metal tensile test by using miniaturised test pieces 2016 ... · −material without upper and...
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(1) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Metal Tensile Test Using Miniaturized Test Pieces
Johannes Aegerter,
Stefan Keller,
Heike Berk
2016-10-12
(2) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Objective
Development and Optimisation of the testing technique for testing ofminiaturised test tensile test pieces for the determination of localstrength properties and flow curves from deformed component areas fore. g. the following applications:
● Verification of component specifications and optimisation of the production of components
● Validation of FE-forming simulations
● Determination of input data for crash and service life calculation
● Characterisation of local properties of weldings
● Evaluation of cases of damage
(3) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Problem definition and boundary conditions
Problem definition
● Clamping of the test piece without bending and shearing forces
● Warranty of uniaxial stress
● Dimensionally accurate machining of the test pieces without workhardening and heat input
● Realisation of small gauge length and accurate measurement of very small extensions
● Largely compliance of normative specifications acc. to ISO 6892-1:2009
Boundary conditions
● Applicable in the normal industrial environment, this means by using mainly standard equipment
● Largely comparability with standard tensile test properties
(4) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Investigated test piece geometries
Form Lt(mm)
B(mm)
bo(mm)
Lc(mm)
Le(mm)
C(mm)
D(mm)
E(mm)
r(mm)
Lc───────
bo
Le───────
bo
Form 1 250 30 20 120 80 35 - - 20 6 4
Form 2 165 20 12.5 75 50 30 - - 20 6 4
Form 3 35 6.5 2.5 15 10 8 3 3 2 6 4
Form 4 32 6.0 2.0 12 10 8 3 3 2 6 5
Form 5 23 4.0 1.25 7.5 5 6 2 2 2 6 4
Form
3
Form
4
Form
5Le = Extensometer gauge length
Form
2
Form
1
Source: ISO 6892-2:2011-02
(5) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Influence of the gauge length on elongation after fracture
Nearly equal elongations after fracture for different test piece geometries only if:
– Equal coefficient of proportionality k of the test pieces (Standard: 5.65)Non proportional test pieces (A50mm, A80mm): Nearly equal thicknesses are necessary.
“Comparisons of percentage elongation are possible only when the gauge length or extensometer gauge length, the shape and area of the cross-section are the same or when the coefficient of proportionality, k, is the same.” (ISO 6892-1:2009)
11.3
5.65
Source: W. Domke
(6) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Coefficient of proportionality of the investigated test piece geometries
Form Lt B bo Lc Le rLc
───────
bo
Le───────
bo
k1,0mm
k0,29mm
Form 1 250 30 20 120 80 20 6 4 17.89 33.22
Form 2 165 20 12.5 75 50 20 6 4 14.14 26.26
Form 3 35 6.5 2.5 15 10 2 6 4 6.32 11.74
Form 4 32 6.0 2.0 12 10 2 6 5 7.07 13.13
Form 5 23 4.0 1.25 7.5 5 2 6 4 4.47 8.30
Form
3
Form
4
Form
5Le = Extensometer gauge length
Form
2
Form
1
Source: ISO 6892-2:2011-02
(7) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Testing machine, clamping system and force measurement
● 250 kN load cell● Hydraulic clamping system● Extensometer class 0.5
● 2.5 kN load cell● Bending and shear force free clamping
by using bolts● Extensometer class 0.5
(8) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Modification of the extensometer
● Extensometer class 0.5− By using standard edges smallest possible
gauge length 10 mm− Reduction of the gauge length to 5 mm: − Spacer, t = 2.5 mm (b)− between edge holder (c)− and edge (a)
