Combined Effects of Surface Adhering Layer and Surface Elastoplastic Deformation in Hydrodynamic Lubricated Line Contacts with Long-Chain-Molecule Fluids

Abstract

In a line contact, when the surface separation is smaller than one hundred times of the thickness of the adsorbed boundary layer on the contact surface, the hydrodynamics should be considered as multiscale and consisting of both the adsorbed layer flows and the intermediate continuum fluid flow. However, for the fluids with long-chain molecules, there may be only one or several fluid molecule layers on the contact surface, which can be considered as a solid layer. The multiscale hydrodynamic film thickness was calculated for such fluids in the line contact which is respectively elastic or fully plastic under different loads. The results show that in the micro line contact with small equivalent curvature radii (R) such as on the 10 micrometer scale like the surface asperity contact, the adsorbed boundary layer has a very strong effect on the hydrodynamic behavior, while in the macro line contact such as with R on the 10 mm scale the adsorbed layer effect is eliminated and it is significant only for small rolling speeds or/and heavy loads.