  Numerical simulations of high-strain-rate and high-temperature deformation of
pure metals and alloys require realistic plastic constitutive models. Empirical
models include the widely used Johnson-Cook model and the semi-empirical
Steinberg-Cochran-Guinan-Lund model. Physically based models such as the
Zerilli-Armstrong model, the Mechanical Threshold Stress model, and the
Preston-Tonks-Wallace model are also coming into wide use. In this paper, we
determine the Mechanical Threshold Stress model parameters for various tempers
of AISI 4340 steel using experimental data from the open literature. We also
compare stress-strain curves and Taylor impact test profiles predicted by the
Mechanical Threshold Stress model with those from the Johnson-Cook model for
4340 steel. Relevant temperature- and pressure-dependent shear modulus models,
melting temperature models, a specific heat model, and an equation of state for
4340 steel are discussed and their parameters are presented.
