Proposal of a Probabilistic Model on Rotating Bending Fatigue Property of a Bearing Steel in a Very High Cycle Regime

In S-N diagrams for high strength steels, the duplex S-N curves for surface-initiated failure and interior inclusion-initiated failure were usually confirmed in the very high cycle regime. This trend is more distinct in the loading type of rotating bending, due to the stress distribution across the section. In the case of interior failure mode, the fish-eye is usually observed on the fracture surface and an inclusion is also observed at the center of the fish-eye. In the present work, the authors attempted to construct a probabilistic model on the statistical fatigue property in the interior failure mode, based on the distribution characteristics of the location and the size of the interior inclusion at the crack initiation site. Thus, the P-S-N characteristics of the bearing steel (SUJ2) in the very high cycle regime were successfully explained.