Effect of irreversible phase change in shock-wave propagation

摘要

New release adiabatic date for vitreous GeO_2 are reported up to ～ 25 GPa using the VISAR technique. Numerical modeling of isentropic release wave induced dynamic states achieved from one dimensional strain-stress waves is consistent with a phase change that induce an increase in zero-pressure density from 3.7-6.3Mg/m~3 starting at ～ 8 GPa. The first release adiabatic data for SiO_2 (fused quartz) are presented (obtained with immersed foil technique). Above 10GPa, the SiO_2 release isentropes, in analogy with GeO_2, are steeper than the Hugoniot in the volume-pressure space, indicating the presence of an irreversible phase transition (to a stishovite-like phase). We simulate propagation of shock-waves in GeO_2, in spherical and planar symmetries, and predict enhanced attenuation for shock pressures (p) above the phase change initiation pressure (8 GPa). The pressure from a spherical source decays with propagation radius r, p～ r~x, where x is the decay coefficient, Modeling hysteresis of the phase change gives x = - 2.71, whereas without the phase change, x = - 1.15.An analytical model is also given.