Estimation of Minimum Thickness for Line Contacts in the Transition Region between the Isoviscous—Elastic and the Piezoviscous-Elastic Lubrication Regimes

1989 ◽  
Vol 203 (6) ◽  
pp. 379-386 ◽  
Author(s):  
M J Jaffar
Keyword(s):  
Film Thickness ◽  
Transition Region ◽  
Approximate Formula ◽  
Line Contact ◽  
Minimum Thickness ◽  
Lubrication Regimes ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Good Agreement

This paper represents a solution for lubricated cylinders in line contact operating in the transition region between isoviscous-elastic and piezoviscous-elastic conditions. The computer solutions are used to generate a formula for the minimum film thickness. The approximate formula is compared with the existing formulae at the boundaries of the lubrication regimes where good agreement is obtained. Also, the influence of the starvation on pressure and film thickness is investigated.

Numerical Analysis for Influence of Plastic and Elastic Deformation of Rough Surfaces on PEHL for Line Contacts

Tribology ◽  
2005 ◽  
Author(s):  
R. J. Niu ◽  
P. Huang
Keyword(s):  
Plastic Deformation ◽  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Paper Analysis ◽  
Line Contact ◽  
Plastic Deformations ◽  
Rolling Contacts ◽  
Line Contacts ◽  
Elastic And Plastic Deformations ◽  
Strain Relationship

In the present paper, analysis of elasto-plasto-hydrodynamic lubrication (PEHL) in the line contact is carried out to investigate the effect of heavily loaded roll-over on the change in profile of indents. The pressure and film thickness profiles are obtained to solve the Reynolds and film thickness equations simultaneously. And, both the elastic and plastic deformations of the contact, featured with an indent, have been considered. A multi-grid numerical algorithm used in EHL of line contacts is modified and then used for the oil lubricated rolling contacts. In the program, stress and plastic deformation of the indent profile are calculated with the hardening plastic stress-strain relationship according to the theories of plasticity when pressure excesses the yield stress. The results, with and without considering plastic deformation, are compared to show the different influences on the pressure and film thickness. Analysis shows that since the plastic deformation will change the surface roughness, it will significantly change the pressure but film thickness.

scholarly journals Lubrication and frictional analysis of cam–roller follower mechanisms

2017 ◽  
Vol 232 (3) ◽  
pp. 347-363 ◽  
Author(s):  
Shivam S Alakhramsing ◽  
Matthijn de Rooij ◽  
Dirk Jan Schipper ◽  
Mark van Drogen
Keyword(s):  
Film Thickness ◽  
Finite Length ◽  
Power Loss ◽  
Fuel Injection ◽  
Contact Forces ◽  
Injection System ◽  
Maximum Pressure ◽  
Line Contact ◽  
Power Losses ◽  
Minimum Film Thickness

In this work, a full numerical solution to the cam–roller follower-lubricated contact is provided. The general framework of this model is based on a model describing the kinematics, a finite length line contact isothermal-EHL model for the cam–roller contact and a semi-analytical lubrication model for the roller–pin bearing. These models are interlinked via an improved roller–pin friction model. For the numerical study, a cam–roller follower pair, as part of the fuel injection system in Diesel engines, was analyzed. The results, including the evolution of power losses, minimum film thickness and maximum pressures, are compared with analytical solutions corresponding to infinite line contact models. The main findings of this work are that for accurate prediction of crucial performance indicators such as minimum film thickness, maximum pressure and power losses a finite length line contact analysis is necessary due to non-typical EHL characteristics of the pressure and film thickness distributions. Furthermore, due to the high contact forces associated with cam–roller pairs as part of fuel injection units, rolling friction is the dominant power loss contributor as roller slippage appears to be negligible. Finally, the influence of the different roller axial surface profiles on minimum film thickness, maximum pressure and power loss is shown to be significant. In fact, due to larger contact area, the maximum pressure can be reduced and the minimum film thickness can be increased significantly, however, at the cost of higher power losses.

Stribeck Curve for Starved Line Contacts

2006 ◽  
Vol 129 (1) ◽  
pp. 181-187 ◽  
Author(s):  
I. C. Faraon ◽  
D. J. Schipper
Keyword(s):  
Film Thickness ◽  
Layer Thickness ◽  
Boundary Lubrication ◽  
Numerical Data ◽  
Contact Model ◽  
Stribeck Curve ◽  
Lubrication Regime ◽  
Straight Line ◽  
Line Contacts ◽  
Good Agreement

This paper discusses a mixed lubrication model in order to predict the Stribeck curve for starved lubricated line contacts. This model is based on a combination of the contact model of Greenwood and Williamson and the elastohydrodynamic (EHL) film thickness for starved line contacts. The starved solution to be implemented in the EHL component is obtained by using numerical data of Wolveridge, who computed the starved film thickness for smooth line contacts. Calculations are presented for different oil supply layer thickness over roughness values (hoil∕σs). For values of the oil layer thickness over roughness ratio larger than approximately 6, the Stribeck curve and separation between the rough surfaces do not change compared to the fully flooded situation. If the oil layer thickness over roughness ratio is in the range of 6 down to 0.7, friction starts to increase and the film thickness decreases. When the oil layer thickness over roughness ratio is less than approximately 0.7, the Stribeck curve tends to transform into a straight line and separation stays at the same value as in the boundary lubrication regime. Comparison between measurements and calculations is made and a good agreement is found.

