Journal Bearing Research Papers - Academia.edu (original) (raw)

We examine the combined effect of variable viscosity, velocity slip, and the couple stress lubricant on a finite journal bearing. In our model, we utilize the Stokes micro-continuum theorem, the Barus formula, and an artificial (homogeneous) slip surface to improve the lubrication performance. Three cases of slip have also been considered: on the journal, the bearing, and both journal and bearing. The finite difference method is used to solve the equations numerically. The results indicate that the highest pressure occurs with slip on the bearing, and the lowest pressure occurs with slip on the journal. A high piezo-viscosity enhances the pressure and load-carrying capacity. Also, the slip parameter improves the load-carrying capacity. With slip on the bearing only, the frictional parameter decreases significantly.

- by
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- Tribology, Couple Stress, Lubricants Additives, Finite Difference Method

A finite-element approach to thermoelastohydrodynamic lubrication analysis is developed by extending a previous mass-and energy-conserving algorithm to include wall-convection boundary conditions, groove-mixing theory, and thermo-mechanical deformations. To this end, the cross-film-averaged energy equation is coupled with the heat conduction equations relevant to the bearing sleeve and the journal by fitting the temperature profile across the film thickness with a fourth-order polynomial. A finite-element condensation technique is used to reduce the unknowns in heat conduction equations in the bush and in the journal to the temperatures of the sleeve surface and journal axis, respectively. Applied to the analysis of steadily loaded journal bearings, the proposed method shows good agreement with published experimental results and incurs low computational cost.

- by Fabrizio Stefani
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- Mechanical Engineering, Chemistry, Convection, Modeling

This paper presents an experimental study of pressure distribution on hydrodynamic journal bearing with SAE 10W30 multi grade oil. Hydrodynamic Journal bearing test rig (HJBTR) is used to test the 40 mm diameter and 40 mm long bearing (l/d = 1) made of Bronze. Test bearing is located between two antifriction bearings and loaded mechanically. The space between the shaft and the bearing is filled with SAE 10W30. A constant load of 800 N is applied at various journal rotational speeds of 1000, 1500, 2000 rpm. Various parameters like frictional torque, oil temperature and pressure at 10 different sensors along circumferential direction were recorded from Hydrodynamic Journal Bearing Test Rig (HJBTR). These results were used for experimental calculations and theoretical verification using Raimondi and Boyd charts for practical design. The experimental plot of pressure ratio vs sommerfeld number indicates that the working conditions are in the stable hydrodynamic regime. Also experimental results were following the same trend as MCKEE‟s investigation curve.

- by Paras Kumar
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- Journal Bearing, Hydrodynamic Bearings

The analysis and design of hydrodynamic journal bearings has a great attention to the engineers. Emphasis has been given to design those bearings so as to avoid metal-to-metal contact .To design these elements, few important characteristics, like load-carrying capacity, maximum pressure and their location lubricant flow requirement between mating surfaces, etc. are to be predicted accurately. These parameters can be determined if the pressure within the clearance space between contact surfaces is known. To study and find this pressure one has to solve in general the Reynolds’s equation that governs the flow of lubricant inside the clearance space. Moreover the accuracy of the results obtained by FEM is mainly depends on the proper finite element modeling that includes proper selection of the type and size of finite elements and solution algorithm. As computing cost and time increases the size (i.e. the number) of elements increases, one has to determine the minimum number of elements those can be used to obtain the accurate solution. Therefore this work is aimed to study the effect of number of finite elements on the computed result of hydrodynamic journal bearing and to determine minimum number of finite elements to be used in the analysis of the journal bearing.

- by badal kudachi and +1
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- FEA with ANSYS, Feature Models, Journal Bearing, Reynolds Number

Steady state thermo-hydrodynamic analysis and its comparison at five different feeding locations of an axial grooved oil journal bearing is obtained theoretically. Reynolds equation is solved simultaneously along with the energy equation and heat conduction equation in bush and shaft. From parametric study it is found that 121 feeding groove position is better in comparison to other feeding locations. Feeding from the bottom is very less preferable since the load capacity is lesser and temperature development is more. It is very difficult to obtain the solution due to numeric instability when the bearing operates at higher eccentricity ratio.

- by Loriene Roy
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- Mechanical Engineering, Heat Transfer, Localization, Tribology

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Thermohydrodynamic study for the analysis of elliptical journal bearings has been presented in the present work for three different grade oils commercially available. Finite difference method has been adopted for numerical solution of the Reynolds and energy equation. Temperature in the oil film is computed using parabolic temperature profile approximation technique. A comparative study for rise in oil-temperatures, thermal pressures and load carrying capacity has been carried out. Comparison amongst three oils elucidates that the thermal degradation for oil 1 is the least, whereas the load carrying capacity for oil 3 is the highest.

