Metal Tensile Test Using Miniaturized Test Pieces Johannes Aegerter, Stefan Keller, Heike Berk 2016-10-12 (1) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Objective Development and Optimisation of the testing technique for testing of miniaturised test tensile test pieces for the determination of local strength properties and flow curves from deformed component areas for e. 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 (2) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th 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 (3) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Investigated test piece geometries Form L t (mm) B (mm) b o (mm) L c (mm) L e (mm) C (mm) D (mm) E (mm) r (mm) L c b o L e b o Form 1 2 30 20 120 80 35 - - 20 6 4 Form 2 165 20 12.5 75 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 L e = Extensometer gauge length Form 1 Form 2 Form 3 Form 4 Form 5 Source: ISO 6892-2:2011-02 (4) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Influence of the gauge length on elongation after fracture Source: W. Domke 5.65 11.3 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 (A mm, A 80mm ): 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) (5) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Coefficient of proportionality of the investigated test piece geometries Form L t B b o L c L e r L c b o L e k 1,0 b o mm k 0,29 mm Form 1 2 30 20 120 80 20 6 4 17.89 33.22 Form 2 165 20 12.5 75 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 L e = Extensometer gauge length Form 1 Form 2 Form 3 Form 4 Form 5 Source: ISO 6892-2:2011-02 (6) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Testing machine, clamping system and force measurement 2 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 (7) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th 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 L e = 10 mm Conversion of extensions to real gauge length necessary: Multiplication of extensions or the measured length change by the factor: L e(set) /L e(real), here: Factor 2 Extensometer with 5 mm gauge length c) b) a) (8) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th 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) (9) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Elastic range for different test piece geometries, material AA 6016-T6 2 200 E-Modulus des of Werkstoffs: the material: 69 GPa 0,9 0.9 E E = = 62,1 62.1 GPa Spannung Stress in in MPa 1 100 1,1 1.1 E E = = 75,9 75.9 GPa GPa Form 1: 1: m E E = 67,5 67.5 GPa Form 2: 2: m E E = 67,4 67.4 GPa Form 3: 3: m E E = 66,8 66.8 GPa Form 4: 4: m E E = 65,5 65.5 GPa Form Form 5: 5: m E E = 66,9 66.9 GPa 0 0.0 0,0 0,1 0.1 0,2 0.2 0,3 0.3 0,4 0.4 0,5 0.5 0,6 0.6 Dehnung Strain in in % (10) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
R p0,2 and R m for different test piece geometries Proof Dehngrenze strength R p0,2 p0,2 and und tensile Zugfestigkeit strength R m R (MPa) m (MPa) 3 300 2 200 1 100 0 AA6016 -T4 Form 1 Geo. Form 1 2Geo. 2Form Geo. 3 3 Form Geo. 4 4 Form Geo. 5 5 Proof Dehngrenze strength R R p0,2 p0,2 Tensile Zugfestigkeit strength R m R m AA6016 AA5182 -T6 -H111 AA3104 AA6016 -H19 -T4 AA6016 AA5182 -T6 -H111 AA3104 -H19 (11) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Stress-strain curve for the material AA 6016-T4 1.0 mm thickness Spannung Stress in in MPa MPa 300 2 200 1 100 0 Form 1 Form 2 Form 3 Form 4 Form 5 Form b o L e K 1.0mm Form 1 20 80 17.89 Form 2 12.5 14.14 L o = k (a o b )^0.5 o k = L o /(a o b )^0.5 o Form 3 2.5 10 6.32 Form 4 2.0 10 7.07 Form 5 1.25 5 4.47 0 5 10 15 20 25 30 35 Dehnung Strain in % (12) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Flow curve for the material AA 6016-T4 1.0 mm thickness Wahre True Spannung stress in in MPa MPa 300 2 200 1 100 Form 1 Form 2 Form 3 Form 4 Form 5 0 0 0.05 0.1 0.15 0.2 Wahre True Dehnung strain (13) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Flow curve for the material AA 6016-T6 1.0 mm thickness 300 Wahre True Spannung stress in im MPa MPa 2 200 1 100 0 Form 1 Form 2 Form 3 Form 4 Form 5 0 0,05 0.05 0,1 0.1 0,15 0.15 0,2 0.2 Wahre True strain Dehnung (14) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Flow curve for the material AA 5182-H111 1.0 mm thickness Wahre True Spannung stress in in MPa MPa 400 3 300 2 200 1 100 Form 1 Form 2 Form 3 Form 4 Form 5 Typical strain marks for alloys of