The existing application feedback and RCF study of silicon nitride ceramic bearings show that the main failure mode of silicon nitride full ceramic bearings is the material spalling on the rolling contact surface. The spalling failure is caused by the expansion of the main surface crack and the initiation and expansion of the secondary surface crack under the rolling contact. Therefore, in the current widespread application of silicon nitride full ceramic bearings, in order to improve the spalling fatigue life of silicon nitride ceramic bearings, we can only start from the perspective of studying the main surface crack propagation and secondary surface crack initiation and expansion mechanism of silicon nitride ceramic bearings. In this paper, on the one hand, the Franc3D and ABAQUS joint simulation calculation of the rolling contact tensile stress of different surface main crack parameters (initial depth and initial inclination angle) and different rolling contact friction coefficients leading to secondary surface crack initiation was completed. On the other hand, based on the fracture toughness experiment of silicon nitride material, the critical initial size of the secondary surface crack generated near the main surface crack is calculated, and many useful conclusions are obtained. The research results will be able to improve the service life of silicon nitride ceramic ball bearings by guiding the development of grinding technology of silicon nitride ceramic ball bearings and the regulation of service parameters of silicon nitride ceramic ball bearings.

Keywords: Silicon nitride full ceramic bearing, Spalling fatigue failure, Fracture toughness test experiment, Joint simulation, Secondary surface crack initiation.