- by Amit Chauhan
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- Mechanical Engineering, Modeling, Tribology, Comparative Study

In Present scenario, any kind of Vehicle transmits Power from the drive systems to differential through the advent use of Drive shafts. Drive Shaft is a shaft for imparting torque from power source or prime mover to machinery. Nearly all of driveshaft is metal shafts or metal tubes that has special joint. The major failure occurred in drive shaft is due vibration, torsional stress and bending stress was experienced by driveshaft due to the weight of the car or misalignment of journal bearing. Drivers will lose control of their vehicle if the drive shafts failure occurs during high speed cornering. And also by varying the material we can reduce the weight of the rotating mass and increase the response. It allows more energy to go into rotating the tires instead of rotating dead weight. The above stated problem can be reduced by adopting the alternative material over it. Our project aims to reduce the weight of the drive shaft and conducting an analysis on it by varying the material in order to reduce the fuel consumption. We are making use of mechanical analysis tool " ANSYS " to conduct the analysis on propeller shaft and coupling. The analysis to be carried out may attain a well-developed Drive shaft which can be utilized in the recent automobile development domain of its first kind.

This paper investigates the effect of surface texturing in a partial pad journal bearing through a series of controlled experiments at operating conditions, promoting mixed or boundary regimes of lubrication. Improvements to load carrying capacity are observed under certain operating conditions. A comprehensive computational finite volume multiphase fluid dynamics analysis, including vapour transport equation and modified finite‐size cavity Rayleigh‐Plesset model, is used to study the effect of indented surface textures in the microscale contact domain and within the individual textures themselves. The results show improved conditions with a textured journal through promotion of micro‐hydrodynamic effect, delaying the effect of lubricant rupture, thus extending the effective load bearing region. A very good agreement is obtained between measurements and predictions.

- by Ramin Rahmani and +1
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- Tribology (Engineering), Lubrication, Surface Texturing, Tribology

The paper presents an integrated tribo-dynamics analysis of elliptic bore overlay big end bearings of internal combustion engines. The analysis focuses on bearing stability, frictional power loss and acoustic emission from these bearings, particularly with cylinder deactivation (CDA) with larger fluctuations in engine loading. The integrated approach represents a multi-physics analysis, not hitherto reported in literature, particularly under CDA. The analysis shows that CDA makes marginal differences in parasitic frictional losses in engine bearing performance and any significant gain would depend on the brake specific fuel consumption. It is also shown that sufficient swept volume with retained residual exhaust gas charge within the deactivated cylinders can ensure bearing whirl stability. Partially deactivated engine configurations exhibit a lower average steady noise emission, but with a higher degree of transient content. This suggests that there would be a greater contribution to engine rumble with deactivated cylinders.

- by Ramin Rahmani
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- Internal Combustion Engines, Tribology, Acoustic Emission, Elastohydrodynamics

This paper investigates the stochastic behaviour of hydrodynamic journal bearings by solving the Reynolds equation with random parameters numerically based on finite difference method. The steady state and dynamic characteristics are quantified considering random variabilities in eccentricity and surface roughness that can closely simulate the uncertain service conditions and inevitable manufacturing imperfections. Based on efficient radial basis function, a Monte Carlo simulation (MCS) algorithm is developed in conjunction with the governing equations for quantifying stochastic characteristics of the crucial performance parameters concerning hydrodynamic bearings. Relative sensitivity to stochasticity for different performance parameters is analysed. Physically insightful new results are presented in a probabilistic framework, wherein it is observed that the stochasticity has pronounced influence on the performance of bearing.

- by TM TM
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- Stochastic dynamics, Journal Bearing

In this study, hydrodynamic characteristics of finite length journal bearings running with incompressible laminar flow under magnetic field are investigated. Ferrofluid as a lubricant contains nanoparticles of magnetite (Fe 3 O 4 ).The analysis is based on the numerical solution of the full Navier-Stokes equations using computational fluid dynamics techniques. Considering the complexity of the physical geometry, conformal mapping is used to generate an orthogonal grid, and the governing equations are transformed in the computational domain. Discretized forms of the transformed equations are obtained by the control volume method and solved by the SIMPLE algorithm. Results indicated that when compared with the conventional lubricant, the ferrofluid as a lubricant enhances the hydrodynamic characteristics of journal bearings and provides a higher load capacity. Besides, it was found that the other bearing characteristics are considerably affected by the applied magnetic field.

