Elastohydrodynamic Line-Contact of Compressible Shear Thinning Fluids With Consideration of the Surface Roughness

Abstract

Applications involving highly loaded elastohydrodynamic lubrication (EHL), particularly when the lubricant experiences shear thinning, operating with small film thicknesses may necessitate consideration of surface asperities. A modified Reynolds equation with provision for surface roughness and shear thinning is treated to predict the pressure and surface asperity effect in an EHL line-contact. The unknown in the Reynolds equation is the hydrodynamic pressure instead of the total pressure to ensure that the pressure boundary condition at the outlet is properly posed. The Carreau viscosity model is used for characterizing the shear thinning behavior, Patir and Cheng flow factors for taking into the influence of roughness on the lubricating film, and Greenwood–Trip for determination of pressure at the asperity level. The modified Reynolds equation is solved for the hydrodynamic pressure instead of the total pressure with appropriately defined boundary conditions.