Effect of cyclic hardening on stress relaxation in SUS316HTP under creep-fatigue loading at 700ºC: experiments and simulations

Cyclic hardening and stress relaxation experiments of SUS316HTP were performed under
creep-fatigue loading with tensile strain holding at 700◦C. Experiments revealed that under
strain holding, the slow stress-relaxation stage satisfying Norton’s law with slight cyclic
hardening followed a rapid stress-relaxation stage that was noticeably affected by cyclic
hardening. This suggests that in the slow stress-relaxation stage, inelastic deformation mechanisms
different from that of viscoplasticity occurred. Experiments were simulated using
a cyclic viscoplastic-creep model in which the inelastic strain-rate was decomposed into
viscoplastic and creep components that were affected differently by cyclic hardening. The
simulation accurately reproduced the experiments.