汽车用高强度钢板的动态变形行为

Dynamic Deformation Behaviour of High Strength Steel Sheet for Automotive

对DP590钢板和CR340LA钢板在应变速率为0.003s-1(准静态)和20~700s-1(动态)下进行了室温拉伸试验,研究了试验钢板的动态拉伸变形行为、应变速率敏感性和动态断裂行为。结果表明:两种试验钢板的动态真应力-真应变曲线均无屈服平台,屈服后真应力随真应变的增加先快速增大后缓慢增大;应变速率对屈服强度的影响略高于对抗拉强度的影响,并且DP590钢板的应变速率敏感性和硬化指数均高于CR340LA钢板的;两种试验钢板的均匀伸长率均随应变速率的增加而降低;随应变速率的增加,DP590钢板中的位错密度增加,当应变速率不小于200s-1时出现位错胞;DP590钢板在准静态拉伸时发生明显颈缩,而动态拉伸时未发生颈缩,且随应变速率的增加,拉伸断口上的C形韧窝数量减少,等轴状韧窝数量增加。

The room temperature tension tests at strain rates of 0.003 s-1（quasi-static）and 20-700 s^-1（dynamic）were conducted on DP590 steel sheet and CR340 LA steel sheet,and then the dynamic tensile deformation behaviour,strain rate sensitivity and dynamic fracture behaviour of tested steel sheets were studied.The results show that no yield platforms were observed on the dynamic true stress-true strain curves of the two tested steel sheets.After yield,the true stress increased rapidly and then slowly with increasing true strain.The effect of strain rate on yield strength was bigger than that on tensile strength,and the strain rate sensitivity and hardening coefficient of DP590 steel sheet were higher than those of CR340 LA steel sheet.The uniform elongation of the two tested steel sheets decreased with strain rate increasing.With increasing strain rate,the dislocation density in DP590 steel sheet increased,and dislocation cells formed at strain rate no less than 200 s^-1.Obvious necking occurred during quasi-static stretching of DP590 steel sheet,while no necking occurred during dynamic stretching.With increasing strain rate,the amount of C-shaped dimples on the tensile fracture of DP590 steel sheet decreased,and the amount of equiaxed dimples increased.