Damage accumulation and fracture life in high-Temperature low-cycle fatigue

An analysis of the interaction of creep and fatigue is made based on the energy expended for the nucleation of damage at the advancing crack front. A rate equation is assumed for the damage nucleation, and the activation energy is taken as a function of the total mechanical energy at the crack tip. The analysis yields a relation in terms of /-integral which is applicable to both crack propagation and final failure. Raw data from various sources have been analyzed for different types of loading and compared with the theoretical prediction. The total energy in tension, which includes the tension-going strain rate, appears to be a good parameter for the prediction of fracture life in creep-fatigue interaction.