Fatigue strength reduction factor of crack initiation life basis for austenitic stainless steel

The fatigue strength reduction factor (K_f) of fatigue crack initiation life (N_c) basis was previously proposed by one of the authors as a function of the elastic stress concentration factor (K_t) and work hardening constants in the cyclic hysteresis loop. The validity of the fundamental relation was shown mainly through the experimental investigations using mild steel, high strength steel and weld metals. In the present study, an applicability of the relation to an austenitic stainless steel was investigated, by tension-compression axial loading fatigue tests of double side notched plate specimens of SUS316NG steel. The K_t was changed from 1.08 to 6. As a result of the fatigue tests, K_f of N_c basis showed a linear relationship against K_t, but the K_f was always lower than K_t, though the former was nearly equal to the latter in the previous investigation, The theoretical equation predicting K_f as a function of K_t was partially modified by applying a new concept on the hysteresis energy per cycle so as to show a good agreement between experimental and theoretical values of K_f.