- by Yahya Sheikhnejad
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- Mechanical Engineering, Computational Fluid Dynamics, Ferrofluid, Laminar Flow

Plain hydrodynamic journal bearings are essential component of various rotating machinery. Vibrations associated with journal bearing have many aspects. Vibrations of journal bearing related with lubricant are important from stability, performance and operational point of view. Lubricant viscosity is one of the major parameter affecting the stability of plain hydrodynamic journal bearing. This experimental work attempts to correlate the lubricant viscosity and vibrations of the plain hydrodynamic journal bearing system. An experimental setup is designed to acquire data in the form of vibration signals in time and frequency domain. Various set of experiments are formed for different combinations of lubricant viscosity, shaft speed and load. Taguchi’s orthogonal array method is utilized for design of experiments. Analysis of data shows that lubricant viscosity has evident effect on vibrations of the system. Thinner oils show fewer vibrations at higher speeds, while thicker oils show less vibration at lower speeds. Thick oils contribute in reducing the overall RMS value of vibration amplitude

- by Abhijeet G Chavan and +1
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- Journal Bearing

-Uneétude théorique du comportement statique et dynamique d'un palier lisse indéformable lubrifié par des huiles additivées en prenant en considération le défaut de mésalignement est présentée. Ces huiles dont le comportement rhéologique est non-newtonien sont modélisées comme des fluidesà couple de contrainte. D'après la théorie des milieux continus de V. K. Stokes qui tient compte de la taille des particules, ces fluides se caractérisent par deux constantes physiques qui sont la viscosité dynamique (μ) et une deuxième caractéristique responsable des couples de contrainte dans le fluide (η). Les effets des couples de contrainte sur le comportement statique et dynamique du palier aligné ou mésaligné sont etudiés en définissant un paramètre du couple de contrainte adimensionnel. Les résultats obtenus montrent que la présence des additifs dans le lubrifiant a une influence non négligeable sur les performances statiques et dynamiques ainsi que la stabilité et la réponse dynamique du palier surtout pour les grandes valeurs du paramètre du couple de contrainte, c'est-à-dire dans le cas des polymères de longue chaîne moléculaire. Toutefois, leur influence sur le débit de fuite est négligeable sauf pour les grandes excentricités de fonctionnement.

- by mustapha lahmar
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- Modeling, Vibration, Stability, Mécanique

The precession behavior of an unbalanced rotor-bearing system with anisotropic supporting stiffness is analyzed. The result shows that the probe-orientation-related problem is still unsolved in the holospectrum technique based rotor balancing method. The deficiency of the balancing object of this method now in use, the Initial Phase Vector (IPV), sometimes makes the description or evaluation of rotor balance state unclear. Necessary modification to this method is made in this paper. A compound balancing object comprised of the magnitude of the major axis and the Initial Phase Angle (IPA) of the precession orbit is presented to replace the IPV as the rotor unbalance response. The amount and angular location of the mass unbalance can be determined precisely by the magnitude of the major axis and the IPA, respectively. Since the isotropic assumption is no longer a prerequisite and the evaluation of the mass unbalance amount is independent of the probe orientation, optimal result then can be ensured. The experiment and real application case verify its capability and feasibility.

- by Yuhe Liao
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- Mechanical Engineering, Vibration Control, Vibration, Behavior Analysis

The performance of finite elastohydrodynamic journal bearings lubricated by ferrofluids with couple stresses has been studied. We derive a Reynolds equation that takes into account magneto elastohydrodynamics, by using the continuity and momentum equations. The equation has been integrated locally across the film thickness and an equation for the pressure gradient obtained as a function of film thickness and total mass flow rate of lubricant, the modified Reynolds equation. The modified Reynolds equation obtained is solved numerically by the finite difference technique since it is highly non-linear. The numerical scheme used is implemented in MATLAB so as to obtain the approximate solutions. The pressure distributions are obtained and the solutions obtained represented in graphs. It is clear from the results that the pressure increases with the increase in magnetism and the couple stress.

- by Daniel Kihuga
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- Fluid Dynamics, Journal Bearing

This study presents a new simple lumped model designed to analyze the thermally induced seizure of fully lubricated eccentric circumferential groove journal bearings (CGJB). The current model represents an upgrade of a previous seizure analysis lumped model developed by , and considers an eccentric bearing operation, introduces the hydrodynamic lubricant flow rate and estimates friction power losses based on the short bearing theory with Barwell's approximation in the divergent zone. The viscosity -clearance variation is approximated using Tipei's relationship, as in the original model. The decrease of viscosity, as a consequence of increase of temperature, does not always reduce the loss of clearance, and the seizure process ends with a concentric journal-bush merged system. Although CGJB's are less sensitive to this seizure mechanism the threat still exists and must be avoided. As a result, designers and users should check wetter if several safe-operation criteria are met. A recent Institute Pprime experiment on CGJB's provided a base set of operating parameters, from which simulations have been performed to determine in what conditions the CGJB fails due to thermally induced seizure.

