SUS 304鋼の高温多軸疲労寿命に及ぼす引張圧縮-ねじり負荷位相の影響

抄録

In order to investigate the effect of axial-torsional straining phase on the elevated-temperature biaxial low-cycle fatigue life, axial-torsional strain controlled fatigue tests were conducted on SUS 304 stainless steel at 550°C under in-phase and out-of-phase conditions between axial and torsional straining. Based on the experimental results, a criterion of biaxial low-cycle fatigue was discussed in this study.
The fatigue life under out-of-phase straining was found to be shorter than that under in-phase straining when compared at the same Mises equivalent strain range or maximum shear strain range. From the observation of slip-bands and micro-cracks on the specimen surface by means of a replica method, this appeared to be due to the change in fracture mode arising from the difference in macroscopic strain condition between in-phase and out-of-phase straining. Accordingly, a unified correlation for both the in-phase and out-of-phase biaxial fatigue lives could be obtained by expanding the Brown-Miller's theory of equivalent shear strain which contains the maximum shear strain and the normal strain across the maximum shear plane as the factors controlling the fatigue crack initiation and propagation under biaxial loading.