Single two-zone elastic-plastic shock waves in solids

A new regime of shock wave propagation in solids, corresponding to a single two-zone elastic-plastic shock-wave, was discovered using a novel moving window molecular dynamics technique. Both leading low-pressure elastic and trailing high-pressure plastic fronts move with the same speed and have a fixed separation that can extend to several microns. The material in the elastic zone is in a metastable state, having a pressure that substantially exceeds the critical shock strength characteristic of the onset of the well-known split-elastic-plastic, two-wave regime. The single two-zone elastic-plastic shock wave is a quite general phenomenon observed in our simulations for a broad class of crystalline materials, including aluminum, nickel, diamond, and Lennard-Jones crystals. It is the existence of the two-zone, elastic-plastic regime that allows for a consistent explanation of the anomalously high elastic wave amplitudes observed in recent experiments.