Molecular dynamics simulation study of void collapse mechanisms in cubic metals under shock compression

Molecular dynamics simulations have revealed the collapse mechanism of a void in cubic metals under shock compression along [100] direction. The results show that the void collapse is caused by emitting dislocations from its surface. The type of cubic metal plays a decisive role in the subsequent microstructural evolution around the void. Void in face-centered-cubic metals collapses by emitting Shockley dislocations from its surface when piston velocity exceeds the threshold; while void in body-centered-cubic metals collapses by emitting prismatic dislocation loops, which are formed by the reaction of edge dislocations. Simulation results also reveal that the type of dislocation that induces void collapse is independent of void size. Finally, based on the elastic theory, we find that the maximum resolved shear stress along the slip direction determines the types of dislocation emitted from the voids.