Theoretical study of the critical dynamic behaviors for pore collapse in explosive

Abstract

The shock loading process of porous explosive is simulated by molecular dynamics for different pore diameters and piston velocities. We find that the defect evolution consists of three steps: pore collapse, stress relaxation and hot spot evolution. The critical dynamic behaviors for each step are investigated. First, at the pore collapse process, the shock wave reflected at pore face induces rarefaction waves. Two reflection types are considered: downside face reflection and upside face reflection. The wave reflection equations are derived. Second, at the stress relaxation process, a spherical rebounding wave is obtained. For low spherical radius, the rebounding wave is supersonic; and for high spherical radius, the rebounding wave is sonic. The propagation of rebounding wave is an adiabatic expansion process for hot spot, therefore, the hot spot temperature decreases quickly at this stage. Third, by considering the thermal diffusion and thermal decomposition effects, the hot spot ignition equation is derived, and the critical temperature for ignition is evaluated. A complete physical picture of defect evolution is obtained.