Few rolling bearing users realize that the fundamentals of bearing life predictions are based on experimental data derived under conditions very different from the ones generally used in RCF testing today. The basic life formulas derived in the 1940s largely were based on tests run on steel with very different characteristics than the materials used to produce bearing components today. Still, the fundamental life calculations are based on the (C/P)n concept, which was experimentally derived by Lundberg and Palmgren (Lundberg, G. and Palmgren, A., "Dynamic Capacity of Rolling Bearings," Acta Polytech. Scand., Mech. Eng. Ser., Volume 1, No. 3, 1947), even if the basic equation has been expanded and adjusted to reflect the lives recorded for modern bearings and to incorporate the concept of a fatigue limit (Ioannides, E., Bergling, G., and Gabelli, A., "An Analytical Formulation for the Life of Rolling Bearings," Acta Polytech. Scand., Mech. Eng. Ser., Volume 137, 1999, pp. 9-12, 21-24). In an attempt to better understand the premature and unpredictable failures that sometimes occur in certain industrial applications today, the test procedures used by Lundberg and Palmgren have been revisited, and data have been derived that might contribute to an understanding of the short lives sometimes experienced in certain industrial bearing applications. Based on this test procedure, a better understanding of the development of micro-crack associated plastic deformations at non-metallic inclusions also has been gained. The propensity of different non-metallic inclusions to drive the formation and growth of micro-cracks has been studied in detail, and this knowledge has been used to develop steel that is less prone to butterfly development and micro-crack growth under very high contact stress conditions. Today's bearing life prediction models presume that the Palmgren-Miner rule of accumulated damage is globally applicable. Experimental data questioning this assumption are presented.

Many of the engineering problems of particular importance to railways arise at interfaces and the safety-critical role of the wheel/rail interface is widely acknowledged. Better understanding of wheel/rail interfaces is therefore critical to improving the capacity, reliability and safety of the railway system.Wheel-rail interface handbook is a one-stop reference for railway engineering practitioners and academic researchers. Part one provides the fundamentals of contact mechanics, wear, fatigue and lubrication as well as state-of-the-art research and emerging technologies related to the wheel/rail interface and its management. Part two offers an overview of industrial practice from several different regions of the world, thereby providing an invaluable international perspective with practitioners' experience of managing the wheel/rail interface in a variety of environments and circumstances.This comprehensive volume will enable practising railway engineers, in whatever discipline of railway engineering – infrastructure, vehicle design and safety, and so on – to enhance their understanding of wheel/rail issues, which have a major influence on the running of a reliable, efficient and safe railway. - One-stop reference on the important topic of wheel rail-interfaces - Presents the fundamentals of contact mechanics, wear, fatigue and lubrication - Examines state-of-the-art research and emerging technologies related to wheel-rail interface and its management

Current bearing life models significantly under predict the life of bearings made of modern ultra-clean steels. New life models that include the constitutive response of the material are needed. However, the constitutive response of bearing steel is known to change during bearing operation. In the current study, the evolution of the mechanical properties of M50 bearing steel due to rolling contact fatigue (RCF) was investigated. A combination of M50 balls and rods were subjected to RCF testing under various conditions (e.g. number of RCF cycles, applied Hertzian stress, and interacting material). Additionally, some of the balls tested went through a proprietary mechanical process to induce compressive residual stresses over the first several hundred microns into the depth of the ball prior to RCF testing. After RCF testing, the specimens were subjected to a number of tests. First, the residual stresses within the subsurface RCF affected region were measured via x-ray diffraction. The residual stresses within the mechanically processed (MP) balls were found to not significantly change due to RCF, while a linear relationship was found between the maximum residual stress with the RCF affected zone and the Hertzian stress for the unprocessed balls. Then, the specimens were sectioned, polished, and chemically etched to study the evolution of the microstructure due to RCF. A similar relationship was found between the size of the dark etching region (DER) and the Hertzian stress.

A description of a novel rolling contact fatigue test for evaluation of bearing steel characteristics is presented. Unlike traditional approaches where bearings are tested until failure, the proposed testing method is based on monitoring the material response during testing. The measurement principles are based on changes of the surface geometry, such as grooving, because of accumulation of subsurface micro-plastic damage and on observations of related changes in the steel micro-structure. The test method is complemented by introducing a detailed material model that is used to model the groove development. The model is used to analyse the groove data and yields dedicated material property parameters, which can be used directly to model general material behaviour under rolling contact fatigue conditions. An example is given to illustrate the method and its use in assessing bearing steel performance.