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

This paper deals with a numerical analysis of creep components until failure. 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 ``uni®edʹʹ viscoplastic model is used to describe primary and secondary creep behaviors, and the tertiary creep description is based on the introduction of a scalar damage variable and the nonlinear e€ects of changes in geometry. Therefore, viscoplastic damage models in nonlinear geometry are de®ned in order to describe di€erent modes of creep damage development. The numerical properties of the models allow us to obtain a di€erent crack growth development, in order to know the post-critical behavior and the damage development until failure. The numerical treatment uses the ®nite element method and the large time increment method in a version adapted to solve nonlinear problems with geometrical nonlinearities, in order to obtain a rapid creep life assessment.