Subsurface propagation of partial ring cracks under rolling contact: Part I. Experimental studies

Surface ring crack defects found on the surface of ceramic balls can reduce the rolling contact fatigue life (RCF) performance. In this study, various crack sizes were selected to identify the failure mechanisms in various lubricants. A modified four-ball machine was used to perform rolling contact fatigue testing. The crack within the contact path was carefully oriented and positioned the same way for all tests. Experimental results showed that the RCF life was influenced most by load, lubricating fluid and crack size. Examination of spalled and unspalled balls showed that the original ring crack propagated during fatigue testing and that crack branching occurred. Also, secondary surface cracks were observed. The consistency of results showed that crack growth was an integral part of the failure mechanism.