Agt
(%) Rp/Rm
(--)
Mat. 1 340,13
398,26 30,93 8,22 0,854
Mat. 2 365,51 400,40 34,56 7,22 0,913
Mat. 3 308,74 408,72 31,22 7,98 0,765
Mat. 4 550,48* 575,46 24,40 8,05 0,956
Table 2 – Tensile test in transverse direction
As it is possible to see from Table 1 and 2, the
behavior of the material in rolling and
transverse direction is strongly different. For
every material, in transverse direction Rp
value raises, becoming nearer to Rm, which is
mainly constant. In transverse direction Rm
peak is also reached at a lower elongation.
These two factors cause a big reduction of the
plastic field of the material, also if the final
elongation is basically the same.
3
Pic. 2- Comparison between rolling and transverse
tensile test results for material n°1
Pic. 3- Comparison between rolling and transverse
tensile test result for material n°3
Crossing the values obtained by tensile test in
rolling and transverse direction and the
practical results obtained in deep drawing
department, was clear that for predicting
realistic results, a more detailed investigation
which can explore deeper the problems
related to anisotropy is needed [3].
3.0 BIAXIAL TENSILE TEST
For all four materials used for deep drawing,
some tensile test using a biaxial electronic
gauge were performed according to standard
EN 10002-1 [4] on specimens with L0=80 mm.
The specimens were orientated along the
rolling direction (longitudinal), perpendicular
to the rolling direction (transverse), and at
45°degrees to the rolling direction (diagonal).
The trials were executed using two different
types of machine controls during the test:
1) Stress rate control → σrate= 12 MPa/s
2) Strain rate control → εrate= 0,00065 1/s
In the elastic field σrate value has been chosen
for staying in the boundaries suggested from
standard EN 10002-1, which for metals with E
< 150.000 recommend staying between 2 – 20
MPa/s. In the plastic field, constant strain rate
condition has been chosen because standards
require specifically for this type of control, and
recommend that strain rate doesn't exceed
0,0025 1/s. The switch between stress rate
control and strain rate control is performed at
1,5% of elongation.
Pic. 4 – Biaxial testing equipment
Performing these tensile tests with biaxial
gauge allow to determinate many different
parameters, which are very important to
predict the plastic behavior of the material:
- General tensile properties (Rp, Rm, A80,
Agt, E modulus)
- Poisson coefficient in elastic field and in
plastic field (νEL and νPL)
- Strain hardening exponent and strain
hardening coefficient (n and K)
- Plastic strain ratio index (r, planar
anisotropy, normal anisotropy)
- Strain-rate sensitivity coefficient and
strain hardening coefficient (m and C)
In order to obtain complete information about
plastic behavior of the alloy, also some
Erichsen cupping tests (performed according
to ISO 20482 [5]) have been executed.
The obtained results, which for every
characteristic are calculate as mean value of
three tests, are listed in the following
paragraphs.
4
3.1 General tensile properties
The collections of data obtained during testing
are listed in the sequel (Table 3, 4 and 5).
Young’s modulus is evaluated using the
method called “Cord Modulus”; this
calculation determines the slope of the
stress/strain curve using two specific points on
the diagram. Furthermore, a straight line
between this lower and upper bounds
previously chosen is constructed. The two
boundaries are different for every material,
because the extension of the elastic field is
not constant. Furthermore, to evaluate Yield
strength limit (Rp0,2) we use the method called
“Offset Yield”. Basically the offset yield
calculation constructs a line parallel to the line
detected for evaluating E modulus and than
offset it by an amount that you specify. In our
case the offset is 0,2% of initial length L0, and
the offset yield point is where the offset line
intersects the diagram σ−ε. Only material n°4
uses a different method because instead of
Rp0,2 the upper and lower limits REH and REL are
evaluated.