the series 5xxx 0 0 0.05 0.1 0.15 0.2 0.25 Wahre Dehnung True strain (15) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Flow curve for the material AA 3104-H19 0.29 mm thickness 400 3 Wahre True Spannung stress in in MPa MPa 300 2 200 1 100 0 Form 1 Form 2 Form 3 Form 4 Form 5 0 0.01 0.02 0.03 0.04 0.05 0.06 Wahre True Dehnung strain (16) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th 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 R p0,2 : 0.00025 s -1, then 0.0067 s -1 ) Used test piece geometry: Form 1 and Form 3 Testing direction: parallel to rolling direction (17) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Testing results for the test piece geometries 1 and 3 testing direction: Parallel to RD Form No. R p0,2 [MPa] R m [MPa] A g [%] A 80mm [%] n 2-20 [-] r 2-20 [-] 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 1.952 Std.-Dev. 1.5 0.3 0.4 0.3 0.001 0.062 Form No. R p0,2 [MPa] R m [MPa] A g [%] A 10mm [%] n 2-20 [-] r 2-20 [-] 3 1 148.3 313.8 26.7 56.9 0.259 2 146.9 313.2 26.8 57.3 0.261 3 1.6 314.4 26.3 59.9 0.255 4 1.2 312.9 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 0.259 Std.-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 (18) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
R p0,2 and R m for the test piece geometry 1 and 3 Material DC04 Proof Dehngrenze strength R p0,2 und Zugfestigkeit R m (MPa) p0,2 and tensile strength R m (MPa) 3 300 2 200 1 100 0 Form 1 Form 3 305,8 305.8 313,7 313.7 147,1 147.1 148.7 148,7 Tensile Zugfestigkeit strength RR mm Proof Dehngrenze strength R p0,2 p0,2 DC04 DC04 (19) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Stress-strain curves for the test piece geometry 1 und 3 Material DC04 3 300 Form 3 Stress Spannung in MPa im MPa 2 200 1 100 0 R m = 8 MPa (2.7%) Form 1 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 0 10 20 30 40 60 Dehnung Strain in in % (20) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Flow curves for the test piece geometries 1 und 3 Material DC04 Wahre True Spannung stress in im MPa MPa 4 400 3 300 2 200 1 100 Form 3 Form 1 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 0 0,00 0 0.05 0,05 0,10 0.1 0.15 0,15 0,20 0.2 0.25 0,25 Wahre True strain Dehnung (21) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
What is the reason for lower tensile strength R m 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 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 Temperature measurement with thermocouple (22) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Stress-strain curves and temperature-strain curves for test piece geometry 1, material: DC04 Stress Spannung in MPa im MPa 3 300 2 200 1 100 0 Stress ϑ / e 0.65 K / % Test piece temperature Form 1 Nr. 2-1 Form 1 Nr. 2-2 Form 1 Nr. 2-3 Form 1 Nr. 2-4 0 10 20 30 40 Dehnung Strain in in %% 90 80 70 60 40 30 20 Test Probentemperatur piece temperature in C in C (23) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Stress-strain curves and temperature-strain curves for test piece geometry 3, material: DC04 3 90 Stress Spannung in MPa im MPa 300 2 200 1 100 Stress ϑ / e 0.067 K / % Form 3 Nr. 2-1 Form 3 Nr. 2-2 Form 3 Nr. 2-3 80 70 60 40 30 Test Probentemperatur piece temperature in C in C 0 Test piece temperature 0 10 20 30 40 60 Dehnung Strain in in %% 20 (24) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Summary (1/2) The testing technique developed by Hydro for the determination of local strength properties and flow curves from deformed component areas by using miniaturised test pieces fulfils the defined requirements and provide results, which are nearly identical with those of standard test pieces 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. (25) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm
Summary (2/2) The presented testing technique is also applicable for soft and intermediate strength steels. This was verified for the steel DC04. A slightly higher tensile strength R m was determined for the steel DC04 by using miniaturised test pieces. This may be caused by the clearly smaller 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. (26) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th 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 E: johannes.aegerter@hydro.com www.hydro.com (27) 2016-10-12 Johannes Aegerter, Stefan Keller, Heike Berk 25 th International Forum for Materials Testing Ulm