A method to calculate frictional effects in oil-lubricated ball bearings

Friction and heat generation in oil-lubricated ball bearings is mainly the result of sliding in the ball-raceway contacts and agitation of the lubrica nt in the free space between the balls, cage, and bearing rings. Endurance of a ball bearing is highly dependent on the thicknesses of the oil films w hich serve to separate the balls from the raceways in a well-lubricated bea ring. The film thicknesses, in turn, are dependent upon the lubricant's vis cous properties. These are functions of bearing temperatures and are determ ined by the balance between the rates of frictional heat generation and hea t dissipation. Therefore, in the design of a ball bearing application such as the high speed rotor and low speed rotor support bearings in an aircraft gas turbine, it is important to be able to predict the bearing frictional heat generation rates with reasonable accuracy. This paper presents a metho d to perform the required calculations considering bearing loading and spee ds, realistic lubricant rheological properties, and a relatively simple hea t transfer system between the bearing rings, balls, and lubricant. The resu lts of the analysis are shown to compare favorably with experimental data.