LIFETME PREDICTION OF TIME-DEPENDENT THERMOMECHANICAL FATIGUE OF HIGH TEMPERATURE ALLOYS

paper discusses the lifetime prediction tecboques of time-dependent thermomechanical fatigue (TMF) of high temperatire alloys. It is based on the stress-strain cyclic behavior described by a non-linear kinematic hardening model in an irreversible thermodynamic system. In order to consider the influence of temperature cycles, a strain energy density combined with a temperature damage factor was deduced as a damage parameter. In the case of the time dependent fatigue, the application of a ductility exhaustion approach for creep-fatigue damage assessment was illustrated. In identifying parameters of the models, isothermal fatigue test results were applied A method using isothermal cycle data for predcting thermomechanical fatigue life bine was developed.