Pressure–shear ignition mechanisms and criteria for melt-cast explosives under high hydrostatic pressure

During high-speed penetration, melt-cast explosive charges experience coupled high hydrostatic pressure, shear deformation, and high strain rates, making ignition strongly loading-path dependent. Here, the 2,4-Dinitroanisole-based melt-cast explosive was investigated using high-pressure plate-impact experiments, oblique flyer-impact ignition tests, and three-dimensional explicit dynamic simulations. Plate-impact results show delayed rise, staged growth, and a quasi-steady plateau in the explosive/window particle velocity, indicating path-dependent volumetric compression controlled by pore closure, plastic pore collapse, and multiphase impedance mismatch. Oblique impact tests show that shear changes both ignition mode and threshold: 0° normal impact produces post-crushing edge ignition at 160.7 m/s without direct front-interface ignition, whereas the 23.5° and 45° pressure–shear cases trigger front-interface ignition at 133.2–155.5 m/s and 131.7–140.0 m/s, respectively. A validated explicit dynamic model coupling a P – α volumetric equation of state, viscoelastic–viscoplastic damage, and multi-source thermal dissipation predicts the 23.5° ignition range as 140.0–150.0 m/s, with a maximum relative deviation of approximately 5.1% between the corresponding interval boundaries. Simulations reveal that hydrostatic pressure promotes pore compaction and volumetric heating but suppresses effective crack sliding through normal closure, whereas shear loading drives damage localization and frictional hot spots. A time-dependent ignition criterion based on cumulative effective ignition work density is proposed to couple deviatoric mechanical power, pressure-induced closure, triaxial constraint, and thermal-deposition history. The results clarify the transition from compression-dominated edge ignition to pressure–shear-driven front-interface ignition and provide a quantitative method for ignition-risk assessment.