Evolution of plastic deformation behavior upon strain-path changes in an A6022-T4 Al alloy sheet
Evolution of plastic deformation behavior upon strain-path changes in an A6022-T4 Al alloy sheet
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DOI：
10.1016/j.ijplas.2020.102913
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发表时间：
2020-12
影响因子：
9.8
通讯作者：
T. Hama;S. Yagi;Koji Tatsukawa;Maeda Yasuhiro;Maeda Yasushi;H. Takuda
中科院分区：
文献类型：
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作者：
T. Hama;S. Yagi;Koji Tatsukawa;Maeda Yasuhiro;Maeda Yasushi;H. Takuda
研究了A6022-T4铝合金板材在不同应变路径变化下的塑性变形行为，重点研究了应变路径突变后塑性应变率θ和应力比φ的方向演变规律。采用十字形试样进行了应变路径突变后塑性变形行为演化的实验测量。应变路径改变前，结合Yld2000-2d屈服函数和各向同性硬化假设的流变规律能很好地表征变形。突变路径改变后，变形暂时偏离关联流动规律，塑性功增加约4.0 MJ·m−3后，可重新用关联流动规律表示，对应于轧制方向单轴拉伸下的应变增量约为0.024。θ和φ随塑性功的变化表明，当最终应变路径角相同时，无论应变路径如何，θ和φ都趋于收敛于某一值。由于φ不能跟随θ的快速变化，在路径突变后，φ和θ之间的关系暂时偏离了相关的流动规律。晶体塑性有限元模拟再现了实验中观察到的定性趋势，但与相关流动规律的偏差更为明显。参数化研究表明，φ随应变速率敏感性的变化而趋于收敛，θ随应变速率敏感性指数的变化而趋于收敛。从宏观应变-应变曲线得到的速率敏感指数为m= 0.002，但从突变路径下的θ和φ的演化情况看，速率敏感指数m= 0.044与实验结果拟合最好。
The plastic deformation behavior under various strain-path changes in an A6022-T4 Al alloy sheet was studied, focusing on the evolution of the direction of the plastic strain rate θ and the stress ratio φ after abrupt strain-path changes. A cruciform specimen was used to measure the evolution of the plastic deformation behavior after abrupt strain-path change experimentally. Before the strain-path change, the deformation was represented well by the associated flow rule with the Yld2000-2d yield function and isotropic hardening assumption. After the abrupt-path change, the deformation temporarily deviated from the associated flow rule, and it could be represented again by the associated flow rule after the plastic work increased roughly 4.0 MJ⋅ m− 3, which corresponded to the strain increment of approximately 0.024 under uniaxial tension in the rolling direction. The transitions of θ and φ as a function of plastic work showed that both θ and φ tend to converge to certain values regardless of the strain path if the final strain-path angles are identical. It was also found that the relationships between φ and θ temporarily deviate from the associated flow rule immediately after the abrupt-path changes because φ cannot follow the rapid change of θ. Crystal plasticity finite-element simulations reproduced the qualitative tendencies observed in the experiments, but the deviations from the associated flow rule were much more pronounced. Parametric studies showed that φ tends to converge to different values depending on the strain rate sensitivity, whereas θ tends to converge to a same value irrespective of the rate sensitivity exponent. The rate sensitivity exponent m= 0.044 gave the best fits with the experimental results in terms of the evolution of both θ and φ under an abrupt-change path, although the rate sensitivity exponent determined from macroscopic strass-strain curves were m= 0.002.