The Influence of Surface Roughness and Piezo-Viscous Lubricant Properties on the Elastohydrodynamic Line Contact Lubrication

Abstract

In this paper a numerical solution of the elastohydrodynamic line (EHL) contact lubrication problem is presented for a cylinder which is rolling over a flat plane. As is well known, the properties of the lubricant play a significant role in the forming of a lubricating film and reducing friction between the contacting surfaces. Pressure profiles and film shapes are shown and variations of the minimum film thickness with dimensionless parameters are also presented. The influence of pressure and temperature on viscosity, limiting shear stress and density, has been taking into account when lubricant models have to be used in numerical calculation of film thickness and friction. The effects of different pressure–viscosity relationships, including the exponential model, the Roelands model and the free-volume model, are investigated on modelling in the best possible way the real piezo-viscous behaviour at pressures as high as the typical EHL pressures. The role of surface roughness on EHD lubrication has become crucial, for this reason its effect on the pressure profile and film thickness in a steady state EHL line contact is, also, investigated by means of numerical simulations. One of the purposes of this work, in fact, is to show how the pressure profile and film thickness are influenced by surface asperity, not only by modelling the roughness using deterministic or averaging techniques, but by introducing a real surface topography of the contact surfaces. The roughness data of a real surface has been collected using a three-dimsional no-contact profilometer based on confocal microscopy technology.