Influence of Surface Roughness and Its Orientation on Partial Elastohydrodynamic Lubrication of Rollers

1983 ◽  
Vol 105 (4) ◽  
pp. 591-597 ◽  
Author(s):  
J. Prakash ◽  
H. Czichos
Keyword(s):  
Reynolds Equation ◽  
Complete Solution ◽  
Elastohydrodynamic Lubrication ◽  
Coupled System ◽  
Line Contact ◽  
Roughness Parameters ◽  
Regime Changes ◽  
Lubrication Regime ◽  
Elasticity Equation ◽  
The Stability

In this paper, a complete solution for a rough, isothermal elastohydrodynamic line contact operating in the partial lubrication regime is presented. The semianalytical EHD line contact model developed recently [12], is used in solving the coupled system of average Reynolds equation and the elasticity equation. The effects of various operating parameters and the roughness parameters are investigated with an emphasis on the outlet behavior. The results indicate that in the partial lubrication regime changes in the outlet may play an important role on the stability of elastohydrodynamic films.

Effect of Surface Roughness on the Point Contact EHL

1988 ◽  
Vol 110 (1) ◽  
pp. 32-37 ◽  
Author(s):  
D. Zhu ◽  
H. S. Cheng
Keyword(s):  
Reynolds Equation ◽  
Point Contact ◽  
Roughness Parameter ◽  
Elastohydrodynamic Lubrication ◽  
Surface Pattern ◽  
Roughness Parameters ◽  
Elasticity Equation ◽  
Asperity Contacts ◽  
Surface Irregularities ◽  
Effect Of Surface

In this paper a full numerical solution for the partial elastohydrodynamic lubrication in elliptical contacts is presented, and the procedure of computation is briefly described. The average Reynolds equation developed by Patir and Cheng, the elasticity equation, and the pressure-viscosity relationship are solved simultaneously. The asperity contacts are also taken into account by using the model contributed by Greenwood and Tripp. The distribution of surface irregularities is assumed to be Gaussian. The effects of various roughness parameters on the film thickness are investigated. Special attention is given to the surface pattern parameter and hydrodynamic roughness parameter.

On the Stability and Uniqueness of Elastohydrodynamic Lubrication Solutions

1988 ◽  
Vol 110 (4) ◽  
pp. 628-631 ◽  
Author(s):  
D. W. Glander ◽  
E. J. Bissett
Keyword(s):  
Standard Model ◽  
Contact Problem ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Multiplicity Of Solutions ◽  
The Standard Model ◽  
Unstable Solutions ◽  
Model Equations ◽  
The Stability

It was suggested in [1] that solutions of the line contact problem of elastohydrodynamic lubrication (EHL) are unstable in a certain parameter regime, and that both stable and unstable solutions can coexist in another regime. The author also suggested that these regimes limit the applicability of the standard model equations. In this work, the present authors repeat this calculation using the highly accurate solutions described in our previous work [3]. In all cases we have considered, we find no evidence of instability or multiplicity of solutions. We conclude that the existence of regions of instability or multiplicity were based on numerical artifacts and that considerations of stability or multiplicity do not limit the applicability of the standard model equations of EHL.

Study on Photoelastic Method for Measuring Elastohydrodynamic Lubrication Pressure in Line Contact

2013 ◽  
Vol 281 ◽  
pp. 329-334
Author(s):  
Jun He ◽  
Huang Ping ◽  
Qian Qian Yang
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Reynolds Equation ◽  
Friction Pair ◽  
Elastohydrodynamic Lubrication ◽  
Ccd Camera ◽  
Measuring System ◽  
Line Contact ◽  
Basic Equations ◽  
Plastic Disk

In the present paper, a new method for measuring elastohydrodynamic lubrication (EHL) pressure in line contact is proposed, which is based on the photoelastic technique. The pressure distribution of EHL film and the inner stresses in the friction pairs are fundamental issues to carry out EHL research. The film thickness, pressure and temperature have been successfully obtained with solving the basic equations such as Reynolds equation and energy equation simultaneously or separately, with numerical model of EHL problem. The film thickness can be also measured with the optical interference technique. However, the pressure measurement is still a problem which has not been well solved yet, so as the inner stresses inside the friction pairs. With the experimental mechanics, the photoelastic technique is a possible method to be used for measuring the pressure distribution of EHL film and inner friction pair in the line contact. Therefore, A flat plastic disk and a steel roller compose the frictional pairs of the photoelastic pressure measuring rig with combining the monochromatic LED light source, polarizer CCD camera and stereomicroscope to form the whole pressure measuring system of the line contact EHL. The experimental results with the rig display the typical features of EHL pressure. This shows that the method is feasible to be used for measuring the pressure of EHL film and the inner stresses of the friction pairs in the line contact.

