RECONSTRUCTION OF ELASTOHYDRODYNAMICLUBRICATION THEORY

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On the basis of direct observations of point contact elastohydrodynamic lubrication (EHL) films under rolling/sliding conditions using the optical interferometric technique, it has been asserted that a new EHL theory should be constructed by taking into account the effects of differences in elastic moduli of the contacting surfaces, surface pressure components parallel to the tangent contact plane, and the solidification phenomenon of lubricating oils. The other main results are summarized as follows :(1)In the EHL conjunction shear flow dominates the fluid flow and pressure induced flow is almost absent.(2)As a result, a local oil film flows approximately at the average speed of the surfaces while holding the shape and thickness.(3)A local reduction in film thickness occurs at a certain area downstream and upstream of a groove or a dent according to a positive and negative values of slide-to-roll ratio, respectively. The local film reduction area increases as the value of slide-to-rol … More l ratio.(4)The recovery of the reduced film thickness to the smooth.surface value is attained by fluid entering the EHL area from the inlet and the flowing into the film reduction area across the groove or the dent in the direction of sliding.(5)If the wavelength of grooves is more than a|SIGMA|, reduced film thicknesses produced by the grooves never interfere, where a is the Hertzian contact radius and SIGMA is the slide-to-roll ratio.(6)Under conditions of a higher frequency of reciprocation and a shorter stroke length, the formation of a stable EHL film is inhibited. This is because air bubbles produced in the preceding stroke result in the oil starvation in the succeeding reverse stroke.(7)When the surface velocity of the body having a lower elastic modulus is faster than that of the body having a higher elastic modulus and when the radius of curvature of the former is larger than that of the latter, a deep conical depression (dimple) is produced in the contact area. The dimple behaves like a solid rather than a liquid, and the formation is dominated by the inside rather than inlet conditions. Less