Role of component configuration in evaluation of accelerated rolling contact fatigue of ball bearings

Four-ball testers are widely used for determining the rolling contact fatigue life of bearing components. The tester simulates the rolling conditions in the bearing where the upper ball and the cup simulate the inner and outer rings, respectively, and the planetary balls represent the rolling elements in the bearing. However, in many studies the upper ball is utilized as the ball whose rolling contact fatigue (RCF) life is investigated, mainly to speed up the fatigue process. In this paper, a four-ball tester is used to study the effect of ball configuration, i.e. upper ball versus the planetary ball, on the RCF life. It was observed that the 52100-steel upper ballʹs L10 life is 7.4 times shorter than that of 52100-steel lower planetary balls. For M50 tool steel, the L10 life of the upper ball was 5.9 times shorter than that of the lower planetary ball. The lesser number of stress cycles per revolution of testerʹs spindle and the skid of lower balls resulting in rolling on multiple rolling tracks are the contributing factors to the longer RCF life of planetary balls.