− Problem: Machine calculates extensions with “set”-gauge length Le = 10 mm− Conversion of extensions to real gauge
length necessary:− Multiplication of extensions or the measured
length change by the factor:Le(set)/Le(real), here: Factor 2 Extensometer with
5 mm gauge length
c)
b)
a)
(9) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Materials, test piece preparation and testing rates
● AA6016 (AlMg0,4Si1,2), condition T4, 1.0mm thickness
● AA6016 (AlMg0,4Si1,2), condition T6, 1.0mm thickness
● AA5182 (AlMg4,5Mn0,4), condition H111, 1.0 mm thickness
● AA3104 (AlMn1Mg1Cu), condition H19, 0.29 mm thickness
● Test piece preparation by using CNC-milling machine
● Testing rates according to ISO 6892-1:2009, Method A (open loop)
(10) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Elastic range for different test piece geometries,material AA 6016-T6
0
50
100
150
200
250
0,0 0,1 0,2 0,3 0,4 0,5 0,6
Span
nung
in M
Pa
Dehnung in %
Form 1: m E = 67,5 GPaForm 2: m E = 67,4 GPaForm 3: m E = 66,8 GPaForm 4: m E = 65,5 GPaForm 5: m E = 66,9 GPa
E-Modul des Werkstoffs: 69 GPa
1,1 · E = 75,9 GPa
0,9 · E = 62,1 GPaE-Modulus of the material: 69 GPa
Stre
ss in
MPa
Strain in %
Form 1: mE = 67.5 GPaForm 2: mE = 67.4 GPaForm 3: mE = 66.8 GPaForm 4: mE = 65.5 GPaForm 5: mE = 66.9 GPa
1.1 · E = 75.9 GPa
0.9 · E = 62.1 GPa
0.0 0.1 0.2 0.3 0.4 0.5 0.6
(11) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Rp0,2 and Rm for different test piece geometries
0
50
100
150
200
250
300
350
AA6016-T4
AA6016-T6
AA5182-H111
AA3104-H19
AA6016-T4
AA6016-T6
AA5182-H111
AA3104-H19
Deh
ngre
nze
Rp0
,2un
d Zu
gfes
tigke
it R
m(M
Pa) Geo. 1 Geo. 2 Geo. 3 Geo. 4 Geo. 5
Zugfestigkeit RmDehngrenze Rp0,2
0
50
100
150
200
250
300
350
AA6016-T4
AA6016-T6
AA5182-H111
AA3104-H19
AA6016-T4
AA6016-T6
AA5182-H111
AA3104-H19
Deh
ngre
nze
Rp0
,2un
d Zu
gfes
tigke
it R
m(M
Pa) Form 1 Form 2 Form 3 Form 4 Form 5
Zugfestigkeit RmDehngrenze Rp0,2
Proo
f str
engt
h R
p0,2
and
tens
ile s
tren
gth
Rm
(MPa
)
Proof strength Rp0,2 Tensile strength Rm
(12) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Stress-strain curve for the material AA 6016-T41.0 mm thickness
0
50
100
150
200
250
300
0 5 10 15 20 25 30 35
Span
nung
in M
Pa
Dehnung in %
Form 1Form 2Form 3Form 4Form 5
Form bo Le K1.0mm
Form 1 20 80 17.89
Form 2 12.5 50 14.14
Form 3 2.5 10 6.32
Form 4 2.0 10 7.07
Form 5 1.25 5 4.47
Lo = k (ao bo)^0.5
k = Lo/(ao bo)^0.5
Stre
ss in
MPa
Strain in %
(13) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
0
50
100
150
200
250
300
0 0.05 0.1 0.15 0.2
Wah
re S
pann
ung
in M
Pa
Wahre Dehnung
Form 1Form 2Form 3Form 4Form 5
Flow curve for the material AA 6016-T41.0 mm thickness
True
str
ess
in M
Pa
True strain
(14) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
0
50
100
150
200
250
300
0 0,05 0,1 0,15 0,2
Wah
re S
pann
ung
im M
Pa
Wahre Dehnung
Form 1
Form 2
Form 3
Form 4
Form 5
Flow curve for the material AA 6016-T6 1.0 mm thickness
True
str
ess
in M
Pa
True strain0 0.05 0.1 0.15 0.2
(15) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
0
50
100
150
200
250
300
350
400
0 0.05 0.1 0.15 0.2 0.25
Wah
re S
pann
ung
in M
Pa
Wahre Dehnung
Form 1
Form 2
Form 3
Form 4
Form 5
Flow curve for the material AA 5182-H1111.0 mm thickness
True
str
ess
in M
Pa
True strain
Typical strain marks for alloys of the series 5xxx
(16) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
0
50
100
150
200
250
300
350
400
0 0.01 0.02 0.03 0.04 0.05 0.06
Wah
re S
pann
ung
in M
Pa
Wahre Dehnung
Form 1
Form 2
Form 3
Form 4
Form 5
Flow curve for the material AA 3104-H190.29 mm thickness
True
str
ess
in M
Pa
True strain
(17) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Is the testing technique used by Hydro useable for steel?
