Unified model for fatigue crack initiation and growth, with emphasis on short-crack behavior, crack closure effects, variable-temperature fatigue and creep-fatigue interaction

A new unified phenomenological model for elevated temperature fatigue has been developed. In this model the incremental nature of failure is represented explicitly in terms of the initiation and growth of cracks occurring by a succession of local fracture events. The local mechanical conditions driving the local fracture processes are predicted by a new 'ligament' model which calculates the full triaxial stress and strain distribution histories around cracks of any length (including short cracks) for deformation behavior which encompasses creep, plasticity, cycling, variable temperature, crack tip blunting, crack closure, plastic flow concentration in near-surface grains, and blockage of slip by grain boundaries. Some of the important predictive capabilities of the new unified fatigue model are presented and discussed.