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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.

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.