Frame conditions for the usability of the Hydro testing technique for steel● Available clamping system− Limitation of the maximum force soft and intermediate strength steels
● Available concept for test piece preparation for miniaturised test pieces− Was used up to now only for aluminium
● Modulus of Elasticity of steel three times higher than for aluminium− For equal stress level in the elastic range only approx. 1/3 of extension as for
aluminium
Test material DC04, soft, 1 mm thickness− Material without upper and lower yield strength− Material is very strain rate sensitive, therefore application of Method A of
ISO 6892-1:2009, open loop, (strain rates: for Rp0,2: 0.00025 s-1, then 0.0067 s-1)− Used test piece geometry: Form 1 and Form 3− Testing direction: parallel to rolling direction
(18) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Testing results for the test piece geometries 1 and 3 testing direction: Parallel to RD
Form No.Rp0,2
[MPa]Rm
[MPa]Ag
[%]A80mm
[%]n2-20
[-]r2-20
[-]
1
1 146.5 306.0 24.3 43.6 0.260 1.908
2 148.8 305.9 24.6 43.1 0.258 ---
3 146.1 305.5 25.0 43.1 0.260 1.996
Average 147.1 305.8 24.6 43.3 0.259 1.952Std.-Dev. 1.5 0.3 0.4 0.3 0.001 0.062
Form No.Rp0,2
[MPa]Rm
[MPa]Ag
[%]A10mm
[%]n2-20
[-]r2-20
[-]
3
1 148.3 313.8 26.7 56.9 0.259
2 146.9 313.2 26.8 57.3 0.261
3 150.6 314.4 26.3 59.9 0.255
4 150.2 312.9 27.2 57.5 0.259
5 147.4 314.4 26.7 61.0 0.260
Average 148.7 313.7 26.7 58.5 0.259Std.-Dev. 1.7 0.7 0.3 1.8 0.002
NOTE: The different elongations after fracture caused on different coefficients of proportionality, see table on page 6
(19) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Rp0,2 and Rm for the test piece geometry 1 and 3Material DC04
147,1
305,8
148,7
313,7
0
50
100
150
200
250
300
350
DC04 DC04
Deh
ngre
nze
Rp0
,2un
d Zu
gfes
tigke
it R
m(M
Pa) Form 1 Form 3
Zugfestigkeit Rm
Dehngrenze Rp0,2
Proo
f str
engt
h R
p0,2
and
tens
ile s
tren
gth
Rm
(MPa
)
Proof strength Rp0,2
Tensile strength Rm147.1
305.8
148.7
313.7
(20) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Stress-strain curves for the test piece geometry 1 und 3 Material DC04
0
50
100
150
200
250
300
350
0 10 20 30 40 50 60
Span
nung
im M
Pa
Dehnung in %
Form 1 Nr. 1 Form 1 Nr. 2 Form 1 Nr. 3
Form 3 Nr. 1 Form 3 Nr. 2 Form 3 Nr. 3
Form 3 Nr. 4 Form 3 Nr. 5
Form 1
Form 3
Rm = 8 MPa (2.7%)
Stre
ss in
MPa
Strain in %
(21) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Flow curves for the test piece geometries 1 und 3Material DC04
0
50
100
150
200
250
300
350
400
450
0,00 0,05 0,10 0,15 0,20 0,25
Wah
re S
pann
ung
im M
Pa
Wahre Dehnung
Form 1 Nr. 1 Form 1 Nr. 2 Form 1 Nr. 3Form 3 Nr. 1 Form 3 Nr. 2 Form 3 Nr. 3Form 3 Nr. 4 Form 3 Nr. 5
Form 1
Form 3
True
str
ess
in M
Pa
True strain0 0.05 0.1 0.15 0.2 0.25
(22) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
What is the reason for lower tensile strength Rm of test piece geometry 1 for the material DC04?
Consideration
● The same strain rates were used for all materials and test piece geometries
● No differences were observed for the aluminium alloys
Temperature measurement with thermocouple
● Will a different temperature increase of the test piece during testing will be the cause?● Different heat conduction Al/Fe● Different ratio of surface/volume of
the two test piece geometries
(23) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
20
30
40
50
60
70
80
90
0
50
100
150
200
250
300
350
0 10 20 30 40 50
Prob
ente
mpe
ratu
r in
°C
Span
nung
im M
Pa
Dehnung in %
Form 1 Nr. 2-1 Form 1 Nr. 2-2Form 1 Nr. 2-3 Form 1 Nr. 2-4
Stress-strain curves and temperature-strain curves for test piece geometry 1, material: DC04
Stress
Test piece temperature
ϑ / e ≈ 0.65 K / %
Stre
ss in
MPa
Strain in %
Test
pie
ce te
mpe
ratu
re in
°C
(24) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
20
30
40
50
60
70
80
90
0
50
100
150
200
250
300
350
0 10 20 30 40 50 60
Prob
ente
mpe
ratu
r in
°C
Span
nung
im M
Pa
Dehnung in %
Form 3 Nr. 2-1Form 3 Nr. 2-2Form 3 Nr. 2-3
Stress-strain curves and temperature-strain curves for test piece geometry 3, material: DC04
Stress
Test piece temperature
ϑ / e ≈ 0.067 K / %
Stre
ss in
MPa
Strain in %
Test
pie
ce te
mpe
ratu
re in
°C
(25) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Summary (1/2)
The testing technique developed by Hydro for the determination of localstrength properties and flow curves from deformed component areas byusing miniaturised test pieces fulfils the defined requirements andprovide results, which are nearly identical with those of standard testpieces geometries.
This was verify for:● Various aluminium alloy types
(3xxx, 5xxx with strain marks and 6xxx)
● Various conditions(soft, artificial aged, as rolled)
● Two very different thicknesses(0.29 mm and 1.0 mm)
● Applicable in the normal industrial environment, this means by using mainly standard testing equipment.
(26) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Summary (2/2)
The presented testing technique is also applicable for soft andintermediate strength steels.
This was verified for the steel DC04.
● A slightly higher tensile strength Rm was determined for the steel DC04 by using miniaturised test pieces.This may be caused by the clearlysmaller temperature increase during testing for these test pieces.
● For high strength steels the clamping device has to be produced out of materials with higher strength.
(27) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25th International Forum for Materials Testing Ulm
Hydro Aluminium Rolled Products GmbH
Forschung & Entwicklung Bonn
Johannes Aegerter
Georg-von-Boeselager-Str. 21
53117 Bonn
T: +49 (0)228-552-2386
F: +49 (0)228-552-2017
www.hydro.com