COUPLED CREEP-ELASTOPLASTIC-DAMAGE ANALYSIS FOR ISOTROPIC AND ANISOTROPIC NONLINEAR MATERIALS

This paper deals with the computational aspects of a coupled creep-elastoplastic-damage analysis for anisotropic, and as a special case isotropic nonlinear materials. A three phase backward Euler integration algorithm for stress update is proposed. For anisotropic nonlinear materials a general direct stress return mapping algorithm, utilising Newton-Raphson iteration, is derived. The stress vector and scalar variables quantifying the incremental creep, plasticity and damage are updated simultaneously. For isotropic materials the elasto-plastic stress update algorithm for plane stress by Jetteur (1986, Engng Comp. 3, 251-253) is extended to include creep and damage. In addition, a simple stress algorithm for the general three-dimensional isotropic case is also presented. The resulting algorithms are suitable for inclusion in general structural analysis codes. The consistent tangent matrix is also formulated for use in a global Newton iterative procedure, in which structural displacements are sought as the problem unknowns. Examples are given using the general purpose code LUSAS in which the algorithms have been implemented.