摘要:
基于光滑粒子流体动力学方法，分别采用实测样品几何缺陷模型和简化V形沟槽模型对铅的微喷射过程进行了模拟。重点分析了金属表面几何缺陷微细结构对微喷射特性的影响，并将数值计算结果与相应的实验测量值进行对比。结果表明，基于实测样品几何缺陷模型计算的最快喷射速度和累积喷射量与实验测量结果符合得很好。进一步研究发现，在实测样品几何缺陷诱导的微喷射过程中存在“二次汇聚喷射”现象，与单次喷射相比，该过程会诱导产生更高的喷射速度并显著影响微喷物的空间密度分布。这说明除了受扰动波长、深度影响外，表面几何缺陷微细结构也是影响金属微喷射过程的重要因素。
Abstract:
When a shock wave releases from a metal-vacuum interface, some high velocity metal particles will be ejected from the metal surface, which is generally caused by some tiny grooves on the metal surface. This phenomenon is often called the “micro-ejecta”. In this paper, we numerically investigate the effect of the micro-structures of these tiny grooves on the property of the micro-ejecta. To verify the numerical simulation model, a strict Pb micro-ejecta experiment is carried out, where the breakout pressure is about 40 GPa and the Pb target surface roughness is Ra1.6. The dynamic processes of the micro-ejection caused by the real surface groove of experimental target and simplified isosceles groove (both have a depth of 5 μm and wavelength of 75 μm), are respectively simulated by a two-dimensional smooth particle hydrodynamics method, and the effects of surface groove micro-structure on the micro-ejecta properties are examined. The simulation results of the tip velocity and accumulated mass, obtained from the real surface groove model, are in good agreement with the corresponding experimental results measured via DISAR and Asay foil, implying that the numerical result is exact. The tip velocity and accumulated mass caused by the real surface groove are much larger than those caused by the simplified isosceles groove, and a second ejection phenomenon is found in the micro-ejecta process from the real surface groove model. The process can produce some faster ejecta than a single ejecta process and influence the density distribution of the micro-ejection. It indicates that the micro-ejecta process can also be affected by the micro-structure of the metal surface groove, besides surface groove wavelength and depth.
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