Thin layer flow in rolling element bearings


Zoelen, Marco Theodorus van (2009) Thin layer flow in rolling element bearings. thesis.

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Abstract:To extend the service life of rolling element bearings lubricant such as oil or grease is used. In the lubricated contacts between the rollers and the raceways pressures of several GPa can occur. In that case the elastic deformation of the rollers and the raceways has a significant effect on the film thickness and shape. Such contacts are referred to as Elasto-Hydrodynamically Lubricated (EHL) contacts.
When the thickness of the lubricant film in an EHL contact is reduced due to insufficient supply of lubricant, it is operating in the so-called starved lubrication regime. This typically occurs in grease lubricated rolling element bearings. As most bearings are lubricated with grease, accurate prediction of the EHL film thickness in starved lubricated rolling element bearings is of great importance.
The film thickness in a starved EHL contact is directly related to the thickness of the lubricant layers on the running tracks supplied to the contact. Therefore, accurate models predicting the thickness of these supply layers are a prerequisite to the reliable prediction of the film thickness in rolling element bearings operating in the starved regime. In rolling element bearings the thickness of these supply layers is determined by many effects. In this thesis in particular two effects are modelled: the centrifugal effect and the contact pressure effect.
The flow of the liquid layers is effectively modelled using the lubrication approximation. The model is successfully validated experimentally using optical interferometry. It can be used to predict the layer thickness for millions of revolutions and for multiple contacts, without having to solve the starved EHL contact problem for each contact individually.
Item Type:Thesis
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