Heterogeneous free-surface profile of B4C polycrystal under shock compression

Observations of the free-surface behavior under shock compression by the gapped-flat mirror method were performed on B4C and Si3N4 ceramics to study their shock-yielding properties. Jagged profiles of the moving free-surface in the plastic region, with a special scale of about one mm and a maximum local displacement of a few 10s of mu m, were observed for B4C polycrystals. Similar profiles for Si3N4 polycrystals were smooth. Such profiles for B4C polycrystals were also observed in the elastic region. It is suggested that these observations reflect the heterogeneous nature of shock compression in solids, and further indicate that a macroscopic slip system plays an important role in the elastoplastic transition of B4C material under shock compression and decompression. (C) 1997 American Institute of Physics.