Purpose Nowadays, the use of Newtonian fluid as a lubricant is diminishing day by day, and the use of non-Newtonian fluids has gained importance. This paper presents an analysis of the static characteristics of Rayleigh step slider bearing lubricated with non-Newtonian Rabinowitsch fluid, which has not been studied so far. The purpose of this paper is to derive the modified Reynolds equation for Rabinowitsch fluids for two regions and to obtain the optimum bearing parameters for the Rayleigh step slider bearings. Design/methodology/approach The governing equations relevant to the problem under consideration are derived. The modified Reynolds equation is derived, and it is found to be highly non-linear and hence small perturbation method is adopted to find solution. Findings From this study it is found that there is an increase in the load-carrying capacity, pressure and frictional coefficients for dilatant fluids as compared to the corresponding Newtonian case. Further, for dilatant lubricants the maximum load-carrying capacity is attained for the slightly larger values of entry region length of Rayleigh step bearing as compared to Newtonian and pseudoplastic lubricants. Originality/value Rabinowitsch fluid is used for the study of lubrication characteristics of Rayleigh step bearings. The author believes that the paper presents these results for the first time.

The effect of surface roughness on static and dynamic characteristics of parabolic slider bearing lubricated with couple stress fluid in the presence of magnetic field is theoretically analysed in this paper. The modified stochastic MHD couple stress Reynolds-type equation is derived on the basis of Christensen stochastic theory and considered two types of roughness pattern namely longitudinal and transverse. Expressions for steady pressure and load, dynamic stiffness and damping coefficients are obtained for both roughness patterns. Compared to smooth surface, transverse roughness pattern provides larger load-carrying capacity, dynamic stiffness and damping coefficients, whereas longitudinal roughness pattern has adverse effects. The presence of couple stress and applied magnetic field improves the bearing performance.

The effect of surface roughness on static and dynamic characteristics of inclined plane slider bearing lubricated with couple stress fluid in the presence of magnetic field is theoretically analysed. The modified stochastic MHD couple stress Reynolds type equation is derived on the basis of Christensen stochastic theory by considering two types of onedimensional roughness patterns namely longitudinal and transverse. Expressions for steady pressure and load, dynamic stiffness, and damping coefficients are obtained for both the types of roughness patterns. Compared to smooth surface, transverse roughness pattern provides larger load carrying capacity, dynamic stiffness, and damping coefficients whereas longitudinal roughness pattern has adverse effects. Further, the presence of couple stress and applied magnetic field improves the bearing performance.Bearings ensure high efficiency and reliability depending on their size, type of functioning, materials used in manufacturing and use of fluid for lubrication. In earlier studies of bearings, the lubricant is assumed to be Newtonian fluid which is not a satisfactory approach for the practical applications. Many researchers worked to overcome this limitation and found that, by adding some amount of long chained polymers to Newtonian fluid, the desirable lubricant can be obtained. Many theories were proposed to represent the use of non-Newtonian fluids. Among these, the simplest generalization of classical theory proposed by Stokes [1], which allows for polar effects such as the presence of body couples and couple stresses. Many investigators used this couple stress fluid theory to study the effect of couple stress on the bearing performance such as, the flow between finite plates by Ramanaiah [2], partial journal bearing by Lin [3] and double layered porous slider bearing by Bujurke et al. [4]. These studies shown that, the use of couple stress fluids enhances bearing performance as compared to Newtonian case.The study of dynamics of flow of electrically conducting fluid with the application of magnetic field is known as magnetohydrodynamic (MHD). Several investigators were studied the effect of applied magnetic field on the performance of bearings such as lubrication of bearing in the presence of magnetic field by Agarwal [5], slider bearing by Snyder [6], squeeze film by Hazma [7] and finite slider bearings by Lin [8]. They concluded that the applied magnetic field increases the load carrying capacity and decreases the frictional force. The results obtained for the effect of MHD and couple stresses motivated several researchers to study combined effects of MHD and couple stress. The combined effect of MHD and couple stress were studied by several investigators, such as slider bearing by Das [9], sphere and plane surface by Naduvinamani and Rajashekar [10], squeeze film between parallel surfaces by Kudenatti et al. [11] and different types of finite plates by Fathima et al. [12]. According to these studies, the combined effect of MHD and couple stresses results in enh...

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