Atomistic-Based Mesoscopic Constitutive Models for High Explosive Constituent Materials

摘要

Large-scale molecular dynamics (MD) simulations of shocks in oriented single crystals of RDX and PETN were used to study the fundamental mechanisms by which inelastic deformation occurs when those materials are shocked to states on the Hugoniot locus modestly above the elastic limit. The goal is to identify, characterize, and quantify the dominant processes leading to localization of energy, and to capture within a statistical framework useful information concerning the local thermodynamic states behind a shock that can aid the development of improved mesoscale constitutive models. Among the homogeneously nucleated defect structures that were observed are dislocations, stacking faults, and shear bands. A method, developed in collaboration with Professor D. L. Thompson at the University of Missouri-Columbia, that enables study of shocked material for times far in excess of the shock transit time across a MD simulation cell was used to study long-time relaxation phenomena in some cases. Probability distribution functions of temperature in RDX crystal were determined for slices of material perpendicular to the shock propagation direction as a function of distance in a reference frame that is stationary relative to the moving shock front.