Chapter 11 | Rolling Contact Fatigue Strength Material Testing

Abstract

Rolling contact fatigue (RCF) strength testing is a fundamental steel technology. Cycles and Hertzian stress thresholds respectively greater than 108 and in excess of 2 GPa are published as hardened bearing steel fatigue limits. However, the existence of bearing steel fatigue limits remains an open discussion. The complexities of the hardened bearing steel microstructure, the loading, the temperature, and the lubrication associated with contact fatigue make this a multiscale topic. Over the years, RCF bearing steel testing has been given considerable attention by the ASTM organization. An ASTM standard RCF test method does not exist and as far as is known the only National Standard is the Chinese JB/T 10510-2005 method. A specialist ASTM symposium on RCF testing was held in 1981 and the resulting STP771 is to this day a standard reference on the topic. Fatigue failure is a statistical process and the bearing industry generally applies Weibull statistics to rationalize the variations in the nonlinear probability versus test cycle distributions. As bearing steel quality has improved the number of test cycles to failure has increased resulting in vastly extended test durations. Increasing the loads to shorten the test times can result in nonrepresentative failures modes. Numerous RCF tests methods exist, such as thee-ball-on-rod, flat washer, and angular contact ball bearing, and various methods are reviewed in this chapter. The effect of the rolling contact test loads on raceway cyclic microplasticization is discussed as it is important to define the maximum test load without unacceptable cyclic plasticization of the raceway contacts. Substitute fatigue testing methods are evaluated. The most frequently applied substitute tests are rotating beam and push-pull testing with ultrasonic frequencies being applied to speed up the testing. In addition, modeling of the effect of microinclusion on RCF strength is reviewed.