A lifetime model for creep-fatigue interaction with applications to the creep resistant steel P92

Methods proposed by current codes and standards to deal with creep-fatigue problems are far from being satisfactory. For a better understanding, a model is developed based on grain boundary cavitation (representing creep damage) and microcrack growth (representing low-cycle fatigue damage). Creep-fatigue interactions occur by (1) contributions of creep deformation to fatigue crack growth, and (2) enhanced creep rates after load variations, as they occur, e.g., during start/stop cycles. Experiments on the steel P92 confirm the predicted lifetimes as a function of the stress-temperature loading history. A creep-fatigue damage parameter, DFC, is introduced to characterize the load cycle.