Rolling Bearing Service Life Based on Probable Cause for Removal—A Tutorial

Abstract

ABSTRACTIn 1947 and 1952 G. Lundberg and A. Palmgren developed what is now referred to as the Lundberg-Palmgren model for rolling bearing life prediction based on classical rolling-element fatigue. Today, bearing fatigue probably accounts for less than 5% of bearings removed from service for cause. A bearing service life prediction methodology and tutorial indexed to eight probable causes for bearing removal, including fatigue, are presented that incorporate strict series reliability; Weibull statistical analysis; available published field data from the Naval Air Rework Facility; and ∼224,000 rolling-element bearings removed for rework from commercial aircraft engines. Bearing service life Lserv can be benchmarked and calculated to the bearing L10 fatigue life as follows: Lserv = X1/m L10, where X is the number of bearings removed from service because of fatigue divided by the total of all bearings removed from service regardless of cause and m is the Weibull modulus of the bearings removed from service. The most conservative bearing L10 service life calculation is obtained assuming an exponential distribution where m = 1.1. Of the ∼224,000 commercial engine bearings removed from service for rework, 1,977 or 0.88% were rejected because of fatigue. From the Naval Air Rework Facility bearing data, eliminating rolling–element fatigue as a cause for removal, the L10 service life of these bearings would increase by approximately 3%.