Volume 7, Issue 3 (March 2010)
A New Methodology for Predicting Fatigue Properties of Bearing Steels: From X-Ray Micro-Tomography and Ultrasonic Measurements to the Bearing Lives Distribution
This work aims at developing a new methodology for predicting the distribution of fatigue lives of bearings versus steel microstructure, namely, concentration, morphology, and properties of residual inclusions in steel. On the experimental side, X-ray micro-tomography and high frequency ultrasonic testing are used to provide the required inclusion characteristics. A physically based model is used to compute the number of cycles to crack nucleation and crack propagation up to the surface. For the statistics predictions, the inclusions and/or stringers are distributed randomly in the bearing steel according to the concentration of stringers provided by ultrasonic data. The distributions of the fatigue lives predicted by the model are compared successfully to the experimental distributions determined by fatigue tests performed on flat washer machines. Finally, it is shown that the model is able to predict the influence of the orientation of stringers on the fatigue lives.