Molecular dynamics simulations of ejecta production from sinusoidal tin surfaces under supported and unsupported shocks

Abstract

Micro-ejecta, an instability growth process, occurs at metal/vacuum or metal/gas interface when compressed shock wave releases from the free surface that contains surface defects. We present molecular dynamics (MD) simulations to investigate the ejecta production from tin surface shocked by supported and unsupported waves with pressures ranging from 8.5 to 60.8 GPa. It is found that the loading waveforms have little effect on spike velocity while remarkably affect the bubble velocity. The bubble velocity of unsupported shock loading remains nonzero constant value at late time as observed in experiments. Besides, the time evolution of ejected mass in the simulations is compared with the recently developed ejecta source model, indicating the suppressed ejection of unmelted or partial melted materials. Moreover, different reference positions are chosen to characterize the amount of ejecta under different loading waveforms. Compared with supported shock case, the ejected mass of unsupported shock case saturates at lower pressure. Through the analysis on unloading path, we find that the temperature of tin sample increases quickly from tensile stress state to zero pressure state, resulting in the melting of bulk tin under decaying shock. Thus, the unsupported wave loading exhibits a lower threshold pressure causing the solid-liquid phase transition on shock release than the supported shock loading.

Rayleigh–Taylor and Richtmyer–Meshkov instabilities: A journey through scales

“…Such measurements provide statistics for the particle population as a whole, which can be applied to cases where the particle number would overwhelm a tracking diagnostic but adds complexity to the interpretation of the results. The details of the ejecta production process have been modelled using both continuum flow [207,309,442,263] and molecular dynamic [586,192,102,151,479,103,153,558] codes. Comparisons between these techniques [103,154,157] tend to emphasize their good agreement on the overall properties of the jet formation, but complementary strengths.…”

Comparative investigation of microjetting generated from monocrystalline tin surface and polycrystalline tin surface under plane impact loading

“…Especially under the low impact strength, surface energy can hinder the jetting. [35] Therefore, this effect that cannot be neglected results in a significant decrease of the jet head velocity. Figure 2(b) shows the relation between jet head velocity and near free surface pressure.…”

Dynamics behavior of porous tin under strong shockwave impact

“…强冲击作用下的金属材料动态破碎过程, 既包含 简单的单次加载微喷、层裂/微层裂破碎 [1][2][3][4][5][6][7][8][9][10][11][12][13] , 也有复 杂多次加载产生的表面微射流、主体区域反复冲击再 破碎、主体区域对微射流颗粒回收等一系列复杂过 程 [14][15][16] , 是耦合材料特性、加载状态、样品初始状态 等多因素的复杂多尺度问题, 在惯性约束核聚变、冲 击防护等领域有重要的工程价值和科学意义, 最近几 十年被广泛研究 [17][18][19] .…”