The Evolution of Retonation During DDT of Low Density HMX

摘要

The weak initiation of low density granular HMX occurs by a complex mechanism that leads to a prompt, "thermal-explosion-like" transition to detonation within the material due to compaction shock interactions. These interactions influence ignition, flame spread, and subsequent transition by affecting dissipative heating within the microstructure during pore collapse. Details of the transition mechanism depend on the initial packing density of the material and the input shock strength. In this study, computations are performed using a macroscale multi-phase reactive flow model to examine how the transition mechanism varies with input shock strength for granular HMX (65-85% TMD). The model accounts for pressure-dependent ignition, and subsequent burn depends on the local dissipative work, porosity, and pressure. The dependence on dissipative work is motivated by mesoscale simulations that indicate a significant increase in hot-spot size and spatial proximity within the microstructure as the effective (or bulk) shock induced dissipative work increases, suggesting an increase in flame spread rate. Predictions highlight the variation in transition mechanism with increasing input shock strength and conditions that favor the formation of retonation during transition are identified.