FAILURE PROCESS OF BEARING STEEL IN ROLLING CONTACT FATIGUE

Abstract

Microcracks appeared on the track surface in a rather early stage of the testing at sites apart from the center of the track. The initiation site was revealed to be at nonmetallic inclusions that exist on or just below the track surface. The incipient extension direction of cracks was about 45 deg to the rolling direction on the surface and it was normal to the contact surface inside. As the crack grows inwards, it inclined to be parallel to the surface at the outer edge of the dark etching zone. The rate of crack growth at this stage was rather small. The final propagation of the crack washrough the dark etching zone and was estimated to take place in a short period. These findings are discussed referring to the model of the flaking failure propose previously by the present authors.