A UNIVERSAL INTEGRATION ALGORITHM FOR RATE-DEPENDENT ELASTOPLASTICITY

An algorithm is developed for integrating rate-dependent constitutive equations of elstoplasticity including isotropic and kinematic hardeni ng, as well as thermal softening and non-coaxiality of the plastic str ain rate and the driving stress. The method is unconditionally stable and accurate for large time steps and all possible ranges of rate-depe ndency. Under a constant loading rate the algorithm gives exact result s at arbitrary step sizes for rate-independent materials without harde ning, and in proportional loading for rate-independency with hardening , and linear viscosity without hardening. The present method is an ext ension of a recently proposed integration algorithm for stiff equation s to domains of high rate-sensitivity like, for example, in power-law creep. The algorithm employs a plastic predictor-elastic corrector sch eme, which, in general, requires less numerical effort in the return m apping process than the assumption of an elastic predictor. Numerical examples underline the efficiency of this integration algorithm in com parison to gradient techniques and an extended radial return method fo r rate-dependent plasticity. Copyright (C) 1996 Elsevier Science Ltd.