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A close examination has been made on the result of experimental research on surface fatigue in the low Lambda regimes. These experiments consist of two kinds. One is the endurance test of needle bearings, ball bearings and roller bearings with different surface and lubrication conditions. The other is the test with disk machines to observe peeling (or micropitting). The study shows that the Lambda ratio is not the only parameter which affects the surface fatigue of bearings. In most cases, the life ratio depends more strongly on the composite rms surface roughness than on film thickness. Thus, in addition to the Lambda ratio, the effects of asperity height/tip radius ratio, nominal contact pressure, mean separation, lubricant inlet starvation, surface defect, hardness and the compressive residual (or tensile hoop) stress on surface fatigue, should be taken into account.

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.