EVOLUTION OF METASTABLE ELASTIC SHOCK WAVES IN NICKEL.

Shock waves in nickel were simulated by molecular dynamics using a new EAM potential. Three distinct regimes of shock propagation were observed, including a single elastic shock wave, two split elastic and plastic shock waves, and a single two-zone elastic-plastic shock wave, in order of increasing piston velocity. The single two-zone wave consists of a leading lower-pressure elastic zone, followed by a higher-pressure plastic wave, both moving with the same average speed. The elastic zone of this wave is compressed to a metastable state having an average pressure above the Hugoniot elastic limit. Similar metastable states appear in the elastic precursor during the early stage of split wave development. The mechanism for relaxation of the metastable elastic state is discussed. [ABSTRACT FROM AUTHOR]