A multi-mechanism damage coupling model

An isotropic continuum damage mechanics (CDM) framework, which can reasonably show the interaction mechanism of , and , is developed in this paper. Three independent damage variables are used to describe the material damage process, with each damage variable being defined according to its own physical nature. The relationship between the total damage and the three independent damage variables is also obtained. A new fatigue–creep damage model, considering the coupling effect of fatigue damage and creep damage, is then derived from this CDM framework. Consequently, the Lemaitre and Plumtree model [J. Eng. Mater. Technol. ASME 101 (1979) 284] has been interpreted as a special case of the proposed CDM model in this paper.