scholarly journals A New Approach for Estimating the Friction in Thin Film Lubrication

2010 ◽  
Vol 2010 ◽  
pp. 1-15 ◽  
Author(s):  
Dag Lukkassen ◽  
Annette Meidell ◽  
Peter Wall
Keyword(s):  
Surface Roughness ◽  
Variational Problem ◽  
Reynolds Equation ◽  
Main Idea ◽  
Thin Film Lubrication ◽  
New Approach ◽  
Fine Mesh ◽  
Load Carrying ◽  
Film Lubrication ◽  
Effect Of Surface

An important problem in the theory of lubrication is to model and analyze the effect of surface roughness on, for example, the friction and load carrying capacity. A direct numerical computation is often impossible since an extremely fine mesh is required to resolve the surface roughness. This suggests that one applies some averaging technique. The branch in mathematics which deals with this type of questions is known as homogenization. In this paper we present a completely new method for computing the friction. The main idea is that we study the variational problem corresponding to the Reynolds equation. We prove that the homogenized variational problem is closely related to the homogenized friction. Finally we use bounds on the homogenized Lagrangian to derive bounds for the friction. That these bounds can be used to efficiently compute the friction is demonstrated in a typical example.

The Present State of Lubrication and Its Relation to Rheology

1968 ◽  
Vol 90 (3) ◽  
pp. 526-530 ◽  
Author(s):  
J. K. Appeldoorn
Keyword(s):  
Thin Film ◽  
Reynolds Equation ◽  
Mathematical Treatment ◽  
Load Carrying Capacity ◽  
Thin Film Lubrication ◽  
Load Carrying ◽  
Viscoelastic Effects ◽  
Viscoelastic Liquids ◽  
Film Lubrication ◽  
Made In

In thick-film lubrication, Reynolds’ equation is generally satisfactory. However, the assumptions made in deriving this equation cannot be justified for non-Newtonian, viscoelastic liquids. It is concluded that no satisfactory mathematical treatment is yet available for calculating the load-carrying capacity of such liquids. In thin-film lubrication, elastohydrodynamic calculations indicate that the lubricant film may be quite thick even under heavily loaded conditions, but discrepancies exist between calculation and experiment. These can be explained by assuming non-Newtonian behavior, or unusual viscoelastic effects, but the assumptions are largely unfounded. There is virtually a complete absence of data on the behavior of liquids under impact loading. Such data are needed to resolve whether thin-film lubrication is primarily chemical or primarily physical.

scholarly journals MULTIGRID METHOD FOR THE SOLUTION OF COMBINED EFFECT OF VISCOSITY VARIATION AND SURFACE ROUGHNESS ON THE SQUEEZE FILM LUBRICATION OF JOURNAL BEARINGS

2017 ◽  
Vol 46 (1) ◽  
pp. 1-8
Author(s):  
Vishwanath B. Awati ◽  
Ashwini Kengangutti ◽  
Mahesh Kumar N.
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Micropolar Fluid ◽  
Reynolds Equation ◽  
Multigrid Method ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Viscosity Variation ◽  
Film Lubrication

The paper presents, the multigrid method for the solution of combined effect of surface roughness and viscosity variation on the squeeze film lubrication of a short journal bearing operating with micropolar fluid. The modified Reynolds equation which incorporates the variation of viscosity in micropolar fluid is analysed using Multigrid method. The governing modified Reynolds equation is solved numerically for the fluid film pressure and bearing characteristics viz. load carrying capacity and squeeze time. The analysis of the results predicts that, the viscosity variation factor decreases the load carrying capacity and squeeze film time, resulting into a longer bearing life. The results are compared with the corresponding analytical solutions.

Combined effect of surface roughness and pressure-dependent viscosity over couple-stress squeeze film lubrication between circular stepped plates

2018 ◽  
Vol 232 (5) ◽  
pp. 525-534 ◽  
Author(s):  
BN Hanumagowda ◽  
BT Raju ◽  
J Santhosh Kumar ◽  
KR Vasanth
Keyword(s):  
Surface Roughness ◽  
Carrying Capacity ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
One Dimensional ◽  
Pressure Dependent Viscosity ◽  
Load Carrying ◽  
Dependent Viscosity ◽  
Film Lubrication ◽  
Effect Of Surface

In this paper, the effect of surface roughness and pressure-dependent viscosity over couple-stresses squeeze film lubrication between circular stepped plates is studied. The modified average Reynolds equation is derived for the one-dimensional roughness structures, namely the radial roughness pattern and azimuthal roughness pattern. Modified equations for the nondimensional pressure, load-carrying capacity, and nondimensional squeeze film time are obtained. Also, the obtained results of our study for some special cases are compared with the previously published smooth surface case, and the results are found to be in very good agreement. It is observed that, one-dimensional azimuthal (radial) roughness pattern on the rough circular stepped plate increases (decreases) the load-carrying capacity and the squeeze film time as compared to the smooth case.

