The most important heterogeneous defects formed due to self-irradiation effects are He atoms, which will coalesce into bubbles because of the low solubility of He in metals. By using molecular dynamics methods, we have investigated the effect of nano-He bubbles on the formation of micro-jets and the various physical mechanisms under multiple supported and unsupported shock wave loading. We categorize the behavior of nano-He bubbles into three types: Type A bubbles are located in the micro-jet forming region, and their expansion increases the velocity and rupture of the jet. Type B bubbles are located between the micro-jets, and their compression and rapid bursting accelerate the free surface. Type C bubbles are situated far from the free surface and mainly affect the propagation of the shock wave and the released damage process. Our further investigation shows that The coupling of spallation damage and RMI (Richtmyer-Meshkov instability) growth of metals with He bubbles has a significant effect on the evolution of micro-jet during the secondary impact. Under high pressure conditions, the morphological characteristics and distribution of the near-interface micro-spall damage zone of helium-containing bubble metals are significantly different from those of pure metals, which makes the total amount and speed of secondary micro-jet increase, the particle size decreases, and the jet morphological characteristics become more complex. Under low pressure conditions, the non-uniform distribution of hot spots in the near-interface damage zone makes the surface of metals with He bubbles more likely to melt than pure metals under the effect of double impact loading and unloading, which induces significant micro ejecta.

[1] Xin-Xin Wang; An-Min He*; Yu Yang; Pei Wang*, Jianguo Wang; Shock responses of nanoporous copper with helium doping by molecular, Computational Materials Science, 2021, 188: 110190.
[2] Xin-Xin Wang, Jian-Li Shao*, Bao Wu, Sheng-Ning Yan, An-Min He, Pei Wang*, Enhancement of metal surface micro-jet by nanoscale He bubbles under supported and unsupported shocks, Physics of Fluid, 2023, 35, 052112.
[3] Qiang Bao, Bao Wu^#, Xin-Xin Wang*, Haonan Sui, Hua-Yun. Geng, Jian-Li Shao, Hai-Quan Sun, An-Min He, and Pei Wang*. Molecular dynamics investigation of unsupported double-shock induced micro-jet behaviors in copper containing helium bubbles, Physics of Fluids, 2024, 36:112101.
[4] Qiang Bao, Haonan Sui, Bao Wu, Xin-Xin Wang*, Qi Zhu, Jian-Li Shao, An-Min He, and Pei Wang*, Near-surface fragmentation in irradiated copper under two successive shock loading: effects of local temperature re-distribution and helium bubble expansion, Materials & Design (Under review)
[5] Sheng-Ning Yan, Bao Wu^#, Xin-Xin Wang*, Qiang Bao, Hao-Nan Sui, An-Min He, Pei Wang*, The mechanisms of temperature rise and wavefront broadening in copper induced by nanoscale He bubbles during shock loadings. Journal of Applied Physics (Under review).

 

dynamic damage and fragmentation,irradiated metal,He bubbles,Micro ejecta,molecular dynamics