Hydrodynamic Lubrication and Elastohydrodynamic Lubrication (Ehl)

Another form of lubrication is the 'elastohydrodynamic' lubrication. In this recipe of lubrication, pressures are large adequate to cause primary elastic deformation of the lubricated surfaces itself. That means there is 'injury' complex for the surfaces in contact. As compared to 'hydrodynamic' lubrication (H.L.), exterior film thickness, sliding appeal and fluid viscosity all play primary roles. Climatic characteristic effects and insufficient lubrication contribute to the 'E.H.L.' film and boundary lubrication also sway the carrying out of lubrication, as much as the 'hydrodynamic' lubrication (H.L.).

The distinguishable ability in the middle of 'H.L.' and 'E.H.L.' involves the added point of material hardness, viscosity increment under high pressure and degree of geometric conformation of the contacting surfaces.

Conformal surfaces will match snugly. Just like the journal in a sleeve bearing with 'hydrodynamic' lubrication, so that the load is carried on a relatively large area. As for 'non' conformal surfaces (2 contacting rollers), the load must be carried on a small area. Commonly, the order of 1000 fold smaller than with a conformal conjunction.

There are the hard 'elastohydrodynamic' lubrication (H.E.H.L.) and soft 'elastohydrodynamic' lubrication (E.H.L.). For 'H.E.H.L.', a best example would be a ball on a flat surface, with load being applied on top of the ball, with the ball rolling on the flat surface. Hence, the rolling action, base in gear teeth, cams and conflict drives. Since the the load is a concentrated one, 'hydrodynamic' lubrication of these 'H.E.H.L.' contacts is ordinarily characterized by a very thin separating oil film that supports local stresses.

As for the 'E.H.L.' or soft 'elastohydrodynamic' lubrication, low experience pressure is involved. Therefore, there is negligible result on fluid viscosity in the conjunction. Analytical relations are simpler for the soft 'E.H.L.', as compared to 'H.E.H.L.' (hard) encountered for rolling element bearings.