Reexamination of Ball-Race Conformity Effects on Ball Bearing Life

Abstract

G. Lundberg and A. Palmgren, in 1947, established the primary relation between rolling-element bearing geometry and bearing life. Their analysis of ball and roller bearings did not consider the life of the bearing's set of rolling elements independent of race life. The analysis in this report considers the life of the ball set as well as the respective lives of the races to reassess the effect of ball-race conformity on ball bearing life. The related changes in ball bearing life are incorporated in life factors that can be used to modify the bearing predicted life using the Lundberg-Palmgren equations and the ANSI/ABMA and ISO Standards. Two simple algebraic relationships were established to calculate life factors LF c to determine the effect of inner- and outer-race conformity combinations on bearing L 10 life for deep-groove and angular-contact ball bearings, respectively. Depending on the bearing type and series as well as conformity combinations, the calculated life for deep-groove ball bearings can be over 40 percent less than that calculated by the Lundberg-Palmgren equations. For angular-contact ball bearings, the life can vary between +16 and −39% from that calculated by the Lundberg-Palmgren equations. Comparing the two ball bearing types, the life factors LF c for the deep-groove bearings can be as much as 40% lower than that for angular-contact ball bearings. The use of a fatigue limit from either the program ASMELIFE or the proposed ISO 281:2006 standard can significantly overpredict bearing life over a range of normal operating Hertz stresses, which can result in the selection of undersized bearings for a particular application.