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Surface damage created by debris significantly reduces the life of rolling element bearings. The metallurgical structure of a bearing raceway can be modified to optimize strength and damage tolerance. The correct balance between raceway strength and damage tolerance can significantly improve bearing life in contaminated environments. Two test procedures exist for measuring the damage tolerance of steels. Both test procedures produce comparable results, which can be correlated using baseline data. Damage tolerant steel produces a significant life improvement in large tapered roller bearings.

Reliability research in hybrid ceramic bearings involves life testing of hybrid bearings and ceramic specimens. New materials for bearings like advanced ceramics have emerged for evaluation in recent years. In fatigue testing to determine the stress-life relationship, the number of sample size in life testing can be limited by consideration of cost and testing time. In the testing of ceramics, some researchers have relied on the use of a stepwise multiple loading approach to increase the failure data points. In this paper, a maximum likelihood method is applied to test data with multiple loads to estimate the stress-life exponent. This method treats the data at different loads or steps at once. Test data from three fatigue experiments using silicon nitride materials have been analyzed to obtain the stress-life exponents. Also, Weibull plots of the ‘equivalent lives' have been presented for all test specimens tested at different loads and load steps.

The performance and microstructural behavior of several bearing steels tested in radial ball bearings were interpreted in terms of their microstructural alterations, residual stress and resistance to tempering. The bearings were fabricated out of 52100, M-50, and M-50 NiL steels and tested under identical conditions: a radial load of 1111 kg to produce a 3.62 GPa maximum Hertzian contact stress and a speed of 3 000 rpm to produce a calculated lambda ratio of 5.5. The plastically deformed region below the ball track surface of bearings which had run for extended periods was examined metallurgically and measurements were made of the hardness and circumferential residual stress. The 52100 steel bearings exhibited a white-etched microstructure in the softened worked region. The M-50 developed much less plastic flow without work softening, and the M-50 NiL exhibited the least microstructural alteration.

In an effort to reduce the design cycle time and to meet increasingly demanding applications, an improved procedure for bearing retainer design has been introduced. This paper discusses a methodology which allows the designer to predict the life and failure modes of a retainer under application conditions. Specific attention is given to the case of fatigue of the retainer due to the dynamic interactions between the retainer, rolling elements and races. The methodology which has been developed for the life prediction of retainers is based on the dynamic loads and retainer structural integrity. Central to this technique is the ability to predict the loads imposed on the retainer as a function of design and application conditions. The bearing analysis code ADORE has been used for this purpose. The technique will be discussed by means of an example.