An atomic view on spall responses of release melted lead induced by decaying shock loading

Abstract

Knowledge of spallation behaviors of partially melted metals, as well as the ones of solids and liquids, is critical for understanding the complete spall responses of metals to a wide range of loading strengths. However, compared with traditional spallation in solids, the spallation of liquids, especially of partially melted metals, receives considerably less attention despite some advancements in recent years. In the present work, spallation behaviors of partially melted/completely melted Pb under various decaying shock loadings are investigated. The effects of peak free surface velocity on the incipient spall strength of the partially melted Pb are uncovered, which is attributed to the difference of melting degree. Our results suggest that the incipient spall strength decreases with the growing melting degree for the partially melted Pb. Besides, incipient spall criterion, as well as damage evolutions at the later stage, is discussed. It is found that, after the incipient spall takes place, the total void volume linearly increases with time evolutions regardless of the detailed void mechanism for the volume increment. The increasing rate grows with the promoting melting degree even under the same tensile strain rate and initial temperature. For a liquid Pb, the increasing rate is governed by the tensile strain rate. Physical reasons for the different behaviors between partially and completely melted metals are analyzed.

Effect of Vacancies on Dynamic Response and Spallation in Single-Crystal Magnesium by Molecular Dynamic Simulation

“…Periodical boundary conditions were applied only in the x and y directions, while the surface along the z direction was regarded as the free surface. The shock simulation was performed by using a rigid piston composed of several layers of atoms on one end of samples along z direction [35]. The moving infinite massive piston impacted the rest of the atoms at a constant loading velocity, V p , to generate the shock pulse.…”

“…A binning analysis [39] was used to obtain the wave profiles by evenly dividing the simulated system into many slices along the z direction, and averaging the thermodynamics quantities, such as local stress, σ ij (i, j = x, y, z), temperature, T, and particle velocity in each slice. Local stress is an important reference quantity, and the expression is defined as follows [35]:…”

Spallation Characteristics of Single Crystal Aluminum with Copper Nanoparticles Based on Atomistic Simulations

“…Periodic boundary conditions along X and Y directions were considered during the above analysis. Other authors have also adopted similar techniques [34,53,54]. fs.…”

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

“…的理论分析结果一致 [47] . 在卸载熔化破碎区, 输出某一个单元内的损 伤、温度变化曲线(图7), 可以清楚显示材料发生 了卸载熔化, 且损伤发生于材料卸载熔化之前, 这 与Lou等 [10] 的MD模拟分析结果一致, 同时也展 示了温度效应对损伤增长的影响.…”

“…物理机理认识的提高有助于发展和完善相关 的物理模型. 当前主要借助于大规模分子动力学数 值模拟分析技术, 对材料动态卸载熔化过程中材料 内部损伤演化到材料破碎微细观物理机理进行研 究. Luo等 [10] 对比分析高应变率加载下固态和液 态铜的层裂问题时, 指出损伤可能发生于材料卸载 熔化之前, 之后进一步分析了液态金属内部孔洞成 核的临界尺寸问题. 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.…”