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This paper focuses on the lubrication behavior of starved elliptical Elasto-HydroDynamic (EHD) contacts. Starvation is governed by the amount of lubricant available in the inlet region and can result in much thinner films than occurring under fully flooded conditions. Therefore, it would be desirable to be able to predict the onset and severity of starvation and to be able to relate film reduction directly to the operating conditions and lubricant properties. The aim of this work is to explore the influence of these parameters on starvation. A combined modeling and experimental approach has been employed. The numerical model has been developed from an earlier circular contact study [1]. In this model, the amount and distribution of the lubricant in the inlet region determines the onset of starvation and predicts the film decay in the contact. Numerical simulations for a uniform layer on the surface show that a single parameter, characteristic of the inlet length of the contact in the fully flooded regime, determines the starved behavior. Film thickness measurements under starved conditions were performed to validate this theory. For a circular contact excellent agreement was found. In theory the same mechanism applies to elliptic contacts, however, the behavior is more complicated.

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.

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