Effect of small defect on the flaking strength of rolling bearings (Part 2: Evaluation of the flaking strength of rolling bearing having a small drilled hole based on stress intensity factor)

Abstract

Rolling contact fatigue (RCF) tests were conducted using rolling bearings with a micro-drilled hole on the raceway. In all the tests, fatigue crack initiated at the edge near the bottom of the hole, and then propagated by shear mode. Even in the unbroken specimens tested up to N = 1×108 cycles, a short fatigue crack was found at the edge. By using stress intensity factor (SIF) range calculated for initial defect size, fatigue life data were uniformly gathered inside a small band irrespective of the diameter and depth of the hole. In addition, it was found that the crack size dependency of threshold SIF range, which is well-known for mode I fatigue crack, also exists in mode II fatigue crack emanating under the rolling contact. The values of threshold SIF ranges obtained by the RCF tests were in good agreement with those obtained in the torsional fatigue tests under a static compression.

Keywords

• rolling contact fatigue
• bearing steel
• flaking
• drilled hole
• shear-mode crack
• stress intensity factor