Micro-Sliding in High-Speed Aircraft Engine Ball Bearings

Abstract

Micro-sliding within the contact ellipse of high-speed ball bearings is a tribological phenomenon that occurs in large, high-speed aircraft turbine engine ball bearings that should be taken into consideration in the design of high-speed ball bearings. This article presents the phenomenon of micro-sliding within the ball bearing contact zone, the parameters that impact its generation, and the extent and the impact of micro-sliding on bearing life. Micro-sliding, especially under poor lubrication conditions, superimposes shear stresses into the contact area surface, which move the depth of maximum stress toward the surface. Whenever there is micro-sliding rather than rolling, there is superimposed frictional heating within the contact ellipse. This localized heating can degrade or break down the oil film, which leads to even more local friction and more local heat generation. The effects from the increased local stressing near the surface combined with the local degradation of the material fatigue strength due to excessive local temperature can initiate micro-spalling in a localized zone within the contact ellipse where the maximum friction energy prevails. Continuous operation of the bearing will propagate the micro-spalling into deep spalling and ultimately lead to bearing failure.