Thin-Film Lubrication Theory for Newtonian Fluids With Surfaces Possessing Striated Roughness or Grooving

1973 ◽  
Vol 95 (4) ◽  
pp. 484-489 ◽  
Author(s):  
H. G. Elrod
Keyword(s):  
Reynolds Equation ◽  
Multiple Scale ◽  
Support Pressure ◽  
Load Carrying Capacity ◽  
Transient Effects ◽  
Thin Film Lubrication ◽  
Load Carrying ◽  
Bearing Design ◽  
First Time ◽  
Film Lubrication

Earlier work by others concerning the effects of striated roughness and grooving upon the load-carrying capacity of lubricating films is summarized, substantiated, and generalized. A multiple-scale double-variable technique is used on such lubrication problems for the first time. The present analysis applies to one-face roughness having striation wavelengths sufficiently long for the applicability of Reynolds equation. Transient effects are included. The final differential equation for support pressure is simple in form. In addition to predicting the effects of striated “Reynolds roughness”, this equation can be directly used in grooved-bearing design.

Effect of surface roughness on couple stress squeeze film lubrication of long porous partial journal bearings

2006 ◽  
Vol 58 (4) ◽  
pp. 176-186 ◽  
Author(s):  
N.M. Bujurke ◽  
N.B. Naduvinamani ◽  
Syeda Tasneem Fathima ◽  
S.S. Benchalli
Keyword(s):  
Surface Roughness ◽  
Couple Stress ◽  
Journal Bearings ◽  
Squeeze Film ◽  
Film Lubrication ◽  
Effect Of Surface

A Porous Media Model for Thin Film Lubrication

1995 ◽  
Vol 117 (1) ◽  
pp. 16-21 ◽  
Author(s):  
J. A. Tichy
Keyword(s):  
Reynolds Equation ◽  
Squeezing Flow ◽  
Thin Film Lubrication ◽  
Porous Layers ◽  
Porosity Parameter ◽  
Porous Media Model ◽  
Molecular Length ◽  
Load Increase ◽  
Thickness Parameter ◽  
Film Lubrication

A rheological model has been developed which can be applied to boundary lubrication. The model is applicable to thin films in which the molecular length scale is the same order as the film thickness. The micro structure is simulated by porous layers attached to the contact surfaces. The model contains three material properties: (1) viscosity, (2) the thickness of the porous layer, and (3) a porosity parameter. A modified Reynolds equation is developed. Behavior in two types of contacts is calculated: squeezing flow between crossed cylinders (Chan and Horn’s, 1985 drainage experiment) and a one-dimensional converging wedge contact. The effect of the layer thickness parameter is to increase the load and reduce the friction coefficient. Increasing the porosity parameter value tends to reduce the magnitude of the load increase.

Calculation of Surface Roughness Effects on Air-Riding Seals

2002 ◽  
Author(s):  
C. Guardino ◽  
J. W. Chew ◽  
N. J. Hills
Keyword(s):  
Surface Roughness ◽  
Compressible Flows ◽  
Reynolds Equation ◽  
Incompressible Flows ◽  
Numerical Solutions ◽  
Cfd Analysis ◽  
Roughness Effects ◽  
Stationary Wall ◽  
Comparative Results ◽  
Effect Of Surface

The effects of surface roughness on air-riding seals are investigated here using the Rayleigh-pad as an example. Both incompressible and compressible flows are considered using both CFD analysis and analytical/numerical solutions of the Reynolds equation for various 2D or 3D roughness patterns on the stationary wall. A ‘unit-based’ approach for incompressible flows has also been employed and is shown to be computationally much less expensive than the full-geometry solution. Results are presented showing the effect of surface roughness on the net lift force. The effects of varying the Reynolds number are demonstrated, as well as comparative results for static stiffness.

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