A COUPLED, ISOTROPIC THEORY OF THERMOVISCOPLASTIC1TY BASED ON TOTAL STRAIN AND OVERSTRESS AND ITS PREDICTIONS IN MONOTONIC TORSIONAL LOADING

Abstract

A coupled, isotropic, infinitesimal theory of thermoviscoplasticity was proposed in [32, 33] and applied to a variety of simple loadings including both mechanical and thermal straining. In this paper we develop this theory by postulating specific forms of the mechanical constitutive equation and the internal energy rate. The heat conduction equation is then obtained from the internal energy rate and the first law of thermodynamics. The predictions of the theory in torsion are examined qualitatively and through numerical experiments. Torsion is simulated at loading rates differing by four orders of magnitude, and both jump-increases and jump-decreases in loading rate are also examined. The theory predicts an initial thermoelastic response followed by nonlinear, rate-dependent plastic behavior. The adiabatic temperature response in torsion is initially isothermal and is followed by inelastic heating. Significant differences are found between the mechanical responses to stress-and strain-controlled loading. ...