Predicting Life of Solid-Lubricated Ball Bearings

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Abstract
Solid-lubricated ball bearing life is limited by several failure modes that normally do not present a significant risk to liquid-lubricated bearings. While conventional subsurface fatigue failure is normally considered to be the primary limiting factor of life in liquid-lubricated ball bearing, other failure modes must be evaluated in assessing the life of solid-lubricated bearings. A quasi-empirical method for assessing life and reliability of solid-lubricated bearings was developed that considers: (1) fatigue, (2) raceway wear, (3) ball separator wear, and (4) lubricant transfer rate control from sacrificial self-lubricating ball separators. Laboratory data on wear of the balls, races, and sacrificial ball separator of a low-speed gimbal bearing was used to create semiempirical wear equations through regression analysis. From the wear equation, projections of race and separator wear were made and estimates of bearing effective wear life determined. Statistical analysis of the race and ball separator data was used to establish “probability of survival;” i.e., reliability of the bearing system based on wear-out.