Multiscale numerical simulation of shock heating of granular explosives

A multiscale model and Arrhenius reaction rate equation are used to analyze the compaction processes in granular high-explosive HMX. Analysis of the steady-state wave structure indicates that for subsonic compaction wave, the model variables, such as solid volume fraction, pressure, density, transit from the initial value to the equilibrium state smoothly. The evolution of the grain temperature shows that the peak hot spot temperature near the intergranular contact surface, which exceeds the melting temperature, would trigger chemical reaction although the bulk average temperature is very low. In case of chemical reaction, the piston speed needed to stimulate chemical reaction for the same initial conditions is higher due to solid-liquid phase change which consumes part of the bulk compaction work. At last, numerical experiments were performed to determine the model sensitivity to variations in key energy localization parameters.