Elastohydrodynamic lubrication of soft viscoelastic materials in line contact

1997 ◽  
Vol 211 (3) ◽  
pp. 185-194 ◽  
Author(s):  
C. J. Hooke ◽  
P Huang
Keyword(s):  
Film Thickness ◽  
Energy Loss ◽  
Elastohydrodynamic Lubrication ◽  
Soft Materials ◽  
Deborah Number ◽  
Line Contact ◽  
Hertz Contact ◽  
Contact Width ◽  
Minimum Film Thickness ◽  
Viscoelastic Effects

The paper discusses the influence of viscoelasticity in elastohydrodynamic lubrication (EHL). It is shown that viscoelastic effects, particularly in soft materials such as rubber and polymers, may significantly affect the lubrication process. The variations of the pressure and film thickness with viscoelasticity are discussed, as is the internal energy loss in the material. Two effects are present. The first, controlled by the Deborah number based on the Hertz contact width, determines the width of the contact, the overall pressure distribution and the energy loss. The second, controlled by the Deborah number based on the entrainment length, largely determines the thickness of the entrained film and the minimum film thickness.

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.

Reflections on Some Aspects of Lubrication of Concentrated Line Contacts

1979 ◽  
Vol 101 (4) ◽  
pp. 528-531 ◽  
Author(s):  
P. H. Markho ◽  
D. B. Clegg
Keyword(s):  
Film Thickness ◽  
Curve Fitting ◽  
Line Contact ◽  
Intermediate Region ◽  
Force Component ◽  
Pressure Force ◽  
Tangential Pressure ◽  
Method Of Least Squares ◽  
End Conditions ◽  
Line Contacts

New formulas are presented for two important lubrication parameters of a flooded, concentrated line contact, namely the tangential pressure force component under elasto-hydrodynamic (EHD) conditions and the film thickness in the “intermediate” region defined by Dowson and Whitaker [1]. The latter region, which separates the rigid-isoviscous region from the elastic-piezoviscous (or EHD) region, has not, so far, been represented by an equation. The first formula was obtained simply by curve-fitting, using the method of least squares, from data largely available in the published literature; while the second is basically a third degree Hermite osculating polynomial with four end conditions.

The Influence of the Roughness Parameters on the EHL Line Contact Using the Free Volume Model

2013 ◽  
Author(s):  
V. D’Agostino ◽  
V. Petrone ◽  
A. Senatore
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Free Volume ◽  
Rough Surfaces ◽  
Random Number Generator ◽  
Elastohydrodynamic Lubrication ◽  
Maximum Pressure ◽  
Line Contact ◽  
Volume Viscosity ◽  
Minimum Film Thickness

A numerical solution of elastohydrodynamic lubrication (EHL) contact between two rough surface cylinders is presented. In the theoretical approach the free-volume viscosity model is used to describe the piezo-viscous behavior of the lubricant in a Newtonian Elastohydrodynamic line contact [1,2]. Random rough surfaces with Gaussian and exponential statistics have been generated using a method outlined by Garcia and Stoll [3], where an uncorrelated distribution of surface points using a random number generator is convolved with a Gaussian filter to achieve correlation. This convolution is most efficiently performed using the discrete Fast Fourier Transform (FFT) algorithm, which in MATLAB is based on the FFTW library [4]. The maximum pressure and average film thickness are studied at different values of RMS, skewness, kurtosis, autocorrelation function and correlation length. Numerical examples show that skewness and kurtosis have a great effect on the parameters of EHD lubrication. Surface roughness, indeed, tends to reduce the minimum film thickness and it produces pressure fluctuations inside the conjunction which tend to increase the maximum stress. In this way the dynamic stress increases and tends to reduce the fatigue life of the components. It can be seen that the pressures developed in the fluid film in the case of rough surfaces fluctuate with the same frequency of the surface roughness. These pressure ripples correspond to the asperity peaks. This indicates that surface roughness causes very high local contact pressures which may lead to local thinning of the film. A significant reduction has been also observed in the minimum film thickness due to surface roughness.

Multigrid, An Alternative Method for Calculating Film Thickness and Pressure Profiles in Elastohydrodynamically Lubricated Line Contacts

1986 ◽  
Vol 108 (4) ◽  
pp. 551-556 ◽  
Author(s):  
A. A. Lubrecht ◽  
W. E. ten Napel ◽  
R. Bosma
Keyword(s):  
Film Thickness ◽  
Multigrid Method ◽  
Computing Time ◽  
Alternative Method ◽  
Pressure Profiles ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Pressure Spike ◽  
Order Of Magnitude

Film thickness and pressure profiles have been calculated for line contacts at moderate and high loads, using a Multigrid method. Influence of the compressibility of the lubricant on the minimum film thickness and on the pressure spike has been examined. The required computing time is an order of magnitude less than when using the previous methods.

The Minimum Film Thickness in Line Contacts During Reversal of Entrainment

1993 ◽  
Vol 115 (1) ◽  
pp. 191-199 ◽  
Author(s):  
C. J. Hooke
Keyword(s):  
Steady State ◽  
Film Thickness ◽  
Rate Of Change ◽  
Radius Of Curvature ◽  
Operating Cycle ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Involute Gears ◽  
Shaft Seals ◽  
Steady State Predictions

In contacts, such as cams, non-involute gears and shaft seals, where the direction of entrainment reverses during the operating cycle, the minimum film thickness is typically found just after the reversal. This paper shows that this minimum film thickness is determined by the rate of change of the entraining velocity and by the fluid and surface properties. For line contacts, four regimes of lubrication are found—as for the steady-state situation—and expressions for the film thickness in each regime are developed. This enables an outline design chart for the minimum film thickness to be constructed. It is shown that this information, together with the steady-state predictions is sufficient to determine the variation of film thickness with time in most situations where load, radius of curvature, and entraining velocity vary.

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