Experiments and modeling of HMX granular explosives subjected to drop-weight impact

The drop-weight impacts on a thin layer of cyclotetramethylene tetranitramine (HMX) explosive particles have been performed. The drop-weight impact machine is equipped with high-speed photographic techniques. Effects of drop heights and the amount of particles on compaction, deformation, and thermal responses were investigated. Considering the contact plasticity, friction, melting, fracture, as well as chemical reaction, an analytical model based on heating and kinematics equations for a single layer of explosive particles has been developed. The calculated average pressure, loading time and time-to-ignition agree well with experimental measured ones. Threshold conditions for ignition can be derived from the predicted temperature history curves. Individual particles' pressure–strain exhibited stress–strain-like relationships, from which close relations can be found between experimental phenomena and the material's softening/hardening characteristics.