Phenomenological modeling and numerical simulation of different modes of creep damage evolution

This paper deals with a numerical analysis of creep components until failur e. We will take an interest in the macroscopic modeling of the creep curves with its three stages based on the irreversible thermodynamics theory with internal variables. A "unified" viscoplastic model is used to describe pri mary and secondary creep behaviors, and the tertiary creep description is b ased on the introduction of a scalar damage variable and the nonlinear effe cts of changes in geometry. Therefore, viscoplastic damage models in nonlin ear geometry are defined in order to describe different modes of creep dama ge development. The numerical properties of the models allow us to obtain a different crack growth development, in order to know the post-critical beh avior and the damage development until failure. The numerical treatment use s the finite element method and the large time increment method in a versio n adapted to solve nonlinear problems with geometrical nonlinearities, in o rder to obtain a rapid creep life assessment. (C) 2000 Elsevier Science Ltd . All rights reserved.