Fatigue Life Prediction for Large-Diameter Elastically-Constrained Ball Bearings

Theapplication of large-diameter bearing rings and the thereof inherited lowstiffness make them susceptible to local distortions caused by theirsurrounding structures, which are often under heavy loads. The standardaccepted design criteria for these bearings are based on theestimation of the internal load distribution of the bearing, underthe assumption of rigid circular and flat supporting structures, thatkeep the bearing inner and outer races in circular, flat,i.e., not deformed shapes. However, in the presence of structuraldistortions, the element load distribution can be severely altered andcannot be predicted via the standard design criteria. Therefore, theapplication of large-diameter ball and roller bearing rings as thecritical components in rotating machines becomes more of a designtask than making a catalog selection. The analytical and finiteelement approach for fatigue life prediction of such a bearing-applicationis presented. The undertaken approach and the results are illustratedbased on the analysis and fatigue life simulation of theCT (Computed Tomography) -scanner's main rotor bearing. It has beendemonstrated that flexibility of the rings can significantly reduce thefatigue life of the ball bearing. ©2007 ASME