- by Alex-florian Cristea and +1
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- Journal Bearing

This study deals with the non-linear dynamic response of a flexible rotor supported by ball bearings. The excitation is due to unbalance force. The finite element rotor system is composed of a shaft with one disk, two flexible bearing supports and a ball bearing element where the non-linearities are due to both the radial clearance and the Herztian contact between races and rolling elements. A numerical analysis is performed to analyze the non-linear behavior of this bearing rotor by using the Harmonic Balance Method with appropriate condensation located only on the non-linear coordinates of the system in order to minimize computer time. The condensation process reduces the original non-linear rotor system by focusing only on the solution of the non-linear equations of the Fourier coefficients associated with the system’s non-linear components.In this study, the procedure is developed for the estimation of the harmonic and super-harmonic responses of the complex rotor system. Consequently, the non-linear unbalance responses and the associated orbits of the bearing rotor will be investigated. Moreover, the transition from contact to no-contact states between rolling elements and races, and the associated restoring contact forces are calculated for different speeds of the unbalanced rotor. Finally, hardening-type non-linearity or softening-type non-linearity due to the effects of radial clearance and unbalance mass are examined.

- by Jean-Jacques Sinou
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- Mechanical Engineering, Modeling, Numerical Analysis, Finite element method

A numerical algorithm for fully-dynamical lubrication problems based on the Elrod-Adams formulation of Reynolds equation with mass-conserving boundary conditions is described. A simple but effective relaxation scheme is used to update the solution maintaining the complementarity conditions on the variables that represents the pressure and fluid fraction. The equations of motion are discretized in time using Newmark's scheme, and the dynamical variables are updated within the same relaxation process just mentioned. The good behavior of the proposed algorithm is illustrated in two examples: Oscillatory squeeze flow (for which the exact solution is available) and a dynamically loaded journal bearing. This article is accompanied by the ready-to-compile source code with the implementation of the proposed algorithm, which is publicly available at www.lcad.icmc.usp.br/∼buscaglia/download.

- by Gustavo Buscaglia
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- Mechanical Engineering, Algorithms, Modeling, Time Use

Journal bearings are widely used in rotating machinery to support shafts. Stability of system is very much important in such cases. Stability of system depends on number of parameters like operating speed, bearing dimensions, eccentricity, load etc. Dynamic coefficients can provide idea about stability behaviour of the system. This work attempts to correlate the viscosity of lubricant with dynamic coefficients. Values of eight dynamic coefficients are calculated for the proposed system considering five various SAE grade lubricating oils. These values are plotted against eccentricity. Dynamic coefficients changes almost linearly with change in viscosity of lubricating oil.

- by Abhijeet G Chavan and +1
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- Journal Bearing

This paper presents a theoretical prediction of selection procedure for fluid film journal bearing by incorporating fuzzy approach. In this paper a fuzzy model is proposed for selection of hydrostatic, hydrodynamic and hybrid journal bearing. Selection criteria is formulated for the choice of space requirement, total cost of bearing and load bearing capacity of the related journal bearing. This method provides a third dimension to the existing method of selection of bearing, which is dynamic and may be further refined to address to every individual needs. Therefore a fuzzy logic approach is used for decision making for selection of correct fluid film bearing

-Cet article fait la synthèse de différents travaux mettant enévidence l'influence que peut avoir un défaut géométrique (de forme ou de position) d'unélément support de ligne d'arbre sur le comportement dynamique du rotor. Sous certaines conditions aussi bien dans le cas des paliers que dans les cas des butées axiales, un défaut géométrique de la partie tournante du support peut faire apparaître des perturbations non négligeables de l'ensemble de la ligne d'arbre. Après une présentation des différents modèles adoptés, quelquesétudes de cas sont exposées. Il s'agit d'un calcul non linéaire (pasà pas dans le temps) de la ligne d'arbre flexible. Le modèle prend en compte simultanément le comportement non linéaire hydrodynamique du support fluide et le comportement flexible de l'arbre. Les comportements mis enévidence font apparaître dans les réponses de l'arbre des fréquences supersynchrones dues aux défauts des supports. Ces réponses peuvent avoir des amplitudes du même ordre de grandeur que celles obtenues sous l'effet d'un balourd.

