Showing papers by "Satish C. Sharma published in 2015"

Two-lobe geometrically imperfect hybrid journal bearing operating with power law lubricant

Abstract: The present paper investigates the influence of journal’s geometric imperfections on the performance of capillary compensated two-lobe hybrid journal bearing system. Different geometric imperfections of journal, viz. barrel, bellmouth and circumferential waviness have been included in the study. A parameter called offset factor has been included in the analysis which distinguishes between two lobe and circular journal bearing. Further, the Reynolds equation has been modified by using power law model in order to deal with non-Newtonian effect of the lubricant. The numerically simulated results indicate that non-circularity of bearing and barrel shape irregularity significantly increase the values of S¯zz,C¯zz and ω¯th by a factor 36.47, 51.34 and 18.52%, respectively, with respect to the base bearing (circular ideal journal bearing) operating with non-Newtonian lubricant.

Combined influence of geometric irregularities of journal and turbulence on the performance of four-lobe hybrid journal bearing:

Abstract: The present study deals with the influence of geometric irregularities of journal (barrel type, bellmouth type and undulation type) on the performance of capillary compensated four-lobe multirecess...

A parametric investigation on the microelastohydrodynamic lubrication of power law fluid lubricated line contact

Abstract: A parametric study of microelastohydrodynamic lubrication contact between rough cylinder and plane lubricated with non-Newtonian power law fluid is carried out. A Gaussian rough surface is considered and modeled using stochastic approach. A theoretical solution of pressure distribution, fluid film thickness, and friction for given speeds, material properties, slide-to-roll ratio, and power law index, is obtained by solution of Reynolds equation using finite element method techniques. An isotropic roughness pattern is considered and results are obtained for wide range of operating parameters. The results indicate that the shear-thickening fluids provide thicker lubricant films as compared to shear-thinning fluids. The minimum fluid film thickness is observed to decrease with an increase of load and it increases with an increase of speed and material parameter. Slide-to-roll ratio has a marginal influence of the minimum film thickness. Under certain operating conditions, softer materials with shear-thickeni...

Effect of vertical track irregularities on the dynamics of freight railway wagon

Abstract: This paper describes mathematical modelling of a freight railway wagon of Indian railways. The freight wagon is modelled as nine-degrees of freedom system. The equations of motion are derived using Newtonian approach. Rail surface vertical profile irregularity of sinusoidal type is taken as input for both the wheels. The frequencies at which these irregularities occur correspond to the natural frequency of the carbody. The equations of motion are solved by MATLAB using a fourth order Runga-Kutta algorithm with a fixed step size. Time domain responses are obtained for different input frequencies and loading conditions while maintaining the wagon speed constant. The effect of variation of the input frequencies of track irregularities and the loading condition on the dynamic behaviour of the carbody is discussed. It has been observed that the empty carbody gets excited to a severe level of acceleration even at lower resonant frequency and a dense region appears near the resonant frequency peak in FFT. The phase trajectories show quasi-periodic nature of response for empty carbody.

Subsurface crack propagation with different inclusion under a wheel–flat LEFM analysis using dynamics conditions

Abstract: Railway wheels fail owing to fatigue during long runs. During running frequent braking and jamming of brakes causes wheels to skid over rails and material to be removed from the tread. This frequent skidding that removes large amounts of metal from the surface is known as wheel–flat defect. In this paper the model of the wheel with 'flat' defect using FEA and a subsurface crack in the vicinity of the defect is studied. Owing to rolling contact fatigue the subsurface crack propagates and removes a large material from the tread. If flat defect is not detected early the subsurface crack can originate in the vicinity owing to the presence of a cavity or inclusion and may lead to fatal accidents. Stress intensity factor has been obtained for the crack propagation caused by the original subsurface crack. The wheel–rail is modelled as a mass–spring–damper system to simulate the basic wheel–rail dynamics.

Computational Fluid Dynamics Analysis of Empty Railway Freight Wagons

Abstract: Increase in the speed of train leads to aerodynamic problems. These problems occur due to turbulent behaviour of air flow around the train. So it is of great concern to study the dynamics of fluid flow. This paper deals with the dynamic analysis of empty freight wagons due to air turbulence using computational fluid dynamics. The effect of important aerodynamic coefficients such as aerodynamic drag, pressure distribution and velocity stream line has been studied on realistic and simplified freight train geometries. The geometry is a scaled model of freight open wagon type‘BOXN25’ from Indian Railways. The aerodynamic analysis for empty wagons shows that the critical stress zone and the air drag effect are comparable between the two considered geometries.

Effect of Multiple Location Defects on the Dynamics of Draft Gear used in Freight Railway Wagon

Abstract: The present work investigates the effect of crack location on the modal frequency of draft gear used in autocouplers of freight railway wagon for various orientations. First seven mode shapes of a healthy draft gear have been determined using finite element approach. Defect of semi-elliptical shape is modelled in the lateral as well as longitudinal direction of the draft pad which is a component of draft gear. Various damage scenarios have been simulated by considering multiple locations of the crack in the draft gear for different orientations. Effect of crack orientation and defective pads location on the natural frequency of draft gear is analysed. It is seen that for single defective pad as well as multiple defective pads, the natural frequency of draft gear is dependent on the dynamics of draft pad. It is also observed that defect in consecutive pads causes more change in frequency as compared to single defective pad. As far as the location of defective pad is concerned, it is seen that the draft gear frequency is more sensitive to defective pads located either near the housing base plate or top follower. This study provides a tool to diagnose crack defect in draft gear based on vibration characteristics.

Influence of wear on the performance of 2-lobe slot entry hybrid journal bearings

Abstract: In the present paper, the influence of wear on the performance of 2-lobe slot entry restrictor bearing has been investigated theoretically The equation of fluid flow field has been solved by using Galerkin’s technique of FEM In this study, Dufrane’s wear model has been used to consider the change in bush geometry due to wear The performance of 2-lobe slot entry restrictor bearing is studied for both symmetric and asymmetric slot configurations The simulated results of the study indicate that the wear defect substantially changes the performance of 2-lobe slot entry journal bearing systems A proper choice of bearing geometry and bearing configuration (12 slots and 6 slots per row) may partially compensate the loss occurred due to wear

A Novel Technique to Measure the Rolling Resistance of Tyres Using Force Transducer

Abstract: A novel laboratory technique has been used to measure the rolling resistance of tyres using a force transducer. The effect of inflation pressure, normal load and speed has been studied for two different bias-ply tyres—with and without treads. As anticipated, the results indicate that a treaded tyre has higher value of the rolling resistance as compared with a tyre with treads removed.