The Role of Lubrication in Propagation of Contact Fatigue Cracks

[+] Author and Article Information
W. E. Littmann

Metallurgy Research, Research Division, The Timken Roller Bearing Co., Canton, Ohio

R. L. Widner

Research Division, The Timken Roller Bearing Co., Canton, Ohio

J. O. Wolfe

Metallurgical Department, Steel and Tube Division, The Timken Roller Bearing Co., Canton, Ohio

J. D. Stover

Physical Laboratories, The Timken Roller Bearing Co., Canton, Ohio

J. of Lubrication Tech 90(1), 89-100 (Jan 01, 1968) (12 pages) doi:10.1115/1.3601565 History: Received July 11, 1967; Online August 23, 2011


Comparative life tests of tapered roller bearings in mineral oils and synthetic fluids, Mil L-7808-F and Mil L-23699, demonstrate a strong influence of lubrication upon bearing life and failure characteristics. The inclusion origin mode of failure propagates very rapidly and takes on the macroscopic appearance of the point surface origin mode when fatigue cracks interact with a lubricant having low viscosity at the operating temperature. Observations indicate that bruises from debris in the lubricant are stress raisers of severity equivalent to nonmetallic inclusions in bearing materials for nucleation of contact fatigue cracking. Surface fatigue by “peeling” or superficial pitting can also act as the nucleus of fatigue cracks which propagate in the same manner as the point surface origin mode. In general, any surface stress concentration in combination with low lubricant film thickness promotes surface origin modes of contact fatigue and low lubricant viscosity at the operating temperature promotes rapid propagation by a hydraulic pressure mechanism.

Copyright © 1968 by ASME
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