Film Thickness and Asperity Load Formulas for Line-Contact Elastohydrodynamic Lubrication With Provision for Surface Roughness

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
M. Masjedi ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Load Ratio ◽  
Material Surface ◽  
Line Contact ◽  
Wide Range ◽  
Minimum Film Thickness

Three formulas are derived for predicting the central and the minimum film thickness as well as the asperity load ratio in line-contact EHL with provision for surface roughness. These expressions are based on the simultaneous solution to the modified Reynolds equation and surface deformation with consideration of elastic, plastic and elasto-plastic deformation of the surface asperities. The formulas cover a wide range of input and they are of the form f(W, U, G, σ¯, V), where the parameters represented are dimensionless load, speed, material, surface roughness and hardness, respectively.

A Generalized Reynolds Equation for Non-Newtonian Thermal Elastohydrodynamic Lubrication

1990 ◽  
Vol 112 (4) ◽  
pp. 631-636 ◽  
Author(s):  
Yang Peiran ◽  
Wen Shizhu
Keyword(s):  
Reynolds Equation ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Generalized Reynolds Equation ◽  
Newtonian Behavior

A new generalized Reynolds equation, which can incorporate most of the rheological laws found in the literature, is derived in this paper. A number of numerical solutions of the line contact thermal elastohydrodynamic lubrication problem has been obtained by using five rheological laws. The results show that, the influence of the non-Newtonian behavior of lubricant is not as important as that of the thermal one, when Roelands’ viscosity is used in the study.

Mixed lubrication of soft contacts: An engineering look

2016 ◽  
Vol 231 (2) ◽  
pp. 263-273 ◽  
Author(s):  
M Masjedi ◽  
MM Khonsari
Keyword(s):  
Elastic Modulus ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Load Ratio ◽  
Soft Materials ◽  
Line Contact ◽  
Soft Contact ◽  
Lubrication Regime ◽  
Low Elastic Modulus ◽  
Stribeck Curves

Mixed elastohydrodynamic lubrication of materials with low elastic modulus (soft materials) is investigated. Expressions for prediction of film thickness and the asperity load ratio in soft line-contact elastohydrodynamic lubrication are presented. The traction behavior of soft contact in mixed elastohydrodynamic lubrication regime is also studied in terms of the Stribeck curves.

The Behaviour of Transverse Roughness in EHL Contacts

1994 ◽  
Vol 208 (2) ◽  
pp. 121-132 ◽  
Author(s):  
J A Greenwood ◽  
G E Morales-Espejel
Keyword(s):  
Reynolds Equation ◽  
Complete Solution ◽  
Elastohydrodynamic Lubrication ◽  
Steady State Solution ◽  
Two Dimensional ◽  
Viscosity Effects ◽  
Complementary Function ◽  
Mean Pressure ◽  
Transverse Roughness ◽  
Transient Case

By assuming the contact geometry in elastohydrodynamic lubrication (EHL) to be that of an infinitely long contact with given nominal film thickness and mean pressure and considering the elastic displacements of the separate components of the initial roughness, it is possible to extend the Greenwood and Johnson analysis for sinusoidal pressure to any two-dimensional roughness. For typical EHL pressures the viscosity effects are negligible, so the Reynolds equation can be linearized and solved analytically; the solution provides a criterion to relate the amplitudes of the undeformed and deformed roughness to the wavelength, and shows that roughness with a short wavelength is likely to persist after deformation. The linearization of the Reynolds equation is extended to the transient case and it is found that the complete solution is made of two separate parts: the particular integral (steady state solution) and the complementary function (which depends on the entry of the partly deformed roughness into the Hertzian zone).

