A review of rolling contact fatigue behavior of silicon nitride focusing on testing practices and crack propagation analysis

Experimental and numerical analyses of the lifetime and crack propagation behavior of silicon nitrides under rolling contact fatigue (RCF) loading are surveyed. Intercomparison of four major test methods for RCF, namely balls-on-flat (BOF), balls-on-rod (BOR), two-roller, and four-ball configurations, are performed. The differences in the implications of the test results between the first three methods, are explored by using a test specimen made of material from the same production batch. With an understanding of the differences, the influences of variables such as the state of lubrication and surface roughness on RCF behavior is discussed. The influence of mechanical properties of test materials is also discussed in chronological order to trace the history of trends in the material development of silicon nitrides. Crack growth models based on observation results of propagation from an artificially induced crack, semi-elliptical or partial ring crack, are comparatively discussed along with the results of numerical analysis for more simplified initial crack models. An observational study of propagation behavior from a natural flaw is also addressed. Finally, future work to improve the reliability of ceramic bearings is discussed.