Abstract
Rolling bearings are the second most used machine components. They work in what it is called elastohydrodynamic lubrication regime. The geometry of rolling element bearings makes the direct measurement of the lubricant film thickness a challenging task. Optical interferometry is widely used in laboratory conditions for studying elastohydrodynamic lubrication however it cannot be used directly in rolling element bearings thus the only suitable methods are electrical techniques. Of these, film thickness measurement based on electrical capacitance of the contacts has been used in the past by a number of authors. One of the limitations of the capacitance method, when used in rolling bearings, is that it cannot distinguish between the contacts of every rolling element and raceway on one hand and on the other between the inner and outer ring contacts. In the present study the authors used an original test rig which can measure the film thickness for only one ball and separately for the inner and outer rings of a radial ball bearing. This paper thus shows for the first-time results of the lubricant film thickness, at the inner and outer raceways, in grease lubricated rolling bearings.
Highlights
Rolling elements bearings are found in most machines and equipment which include parts in relative rotation which makes them the second most numerous machine elements in use nowadays
The principles of optical interferometry and its various ways in which it is applied to the study of elastohydrodynamic contacts has been published extensively during the past fifty years[1,2,3,4,5] and it will not be detailed in this paper
In normal operation of rolling element bearings, where the outer ring is usually fixed, the entrainment velocity at both contacts is given by the relationship: U
Summary
Rolling elements bearings are found in most machines and equipment which include parts in relative rotation (or translation) which makes them the second most numerous machine elements in use nowadays. One element of greatest importance for the proper operation of bearings is the lubricant, more precisely the lubricant film formed between the rolling elements and the raceways. This ensures that the metallic surfaces are in no direct contact, avoiding seizure, premature wear, and catastrophic failure of the elements and of the whole assembly they are part of. The small contact area and large pressures between rolling elements and raceways due to the non– conformity of their surfaces lead to very thin lubricant films, a regime of lubrication known as elastohydrodynamic (EHD). The principles of optical interferometry and its various ways in which it is applied to the study of elastohydrodynamic contacts has been published extensively during the past fifty years[1,2,3,4,5] and it will not be detailed in this paper
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Schedule a callMore From: Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology
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