Table 3 – Tensile test in rolling direction (L)
Table 4 – Tensile test in diagonal direction (D)
Table 5 – Tensile test in transverse direction (T)
3.2 Poisson coefficient
According to the standard ASTM E132 [6],
Poisson coefficient ν is an absolute value of
the ratio between transverse strain and
longitudinal strain. Poisson's ratio is variable in
case the material is not isotropic; in our case
we evaluated it, according to standard, as the
ratio between the average transverse strain εt
and the average longitudinal strain εl using the
same range used for calculating E modulus
(variable for every material). Moreover, also a
single value of ν at 0,25% elongation has been
considered.
Also in the plastic field Poisson ratio has been
calculated using average value in the range
between 2% of elongation and Rm. The
obtained data are listed below.
Table 6 – Poisson ratio in rolling direction (L)
Table 7 – Poisson ratio in diagonal direction (D)
Table 8 – Poisson ratio in transverse direction (T)
Pic. 5 – Trend of Poisson Ratio (elastic and plastic field)
Rp0,2 (MP)
Rm
(MPa)
A80 (%)
Agt
(%) Rp/Rm
(--) E
(MPa) M1 293,2 414,9 35,3 15,5 0,706 100.719
M2 321,8 455,6 30,8 17,8 0,706 98.539
M3 291,5 415,0 35,7 18,5 0,702 92.674
M4 433,5 521,6 24,6 14,2 0,831 91.667
Rp0,2 (MP)
Rm
(MPa)
A80 (%)
Agt
(%) Rp/Rm
(--) E
(MPa) M1 325,6 389,1 33,6 9,6 0,836 101.405
M2 324,2 378,5 38,2 12,1 0,856 98.285
M3 297,6 381,1 41,3 13,9 0,781 96.091
M4 473,1 489,1 26,3 10,2 0,967 98.167
Rp0,2 (MP)
Rm
(MPa)
A80 (%)
Agt
(%) Rp/Rm
(--) E
(MPa) M1 336,5 393,8 27,5 7,8 0,854 103.230
M2 366,6 401,9 34,9 7,1 0,912 99.525
M3 297,1 390,3 36,3 8,6 0,761 94.534
M4 541,0 545,8 31,5 8,1 0,991 109.208
νννν0,25%
(--) ννννelastic
(MPa)
ννννplastic
(%)
M1 0,399 0,343 0,731
M2 0,343 0,300 0,562
M3 0,364 0,316 0,588
M4 0,315 0,321 0,435
νννν0,25%
(--) ννννelastic
(MPa)
ννννplastic
(%)
M1 0,395 0,356 0,796
M2 0,369 0,343 0,685
M3 0,405 0,314 0,710
M4 0,343 0,333 0,617
νννν0,25%
(--) ννννelastic
(MPa)
ννννplastic
(%)
M1 0,395 0,351 0,813
M2 0,389 0,333 0,737
M3 0,561 0,341 0,769
M4 0,335 0,322 0,655
5
3.3 Strain hardening exponent and coefficient
According to standards ISO 10275 [7] and
ASTM 646 [8], the strain hardening exponent
n is defined as the exponent of true plastic
strain in Hollomon equation, which describes
a relation between true stress σ and true
strain ε in the plastic region. This equation can
be taken as follows:
ε� (1)
Equation 1 can be transformed in logarithmic
one as follows:
(2)
Pic. 6 - Difference between true stress –true strain
curve and engineering stress – engineering strain curve
From a practical point of view, strain
hardening exponent “n” is the parameter that
provides an indication about the increase in
hardness and strength occurring during plastic
deformation of the material.
The n value has been calculated using a linear
regression of the logarithm of true stress vs.
the logarithm of true strain; the obtained
values are listed in Table 9.