- by Olivier Bonneau
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- Journal Bearing

Hydrodynamic and elastohydrodynamic lubrication models were applied to compare the performance of oil lubricated metallic journal bearings with that of sea water lubricated polymer journal bearings in ship propulsion systems. A numerical model based upon the finite difference method and an isoviscous model, together with a computer program with two modules have been used to evaluate the process parameters. The method and model calculations were tested using the data collected from two different types of actual vessels in service. Regarding the stern tube journal bearings, results indicate that the developed software applications attain high approximation accuracy regardless of the relatively simple numerical model.

- by Liane Roldo
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- Journal Bearing

The purpose of this paper is to study the performance of a finite length journal bearing, taking into account effects of non-Newtonian Rabinowitsch flow rheology and elastic deformations of the bearing liner. According to the Rabinowitsch fluid model, the cubic-stress constitutive equation is used to account for the non-Newtonian effects of pseudoplastic and dilatant lubricants. Integrating the continuity equation across the film, the nonlinear non-Newtonian Reynolds-type equation is derived. The elasticity part of the problem is solved on the base of Vlassov model of an elastic foundation. The numerical solution of the modified Reynolds equation is carried out by using FDM with over-relaxation technique. The results for steady state bearing performance characteristics have been calculated for various values of nonlinear factor and elasticity parameters. It was concluded that in comparison with the Newtonian lubricants, higher values of film pressure and load carrying capacity have been obtained for dilatant lubricants, while the case was reversed for pseudoplastic lubricants.

A generalized Reynolds equation, in which is adopted specified rheological model to express the non-Newtonian properties of the lubricant, is derived for journal bearing with finite length. The shaft is covered with a thin resilient layer, whose elastic distortions are of the same order of magnitude as the film thickness. The 2-D non-steady EHD problem is investigated under elasticity conditions in accordance to the Vlassov model of an elastic foundation. It is used an adiabatic solution of the thermal problem. The viscosity - pressure, temperature relationship, proposed by Roelands, is employed. The numerical solutions are carried out to the incorporated the Reynolds, elasticity, energy and state equations for pressure, deformations and film thickness. The results are obtained for prescribed loci of the shaft center.

The purpose of the present paper is to demonstrate the influence of convective inertia forces of the lubricant on the hydrodynamic pressure values of a finite journal bearing under isothermal and isoviscous condition. The 2-D steady state EHD problem is investigated for the case of an elastic layer on a rigid foundation, with the displacements calculated without linear approximations. To this end a new, more precise, method of determination of the deflections is used. The generalized Reynolds equation is obtained by the averaged acceleration method. The differential equation is solved numerically by the successive over-relaxation technique on a finite difference grid.

- by Juliana Javorova
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- Tribology, Journal Bearing, Hydrodynamic Lubrication, Fluid Inertia

An attempt has been made to analyse to performance of an infinitely rough short bearing. Here in solving the associated Reynold`s type equation in new boundary conditions involving the standard deviation associated with roughness has been used. The pressure, load carrying capacity and friction are calculated. It is found that the roughness parameter significantly affects all the above performance characteristic. It is observed that effect due to the roughness compounded by taking the effect of standard deviation on the boundary conditions.

- by IJSRD Journal
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- Friction, Roughness, Journal Bearing, Pressure Distribution

The paper presents a mixed thermo-hydrodynamic analysis of elliptic bore bearings using combined solution of Navier–Stokes, continuity and energy equations for multi-phase flow conditions. A vapour transport equation is also included to ensure continuity of flow in the cavitation region for the multiple phases as well as Rayleigh–Plesset to take into account the growth and collapse of cavitation bubbles. This approach removes the need to impose artificial outlet boundary conditions in the form of various cavitation algorithms which are often employed to deal with lubricant film rupture and reformation. The predictions show closer conformance to experimental measurements than have hitherto been reported in the literature. The validated model is then used for the prediction of frictional power losses in big end bearings of modern engines under realistic urban driving conditions. In particular, the effect of cylinder deactivation (CDA) upon engine bearing efficiency is studied. It is shown that big-end bearings losses contribute to an increase in the brake specific fuel consumption with application of CDA contrary to the gains made in fuel pumping losses to the cylinders. The study concludes that implications arising from application of new technologies such as CDA should also include their effect on tribological performance.

A simple partial tilting pad journal-bearing rig is developed. The journal diameter to pad width is so chosen as to render a short width bearing. The attitude angle is recorded by reading from a graduated scale.........

