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Research Papers

Strain-Rate Sensitivity of Aluminum Alloys AA1200 and AA3103

[+] Author and Article Information
O.-G. Lademo1

 SINTEF Materials and Chemistry, Applied Mechanics and Corrosion, N-7465 Trondheim, Norway; Structural Impact Laboratory—SIMLab, Centre for Research-Based Innovation (CRI), and Department of Structural Engineering, NTNU, N-7491 Trondheim, Norwayodd-geir.lademo@sintef.no

O. Engler

 Hydro Aluminium Deutschland GmbH, R&D Center Bonn, P.O. Box 2468, D-53014 Bonn, Germany; Structural Impact Laboratory—SIMLab, Centre for Research-Based Innovation (CRI), and Department of Structural Engineering, NTNU, N-7491 Trondheim, Norway

J. Aegerter

 Hydro Aluminium Deutschland GmbH, R&D Center Bonn, P.O. Box 2468, D-53014 Bonn, Germany

T. Berstad

 SINTEF Materials and Chemistry, Applied Mechanics and Corrosion, N-7465 Trondheim, Norway; Structural Impact Laboratory—SIMLab, Centre for Research-Based Innovation (CRI), and Department of Structural Engineering, NTNU, N-7491 Trondheim, Norway

A. Benallal

 LMT-ENS Cachan/CNRS/Université Paris 6/PRES UniverSud Paris, 61 Avenue du Président Wilson, F-94230 Cachan, France

O. S. Hopperstad

Structural Impact Laboratory—SIMLab, Centre for Research-Based Innovation (CRI), and Department of Structural Engineering, NTNU, N-7491 Trondheim, Norway

This device called “lost motion unit” is now proposed for ISO 26203-2: “tensile testing method at high strain-rates—part 2: servohydraulic and other test systems.”

1

Corresponding author.

J. Eng. Mater. Technol 132(4), 041007 (Sep 29, 2010) (8 pages) doi:10.1115/1.4002160 History: Received March 24, 2010; Revised May 31, 2010; Published September 29, 2010; Online September 29, 2010

Tensile tests are carried out for the aluminum alloys AA1200 and AA3103 at various strain-rates in the range from 104s1 to 1s1. Tests with constant nominal strain-rate and strain-rate jump tests are conducted, and the instantaneous rate sensitivity and the rate sensitivity of strain hardening are investigated. For both materials, the instantaneous rate sensitivity is found to be rather independent of strain, while the rate sensitivity of the strain hardening is important and the saturation stress increases with increasing strain-rate. A phenomenological constitutive model is described that comprises a kinetic equation governing the instantaneous rate sensitivity of the flow stress and a structural parameter that determines the mechanical state of the material. The evolution of the structure parameter is assumed to depend on strain-rate. The model parameters are determined for the two materials using the available experimental information. It is found that the constitutive model provides a good representation of the experimental results.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

Grahic Jump Location
Figure 1

Microstructure of (a) AA1200 and (b) AA3103

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Figure 2

Results from constant strain-rate tests for AA1200: (a) Cauchy stress versus logarithmic plastic strain curves up to incipient necking from tensile tests at nominal strain-rates of 10−4 s−1, 10−3 s−1, 10−2 s−1, 10−1 s−1, and 100 s−1; (b) logarithmic plastic strain versus normalized time; (c) ratio of plastic to nominal strain-rate versus plastic strain; (d) Cauchy stress at fixed logarithmic plastic strains (0.025, 0.05, 0.10, 0.15, and 0.2) versus average logarithmic plastic strain-rate (the numbers in parentheses in the legend represent the slope of the log-linear trend curves)

Grahic Jump Location
Figure 3

Results from strain-rate jump tests for AA1200: (a) jump from 10−3 s−1 to 10−1 s−1 and (b) jump from 10−1 s−1 to 10−3 s−1. The dashed curve represents the stress-strain behavior at 10−1 s−1 in (a) and 10−3 s−1 in (b).

Grahic Jump Location
Figure 4

Results from constant strain-rate tests for AA3103: (a) Cauchy stress versus logarithmic plastic strain curves up to incipient necking from tensile tests at nominal strain-rates of 10−4 s−1, 10−3 s−1, 10−2 s−1, 10−1 s−1, and 100 s−1; (b) logarithmic plastic strain versus normalized time; (c) ratio of plastic to nominal strain-rate versus plastic strain; (d) Cauchy stress at fixed logarithmic plastic strains (0.025, 0.05, 0.10, 0.15, and 0.2) versus average logarithmic plastic strain-rate (the numbers in brackets in the legend represent the slope of the log-linear trend curves)

Grahic Jump Location
Figure 5

Results from strain-rate jump tests for AA3103: (a) jump from 10−3 s−1 to 10−1 s−1 and (b) jump from 10−1 s−1 to 10−3 s−1. The dashed curve represents the stress-strain behavior at 10−1 s−1 in (a) and 10−3 s−1 in (b).

Grahic Jump Location
Figure 6

Comparison of model results with experimental data from the steady-state tensile tests for AA1200: (a) Cauchy stress versus average logarithmic plastic strain curves up to incipient necking at nominal strain-rates of 10−4 s−1, 10−3 s−1, 10−2 s−1, 10−1 s−1, and 100 s−1 (solid lines represent experimental curves and dashed lines are model results); (b) Cauchy stress at fixed logarithmic plastic strains (0.025, 0.05, 0.10, 0.15, and 0.2) versus logarithmic plastic strain-rate (symbols represent experimental data and dashed lines are model results)

Grahic Jump Location
Figure 7

Comparison of model results with experimental data from the steady-state tensile tests for AA3103: (a) Cauchy stress versus average logarithmic plastic strain curves up to incipient necking at nominal strain-rates of 10−4 s−1, 10−3 s−1, 10−2 s−1, 10−1 s−1, and 100 s−1 (solid lines represent experimental curves and dashed lines are model results); (b) Cauchy stress at fixed logarithmic plastic strains (0.025, 0.05, 0.10, 0.15, and 0.2) versus average logarithmic plastic strain-rate (symbols represent experimental data and dashed lines are model results)

Grahic Jump Location
Figure 8

Saturation stress σs versus logarithmic plastic strain rate ε̇p, as obtained from Eq. 11

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Figure 9

Simulation of strain-rate jump tests for AA1200: (a) jump from 10−3 s−1 to 10−1 s−1 and (b) jump from 10−1 s−1 to 10−3 s−1

Grahic Jump Location
Figure 10

Simulation of strain-rate jump tests for AA3103: (a) jump from 10−3 s−1 to 10−1 s−1 and (b) jump from 10−1 s−1 to 10−3 s−1

Grahic Jump Location
Figure 11

Nominal force versus elongation in plane-strain tensile tests of AA3103 at two different strain-rates (ė=10−4 s−1 and ė=10−2 s−1)

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