The application of a biaxial isothermal fatigue model to thermomechanical loading for austenitic stainless steel

A biaxial thermomechanical fatigue (TMF) model has been developed by extending a biaxial fatigue model for isothermal condition. The proposed model assesses the in-phase and out-of-phase type cycle incorporating the effect of oxidation and creep. The isothermal fatigue model utilizes the concept of triaxiality factor (TF), which accounts for the state of stress effect on the material's fracture ductility. The TMF biaxial strain ratios varied from 0 to 3.65 at cyclic temperatures of 399 to 621 degreesC (750 to 1150 degreesF). All tests were strain controlled using tubular specimens. Heating was by induction and the cooling was by natural convection.