Semi-circular surface cracks and flaking failures in silicon nitride bearings

There is a well-known pattern of flaking failure under spherical ball-on-plate contact, i.e., the network between multiple Hertzian cracks causes the surface layer’s separations. Based on this pattern previous researchers studied the failures of silicon nitride bearings. However, contrary to their explanation, we found that the surface cracks did not explain the process of the flaking failure of bearing plates. In the present work we calculate the stress concentration of surface crack in order to find out which crack is more dominant in the process of the flaking failure.