An Approach to Predicting the Threshold of Damage to an Angular Contact Bearing During Truncation

Abstract : A simple, approximate expression is developed, relating the mean stress with the fraction truncated at the contact between a ball and raceway of a loaded angular contact ball bearing. This expression is to serve as a rule-of-thumb for the bearing analyst to predict the likelihood of bearing damage due to truncation. The contact is said to be truncated when the contact area reaches beyond the edge of the raceway. We derive approximate expressions for the damage criteria due to excessive stress at the center of the contact ellipse and at the truncated edge of the contact. When either of these stresses exceeds the yield stress of the bearing materials, the damage threshold has been reached, and brinnelling will occur. Furthermore, we assert that when the fraction of the contact ellipse that is truncated exceeds 0.5, the ball will jam, and the bearing will be inoperable. These three criteria for successful operation beyond the initiation of truncation are combined into a single expression to be used for assessment of the danger of bearing damage. Our analysis provides for a first-order prediction of the conditions under which damage will result from a truncated contact.