Predictions for Weak Mechanical Ignition of Pre-Compacted Energetic Solids

摘要

The physical response of damaged energetic solids (e.g., explosives and propellants) to accidental impact is a ongoing safety concern. Here, a damaged material is one that has been inadvertently fractured and, thus, contains granular regions. Damage increases the material's sensitivity to subsequent impact by enabling significant thermal energy localization near intergranular contact surfaces due to plastic deformation and friction. If the local heating rate is sufficiently fast, then combustion initiation will occur as there is little time for cooling by thermal conduction. Importantly, quasi-static compaction experiments on HMX (octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine) indicate substantial changes in its mechanical behavior as it is compacted; it exhibits elastic-plastic deformation with strain hardening. As such, is reasonable to expect that pre-compaction will affect the subsequent dynamic loading behavior of granular explosives. Analysis of this problem is particularly relevant to loading processes involving multiple, successive shocks [2]. Here, we summarize predictions for the dynamic loading of pre-compacted HMX. Emphasis is placed on describing and resolving in a simple way the interplay between bulk compaction induced dissipation and grain scale heating and combustion. To this end, multiphase processes are omitted, and simple chemistry is used.