Unsupported shock wave induced dynamic fragmentation of matrix in lead with surface grooves

Abstract

The material damage and fragments features under certain shock waveform are of great significance in the shock compression phenomena. Herein, molecular dynamics simulations were performed to investigate the dynamic fragmentation process under unsupported shock of bulk Pb with sinusoidal surface grooves and the corresponding clusters distribution during the disintegration. Significant subsurface damage was observed when compared with the typical spike-bubble structure under supported shocks. Due to periodic surface grooves, the superposition of the intrinsic decaying shock wave and the reflected waves resulted in the generation of strong tension stress beneath free surface. Consequently, accompanying the evolution of micro-jets, the subsurface area Pb experienced multiple fracture processes, characterized by the lateral stretching damage and the formation of slugs. In the following process, the slugs fragmented in a similar way as the jets, with the volume distribution of clusters changing from power law to exponential function. Thus, the relationship of characteristic volume from steady-state clusters between jets and slugs could be predicted by their strain rate difference based on the Grady’s energy principle.