Static and Dynamic Characteristics of Rough Porous Rayleigh Step Bearing Lubricated with Couple Stress Fluid

In tribology, the Rayleigh step bearing has the maximum load capacity of any feasible bearing geometry. Traditional tribology resources have demonstrated that the Rayleigh step has an ideal geometry which maximizes load capacity. Both in nature and technology, rough and textured surfaces are essential for lubrication. While surface roughness enhances the performance of the bearings as an efficiency measure, it still has a significant impact on the load-carrying capacity of the bearing. In the present study, we investigate the dynamic characteristics of the Rayleigh step bearing with the impact of surface roughness and a porous medium by considering a squeezing action. Couple stress fluid is considered a lubricant with additives in both the film as well as the porous region. Based on Stokes constitutive equations for couple stress fluids, Darcy’s law for porous medium, and stochastic theory for rough surfaces, the averaged Reynolds-type equation is derived. Expressions are obtained for the volume flow rate, steady-state characteristics, and dynamic characteristics. The influence of surface roughness and the porous medium on the Rayleigh step bearing is analyzed. We investigated the static and dynamic characteristics of the Rayleigh step bearing. As a result, the couple stress fluid increases (decreases) the steady load-carrying capacity, dynamic stiffness, and dynamic damping coefficients, and decreases (increases) the volume flow rate negatively (positively) skewed roughness in comparison with that of the Newtonian case. The results are compared with those of the smooth case

Static and Dynamic Characteristics of Rough Porous Rayleigh Step Bearing Lubricated with Couple Stress Fluid

In tribology, the Rayleigh step bearing has the maximum load capacity of any feasible bearing geometry. Traditional tribology resources have demonstrated that the Rayleigh step has an ideal geometry which maximizes load capacity. Both in nature and technology, rough and textured surfaces are essential for lubrication. While surface roughness enhances the performance of the bearings as an efficiency measure, it still has a significant impact on the load-carrying capacity of the bearing. In the present study, we investigate the dynamic characteristics of the Rayleigh step bearing with the impact of surface roughness and a porous medium by considering a squeezing action. Couple stress fluid is considered a lubricant with additives in both the film as well as the porous region. Based on Stokes constitutive equations for couple stress fluids, Darcy’s law for porous medium, and stochastic theory for rough surfaces, the averaged Reynolds-type equation is derived. Expressions are obtained for the volume flow rate, steady-state characteristics, and dynamic characteristics. The influence of surface roughness and the porous medium on the Rayleigh step bearing is analyzed. We investigated the static and dynamic characteristics of the Rayleigh step bearing. As a result, the couple stress fluid increases (decreases) the steady load-carrying capacity, dynamic stiffness, and dynamic damping coefficients, and decreases (increases) the volume flow rate negatively (positively) skewed roughness in comparison with that of the Newtonian case. The results are compared with those of the smooth case

Effect of Surface Roughness and Viscosity-Pressure Dependency on the Couple Stress Squeeze Film Characteristics of Parallel Circular Plates

Combined effects of surface roughness and viscosity-pressure dependency on the couple stress squeeze film characteristics of parallel circular plates are presented. On the basis of Christensen’s stochastic theory, two types of one-dimensional roughness structures, namely, the radial roughness and azimuthal roughness patterns, are considered and the stochastic modified Reynolds equation for these two types of roughness patterns is derived for Stokes couple stress fluid by taking into account variation of viscosity with pressure. The standard perturbation technique is employed to solve the averaged Reynolds equation and closed form expressions for the mean fluid film pressure, load carrying capacity, and squeeze film time are obtained. It is found that the effects of couple stresses and viscosity-pressure dependency are to increase the load carrying capacity, and squeeze film time for both types of roughness patterns. The effect of azimuthal (radial) roughness pattern is to increase (decrease) these squeeze film characteristics as compared to the corresponding smooth case

On Non-Newtonian Rabinowitsch Fluid Squeeze Film Lubrication between Rough Circular Stepped Plates

In this paper the effect of surface roughness on squeeze film lubrication between circular stepped plates is analysed. The modified non-linear averaged Reynolds type equation is derived on the basis of Christensen’s stochastic theory for rough surfaces for Rabinowitsch fluid model. Accordingly two types of one-dimensional surface roughness patterns, viz., azimuthal roughness pattern and radial roughness pattern are considered. Averaged non-linear Reynolds equation is solved by using the small perturbation method. Expressions are obtained for the load carrying capacity, squeeze film time. It is observed that the effect of azimuthal (radial) surface roughness pattern on squeeze film lubrication between circular stepped plates with Rabinowitsch fluid is to increase (decrease) the load carrying capacity and squeeze film time significantly as compared to the smooth case and the squeeze film performance improves (suffers) due to the use of dilatant (pseudo plastic) lubricants

Combined Effects of Viscosity Variation and Surface Roughness on the Squeeze Film Lubrication of Journal Bearings with Micropolar Fluids

In this paper, a theoretical study of the combined effects of viscosity variation and surface roughness on the squeeze film performance of journal bearings lubricated with micropolar fluid is made. The modified averaged Reynolds equation for micropolar fluids accounting for the randomized surface roughness structure and variation of viscosity is mathematically derived. The Christensen’s stochastic theory for hydrodynamic lubrication of rough surfaces is used to study the effect of two types of one dimensional surface roughness patterns on the squeeze film characteristics of a journal bearing with micropolar fluid. Closed form expressions for the mean pressure load carrying capacity are obtained for the infinitely short journal bearing. It is observed that, the transverse surface roughness pattern improves the squeeze film characteristics where as the adverse effects are observed for the one-dimensional longitudinal surface roughness pattern. The effect of variation of viscosity in micropolar fluid on the squeeze film characteristic of rough short journal bearings is analyzed