Modeling Nonlinear Elastic-plastic Behavior of RDX Single Crystals During Indentation
Final rept. Oct 2010-Jan 2012
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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A nonlinear anisotropic elastic-plastic model is developed for single crystals of the energetic material cyclotrimethylene trinitramine RDX. The model accounts for orthorhombic symmetry of elastic constants, pressure-dependent compressibility, and dislocation glide on six slip systems. Numerical simulations of spherical indentation on oriented single crystals are performed. Model predictions are compared with experimental data and observations from the literature. Results demonstrate significant influences of elastic anisotropy and elastic nonlinearity. Model predictions for elastic response using elastic constants obtained from resonant ultrasound spectroscopy agree with experimental data predicted forces obtained using constants obtained from Brillouin scattering tend to exceed experimental data. Predicted slip system activity is compared with that deduced from experimental observations of residual surface profiles. Indentation forces predicted by the nonlinear anisotropic elastic-perfectly plastic slip model exceed those observed in experiments, suggesting that surface and possibly subsurface fractures may contribute to a loss of stiffness in experiments at larger indentation depths.
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