Effects of couple stresses and surface roughness on the film thickness of heavily loaded rollers

Abstract

PurposeThis paper aims to study the effects of couple stresses and surface roughness on the minimum film thickness of heavily loaded rollers and to discuss these by following Grubin's approach and Crook's approximations.Design/methodology/approachA generalised form of Reynolds equation for rough surfaces with lubricant as couple stress fluid is derived. This equation is then used to study the combined effect of couple stresses and surface roughness on the roller bearings under heavily loaded conditions. EHD minimum film thickness expressions is obtained by following Grubin's approach and Crook's approximation and it is studied numerically.FindingsIt is found that, as the chain length of the additive molecules increases, the elastohydrodynamic minimum film thickness increases. Also, as the mean height of roughness asperities increases, the elastohydrodynamic minimum film thickness increases for the transversal roughness and it decreases in the case of longitudinal roughness.Research limitations/implicationsThese effects are studied theoretically by the mathematical equations in heavily loaded roller bearings.Practical implicationsReduction of the film thickness in the EHD lubrication between the rollers can be compensated by the use of lubricants containing additives of molecules of size. As a result the bearing performance can be improved.Originality/valueThis research paper provides a closed form of the expressions for the bearings in EHD lubrication and is studied with regard to couple stress parameter. This paper helps to manufacture better bearings.