Table 9 – Strain hardening exponent and coefficient
3.4 Plastic strain ratio index
A parameter than can be used to have an
impression of anisotropic properties of the
alloys is the ″plastic strain ratio″ r; according
to standards ISO 10113 [9] and ASTM E517
[10] this value is defined as follows:
��
�� (Lankford value) (3)
Where εw is the width strain and εt is the
transverse strain. Moreover, performing
tensile test with double extensimeter in
different direction (rolling direction 0°,
transverse direction 90°, diagonal direction
45°) and evaluating Lankford value in every
orientation, also other parameter are
definable as follow:
�0°+2�45°
+�90°
4 (normal anisotropy) (4)
∆��°�����°
����°�
(planar anisotropy) (5)
Pic. 7- Normal and planar anisotropy [[[[Ref. 2]]]]
The obtained values are listed in Table 10.
Table 10 – Strain ratio index
ROLLING DIAGONAL TRANSVERSE
n (--)
K
(MPa)
n (--)
K
(MPa)
n
(--) K
(MPa) M1 0,138 629,9 0,104 550,8 0,087 534,5
M2 0,134 680,4 0,093 518,8 0,067 517,1
M3 0,139 623,3 0,103 533,6 0,080 520,5
M4 0,138 795,5 0,105 693,1 0,093 758,4
rL
(--) rD
(--)
rT
(--)
(--) ∆∆∆∆r (--)
M1 4,202 5,764 6,224 5,488 -0,551
M2 1,601 2,861 3,386 2,677 -0,367
M3 1,754 3,147 3,703 2,937 -0,418
M4 0,888 1,994 2,496 1,843 -0,302
6
3.5 Strain rate sensitivity
The rate at which strain is applied to the
tension specimen has an important influence
on the stress-strain curve. Strain rate should
be defined as follows:
= �ε
�� (6)
The strain-rate dependence of flow stress at
constant strain and temperature is given by:
σ = C· m
(7)
Where:
m = strain-rate sensitivity coefficient
C = strain hardening coefficient
In order to determine the strain rate
sensitivity, we use the speed change
performed at 1,5 % of elongation. In that
point, we change the test speed and also the
type of control of the machine from stress to
strain.
Pic. 8 - Rate change during test [[[[Ref. 2]]]]
The strain-rate sensitivity, at constant strain
and temperature, can be determined from
equation 8:
(��
��)
(�
�
)
(8)
The obtained values are listed in Table 11.
Table 11 – Strain hardening exponent and coefficient
3.6 Erichsen cupping test
The tests have been performed using a
standard tool; the geometry of this tool is in
accordance with the prescription of standard
ISO 20482. According to standard, the
specimens have been slightly lubricated with a
graphite based lubricant; the speed of the
crosshead during the test has been kept
constant at 8 mm/min. The torque applied to
the two screws, which lock the specimen in
the correct position in 15 N·m, in order to
obtain a holding load equal to 10 KN.
Pic. 9 – Erichsen equipment
The obtained values are listed in Table 12.
ROLLING TRANSVERSE
F (N)
E.I. (mm)
F (N)
E.I. (mm)
M1 18.920 7,773 20.122 7,995
M2 24.099 8,612 24.886 8,892
M3 24.123 10,257 24.494 10,514
M4 25.939 9,117 26.338 9,250
Table 12 – Erichsen cupping test results
ROLLING DIAGONAL TRANSVERSE
m (--)
C
(MPa)
m (--)
C
(MPa)
m
(--) C
(MPa) M1 0,032 387,2 0,064 550,1 0,047 501,1
M2 0,032 426,2 0,037 441,8 0,056 580,8
M3 0,064 509,3 0,058 497,5 0,075 593,4
M4 0,027 487,6 0,049 465,5 0,051 598,2
7
4.0 CONCLUSION
The trials performed with a biaxial electronic
gauge had the purpose to investigate in depth
the plastic properties of the four materials
used by Akrapovič for deep drawed parts. The
performed trials allow finding a precise
relation between the experimental collected
values and the practical results obtained
during formability tests carried out in
production.
