Showing papers by "Satish C. Sharma published in 2018"

Influence of dimple geometry and micro-roughness orientation on performance of textured hybrid thrust pad bearing

Abstract: The present study deals with numerical simulation of textured hybrid thrust pad bearing. Influence of providing micro-dimples of different cross-sectional shapes on the bearing surface has been theoretically investigated on the performance of thrust pad bearing. Reynolds equation has been solved using mass-conserving algorithm based on Jakobsson–Floberg–Olsson cavitation boundary conditions. A parametric study is carried out to optimize dimple shapes from the viewpoint of load carrying capacity of bearings. The textured bearing surface is noticed to be beneficial in reducing the frictional power losses. Providing half-section dimples (second half in the direction of runner rotation) towards the leading edge of thrust pad, enhance the load carrying capacity and fluid film stiffness coefficient of bearings. Micro-roughness in a textured surface having transverse orientation is seen to improve the dynamic characteristics of hybrid thrust pad bearings.

Dynamic characteristics of compensated hydrostatic thrust pad bearing subjected to external transverse magnetic field

Abstract: This article presents finite element analysis to evaluate the performance of a compensated hydrostatic circular thrust pad bearing in the presence of a magnetic field. The influence of the magnetic field on the flow of an electrically conducting lubricant is expressed by incorporating the Lorentz force in the momentum equation, described by Maxwell equations and Ohm’s law. The modified Reynolds equation has been derived for a lubricant blended with long-chain polymer additives flowing in the presence of a transverse magnetic field. The Stokes couple stress theory has been used to describe effect of such additives on lubricant rheology. A source code has been developed in MATLAB to solve the modified Reynolds equation coupled with restrictor flow equations using the finite element method. The performance characteristics of the bearing system are evaluated in terms of pocket pressure, load-carrying capacity, lubricant flow rate, fluid film stiffness and damping coefficient. Comparative studies have been carried out for orifice and capillary compensated bearings. The limiting cases of the modified Reynolds equation yield performance characteristics of specific lubricants such as electrically conducting couple stress lubricant, couple stress lubricant, electrically conducting lubricant and Newtonian lubricant. It is noticed that the load-carrying capacity, fluid film stiffness and damping capabilities of the bearing get enhanced quite substantially in the presence of couple stress additives and a magnetic field.

Finite element method analysis of hydrostatic thrust pad bearings operating with electrically conducting lubricant

Abstract: A theoretical investigation has been carried out to explore the use of electrically conducting fluids as lubricants in circular and elliptical hydrostatic thrust pad bearings subjected to transverse magnetic field. Flow of electrically conducting fluid in the presence of external transverse magnetic field is represented by the addition of Lorentz force in Navier–Stokes equation. A MATLAB source code based on finite element formulation of the modified Reynolds equation is developed for obtaining static and dynamic characteristics parameters of the bearing. Influence of aspect ratio (major/minor-axis) and magnetic field (Hartmann number) are analyzed on the performance of elliptical pad bearing. Application of electrically conducting lubricant in the elliptical pad is observed to provide higher values of fluid film stiffness (44.93%) and damping (139.37%) coefficients as compared to the circular pad operating with Newtonian lubricant.

A direct numerical approach to compute the nonlinear rotordynamic coefficient of the noncircular gas journal bearing

Abstract: Gas bearings are extensively used in several industrial applications to support the rotating load at high speed due to its favorable characteristics. The numerical computation of the gas film dampi...

A study on performance of slot entry hybrid journal bearing considering effect of surface irregularities

Abstract: Purpose This study aims to deal with the performance of symmetric/asymmetric slot entry hybrid journal bearing system considering the effect of three dimensional irregularities in the analysis. Design/methodology/approach The asperity profile of three-dimensional irregularities has been modeled in both circumferential and axial directions. To compute the bearing performance characteristics parameter, finite element formulation of governing Reynolds equation has been derived using Galerkin’s technique. Findings Based on the numerically simulated results, it has been observed that the three-dimensional irregularities enhance the value of minimum fluid film thickness (hmin), lubricant flow (Q) and fluid film damping coefficients (C11,C22) approximately by order of magnitude of 24-26, 43-51 and 18-66 per cent, respectively, for the case of asymmetric slot entry configuration. Whereas, the values of fluid film stiffness coefficients (S11,S22) and threshold speed (ωth) reduces approximately by order of 1-6 and 0-3 per cent, respectively, for the case of symmetric slot entry configuration. Originality/value The present paper describes that the influence of three-dimensional irregularities on bearing surface on the performance of slot entry hybrid journal bearing is original in literature gaps. The numerically simulated results presented in this study are expected to be quite useful to the bearing designers.

Numerical modeling of elastohydrodynamic lubrication of line contact lubricated with micropolar fluid

Abstract: This paper presents numerical investigation on elastohydrodynamic lubrication (EHL) of line contacts lubricated with micropolar fluids. Numerical model of EHL line contact has been developed by coupled solution of Reynolds equation, elastic deformation equation, load balance equation and fluid rheology equation from inlet to the outlet region. This system of equations has been solved using finite element method techniques. The influence of micropolar fluid parameters and operating parameter on the performances EHL line contacts has been investigated. Further, a comparative assessment on the micropolar and Newtonian fluid-lubricated contact has been presented. It has been observed that the use of micropolar fluid parameters enhances the values of minimum and central fluid film thickness and contact pressure within the EHL line contacts. The empirical formulae for minimum $$\left( {\bar{H}_{\hbox{min} } } \right)$$ and central $$\left( {\bar{H}_{\text{cent}} } \right)$$ fluid film thickness are formulated based on the numerically simulated results. The study reveals that overall performances of EHL line contacts increases significantly with micropolar fluid parameter. Further, it has been observed due to micropolar lubricant in EHL line contacts, chances of metal-to-metal contact reduces.

An experimental study on tribological performance and surface characteristics of lubricated point contact

Abstract: The aim of the present study is to investigate the effect of operating parameters (load, speed, and temperature) on the tribological performance and surface characteristics (skewness and kurtosis) of lubricated point contacts. For this purpose, experimental studies were carried out on a four-ball wear tester, using the Taguchi design of experiments concept. The tribo-contact performance in terms of contact friction and wear is monitored and recorded. The used test specimens thereafter were examined using the microscope and 3D surface profilometer at the end of the experiments. The combined effects of operating parameters on tribological performance and surface characteristics have been analyzed using the statistical technique of analysis of variance. Further, the composite desirability optimization method associated with response surface methodology has been employed to develop the regression equations in order to predict the contact performance characteristics for any given combination of operating conditions. The study undertaken reveals that the operating parameters significantly influence the tribo-performance and surface characteristics of lubricated point contacts. The developed regression equations are expected to offer an effective analytical tool for accurately predicting the performance characteristics of lubricated point contacts.

Finite Element Simulation of Wheel-Rail Interaction: Technical Note

Abstract: This paper deals with quasi-static analysis of wheel-rail interaction. The model has been developed for analysing the contact patches behaviour, pressure distribution, von mises stress and strain. A solid model has been developed using SOLIDWORKS on the basis of UIC-60 rail profile and S-1002 wheel profile. Finite element analysis of the solid model has been done using ANSYS software. It has been observed that wheel-rail interaction is nonlinear and exceeded the yield strength of wheel material. The analysis of the worn thread of wheel has enabled the identification of the contact patches and critical sections of the wheel-rail interface.