Strain Rate-temperature-dependent Deformation and Failure Behavior of HMX Single Crystals

The influences of strain rate and temperature on the deformation and failure behavior of energetic single crystals under low-speed impact conditions are investigated. The split Hopkinson pressure bar tests are conducted at different temperatures (298 K, 337 K, 383 K) and strain rates (800 s⁻¹, 1700 s⁻¹, 2200 s⁻¹) to obtain the stress-strain curves and fracture images of cyclotetramethylene tetranitramine (HMX) single crystals. Based on this, a strain rate-temperature-dependent finite element model is constructed, and the strain localization and damage evolution laws are obtained through simulation. The deformation and failure mechanisms of HMX single crystals under low-speed impact are clarified. The results show that HMX single crystals exhibit significant strain rate hardening and temperature softening characteristics. The plastic strain localization behavior is affected by shear stress. The sample exhibits an "edge-center-edge" symmetric expansion damage mode, and the degree of damage increases with the rise of strain rate. The main crack presents a slanted crack propagation mode, and the crack propagation is affected by shear stress. A clear single crystal face-multicrystal face cleavage feature appears at the fracture surface. This research helps to deeply understand the damage ignition mechanism at the crystal scale of explosives and can lay a foundation for the construction of multiscale ignition prediction models.