Modifications to Oh-Persson equation of state

Abstract

The theory and prior experimental studies for the high pressure shock compaction of porous metals are reviewed. The Mie-Gruneisen and Constant Derivative Mie-Gruneisen equations of state are not accurate for materials of high initial porosity shocked to high pressures. The equation of state proposed by Oh and Persson for these highly porous materials reduces the Gruneisen parameter of high internal energy states. The Oh-Persson equation of state does not predict the larger volumes at higher shock pressures known to exist for material of low initial porosity. We have modified the Oh-Persson equation of state by using an approximate Oh-Persson equation of state that has two asymptotes: the Mie-Gruneisen constant at low energy states and 0.5 at high energy states. The equation of state was applied to porous tungsten and compared with experimental data from the literature and other equations of state. The proposed equation of state shows improved correlation to experimental data for tungsten with high initial porosity, and reflects the larger volumes at high shock pressures for materials with low initial density. This is achieved while maintaining the close correlation to data obtained by most equations of state at higher initial densities.