Abstract
Ball bearings are an integral part of many machines and mechanisms and often determine their performance limits. Vibration, friction and power loss are some of the key measures of bearing performance. Therefore, there have been many predictive analyses of bearing performance with emphasis on various aspects. The current study presents a mathematical model, incorporating bearing dynamics, mechanics of rolling element-to-races contacts as well as the elastodynamics of the bearing outer ring as a focus of the study. It is shown that the bearing power loss in cage cycles increases by as much as 4% when the flexibility of the outer ring is taken into account as a thick elastic ring, based on Timoshenko beam theory as opposed to the usual assumption of a rigid ring in other studies. Geometric optimisation has shown that the lifetime power consumption can be reduced by 1.25%, which is a significant source of energy saving when considering the abundance of machines using rolling element bearings. The elastodynamics of bearing rings significantly affects the radial bearing clearance through increased roller loads and generated contact pressures. The flexible ring dynamics is shown to generate surface waviness through global elastic wave propagation, not hitherto taken into account in contact dynamics of rollers-to-raceways which are generally considered to be subjected to only localised Hertzian deflection. The elastodynamic behaviour reduces the elastohydrodynamic film thickness, affecting contact friction, wear, fatigue, vibration, noise and inefficiency.
Highlights
Key issues affecting the performance of rolling element bearings are wear and fatigue of rolling mating surfaces,[1,2,3] as well as vibration and noise.[4,5,6,7] Thermal stability plays an important role in terms of bearing’s limiting performance.[8,9] All these parameters act in an integrated manner, determining the eventual bearing performance
The predicted power loss in motors, rotors and gearboxes where bearings are used in abundance increase with realistic bearing models such as the one presented in this study
A geometric investigation has shown that the losses induced by an elastic outer ring can be reduced by up to 1.25%
Summary
Key issues affecting the performance of rolling element bearings are wear and fatigue of rolling mating surfaces,[1,2,3] as well as vibration and noise.[4,5,6,7] Thermal stability plays an important role in terms of bearing’s limiting performance.[8,9] All these parameters act in an integrated manner, determining the eventual bearing performance. Sunnersjo€11 was one of the first to investigate the effect of applied inertial forces using a two degree of freedom lateral transverse analytical bearing dynamics model. Meyer et al.[12] studied the effect of distributed defects such as waviness of the rolling mating surfaces upon the bearing vibration response using an analytical two degrees of freedom bearing model. Rahnejat and Gohar[5] presented a 2-degree of freedom radial deep groove ball bearing model with lubricated ball-to-races contacts under various regimes of lubrication. They studied the effect of inner race waviness. The effect of roller tilting, yawing and squeeze film motions, as well as lubricated contacts were taken into account by various researchers.[10,14,15] Misaligned rollers cause high edge contact
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