NUMERICAL INTEGRATORS FOR ELASTIC-SECONDARY CREEP

A method has been developed for building error maps to present the acc uracy of time-dependent inelastic material models similar to the error maps used for time-independent plasticity. The elastic-secondary cree p constitutive model with a Norton creep behavior is used throughout t he paper to illustrate the method. It is noted that this is very simpl e unified creep-plasticity model with no internal state variables, i.e ., no back stress or change in the drag stress. The error maps for nin e integrators, which are used or have been proposed to be used for cre ep or unified creep-plasticity models, are then presented. Included ar e an explicit Euler integrator, explicit Runge-Kutta methods of second , third, and fourth orders, three implicit integrators, and two integr ators, which have been specially designed for this equation. A quantit ative measure of the accuracy of an integrator is also defined and app lied to the nine integrators. A special integrator for the equation wa s found to be best and the Euler method ranked sixth. Other considerat ions for choosing an optimum integrator is also discussed.