The Influence of Surface Roughness on Elastohydrodynamic Traction

If the ratio λ of the nominal elastohydrodynamic film thickness h₀ to the root-mean-square roughness is greater than about 5, the traction between two rolling and sliding surfaces is negligibly influenced by surface roughness. The traction is then primarily a function of the parameter _α0 , as described in reference (4), where is the mean contact pressure and α_o is the pressure–viscosity index of the lubricant. When λ lies in the range 0.5–6, it is shown that the effect of asperity interaction is for the traction to still be governed by the bulk rheological properties of the oil, but at a pressure corresponding to the mean contact pressure of the asperities.