  When a material is plastically deformed the majority of mechanical work is
dissipated as heat, and the fraction of plastic work converted into heat is
known as the Taylor-Quinney coefficient (TQC). Large-scale molecular dynamics
simulations were performed of high strain rate compression of single-crystal
tantalum, and the resulting integral and differential TQC values are reported
up to true strains of 1.0. A phenomenological model is proposed for the energy
stored in the material as a function of time with an asymptotic limit for this
energy defined by the deformation conditions. The model reasonably describes
the convergence of TQC values to 1.0 with increasing plastic strain, but does
not directly address the physical nature of thermo-mechanical conversion. This
is instead developed in a second more detailed model that accurately accounts
for energy storage in two distinct contributions, one being the growing
dislocation network and the other the point defect debris left behind by the
moving dislocations. The contribution of the point defect debris is found to
lag behind that of the dislocation network but to be substantial under the
high-rate straining conditions considered here.
