Grain-scale modeling, a simulation technique that employs discrete microstructural features in order to understand "sub-grid' phenomena, has been used in shock-physics primarily to characterize the mechanisms for hot-spot formation at voids and/or inclusions. More recently, these methods have been used on length scales of engineering interest. In this work, the unreacted equation of state (EOS) for porous hexanitrostilbene (HNS) and hexanitrohexaazaisowurtzitane (CL-20) are determined using simulated and measured microstructure grain-scale models. Calibrated Arrhenius reactive burn models are shown to be capable of predicting observed shock-to-detonation transition (SDT) behavior. Not only are measured threshold impact velocities obtained, but correct trends in pressure history for heterogeneous materials, and trends in sensitivity with pore size distribution are also reproduced. The capabilities of grain-scale methods are discussed, and a workflow is proposed for physics based performance predictions of energetic materials.
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