Investigations on the power losses and thermal behaviour of rolling element bearings

Temperature levels and distributions in rolling element bearings (REBs) depend on many parameters such as load, rotational speed, lubricant, etc. In this context, the understanding of power loss and heat generation mechanisms is a major issue especially for REBs operating at high speeds, since they largely control the component behaviour, its capacity to operate at high temperatures, and ultimately its integrity. It is commonly accepted that the power losses in high-speed bearings can be divided into (a) sliding friction losses in the contacts between the rolling elements and races, (b) sliding friction losses (Couette flow) at the cage/race and cage/rolling elements contacts, (c) oil churning losses for splash and dip lubrication. However, there is no general agreement about two other sources namely rolling friction and drag forces, but it seems that whatever the chosen model be the resulting total power losses are equivalent. In the present study, a thermal network approach is presented in order to estimate the temperatures at different locations within a thrust angular ball bearing. Several power loss distributions inside the REBs are considered and their influences on different power losses and on temperatures along with the important role of the oil—air mixture are highlighted.