基于SHPB实验的挤压AZ91D镁合金动态力学行为数值模拟

摘要

Dynamic compression experiments of extruded AZ91D magnesium alloy at three different strain rates were carried out based on split Hopkinson pressure bar (SHPB) technique, and a Johnson-Cook dynamic constitutive equation was obtained by fitting the experimental data. The SHPB dynamic compression of the material was simulated by using LS-DYNA software with the fitted Johnson-Cook constitutive parameters. Calculated incident, reflected, and transmitted waves were correlated with the stress-strain response of the extruded AZ91D sample using two-wave analytical method;the stress-strain curves at different strain rates obtained in the simulations were compared with the experimental and fitted stress-strain responses. The results show that the strain rate sensitivity of the extruded AZ91D Mg alloy increases with increasing the strain rate from 400 s-1 to 1000 s-1. The numerical simulation results and fitted results based on the Johnson-Cook strain-rate dependent constitutive model for the extruded AZ91D Mg alloy are basically in agreement with the experimental results.%使用霍普金森压杆技术对挤压AZ91D镁合金进行3种应变速率下的动态压缩实验，基于实验数据的拟合确定了其动态压缩的Johnson-Cook (J-C)本构方程。采用拟合的J-C本构参数和LS-DYNA有限元软件对挤压AZ91D镁合金在3种应变速率下的SHPB实验进行了数值模拟，根据模拟得到的入射波、反射波和透射波形计算得到各应变速率下完整的应力-应变曲线，并与实验及拟合的应力-应变响应进行了对比。结果表明：当应变速率在400~1000 s-1之间变化时，AZ91D镁合金的应变速率敏感性随应变率增大而增大；基于J-C材料模型描述的AZ91D镁合金应变速率相关的应力-应变本构模型，其数值模拟结果与拟合结果及实验结果基本吻合。