Tribological behavior of a rough Rayleigh step slider bearing under variable viscosity and couple stress lubrication with slip boundary condition

Abstract

The dynamics of lubrication in bearing systems are investigated in this work, with a specific focus on couple stress fluids and surface roughness. The impact of surface roughness significantly influences the pressure distribution and load-carrying capacity in hydrodynamic bearings, particularly in thin-film and transient lubrication settings where microscale effects become more noticeable. In this study, the properties of a rough Rayleigh step slider bearing are investigated by considering the combined effects of slip velocity, couple stress and variable viscosity. The Stokes couple-stress fluid model is used to generalize derived Reynolds equation, and a perturbation method is used to generate solutions of the associated non-dimensional governing equation in a closed-form. The study reveals dimensionless frictional force, load carrying capacity and pressure increases as the transverse roughness, viscosity variation and couple stress increases and decreases with longitudinal roughness, slip velocity and minimum film thickness. Whereas coefficient of friction shows the opposite trend with surface roughness, slip velocity and minimum film thickness. The findings of this study are applicable to the design and performance optimization of high precision tribological components such as, thrust bearings, mechanical seals and micro-scale lubrication system operating under non-Newtonian and surface roughness effects.