Here, we provide a systematic molecular dynamics (MD) study of the pulse duration and temperature dependence of spall strength in Al and Mg with a nonequilibrium concentration of vacancies. A superconcentration of single vacancies are randomly introduced into an otherwise perfect lattice, and the systems are allowed to evolve for up to 500 nanoseconds as a proxy for the pulse duration of a shock compression wave. Since these systems are nonequilibrium in nature, a time-dependent and temperature-dependent evolution of the microstructure ensues, which leads to a time- and temperature-dependent softening of the spall strength. Here, we report a large parametric study consisting of 196 MD calculations to quantify this softening in Al and Mg. We invoke the notion of time–temperature superposition from the field of viscoelasticity, and show that the results of our 196 MD calculations remarkably collapse onto a single master curve when normalized by an appropriate relaxation timescale. Lastly, a favorable agreement between the MD calculations and experimental measurements of thermal softening of spall strength is reported.

在这里，我们提供了一个空洞浓度不均衡的铝和镁中剥落强度的脉冲持续时间和温度依赖性的系统分子动力学（MD）研究。单个空位的超浓度被随机引入一个本来是完美的晶格中，并且允许该系统演化长达500纳秒，以替代冲击压缩波的脉冲持续时间。由于这些系统本质上是非平衡的，因此会发生随时间和温度变化的微观结构演变，这导致剥落强度随时间和温度变化的软化。在这里，我们报告了一项由196个MD计算组成的大型参数研究，以量化Al和Mg中的这种软化。我们从粘弹性领域调用时间-温度叠加的概念，并表明，通过适当的弛豫时间尺度进行归一化后，我们196次MD计算的结果显着倒塌到一条主曲线上。最后，据报道在MD计算和剥落强度的热软化的实验测量之间达成有利的一致性。