Affine Particle-in-cell simulations of shock-induced pore collapse in HMX crystal with multiplicative pressure-sensitive crystal plasticity*

Cyclotetramethylene-Tetranitramine (HMX) is a secondary explosive used in military and civilian applications. Its plastic deformation under shock is of importance in the initiation of the decomposition reaction. It has been recently shown through continuum-scale parameter study that the pressure sensitivity of the elastic stiffness, the critical resolved shear stress (CRSS), and the melting temperature influences the prediction of the hot spot evolution during the shock. In this talk, we present an atomistic-informed crystal plasticity model with pressure-dependent hyperelasticity, critical resolved shear stress, and melting temperature. This constitutive law is incorporated in an affine particle-in-cell material point solver that conserves energy and momentum. The resultant model is capable of reproducing the monoclinic elastoplastic responses as well as the pressure sensitivity of crystalline HMX even undergoing extremely large deformation. We further employ this model in pore collapse simulations under shock loading, and we perform a head-to-head comparison with corresponding atomistic-scale simulations. The onset of shear banding, the contact mechanisms and the shock wave propagation are compared with benchmark cases.