Elastohydrodynamic Lubrication of Rough Surfaces Under Oscillatory Line Contact With Non-Newtonian Lubricant

2007 ◽  
Author(s):  
Mongkol Mongkolwongrojn ◽  
Khanittha Wongseedakaew ◽  
Francis E. Kennedy
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Power Law ◽  
Reynolds Equation ◽  
Initial Conditions ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Oscillatory Motion ◽  
Line Contact ◽  
Minimum Film Thickness

This paper presents the analysis of elastohydrodynamic lubrication (EHL) of two parallel cylinders in line contact with non-Newtonian fluids under oscillatory motion. The effects of transverse harmonic surface roughness are also investigated in the numerical simulation. The time-dependent Reynolds equation uses a power law model for viscosity. The simultaneous system of modified Reynolds equation and elasticity equation with initial conditions was solved using multi-grid multi-level method with full approximation technique. Film thickness and pressure profiles were determined for smooth and rough surfaces in the oscillatory EHL conjunctions, and the film thickness predictions were verified experimentally. For an increase in the applied load on the cylinders, the minimum film thickness calculated numerically becomes smaller. The predicted film thickness is slightly higher than the film thickness obtained experimentally, owing to cavitation that occurred in the experiments. For both hard and soft EHL contacts, the minimum film thickness under oscillatory motion is very thin near the trailing edge of the contact, especially for stiffer surfaces. The surface roughness and power law index of the non-Newtonian lubricant both have significant effects on the film thickness and pressure profile between the cylinders under oscillatory motion.

Elastohydrodynamic Line-Contact of Compressible Shear Thinning Fluids With Consideration of the Surface Roughness

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
J. Y. Jang ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Total Pressure ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Shear Thinning ◽  
Line Contact ◽  
Lubricating Film ◽  
Shear Thinning Fluids ◽  
Modified Reynolds Equation

Applications involving highly loaded elastohydrodynamic lubrication (EHL), particularly when the lubricant experiences shear thinning, operating with small film thicknesses may necessitate consideration of surface asperities. A modified Reynolds equation with provision for surface roughness and shear thinning is treated to predict the pressure and surface asperity effect in an EHL line-contact. The unknown in the Reynolds equation is the hydrodynamic pressure instead of the total pressure to ensure that the pressure boundary condition at the outlet is properly posed. The Carreau viscosity model is used for characterizing the shear thinning behavior, Patir and Cheng flow factors for taking into the influence of roughness on the lubricating film, and Greenwood–Trip for determination of pressure at the asperity level. The modified Reynolds equation is solved for the hydrodynamic pressure instead of the total pressure with appropriately defined boundary conditions.

Elastohydrodynamic analysis of one-layered journal bearings

1998 ◽  
Vol 212 (3) ◽  
pp. 193-205 ◽  
Author(s):  
M Lahmar ◽  
A Haddad ◽  
D Nicolas
Keyword(s):  
Reynolds Equation ◽  
Mathematical Problem ◽  
Elastohydrodynamic Lubrication ◽  
Stability Margin ◽  
Journal Bearings ◽  
Perturbation Approach ◽  
Variable Approach ◽  
Load Carrying ◽  
Fast Solution ◽  
The Stability

Steady state and dynamic solutions to the problem of isothermal elastohydrodynamic lubrication of single-layered journal bearings are derived and presented. The mathematical problem comprises two parts: fluid and elasticity. The elasticity problem is governed by the elastostatic equations which are solved by application of a complex variable approach using the complex Kolosov-Muskhelishvili potentials. The fluid problem is described by the two-dimensional Reynolds equation which is discretized using a finite difference approach and solved by application of the Gauss-Seidel scheme with the Swift-Stieber boundary conditions. The fluid-structure coupling is achieved by an iterative procedure with an under-relaxation algorithm. The dynamic coefficients are obtained by use of a first-order perturbation approach. The results obtained show that the proposed elasticity model permits a fast solution of the problem, particularly under dynamic conditions. They also show that, under the effect of coating elastic deformation, the contact geometry is modified and the load-carrying capacity decreases while the stability margin of the journal bearing system increases.

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