In order to investigate about plastic properties
of titanium heat resistant alloys, the best way
to take advantage by the series of data
collected during these trials is use them as
material data for some FEA (Finite Elements
Analysis) activities. In fact, FEA simulations are
important instruments in trying to predict
formability of materials. Anyway, the accuracy
of these numerical analysis depend on the
preciseness of the constitutive model used to
describe the behavior of the alloy; in case of
anisotropic materials, mathematical models
are just developed taking in account all the
plastic parameters evaluated during biaxial
tests, like Poisson and strain hardening
coefficients, plastic strain ratio and so on. For
simulating deep drawing, 3D parameter Barlat
equation has been chosen; this model was
developed by Barlat and Lian in 1989 for
modeling sheets with anisotropic behavior
loaded in plane stress condition [12].
According to this equation, the anisotropic
yield criterion Φ is defined in the following
equation (9):
� ��
� ��
��
σ��
Where: σY = yield stress
K1, K2 = principal values of stress
deviator
a, c = anisotropic material coefficient
(Calculated using r0, r45, r90)
m = Barlat coefficient depending on
type of lattice
This macroscopic yield criterion, expressed in
terms of the principal values of stress
deviator, has been used several times to
predict the anisotropic behavior of hexagonal
closed packet metals (i.e. titanium,
magnesium and zirconium alloys) obtaining
very good results. Using this model the
anisotropy of the material and the yielding
asymmetry between tension and compression
is perfectly represented [13].
The first trial actually under development is a
model for simulating Erichsen cupping test.
This choice has been made because Erichsen is
a symmetric model with a single axial load;
moreover, practical tests with this equipment
have been already carried out, and the
collection of experimental results is ready for
comparison with the theoretical results.
Pic. 10, 11 – FEA model of Erichsen cupping test
5.0 REFERENCES
1. G. Lutjering, J.C. Williams, Titanium – Springer,
second edition
2. T.L. Sullivan, Texture strengthening and
fracture toughness of titanium alloy sheet at
room and cryogenic temperature – N.A.S.A.
Technical Note D-4444
3. K.S. Chan, D.A. Koss, Deformation and fracture
of strongly textured Ti alloy sheet in uniaxial
tension – Office of Naval Research, technical
report n°19
8
4. EN 10002/1 - Metallic materials - Tensile
testing - Part 1: Method of test at ambient
temperature
5. ISO 20482 - Metallic materials - Sheet and
strip - Erichsen cupping test
6. ASTM E132 - Standard Test Method for
Poisson's Ratio at Room Temperature
7. ISO 10275 – Metallic materials - Sheet and
strip - Determination of tensile strain hardening
exponent
8. ASTM E646 – Standard Test Method for
Tensile Strain-Hardening Exponents (n-Values) of
Metallic Sheet Material
9. ISO 10113 – Metallic materials – Sheet and
strip – Determination of plastic strain ratio
10. ASTM 517 - Standard Test Method for
Plastic Strain Ratio r for Sheet Metal
11. ASM Metal Handbook Vol. 08 – Mechanical
testing and evaluation
12. F. Barlat, J. Lian, Plastic behavior and
stretchability of sheet metals, Part. 1: A function
for orthotropic sheet under plane stress
condition - International journal of plasticity,
Vol. 5 (1989) pp. 51-66
13. F. Barlat, O. Cazacu, B. Plunkett, Orthotropic
yield criterion for hexagonal closed packed
metals – International journal of plasticity 22
(2006)
6.0 CONTACTS
Dr. Eng. Silvia Gaiani
Akrapovič d.d.
