A new stress-based fatigue life model for ball bearings

Life prediction is an essential tool in optimizing the selection of rolling bearings in machinery. Over the last several decades, the life factor-based model, based on the Lundberg and Palmgren (LP) model, has been widely accepted both for industry standards and in manufacturer catalogs in the bearing industry. However modeling the increasingly demanding operating conditions of modem machinery, the LP model, even modified by life factors, tends to underestimate bearing fatigue lives, particularly for lower load applications. This is particularly critical for aerospace engine and power transmission applications. A new stress-based fatigue life model is proposed (2). It has been developed in a way such that fatigue life is associated pure Ey with the induced stress field in a power function form. Because the model is stress-based, the empirical data required to complete the model can be obtained using element testing in lieu of the complete bearing testing employed by LP. The fatigue data for the new fatigue life model were generated using a ball/v-ring test rig in which balls are endurance tested to failure. This model, proposed based on element resting, has been compared with LP and the Ioannides-Harris model (IH) models in a meaningful number of actual applications. This research is basically the extension of the previous work by Yu. To demonstrate the feasibility of the proposed model, it is desired, from a practical standpoint, to develop relatively simple equations which relate bearing life to the applied load. It starts with the assumption LP made that bearing life could be represented by bearing geometry and applied load under a simple Hertz loading. The actual deep groove ball bearing data are wed to evaluate the results among these models. The result of the analysis shows that this simple model derived from the stress-based model could also be a more accurate predictor of bearing life than either the LP or IH model.