Numerical Investigation of a High Explosive Response to a Fragment Impact

The High Explosive Response to MEchanical Stimulus model, HERMES, was designed to predict the response of explosive materials and propellants to mechanical insults. Developed to address safety concerns, it is also a useful tool to investigate complex explosive processes as it combines material constituent models such as stress, deformation, and porosity with reactive rate laws. HERMES can capture the response of explosive materials under conditions of Shock to Detonation Transition (SDT), Deflagration to Detonation Transition (DDT) and Unknown to Detonation Transition (XDT). A detailed understanding of these processes is critical for safety assessments. In particular, fragments impacting an explosive are a concern as they may cause a detonation, either prompt or delayed. Further, if the explosive confinement is weak or opened, a shock wave produced by propelled unreacted material striking a nearby solid surface may induce the detonation of the remaining explosive undamaged by the fragment. We present a parametric study of the response of a slab of HMX-based explosive LX-14 to a fragment impact. Size, speed, and shape of the fragment are the variables of interest while we seek to characterize the realization of detonation under the processes of SDT and DDT. A steel back plate is added to our original setup to investigate XDT. In this new configuration, the distance between the back plate and the HE slab becomes an additional control parameter.