Malo Hudo 8 – Ivancna Gorica (SLO)
TITANIUM 2008Las Vegas, Nevadag
21 – 24 September 2008
MECHANICAL CHARACTERIZATION OF HEAT RESISTANT TITANIUM ALLOYS
FOR AUTOMOTIVE APPLICATIONSDr. Eng. Silvia Gaiani
Akrapovič d.d. – Technology Supervisor
TITANIUM 2008Las Vegas NevadaLas Vegas, Nevada
21 – 24 September 2008
In the last five years, the marketdemand of high performancedemand of high performancecars and bikes oblige vehiclesmanufacturer to design andproduce engines increasinglyp g g yextreme and powerful
This aspect obliges consequentlythe exhaust systems producersthe exhaust systems producersto use materials which presentawfully high mechanical andphysical characteristicsphysical characteristics
TITANIUM 2008Las Vegas NevadaLas Vegas, Nevada
21 – 24 September 2008
Titanium alloys have the following benefits:following benefits:
Low Density
Excellent Heat Resistance(low oxidation at elavated temperature)
Interesting Mechanical Properties
Weldability
TITANIUM 2008Las Vegas, Nevadag
21 – 24 September 2008
Titanium alloys have the following problems:
High Manufactoring Costs
Poor Formability
TITANIUM 2008Las Vegas Nevada Formability problems of titanium are related to its Las Vegas, Nevada
21 – 24 September 2008
Formability problems of titanium are related to its type of lattice, which is Hexagonal Close Packed (HCP)
HCP lattice shows the following singularity:
Properties ara related to the ratio between height and widthof the lattice (c/a ratio for Titanium is 1,587)( / )
Depending on c/a ratio, only 4 independentslip system are active, and they’re not enoughto allow plastic deformation (minimum 5)to allow plastic deformation (minimum 5)
To allow plastic deformation, also a systemwith a non-basal Burger vector must be
ti t d Th t it t ti t thiactivated. The oppurtunity to activate thisplane is tightly related to the direction ofthe load
If stress axis // to c axis → NO ACTIVATION
TITANIUM 2008Las Vegas, Nevada
21 – 24 September 2008
TWINNING occours when two separate crystalsshare a part of the same lattice in a symmetricalshare a part of the same lattice in a symmetricalmanner. Deformation twinning is important forplasticity of the HCP metals, in some conditionsdepending from stress direction and temperature
TEXTURING is a preferential orientation of the
p g pis also predominant than dislocation slipping
crystallographic structure. Texture is mainlydeterminated from cold rolling conditions, heattreatments, alloying elements.
Because of the reasons mentioned above TitaniumBecause of the reasons mentioned above, Titaniumalloys exhibit a strong anisotropic behavior
TITANIUM 2008Las Vegas, Nevada
21 – 24 September 2008 AKRAPOVIČ TECHNOLOGY
Tube Production Bending Hydroforming Deep Drawing
Welding Rolling Machining Surface Finishing
TITANIUM 2008Las Vegas NevadaLas Vegas, Nevada
21 – 24 September 2008
For the production of exhaust systems forbikes and cars Akrapovič d d uses sevenbikes and cars, Akrapovič d.d. uses sevendifferent types of titanium alloys.Some of these alloys are standard alloyslike Grade 2 Grade 5 Grade 9 and gradelike Grade 2, Grade 5, Grade 9 and grade37; other alloys are patented products.
Deep drawing and tube bending are thep g gtechnologies where titanium formabilityproblems are more noticeable.Therefore, on the four types of alloys, yp ymore used for these purposes, a completemechanical characterization has beencarried out in order to better understandcarried out in order to better understandthe behavior of these different materials.