- by Nicholas Morris
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- Surface Texturing, Tribology, Journal Bearing

The effect of the non-Newtonian behaviour of lubricants, resulting from the addition of polymers, on the performance of hydrodynamic journal bearings is investigated. The model of non-Newtonian lubricant developed by Dien and Elrod is taken into consideration. An attempt has been made to evaluate the mass parameter (a measure of stability) besides finding out the steady-state characteristics of finite journal bearings with non-Newtonian lubricants. A non-linear time transient analysis is carried out for the stability analysis.

- by Raghunandana Kurkal
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- Chemical Engineering, Stability, Journal Bearing

The aim of this investigation is analysis of the influence of the shaft’s liner elastic deformation on stability of the dynamic system “lubricant film-shaft” in elastohydrodynamic (EHD) journal bearing with finite length. The shaft motion, which is arose from unbalanced hydrodynamic (HD) forces of lubricant film, is considered. The verification for the system stability in this case requires simultaneously problems solution of the oscillation theory and of the EHD theory of lubrication. In present study modified stability criteria by Hurwitz and Ljapunov are used. An adaptive procedure for determination of critical stability of the considered system is constituted and used. On this base bearing’s simulative models are created and the numerical solution are made.

- by Juliana Javorova
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- Tribology, Stability, Journal Bearing, Hydrodynamic Stability Theory

This paper presents an analysis of the pressure development of journal bearing in a various shaft surface texture and velocity variations using a proposed neural network. The effects of the parameters, which act on performances of journal bearing, on the pressure development and load-carriage capacity have been examined such as the number of revolution and shaft surface texture.

- by FEHMİ NAİR
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- Materials Engineering, Mechanical Engineering, Neural Networks, Neural Network

Turbochargers are progressively used in modern automotive engines to enhance engine performance and reduce energy loss and adverse emissions. Use of turbochargers along with other modern technologies has enabled development of significantly downsized internal combustion engines. However, turbochargers are major sources of acoustic emissions in modern automobiles. Their acoustics has a distinctive signature, originating from fluid-structure interactions. The bearing systems of turbochargers also constitute an important noise source. In this case, the acoustic emissions can mainly be attributed to hydrodynamic pressure fluctuations of the lubricant film. The developed analytical model determines the lubricant pressure distribution in the floating journal bearings used mainly in the modern turbocharges. This allows for an estimation of acoustic emissions. The use of such an analytical approach is computationally efficient when compared with full numerical analysis approaches, whilst also providing reliable predictions. The results from the developed analytical model are used to determine the power loss as well as sound pressure levels generated in the turbocharger bearings due to oil flow which can be correlated with the acoustic emissions of turbochargers.

The steady state and dynamic characteristics including whirl instability of oil journal bearings with single axial groove located at the top of the bearing and then at some angular interval from the top from which oil is supplied at constant pressure are obtained theoretically. The Reynolds equation is solved numerically by finite difference method satisfying the appropriate boundary conditions. The dynamic behaviour in terms of stiffness and damping coefficients of fluid film and stability are found using a first-order perturbation method for each location of the groove. It has been shown that both load capacity, end flow is maximum when the feeding groove is at 121 location and thereafter the load capacity falls, stability improves for smaller groove angle and groove length at higher value of eccentricity ratio and speed. The stiffness and damping coefficient magnitude is found to be higher for the bearing with smaller groove angle and groove length, the difference between the hydrodynamic and hydrostatic load increases at 121 groove location.

- by Loriene Roy
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- Mechanical Engineering, Localization, Tribology, Stability

Since there are manufacturing and assembling inaccuracies rotors are always slightly imbalanced. Their rapid angular acceleration leads to an increase in the magnitude of the tangential component of the imbalance forces. The slow acceleration enables the development of an almost steady state vibration. In both cases the amplitude of their oscillation is high. The frequency tuning achieved by changing the stiffness of the rotor supports represents one approach to its attenuation. Stiffness decreases shortly before reaching the critical speed, and after crossover, the stiffness increases again. As almost all publications and computer procedures from the field of rotor dynamics deal only with the case when the rotor turns at a constant angular speed, derivation of the equations of motion of the rotor rotating at variable velocities and investigation of the operating conditions and individual parameters of the supports on the vibration of the rotor passing critical speeds represent the fully new contribution of this paper. The critical revolutions are determined from the Campbell diagram. To solve the equations of motion the Newmark method has been proposed and tested.

