Implementation algorithm for a single hardening constitutive model for frictional materials

An advanced elasto-plastic constitutive model for frictional materials, whose incremental version is presented in a companion paper (Int. J. Numer. Anal. Meth. Geomech., 2002; 26:647), is implemented in a user-defined material module. The general calculation strategy inside this module is presented and discussed, including the initial intersection of the yield surface and the techniques for updating of stresses and hardening modulus. Several integration schemes are implemented in the module and their capabilities in relation to the advanced, three-dimensional constitutive model are evaluated. The forward Euler, modified Euler, and Runge-Kutta-Dormand-Prince integration schemes are explained in detail, compared, and evaluated in view of error tolerances and computational efficiency. Copyright (C) 2002 John Wiley Sons, Ltd.