A dislocation-based constitutive model for viscoplastic deformation of fcc metals at very high strain rates
A dislocation-based constitutive model for viscoplastic deformation of fcc metals at very high strain rates
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DOI：
10.1016/j.ijplas.2010.03.002
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发表时间：
2011-01-01
影响因子：
9.8
通讯作者：
McDowell, David L.
中科院分区：
文献类型：
--
作者：
Austin, Ryan A.;McDowell, David L.
在这项工作中，一个基于物理的模型，以解决在多晶金属和合金受到非常高的变形率（10（4）-10（8）s（-1））的滑移。提供了具有微米级晶粒的面心立方金属的运动学、动力学和亚结构的本构关系。这项工作的主要创新特点是在弱冲击加载制度的位错亚结构的处理。在这里，移动的和im移动的位错密度被指定为内部状态变量和路径相关的微分方程制定其演变。这使得能够对滑动阻力和塑性流动速率进行物理描述。将本构模型应用于6061-T6铝合金，并采用粘塑性关系进行稳态塑性波计算，使模型与实验进行比较。对于2-10 GPa的冲击应力振幅的模型准确地再现直接测量的材料速度和间接测量的宏观剪切应力和塑性变形率在冲击波前。模型结果也与冲击应力高达15 GPa的Hugoniot材料强度的测量值一致。在弱冲击加载制度的计算精度表明，所提出的本构模型可能是有用的，在模拟高应变现象在各种技术应用，包括在小的长度尺度的动态材料响应。本构模型的改进建议，使模型更好地符合实验在较高的冲击应力。(C)2010爱思唯尔有限公司版权所有。
In this work a physically-based model is developed to address slip in polycrystalline metals and alloys subjected to very high rates of deformation (10(4)-10(8) s(-1)). Constitutive relations are provided for the kinematics, kinetics, and substructure of fcc metals with micron-scale grains. The main innovative feature of this work is the treatment of the dislocation substructure in the weak shock loading regime. Here, the mobile and immobile dislocation densities are assigned as internal state variables and path-dependent differential equations are formulated for their evolution. This enables physical descriptions of slip resistance and the plastic flow rate. The constitutive model is applied to 6061-T6 Al alloy and the viscoplastic relations are employed in steady plastic wave calculations that enable comparison of the model to experiments. For shock stress amplitudes of 2-10 GPa the model accurately reproduces direct measurements of material velocity and indirect measurements of the macroscopic shear stress and plastic rate of deformation in the shock front. Model results are also in agreement with measurements of material strength on the Hugoniot for shock stresses up to similar to 15 GPa. The accuracy of calculations in the weak shock loading regime indicates the proposed constitutive model may be useful in simulating high-strain-phenomena in a variety of technical applications, including dynamic material responses at small length scales. An improvement to the constitutive model is suggested to bring the model into better agreement with experiments at higher shock stresses. (C) 2010 Elsevier Ltd. All rights reserved.