Nearly five decades have passed since G. Lundberg and A. Palmgren published their life theory in 1947 and 1952 and it was adopted as an ANSIIABMA and ISO standard in 1950 and 1953. Subsequently, many variations and deviations from their life theory have been proposed, the most recent being that of E. Ioannides and T.A. Harris in 1985. This paper presents a critical analysis comparing the results of different life theories and discussing their implications in the design and analysis of rolling-element bearings. Variations in the stresslife relation and in the critical stress related to bearing life are discussed using stress fields obtained from three-dimensional, finite-element analysis of a ball in a nonconforming race under varying load. The results showed that for a ninth power stress-life exponent the Lundberg-Palmgren theory best predicts life as exhibited by most air-melted bearing steels. For a 12th power relation reflected by modem bearing steels, a Zaretsky-modified Weibull equation is superior. The assumption of a fatigue-limiting stress distorts the stress-life exponent and overpredicts life. in-plane shear stress, Pa (psi)

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A roller bearing model, which includes the effects of full film lubrication at the race contacts, was developed for use in estimating cage slip, roller slip, film thickness, and cage forces for a given bearing geometry and operating condition.The model includes churning loss, cage pilot surface friction, roller pocket friction, cage unbalance as well as the drag due to the unloaded rolling elements. Roller skew and misalignment have been neglected, however these effects could be introduced if desired.The description of the lubricant film thickness, traction, and pressure forces are based upon assumptions introduced by Dowson, which reduce the complex numerical procedure required for a rigorous solution to the isothermal elastohydrodynamics problem to a set of nonlinear equations. A parametric study on a 1907 basic roller bearing is included to illustrate the use of such a model as a design tool.

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