Assessment of fatigue strength of low alloy steels for ships' crankshaft

Rotational bending fatigue tests for low alloy steels, KSFA80, KSFA110 were carried out to clarify the property of fatigue strength of high tensile forged materials. Fatigue fractures occurred even though the repeated stress exceeded 10 cycles, which started at an interior inclusion. Fatigue strength of forged materials show anisotropy depending on the relative direction of specimen to forged fiber flow, and it is shown that this anisotropy of fatigue strength is due to the projective shape and size of inclusions at crack origin to a plain perpendicular to the maximum stress direction. The effect of non-metallic inclusion to fatigue strength was estimated using the area parameter model.