Life prediction in rolling element bearings

Rolling elements were the first components to be subjected to stochastic life prediction methods. The Weibull life model was adopted by Lundberg and Palmgren as early as 1947 and since then it has been used as the basis of National and International Standards and has gradually been modified to incorporate emerging knowledge of lubrication and to predict the life increases of the constantly improving bearings. It focuses on the most appropriate failure mode of those times, the subsurface-originated fatigue. Bearings have however, been continuously improved in terms of design, manufacturing precision, steel integrity and heat treatment and their calculated lives, according to the above methodology, are now seriously under-predicted. Moreover, bearing failures now predominantly occur on the surface. This paper reviews all levels of modern modelling which increasingly use realistic stress distributions in the steel, generalised fatigue criteria and an endurance limit. It is therefore now possible to calculate the life of rolling bearings under more realistic application conditions where the site of failure shifts to the surface and effects of roughness, contamination, edge and internal (hoop and residual) stresses can be included in the life calculations.