The mechanisms of temperature rise and wavefront broadening induced by nanoscale He bubbles in copper during shock loadings

A molecular dynamics simulation study is conducted to investigate the evolution of nanoscale helium bubbles with varying morphologies under shock wave loadings. The investigated morphologies consist of three types of ellipsoidal configurations with axes aligned with the shock propagation direction: prolate (HB-I, major axis aligned), oblate (HB-II, minor axis aligned), and spherical (HB-III, equal axes). The results show that HB-I induces the most severe temperature rise and the highest thermal energy accumulation in the copper matrix due to its largest interface curvature. When an incident shock wave enters the helium bubble, it undergoes refraction at the helium bubble interface, resulting in the broadening of the shock wave front. The broadening effect is most pronounced in HB-I compared to the other two morphologies. In addition, we compared the surface breakage behavior induced by three types of near-surface helium bubbles in copper at different impact velocities and found that HB-I was the most susceptible to induce interface damage, with the lowest particle velocity threshold for interface breakage.