Creep After Cyclic-Plasticity Under Multiaxial Conditions for Type 316 Stainless Steel at Elevated Temperature

Abstract

History effects of cyclic-plasticity on subsequent creep have been elucidated for type 316 stainless steel at 600°C under multiaxial states of stress. Tension-compression and circular strain paths were specified for the prior cyclic plasticity. Constant stress creep experiments under simple tension, simple torsion, and combined tensiontorsion were first performed after uniaxial tension-compression cycles stabilized under a constant total strain amplitude. Then, in order to elucidate the path shape effects of prior strain cycles, the subsequent creep curves under uniaxial tension were compared for the uniaxial tension-compression and the non-proportional circular strain cycles which stabilized at identical stress amplitudes. The experimental results showed that the prior tension-compression cycles induced the anisotropy in creep behavior; creep resistance which was initially isotropic was enhanced in torsional direction, while it was decreased in tensile one. Another significant observation was that the circular strain cycles showed much larger hardening effect on creep than the tension-compression cycle. Regarding the creep flow direction, the effect of the prior cycles was negligible.