Observations on the theoretical and experimental foundations of thermoplasticity

Abstract

The thermodynamics of materials with internal state variables has been employed to study the properties of a class of thermoplastic materials in which the evolution equation for the internal variables is given by equation k = g(σkl, ε{lunate}kl, k, θ, · ε{lunate}kl) where g is homogeneous of order one in · ε{lunate}kl. The most general form of the Helmholtz potential consistent with the assumption of insensitivity of the elastic relations to inelastic deformation has been derived and a geometric interpretation of the Clausius-Duhem restriction has been made employing the concept of a thermodynamic reference stress. Experimental results of one of the authors have been correlated with the theory. © 1977.