TITANIUM 2008Las Vegas, Nevada UNIAXIAL TENSILE TESTSg
21 – 24 September 2008UNIAXIAL TENSILE TESTS
*REH instead that RP0 2
LONGITUDINAL → TRANVERSE
Rp raises
REH instead that RP0,2
Rp raises
Rm decreases
Total elongation is equal butTotal elongation is equal, butelongation at Rm is strongly reduced
TITANIUM 2008Las Vegas NevadaLas Vegas, Nevada
21 – 24 September 2008 BIAXIAL TENSILE TESTS
Performing biaxial tensile tests, manyi t h t i ti b d t i t dimportan characteristic can be determinated:
General tensile properties Rp, Rm, A80, Agt, E
Poisson coefficient in elastic field νEL and inplastic field νPL
Strain hardening exponent n and strainhardening coefficient K
Plastic strain ratio index r, planar anisotropy ř, normal anisotropy Δr
Strain-rate sensitivity coefficient m and strain hardening coefficient C
To complete plastic properties characterizationp p p palso Erichsen cupping tests have beenperformed
TITANIUM 2008Las Vegas, Nevada
21 – 24 September 2008GENERAL TENSILE PROPERTIES
Rp0,2
(MP)Rm
(MPa)A80
(%)Agt
(%)Rp/Rm
(--)E
(MPa)
LLIN
G
M1 293,2 414,9 35,3 15,5 0,706 100.719M2 321,8 455,6 30,8 17,8 0,706 98.539
RO
L M3 291,5 415,0 35,7 18,5 0,702 92.674M4 433,5* 521,6 24,6 14,2 0,831 91.667
GO
N
M1 325,6 389,1 33,6 9,6 0,836 101.405M2 324,2 378,5 38,2 12,1 0,856 98.285
DIA
G
M3 297,6 381,1 41,3 13,9 0,781 96.091M4 473,1* 489,1 26,3 10,2 0,967 98.167
AN
SV
M1 336,5 393,8 27,5 7,8 0,854 103.230M2 366,6 401,9 34,9 7,1 0,912 99.525
TR
A M3 297,1 390,3 36,3 8,6 0,761 94.534M4 541,0* 545,8 31,5 8,1 0,991 109.208
*REH instead that RP
TITANIUM 2008POISSON COEFFICIENT Las Vegas, Nevada
21 – 24 September 2008POISSON COEFFICIENT
Poisson Coefficient: ν =
Poisson's ratio is variable in case thematerial is not isotropic; in elastic field it isthe mean value in the same range used togcalculate E modulus (variable for everymaterial). Moreover, also a single value ofν at 0,25% elongation has beenconsidered.In plastic field is the mean value between2% and Rm peak.
ROLLING DIAGONAL TRANSVERSEν0,25%
(--)νelastic
(MPa)νplastic
(%)ν0,25%
(--)νelastic
(MPa)νplastic
(%)ν0,25%
(--)νelastic
(MPa)νplastic
(%)M1 0,399 0,343 0,731 0,395 0,356 0,796 0,395 0,351 0,813M2 0,343 0,300 0,562 0,369 0,343 0,685 0,389 0,333 0,737M3 0,364 0,316 0,588 0,405 0,314 0,710 0,561 0,341 0,769M4 0,315 0,321 0,435 0,343 0,333 0,617 0,335 0,322 0,655
TITANIUM 2008 S G OTITANIUM 2008Las Vegas, Nevada
21 – 24 September 2008
STRAIN HARDENING EXPONENT ANDSTRAIN HARDENING COEFFICIENT
Hollomon Equation:
I l ith i l In logarithmic scale:
ROLLING DIAGONAL TRANSVERSEn K n K n K
(--) (MPa) (--) (MPa) (--) (MPa)M1 0,138 629,9 0,104 550,8 0,087 534,5M2 0,134 680,4 0,093 518,8 0,067 517,1M3 0 139 623 3 0 103 533 6 0 080 520 5M3 0,139 623,3 0,103 533,6 0,080 520,5M4 0,138 795,5 0,105 693,1 0,093 758,4
TITANIUM 2008Las Vegas Nevada PLASTIC STRAIN RATIO INDEX Las Vegas, Nevada
21 – 24 September 2008PLASTIC STRAIN RATIO INDEX
Plastic Strain Ratio:
N l i tNormal anisotropy:
Planar anisotropy:
rL
(--)rD
(--) rT
(--)ř
(--)Δr(--)( ) ( ) ( ) ( ) ( )
M1 4,202 5,764 6,224 5,488 -0,551M2 1,601 2,861 3,386 2,677 -0,367M3 1 754 3 147 3 703 2 937 -0 418M3 1,754 3,147 3,703 2,937 -0,418M4 0,910 1,994 2,515 1,853 -0,281
