MD-Informed Material Point Method Study of Shock-Induced Pore Collapse in an Explosive Crystal

  • Sewell, Tommy (University of Missouri)

Please login to view abstract download link

Heterogeneous energetic materials (EMs) subjected to mechanical shock loading undergo complex thermo-mechanical processes. These are driven by the high temperature, pressure, and strain rate behind the shock and lead to spatial energy localization in the microstructure. These regions of localization are known colloquially as “hotspots” and are where chemistry will commence possibly culminating in an explosion or detonation. Shock-induced pore collapse is one of the dominant mechanisms by which localization occurs. The Material Point Method (MPM) is an attractive approach for handling the extremely large deformation and the evolving geometry of the self-contact that accompany pore collapse. Here, we apply MPM to study shock-induced pore collapse in the widely studied explosive β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (β-HMX), using an MD-informed continuum material description that includes a multiplicative description of crystal plasticity. Treating MD predictions of the pore collapse as ground truth, head-to-head validation comparisons between MD and MPM predictions will be shown for specimens with identical geometry and similar boundary conditions, for reverse-ballistic impact speeds 0.5 ≤ u_p ≤ 2.0 km s−1. Additional comparisons, focusing on MPM predictions, will reveal the importance of incorporating a frictional contact algorithm, pressure-dependent elastic stiffness, and non-Schmid critical resolved shear stress in the mesoscale model.