An atomic view on the evolution of spall damage in solid–liquid mixed aluminum at high strain rates through stretching simulations

Abstract

Using the classical molecular dynamic method, we investigated the evolution of spall damage through a series of stretching simulations for solid–liquid mixed aluminum at several initial temperatures. The results show that a turning point appears before void nucleation when the initial temperature is higher than 940 K in mixed Al at a strain rate of 3 × 108 s−1. The formation mechanism of the turning point is due to the local liquid phase nucleation. The growth of the local liquid phase gradually destroys the consecutive solid phases. The lower tensile strength of liquid Al than solid Al leads to the formation of the turning point. The voids tend to nucleate in the liquid phase in mixed Al at different initial temperatures except at 940 K. The time of void nucleation will be delayed due to the melting process before void nucleation in mixed Al. A nucleation and growth (NAG) model can describe the nucleation and growth of voids very well in mixed Al at 900, 920, 960, and 980 K. By adding the criterion of liquid phase proportion, the NAG model can also well describe the void volume fraction history of mixed Al at 940 K. We clarified the micro-mechanisms of spall damage evolution in mixed Al through tension simulation. The relevant results can provide a reference for future work on spall damage studies in solid–liquid mixed metals.

Modelling of spall damage evolution and fragment distribution for melted metals under shock release

“…Wang等 [11] 研究了近熔化状 态下铅的微层裂行为, 重点考虑了不同脉冲波形下 降时间对层裂强度的影响, 发现不同情况下自由面 附近的拉伸应变率非常接近, 且孔洞体积的增长速 率趋近于恒定的(拉伸)应变率. Zhou等 [12] 分析 了强冲击性下材料的温升机制, 并指出金属熔化后 预置孔洞的膨胀与汇合由速度梯度下的拉伸变形 为主导, 并阻碍了周围新孔洞的成核和增长, 且逐 步吸收临近的孔洞. Wang等 [13] I n P r e s s 合为主(而不是目前损伤研究中所采用的孔洞颈缩 汇合模式), 且孔洞分布特征随着损伤的发展, 以及 孔洞不断汇合逐渐演化为以大孔洞占主导地位 [14,15] .…”