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N B Naduvinamani - One of the best experts on this subject based on the ideXlab platform.

  • Modified Reynolds Equation for different types of finite plates with the combined effect of mhd and couple stresses
    Tribology Transactions, 2015
    Co-Authors: Syeda Tasneem Fathima, N B Naduvinamani, B N Hanumagowda, Santhosh J Kumar
    Abstract:

    We make an effort to analyze the behavior of squeeze film characteristics of different finite plates with couple stress fluid in the presence of a transverse magnetic field. On the basis of the Stokes couple stress fluid model and hydromagnetic flow model, a Modified Reynold's Equation is derived, which is solved by using appropriate boundary conditions to obtain squeeze film pressure, load-carrying capacity, and squeeze film time. The graphical representation of the results suggests that the different bearing systems register an enhanced performance with couple stresses compared to that of a bearing system working with a conventional lubricant in the presence of a transverse magnetic field. It is observed that the effect of applied magnetic field on the squeeze film lubrication between different finite plates with conducting couple stress fluids is to increase the load-carrying capacity significantly and to delay the time of approach compared to the corresponding nonconducting Newtonian case. It is seen ...

  • squeeze film lubrication between rough poroelastic rectangular plates with micropolar fluid a special reference to the study of synovial joint lubrication
    International Scholarly Research Notices, 2013
    Co-Authors: N B Naduvinamani, G K Savitramma
    Abstract:

    The effects of surface roughness and poroelasticity on the micropolar squeeze film behavior between rectangular plates in general and that of synovial joints in particular are presented in this paper. The Modified Reynolds Equation, which incorporates the randomized surface roughness structure as well as elastic nature of articular cartilage with micropolar fluid as lubricant, is derived. The load-carrying capacity and time of approach as functions of film thickness during normal articulation of joints are obtained by using Christensen stochastic theory for rough surfaces with the assumption that the roughness asperity heights are to be small compared to the film thickness. It is observed that the effect of surface roughness has considerable effects on lubrication mechanism of synovial joints.

  • effect of viscosity variation on the micropolar fluid squeeze film lubrication of a short journal bearing
    Advances in Tribology, 2013
    Co-Authors: N B Naduvinamani, A K Kadadi
    Abstract:

    A theoretical study of the effect of the viscosity variation on the squeeze film performance of a short journal bearing operating with micropolar fluid is presented. The Modified Reynolds Equation accounting for the viscosity variation in micropolar fluid is mathematically derived. To obtain a closed form solution, the short bearing approximation under constant load is considered. The Modified Reynolds Equation is solved for the fluid film pressure and then the bearing characteristics, such as obtaining the load carrying capacity and the squeeze film time. According to the results evaluated, the micropolar fluid as a lubricant improves the squeeze film characteristics and results in a longer bearing life, whereas the viscosity variation factor decreases the load carrying capacity and squeezes film time. The result is compared with the corresponding Newtonian case.

  • micropolar fluid squeeze film lubrication between rough anisotropic poroelastic rectangular plates special reference to synovial joint lubrication
    Tribology - Materials Surfaces & Interfaces, 2012
    Co-Authors: G K Savitramma, N B Naduvinamani
    Abstract:

    The effect of anisotropic permeability on micropolar squeeze film lubrication between poroelastic rectangular plates is studied. The non-Newtonian synovial fluid is modelled by Eringen’s micropolar fluid, and the poroelastic nature of cartilage is taken in to account. The stochastic Modified Reynolds Equation, which incorporates the elastic as well as randomised surface roughness structure of cartilage with micropolar fluid as lubricant, is derived. Modified Equations for the mean fluid film pressure, mean load carrying capacity and squeeze film time are obtained using the Christensen’s stochastic theory for the study of roughness effects. The effects of surface roughness, micropolar fluid and anisotropic permeability on the squeeze film characteristics of synovial joint are discussed. It is found that the surface roughness effects are more pronounced for micropolar fluids as compared to the Newtonian fluids, and the anisotropic nature of permeability of cartilage off-squares the plate size for optimum pe...

  • micropolar fluid squeeze film lubrication of finite porous journal bearing
    Tribology International, 2011
    Co-Authors: N B Naduvinamani, S Santosh
    Abstract:

    In this paper, the effect of micropolar fluid on the static and dynamic characteristics of squeeze film lubrication in finite porous journal bearings is studied. The finite Modified Reynolds Equation is solved numerically using the finite difference technique and the squeeze film characteristics are obtained. According to the results obtained, the micropolar fluid effect significantly increases the squeeze film pressure and the load-carrying capacity as compared to the corresponding Newtonian case. Under cyclic load, the effect of micropolar fluid is to reduce the velocity of the journal centre. Effect of porous matrix is to reduce the film pressure, load-carrying capacity and to increase the journal centre velocity.

