Fatigue tolerant design of rolling bearings

A quantitative method for assessing the influence of steel cleanliness on the fatigue life of rolling bearing raceways is presented. The approach systematically accounts for the effect of the highly variable stress state within raceways. Finite element analysis is used to determine the stress state in the bearings. A fracture mechanics model for the safe stress amplitude as a function of inclusion size is employed from Lewis and Tomkins. The size and number of large inclusions in a large volume of steel are estimated by the Generalised Pareto Distribution. These three elements are combined to determine the failure probability of the raceway in an example rolling bearing. A sensitivity analysis to the various microstructural input parameters is conducted. It is found that the size distribution of the larger inclusions is the most important factor in controlling the fatigue resistance of rolling bearings, and that residual stresses must be considered to produce realistic predictions.