Non conventional elastohydrodynamic lubrication

Experimental evidence concerning a mechanism of fluid film lubrication of highly stressed contacts, controlled by both the initial wear and the elastic deformation of surfaces, is presented. This mechanism, designated non-conventional elastohydrodynamic (EHD) lubrication, is likely to occur in point and line contacts with one surface at rest or in other types of contacts if the pressure is extremely high. The mechanism is similar to standard EHD lubrication, the main difference being due to the shape of the surfaces close to the contact zone (non-hertzian), which determines the actual value of film thickness and which may be modified by wear. The friction coefficient is of the same magnitude as in EHD lubrication and an excellent surface finish is achieved. Non-conventional EHD lubrication is sometimes observed in most oiltesting machines, so that care has to be taken when screening oil performance with such machines because the oil viscosity and the pressure coefficients may considerably influence test results. Using a flat pin loaded against a cylindrical surface which moves at low speed, significant test results are reported