Journal bearings are widely used in many industrial applications. In journal bearings, under boundary lubricated conditions, the surfaces are considered to be technically dry or only slightly lubricated, so that the resistance to relative motion is due to the interaction between the highest asperities covered by the boundary film. A thin film of lubricating oil exists under this condition and there is partial metal to metal contact. The ideal situation where the two sliding surfaces are completely separated by a thin film of a viscous fluid or a gas is referred to as hydrodynamic lubrication. In hydrodynamic bearings, due to frequent starting and stopping, misalignment of the shaft with the bearing, application of heavy loads and unexpected sudden non flow of lubricant and such other service conditions result in boundary lubrication by squeezing out the lubricating film or allow the surface asperities to break through the film so that the shaft and bearing are pressed into contact with one another. The maximum wear occurs in fluid film bearings during boundary lubricated conditions. The use of dry bearings has therefore become more essential as it requires practically no lubricant to function. Moreover it is less expensive, resist contamination better compared to rolling element bearings and easier to design.

This content is only available via PDF.
You do not currently have access to this content.