Shock compression of porous copper containing helium is studied via non-equilibrium molecular dynamic simulations. The results show that the shock propagation exhibits an elastic-plastic double-shockwave structure at low shock velocity. The shock Hugoniot elastic limit increases with higher gas concentration, and decreases with larger porosity, while almost independent of the shock velocity. The back-and-forth propagation of elastic shockwave between plastic shockwave and free surface leads to the occurrence of the special structure of “surface cap”, which can protect the porous metal in the vicinity of the free surface from collapse. The plastic shock propagates faster with higher gas concentration and gradually catches up with the elastic shockwave as shock intensity increases. Compared with porous copper without gas, the presence of helium significantly inhibits the post-shock temperature rising and the shock melting behavior. A new theoretical model was proposed to quantify the shock Hugoniot of porous materials containing gas. The model's predictions align well with MD simulations across a wide pressure range up to 100 GPa with different gas concentrations and porosities.

中文翻译：

---

含氦多孔铜的冲击压缩：分子动力学模拟和理论模型

通过非平衡分子动力学模拟研究了含氦多孔铜的冲击压缩。结果表明，低冲击速度下冲击传播呈现弹塑性双冲击波结构。冲击休格尼奥弹性极限随着气体浓度的增加而增加，随着孔隙率的增加而减小，而几乎与冲击速度无关。弹性冲击波在塑性冲击波与自由表面之间来回传播，导致“表面盖”特殊结构的出现，可以保护自由表面附近的多孔金属免于塌陷。随着气体浓度的增加，塑性冲击传播得更快，并随着冲击强度的增加而逐渐赶上弹性冲击波。与不含气体的多孔铜相比，氦气的存在显着抑制了冲击后温升和冲击熔化行为。提出了一种新的理论模型来量化含气体多孔材料的休贡尼奥激波。该模型的预测与 MD 模拟在高达 100 GPa 的宽压力范围内以及不同的气体浓度和孔隙率非常吻合。