- by Petr Ferfecki
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- Mechanical Engineering, Modeling, Finite element method, Vibration Control

- by Dr. Dhananjay G Thombare
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- Journal Bearing

Radial vibration of a vertical rotor with externally pressurized gas bearings is analyzed. The timedependent Reynolds equation is solved together with the journal equation of motion to obtain the response characteristics of the bearing system. The bearings are supplied with either one or two sets of supply orifices. Stiffness and flow rate are compared for both cases. Stability maps are obtained at different supply pressures and with different supply orifice diameters. The mass range from orbital stability to instability is studied as a function of supply hole downstream pressure level.

- by Vladimir Viktorov
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- Mechanical Engineering, Modeling, Lubrication, Tribology

The objective of the study is to investigate the combined effects of interaction of surface asperities and the non-Newtonian nature of lubricant on the HD performance of finite journal bearings bearings. The roughness takes the form of sinusoidal ridges and furrows aligned in the transverse direction of lubricant entrainment. The modified Reynolds equation for pseudo-plastic lubricant is solved numerically by successive over-relaxation technique on a finite difference grid. The presented results demonstrate the influences of non-linear factor of lubricant and characteristics of surface roughness on the pressure distribution and some basic bearing characteristics.

- by Juliana Javorova
- •
- Tribology, Surface Roughness, Journal Bearing, Hydrodynamic Lubrication

In a companion paper, part 1, a computer-aided design method for pocket elliptical bearings has been developed. Its application is discussed in the current paper, which mutually related goals are: to understand how bearing design and particularly pocket geometry affect the bearing performance, to determine optimal values of the driving variables that control bearing profile and pocket width, to choose a suitable supply groove layout. As explained in part 1, the developed method does not include an automatic optimization tool. Therefore, in order to reduce the number of the variables that control the bearing geometry involved in the optimization task, the clearance of the assembled bearing (pocket clearance) is kept constant. Hence, the optimization of the bearing shape is performed by changing pocket opening, pad eccentricities, pocket width, lubricant supply mode.

- by Fabrizio Stefani
- •
- Engineering, Computer Aided Design, Finite element method, Lubrication

This paper describes a mixed elastohydrodynamic lubrication (EHL) model for finite length elastic journal bearings. The finite element method was employed to discretise the coupled system of 2D-3D Reynolds-structure equations and to compute Stribeck curves at constant load. As underrelaxation strategies have been found to be insufficient for an iterative solution of this problem, artificial dynamics have been added to the numerical structure equations in order to solve for stationary solutions of the fluid-structure problem. An ideal plastic asperity contact model together with an effective film thickness formulation according to Chengwei and Linqing was employed in order to compute the contact pressure in mixed lubrication. The method presented in this paper is applied to a typical water lubricated journal bearing problem. Computed Stribeck curves are presented and the numerical performance of the method is evaluated.

- by Ron van Ostayen
- •
- Mechanical Engineering, Water, Modeling, Fluid structure interaction

This paper describes the pressure distribution in the bearing clearance of circular aerostatic thrust bearings with a single air supply inlet. For high air supply pressure, large bearing clearance, and a relatively small bearing outer radius, it was believed that shock waves are caused and that a complex fluid flow structure is formed in the bearing clearance. Accordingly, analytical models based on the occurrence of shock wave in the bearing clearance have been proposed. Recently, very small aerostatic bearings have been used in various machine devices where the pressure distribution near the air inlets has a large influence on the bearing characteristics due to a short distance between air inlets and the bearing edge. In order to predict various bearing characteristics accurately for these kinds of bearings, a proper analytical model has to be established. However, it is very difficult to obtain the detailed information about the flow structure from flow visualization because of a...

- by Makoto Yamamoto
- •
- Mechanical Engineering, Computational Fluid Dynamics, Turbulence, High Pressure

The premature failure of journal bearings may be observed on account of lack of lubricating oil flow inside the bearing, misalignment on the shaft, surface irregularity on journal bearing and contamination blend with lubricating oil, etc., which may affect the production cost of the industry and also dangerous for human life. Sugar mill bearing is commonly known for operating with high load and low-speed conditions. The rise in temperature and wear of sugar mill bearing has been noticed in the sugar industry while working with contamination oil conditions. Hence the experimental investigation of the straight and spiral textured phosphorous bronze journal bearings lubricated with contamination oil has been conducted with a downsize of sugar mills. Dried and crushed bagasse of sugar cane is used as a contamination for entire experimental work. An internal knurling operation has been performed on the inner diameter of bearing through the lathe machine. The results of both textured bearings have been compared in the matter of temperature rise, change in internal diameter and wear loss with various contamination oil conditions. Improvement has been observed on the performance of straight textured bearing as compared to spiral textured bearing under contaminated lubricating oil conditions.

