Material strength in high energy density conditions

We derive a continuum-level plasticity model for polycrystalline materials in the high energy density regime, based on a single dislocation density and single mobility mechanism, with an evolution model for the dislocation density. The model is formulated in terms of quantities connected closely with equation of state (EOS) theory, in particular the shear modulus and Einstein temperature. We used the atom-in-jellium model to estimate the Einstein frequency, EOS, shear modulus, and Peierls barrier from ambient to white dwarf conditions. The Peierls barrier was adjusted to match a single flow stress datum. The configurational energy of the dislocations is accounted for explicitly, giving a self-consistent calculation of the conversion of plastic work to heat. The dislocation and elastic strain energies are predicted to contribute to the mean pressure, and may be significant when inferring scalar EOS data from dynamic loading experiments. The deduced flow stress reproduces systematic trends observed in elastic waves and instability growth experiments.