TITANIUM 2008Las Vegas Nevada STRAIN-RATE SENSITIVITY COEFFICIENT
=
Las Vegas, Nevada21 – 24 September 2008
STRAIN RATE SENSITIVITY COEFFICIENT
=Strain rate:
Strain-rate equation: σ=C ·
Strain-rate sensitivity:
In order to determinethe strain rate
ROLLING DIAGONAL TRANSVERSE
m( )
C(MPa)
m( )
C(MPa)
m( )
C(MPa) sensitivity, the speed
change performed at1,5 % of elongationh b d
(--) (MPa) (--) (MPa) (--) (MPa)M1 0,032 387,2 0,064 550,1 0,047 501,1M2 0,032 426,2 0,037 441,8 0,056 580,8M3 0 064 509 3 0 058 497 5 0 075 593 4 has been used.M3 0,064 509,3 0,058 497,5 0,075 593,4M4 0,027 487,6 0,049 465,5 0,051 598,2
TITANIUM 2008Las Vegas Nevada ERICHSEN CUPPING TESTS Las Vegas, Nevada
21 – 24 September 2008
ERICHSEN CUPPING TESTS
According to standard, the speed of thecrosshead during the test has been keptconstant at 8 mm/min. The torque applied tothe two screws, which lock the specimen inth t iti i 15 N i d tthe correct position in 15 Nm, in order toobtain a holding load equal to 10 KN.
ROLLING TRANSVERSEROLLING TRANSVERSEF
(N)E.I.
(mm)F
(N)E.I.
(mm)M1 18.920 7,773 20.122 7,995M2 24.099 8,612 24.886 8,892M3 24.123 10,257 24.494 10,514M4 25.939 9,117 26.338 9,250
TITANIUM 2008Las Vegas NevadaLas Vegas, Nevada
21 – 24 September 2008
All the information collected with biaxiall testing are used for FEA simulation testing are used for FEA simulation
To describe anisotropic behavior of Titanium ll th h th ti l d l i th alloys, the chosen mathematical model is the
3D parameter BARLAT equation.This equation describe yielding condition as follow:follow:
The first simulation test is Erichsen cupping test, in order to able to compare theoretical and experimental resultsp
TITANIUM 2008Las Vegas Nevada THERMAL PROPERTIES DETERMINATIONLas Vegas, Nevada
21 – 24 September 2008
To investigate about thermal properties and
THERMAL PROPERTIES DETERMINATION
oxidation resistance of different alloys, also somedurability test are performed on a roller bench
Using an infrared thermal camera, all thetemperature variations occuring during theaccelerated durability test performed on a specialaccelerated durability test performed on a specialbench can be evaluated in real time
TITANIUM 2008Las Vegas Nevada MICROSTRUCTURAL EXAMINATIONSLas Vegas, Nevada
21 – 24 September 2008MICROSTRUCTURAL EXAMINATIONS
On parts submitted to funcionality and durability test,
i t t l microstructural and grain size examinations are normally are normally performed in order to guarantee guarantee quality and reliability of the exhaust systemsy
TITANIUM 2008Las Vegas NevadaLas Vegas, Nevada
21 – 24 September 2008
Defects measurments and examinations
TITANIUM 2008Las Vegas Nevada
MACROSCOPIC EXAMINATION OF WELDSLas Vegas, Nevada
21 – 24 September 2008
Härteverlauf über Schweißnähte
240
Härte HV 0,5 über Schweißnaht 8 Härte HV 0,5 über Schweißnaht 12
GEOMETRY AND MICROARDNESS MEASURMENT
140
160
180
200
220
Härt
e HV
0,5
100
120
0,00 1,00 2,00 3,00 4,00 5,00 6,00 7,00 8,00 9,00 10,00 11,00 12,00 13,00 14,00
Weg x in mm
TITANIUM 2008Las Vegas NevadaLas Vegas, Nevada
21 – 24 September 2008
Thanks for your Thanks for your attentionattention