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Inner ring fatigue analysis of rolling element bearings

Eroğlu, Barış
Rolling element bearings are the one of the most widely used machine elements in the industry. The most important criterion in bearing selection is the endurance life. The first attempts on the prediction of the endurance life of rolling elements bearings are done by Lundberg and Palmgren in 1950s (Harris, 1999). Their work adopted as an ANSI, ABMA and ISO standard which is widely used in industry today. The basic assumption of Lundberg-Palmgren formulation is that no matter how small the load applied on rolling element bearing, all material in the stressed volume is subject to fatigue failure. In this study, four main life theories; Weibull, Lundberg-Palmgren, Ioannides-Harris, and Zaretsky on rolling element bearings have been investigated. Three-dimensional finite element models of a bearing’s inner ring and rolling element have been prepared. The stress fields within the inner ring and the ball with respect to the applied load are obtained numerically. The fatigue life of the inner ring has been predicted by two methods that are widely used for fatigue analysis; Total Life Analysis (S-N method) and Crack Initiation Analysis (-N method). Obtained results are compared with ISO formulation. As a result of the investigation, S-N and -N methods are determined to give more conservative results than ISO method for higher loads that cause stresses above the fatigue limit of the material. The used methods for bearing life prediction recognize the existence of the fatigue limit stress. Hence as the stresses within an operating bearing do not exceed the limit stress, the bearing can achieve infinite life. It is also observed that load variation has a direct influence on the bearing life. When the load significantly changes from the levels which create stress above the fatigue limit to the levels that result stress is below the fatigue limit, the bearing would have higher endurance life than predicted by ISO method.