Quantitative Evaluation of the Flaking Strength of Rolling Bearings with Small Defects

Rolling contact fatigue (RCF) tests were conducted on rolling bearings, with holes micro-drilled at the mid-point of the tracks. In all of the RCF tests, fatigue cracks initiated at the edge, near the base of the drilled holes, later propagating by shear-mode. Even in the un-flaked specimens tested up to N = 2×108 cycles, short fatigue cracks were discovered at the edges. Using the stress intensity factor (SIF) range, as calculated for the initial defect size, fatigue life data were uniformly gathered inside a narrow band, irrespective of the diameters and depths of the holes. In addition, it was determined that the crack-size dependency of the threshold SIF range, well-known for Mode I fatigue cracks, also exists for Mode II fatigue cracks, as produced after rolling contact. The values of the threshold SIF range obtained by the RCF tests were in good agreement with those obtained in the torsional fatigue tests under static compression.