Effect of Component Differential Hardnesses on Residual Stress and Rolling-contact Fatigue

Residual stress measurements were made in the zone of resolved shearing stress on five SAE 52100 upper test ball specimens with an average Rockwell C hardness of 63.2. These upper test ball specimens were run against lower test balls of nominal Rockwell C hardnesses of 60, 62, 63, 65, and 66 until either ft conditions included an or both components failed because of fatigue. Test conditions included an average race temperature of 150 F, a maximum (Hertz) compressive stress of 800,000 psi, and a highly purified naphthenic mineral oil lubricant. Fatigue lives of the upper test balls were compared with measured residual stresses in the subsurface zone of resolved shearing stress. The compressive residual stress induced in the upper test ball during running is a function of delta H, the hardness of the lower test balls minus the upper test ball hardness An interrelation is indicated among differences in com- ponent hardness, induced compressive residual stress, and fatigue life. Measured values of compressive residual stress within the zone of resolved maximum shearing stress ranged from 178,000 and 294,000 psi. The apparent maximum residual stress occurs above where delta H = 0.