A New Thermal Model of an Angular Contact Ball Bearings, in a Standard Arrangement, subjected to Radial Loads, based on State Variables and Control Volumes

Permanent or temporary failures in bearing systems are often caused by excessive or prolonged heat generation, within an angular contact ball bearing, during operations arising from external loads. Considering the complexity of getting experimental thermal measurements in an angular ball bearing arrangement, analytical techniques must be utilized in order to predict the thermal behavior thereof, taking into account variables such as rotational speed, the type of load and the operational conditions. The aim of this study is the development of a thermal model applying the state -space approach, able to predict thermal characteristics of an angular contact ball bearing in standard arrangement subjected to radial loads. For this purpose, an angular ball bearing, model 7203BEP, in standard arrangement, was treated as the representative model. The arrangement was divided into three independent control volumes, these are, the inner -race, the ball and the outer-race/housing. Thereafter, the energy equation and the theory of rolling contact heat transfer are utilized to determine heat fluxes and temperature variations between the contact regions. The thermal resistances developed between the ball/ inner -race, outer -race/ ball, inner -race/ shaft and outer -race/ housing were calculated as variables depending on the rotational speed, wherewith the thermal analysis is performed. Space variables including, temperature of the inner -race Ti , temperature of the balls Tb and temperature of the outerrace/ housing Toh were calculated and the results were compared by Finite Element Analysis simulations using Ansys transient thermal software. The findings herein, show that the maximum value of mean deviation of temperature obtained with the proposed thermal model and the Finite Element Analysis (FEM) simulations was less than sd < 3.50%, hence, indicating that the model is in good agreement with the numerical solutions. In this manner, the presented thermal model can be utilized, as an observer, to predict the thermal behavior, in different types of angular contact ball bearings, that undergo radial loads. Furthermore, the thermal model provides relevant information for further studies, related to thermal distribution in machine components.