Molecular dynamics-guided material model for the simulation of shock- induced pore collapse in beta- octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (beta-HMX)
P Das and P Zhao and D Perera and T Sewell and HS Udaykumar, JOURNAL OF APPLIED PHYSICS, 130, 085901 (2021).
Material models for single-crystal beta-HMX are systematically examined in the context of continuum pore-collapse simulations. Continuum predictions using five different isotropic material models are compared head-to-head with molecular dynamics (MD) predictions for a 50 nm cylindrical pore in beta-HMX subject to a range of shock strengths. Shock waves were generated using a reverse-ballistic configuration, propagating along 010 in the MD simulations. The continuum models are improved hierarchically, drawing on temperature- and pressure-dependent MD-derived material parameters. This procedure reveals the sensitivity of the continuum predictions of pore collapse to the underlying thermophysical models. The study culminates in an MD-calibrated isotropic rate- and temperature-dependent strength model, which includes appropriate submodels for the temperature-dependent melting point of beta-HMX M. P. Kroonblawd and R. A. Austin, Mech. Mater. 152, 103644 (2021), pressure-dependent shear modulus A. Pereverzev and T. Sewell, Crystals 10, 1123 (2020), and temperature-dependent specific heat, that produces continuum pore-collapse results similar to those predicted by MD. The resulting MD-informed model should improve the fidelity of simulations to predict the detonation initiation of HMX-based energetic materials containing micrometer-scale pores.
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