CYCLIC STRESS-STRAIN RESPONSE DURING ISOTHERMAL AND THERMOMECHANICAL FATIGUE

Isothermal high-temperature low-cycle fatigue and in-phase and out-of- phase thermomechanical fatigue tests were carried out on 316L austenit ic stainless steel specimens controlled by computer. A nonlinear kinem atic hardening model with internal variables was used to simulate the cyclic stress-strain behaviour of isothermal fatigue. This model was m odified by considering thermal cyclic effects in order to describe the cyclic stress-strain behaviour of thermomechanical fatigue (TMF) usin g only isothermal fatigue data and the material performance data. A ve ry good approximation of the hysteresis loops was obtained by comparin g with experiments of both in-phase and out-of-phase cases. The thermo mechanical fatigue behaviour described by isothermal fatigue data give s the possibility of developing the TMF lifetime prediction technique.