平面碰撞与强激光加载下金属铝的层裂行为

在轻气炮和神光Ⅱ强激光装置上开展了金属铝的层裂实验。针对激光打靶层裂实验中样品自由面速度剖面后期振荡容易丢失问题，改进靶设计，获得很好效果。利用轻气炮加载和强激光加载层裂实验应变率的显著差异，并通过数值模拟，讨论了在建立具有预测能力的理论建模中需要关注的损伤成核、演化与汇合问题中的材料特性与应变率相关特性因素。结果表明，对于我们以前建立的动态损伤与断裂模型，微孔洞成核的平均半径、阈值压力、成核速率相关参数以及微孔洞长大的阈值压力等具有材料特性属性，但微孔洞的表面能以及决定材料发生完全层裂的临界损伤度等具有明显的应变率效应。另外，分析还发现，虽然层裂强度具有明显的应变率效应，但是在样品层裂当地，样品由持续拉伸向收缩转变的临界行为，取决于一个很小的临界损伤，这个临界值很可能是材料常数，与应变率无关。

Spall behavior of pure aluminum under plate-impact and high energy laser shock loadings

Spall experiments of pure aluminum were performed on the light-gas gun equipment and SG Ⅱ high energy laser facility. An improved target configuration was applied to address the problem that the residual vibration was often lost in laser-loading spall experiments. By virtue of distinguishing the obvious difference in the strain rate between the two experiments, the material and rate-dependent issues related with the nucleation, growth and coalescence of micro-damage were examined using numerical simulations, which is important for developing predictive theoretical models. Results show that for our previously proposed model the average diameter, the critical pressure, and the nucleation rate parameter for micro-void nucleation can be regarded as material constants and the same is true with the critical pressure for micro-void growth, whereas the specific effective surface energy for micro-void growth and the critical damage for coalescence are typical rate-dependent. Furthermore, our simulations indicate that at the local spall position, although the spall strength has an apparent strain rate effect, the critical behavior of the transformation of the sample from continuous stretch to compression is determined by a critical damage, whose value is very small and is probably a material constant.