Recently, herringbone-grooved journal bearings (HGJBs) have important applications in high-speed rotating machinery. The groove action in pumping the lubricating fluid inward generates supporting stiffness and improves the stability of the bearing when operating concentrically. Several researchers have investigated the static and dynamic characteristics of HGJBs and grooved thrust bearings. Most of these investigations were theoretical and concentrated on HGJBs with rectangular-profile grooves. In the present work, the static and dynamic characteristics of the beveled-step HGJBs are experimentally investigated. The bearing attitude angle, pressure distribution, and bearing friction torque were measured on a hydrodynamic lubrication unit, and then the static and dynamic characteristics were determined. The obtained experimental results are compared to the obtained experimental results for plain journal bearing. The merits as well as the demerits of the groove profile were discussed through comparisons with plain journal bearings.

- by Ahmed Gad
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- Mechanical Engineering, Tribology, Stability, Groove

Joining two tubes of different diameters has important concerns in many industries and engineering applications. An eccentric reducer is often used in such applications. Therefore, a simple and easy technique for manufacturing an eccentric reducer is of much importance. The simplest technique for producing the eccentric reducers is the tube nosing through eccentric conical dies. In this paper the finite element simulation is used to investigate the eccentric nosing of circular tubes through an eccentric conical die. Simulation is performed to investigate the plastic deformations of the deformed tube and all the possible modes of failure during the eccentric nosing process. Identification of unfavorable modes of failure in the tube nosing process lead to design modification guidelines, design of preform, and the die shape, for the eccentric nosing process. The results obtained confirmed that the modified design of the tube blank not only improves the quality of the nosed-tube product but also reduces nosing load and improves the limiting nosing ratio. Comparison with the experimental results shows that the nosing load and the modes of failure are successfully predicted by the finite element simulation. Also, a preform design for the tube blank that can produce an eccentric reducer with collar end that did not need a trimming process is introduced.

- by Ahmed Gad
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- Mechanical Engineering, Design, Modeling, Tribology

In this paper, the cross-coupled bending vibrations of a rotating shaft, with a breathing crack, mounted in resilient bearings are investigated. The equations of motion of the continuum and isotropic rotating model of the shaft follow the theory of Rayleigh. The governing equations are coupled in the two main directions, and the partial solution is obtained by solving a linear system of equations, for each time step, taking into account the non-linearity due to the breathing crack. The coupling is introduced in three different ways: the equations of motion, the resilient bearings and the crack.

- by Chris Papadopoulos and +1
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- Mechanical Engineering, Modeling, Equation of Motion, Coupling

The object of a current investigation is the problem of hydrodynamic (HD) instability of finite journal bearings. The rigid rotor is good balanced, such is investigated the motion of the shaft centre, provoked from the unbalanced HD forces of the lubricant. Modified criteria for stability by Hurwitz and Ljapunov are used, as well as an original program system, which is adequate of the theoretical treatment. On the base of large number bearings' simulative models and numerical solutions a graph-analytical calculation of the critical stability is presented. The suggested method is intended for scientific investigation, but can be used also in direct engineering practice.

- by Juliana Javorova
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- Tribology (Engineering), Tribology, Stability, Graph Analytics

This book is concerned with theoretical study for the thermal effects of the hydrodynamic journal bearings lubricated by ferrofluids with couple stresses. The study is generalize such that it covered both Newtonian and non-Newtonian behavior of the lubricant. Based on the momentum and continuity equations for ferrofluid under an applied magnetic field, a pressure differential equation (modified Reynolds equation) has been obtained. Assuming linear behavior for the magnetic material of the ferrofluid, and using carrying current concentric finite wire magnetic field model, the magnetic force was calculated. A modified Reynolds equation is obtained and it is simultaneously solved with the energy equation numerically by the finite difference technique. The pressure and temperature distributions have been obtained. The solution renders the bearing performance characteristics namely; load carrying capacity, attitude angle of the journal center, frictional force at the journal surface, friction coefficient and bearing side leakage.

- by Hany S. Abdo
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- Hydrodynamics (Physics), Magnetic field, Lubrication and Friction, Ferrofluids

The objective of this paper is to predict the performance of rotor bearing system lubricated with couple stress fluid accounting the cross effect of velocities. Modified Reynold's equation and the Stokes' Constitutive equation have been obtained. Narrow bearing approximations have been used to obtain the solutions in the closed form. The effects of couple stress, frame rotation and the Viscosity-density effects have been obtained numerically. The results so obtained are consistent with the physical situation of the problem.

- by Udaya Pratap Singh
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- Applied Mathematics, Fluid Dynamics, Journal Bearing, Couple Stress Fluids