A K Chattopadhyay - One of the best experts on this subject based on the ideXlab platform.

  • linear stability analysis of hydrodynamic journal bearings under micropolar lubrication
    Tribology International, 2005
    Co-Authors: Santanu Das, Sisir Kumar Guha, A K Chattopadhyay
    Abstract:

    The dynamic characteristics of hydrodynamic journal bearings lubricated with micropolar fluids are presented. The Modified Reynolds Equation is obtained using the micropolar lubrication theory. Applying the first order perturbation of the film thickness and steady state film pressure, the dynamic characteristics in terms of the components of stiffness and damping coefficients, critical mass parameter and whirl ratio are obtained with respect to the micropolar property for varying eccentricity ratios and slenderness ratios. The results show that micropolar fluid exhibits better stability in comparison with Newtonian fluid.

  • theoretical analysis of stability characteristics of hydrodynamic journal bearings lubricated with micropolar fluids
    Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 2004
    Co-Authors: Subrata Das, Sisir Kumar Guha, A K Chattopadhyay
    Abstract:

    AbstractThe aim of the present paper is to study theoretically, using finite difference techniques, the stability characteristics of hydrodynamic journal bearings lubricated with micropolar fluids. The theoretical study has been presented using both the linear analysis based on the perturbation method and non-linear analysis using the Runge-Kutta method. Parametric studies have been conducted and stability characteristics have been obtained and a comparison of the results of linear and non-linear analyses for different parameters have been compared and presented. A Modified Reynolds Equation has been obtained using micropolar lubrication theory and the solution of pressure obtained from this Equation is used in the governing differential Equations of motion to arrive at a stability threshold. The results show that the micropolar fluid exhibits better stability in comparison with the Newtonian fluid.

  • on the steady state performance of misaligned hydrodynamic journal bearings lubricated with micropolar fluids
    Tribology International, 2002
    Co-Authors: Santanu Das, Sisir Kumar Guha, A K Chattopadhyay
    Abstract:

    The present work deals with the micropolar lubrication theory to the problem of the steady-state characteristics of hydrodynamic journal bearings considering two types of misalignment, e.g. axial (vertical displacement) and twisting (horizontal displacement). Using a finite difference method, the steady-state film pressures are obtained by solving Modified Reynolds Equation based on the micropolar lubrication theory. With the help of the steady-state film pressures, the steady-state performance characteristics in terms of load-carrying capacity, misalignment moment and friction parameter of a journal bearing are obtained at various values of eccentricity ratio, degree of misalignment and micropolar fluid characteristic parameters viz. coupling number and non-dimensional characteristic length.

Jawren Lin - One of the best experts on this subject based on the ideXlab platform.

  • squeeze film characteristics of parallel circular disks lubricated by ferrofluids with non newtonian couple stresses
    Tribology International, 2013
    Co-Authors: Jawren Lin, Mingchung Lin, Pinyu Wang
    Abstract:

    Abstract The parallel circular squeeze film disks with a non-Newtonian ferrofluid in the presence of transverse magnetic fields are investigated in this paper. A Modified Reynolds Equation is derived by applying the Shliomis ferrohydrodynamic model incorporating the Stokes microcontinuum theory. Some special cases can be recovered from the present study. Comparing with the Newtonian non-ferrofluid case, the non-Newtonian ferrofluid lubricated squeeze films provide a higher load capacity and lengthen the approaching time. Some numerical results of the load capacity for various parameters are also included in a table for engineering applications.

  • non newtonian effects on the dynamic characteristics of one dimensional slider bearings rabinowitsch fluid model
    Tribology Letters, 2001
    Co-Authors: Jawren Lin
    Abstract:

    The non-Newtonian effects of an isothermal incompressibe laminar-flow lubricant on the dynamic stiffness and damping characteristics of one-dimensional slider bearings are theoretically examined. On the basis of Rabinowitsch fluid (cubic Equation) model, the Modified Reynolds Equation considering bearing-squeeze action is derived to take into account the transient motion of the slider, and the non-Newtonian properties of lubricants. Applying a small perturbation technique, both the steady-state performance and the dynamic characteristics are evaluated. According to the results, the steady film pressure, load-carrying capacity, and the dynamic stiffness and damping behaviors are significantly affected by the values of the dimensionless nonlinear factor accounting for non-Newtonian effects, the wedge parameter of a slider profile and the squeeze number of bearing-squeeze action.

  • squeeze film characteristics between a sphere and a flat plate couple stress fluid model
    Computers & Structures, 2000
    Co-Authors: Jawren Lin
    Abstract:

    Abstract On the basis of the microcontinuum theory, a theoretical analysis of the effects of couple stresses on the squeeze film behavior between a sphere and a flat plate is presented. The Modified Reynolds Equation governing the squeeze film pressure is derived by using the Stokes constitutive Equations to take an account of the couple stress effects due to the lubricant blended with various additives. According to the results obtained, the influence of couple stresses signifies an enhancement in the film pressure. On the whole, the couple stress effects characterized by the couple stress parameter produce an increase in value of the load-carrying capacity and the response time as compared to the classical Newtonian-lubricant case. It improves the squeeze film characteristics of the system.

  • static and dynamic characteristics of externally pressurized circular step thrust bearings lubricated with couple stress fluids
    Tribology International, 1999
    Co-Authors: Jawren Lin
    Abstract:

    The combined effects of couple stresses, fluid inertia and recess volume fluid compressibility on the steady-state performance and the dynamic stiffness and damping characteristics of hydrostatic circular step thrust bearings are presented theoretically. Based on the micro-continuum theory, the Modified Reynolds Equation and the recess flow continuity Equation are derived by using the Stokes constitutive Equations to account for the couple stress effect resulting from a lubricant blended with various additives. Using a perturbation technique, results in terms of steady-state load-carrying capacity, oil flow rate, stiffness and damping coefficients are presented. A design example is also illustrated for engineering and industrial applications.

Satish C Sharma - One of the best experts on this subject based on the ideXlab platform.

  • finite element method analysis of hydrostatic thrust pad bearings operating with electrically conducting lubricant
    Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 2018
    Co-Authors: Vivek Kumar, Satish C Sharma
    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.

  • performance analysis of a fully textured hybrid circular thrust pad bearing system operating with non newtonian lubricant
    Tribology International, 2014
    Co-Authors: Satish C Sharma, Saurabh K Yadav
    Abstract:

    Abstract The present paper deals with the theoretical investigation of the influence of dimple geometry on fully textured hybrid thrust pad bearing and operating with non-Newtonian lubricant. The Modified Reynolds Equation which governs the flow of non-Newtonian lubricant in the clearance space has been solved using Finite Element Method. The simulated results indicate that the values of load carrying capacity, frictional power loss, maximum pressure and fluid film stiffness coefficient are significantly affected by the behavior of lubricant. The results presented in the study are expected to aid in determining the optimum value of dimple diameter and depth for the optimum bearing performance.

  • influence of wear on the performance of a 2 lobe multirecess hybrid journal bearing system compensated with membrane restrictor
    Tribology International, 2011
    Co-Authors: Vikas M Phalle, Satish C Sharma, S C Jain
    Abstract:

    Abstract In the present paper, an analytical study concerning the influence of wear on the performance of a membrane compensated 2-lobe four-pocket hybrid journal bearing system has been presented. The Modified Reynolds Equation governing the flow of lubricant in the clearance space of a journal bearing system was solved using FEM and Newton–Raphson method. The numerically simulated results clearly indicates that the performance of the bearing is greatly affected by wear. A judicious selection of parameters such as δ, δ ¯ w and C ¯ m may provide better bearing performance.

Guang Meng - One of the best experts on this subject based on the ideXlab platform.

  • performance and stability analysis of gas lubricated journal bearings in mems
    Tribology International, 2011
    Co-Authors: Wenming Zhang, Jianbi Zhou, Guang Meng
    Abstract:

    A mathematical model and a computational methodology are presented to simulate the complicated flow behaviors of the journal microbearing in the slip regime, at which the Knudsen number ranges from 0.01 to 0.06. A Modified Reynolds Equation is derived with the slip effect. Static performances of the microbearing are analyzed using spectral collocation method. The effects of the length-to-diameter ratio and slip on the stability of the system are analyzed and the corresponding stability boundaries are calculated numerically. The results indicate that the slip-flow boundary condition enhances the stability of the equilibrium points of the gas-lubricated journal bearing-rotor system.

  • slip model for the ultra thin gas lubricated slider bearings of an electrostatic micromotor in mems
    Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems, 2009
    Co-Authors: Wenming Zhang, Guang Meng, Jianbin Zhou, Jieyu Chen
    Abstract:

    A new slip model derived by molecular dynamics has been used to investigate the ultra-thin gas-lubricated slider bearings beneath the three bushings of an electrostatic micromotor in micro-electro-mechanical systems (MEMS). Modified Reynolds Equation is proposed based on the Modified slip model. Analytical solutions for flow rate, pressure distribution, load carrying capacity and streamwise location using the Modified Reynolds Equation are obtained and compared with the results gained from those in the literature. It demonstrates that the new second-order slip model is of greater accuracy than that predicted by the first-order, second-order slip models and MMGL model and produces a good approximation to variable hard sphere (VHS) and variable soft sphere (VSS) models, which agree well with the solution obtained from the linearized Boltzmann Equation. It is indicated that the slip effect reduces the pressure distribution and load carrying capacity, and shifts the streamwise location of the load carrying capacity, which should not be ignored to study the step-shaped slider bearings in micromotors for MEMS devices.