Surface roughness modification in elastohydrodynamic line contacts operating in the elastic piezoviscous regime

1998 ◽  
Vol 212 (2) ◽  
pp. 145-162 ◽  
Author(s):  
C. J. Hooke
Keyword(s):  
Surface Roughness ◽  
Spatial Distribution ◽  
Analytical Solution ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Entrainment Velocity ◽  
Original Surface ◽  
Ehd Lubrication ◽  
Line Contacts

In heavily loaded elastohydrodynamic (EHD) lubrication contacts operating in the piezoviscous regime, the original surface roughness is largely flattened as it enters the conjunction and is replaced by an inlet generated clearance variation. This clearance variation is convected through the contact at the entrainment velocity. It has a spatial distribution that differs (except for rolling without slip) from the original surface and a different amplitude. This amplitude may be smaller or greater than that of the original profile. An analytical solution of this behaviour is presented for contacts operating well inside the elastic piezoviscous regime for the situation where the roughness is relatively small compared with the film thickness. This solution allows the main features of surface roughness modification to be understood and produces results that compare well with the few numerical solutions available.

The behaviour of heavily loaded line contacts with transverse roughness

1999 ◽  
Vol 213 (4) ◽  
pp. 309-320 ◽  
Author(s):  
C. J. Hooke
Keyword(s):  
Surface Roughness ◽  
Full Range ◽  
Numerical Results ◽  
Operating Conditions ◽  
Entrainment Velocity ◽  
Original Surface ◽  
Line Contacts ◽  
Transverse Roughness ◽  
Inlet Length

In heavily loaded, piezoviscous contacts the surface roughness tends to be flattened inside the conjunction by any relative sliding of the surfaces. However, before it is flattened, the roughness affects the inlet to the contact, producing clearance variations there. These variations are then convected through the contact, at the entrainment velocity, producing a clearance distribution that differs from the original surface. The present paper explores this behaviour and establishes how the amplitude of the convected clearance varies with wavelength and operating conditions. It is shown that the primary influence is the ratio of the wavelength to the inlet length of the conjunction. Where this ratio is large, the roughness is smoothed and there is little variation in clearance under the conjunction. Where the ratio is small, significant variations in clearance may occur but the precise amplitude and phasing depend on the ratio of slide to roll velocities and on the value of a piezoviscous parameter, c. The numerical results agree closely with existing solutions but extend these to cover the full range of operating conditions.

Thermoelastic Effects in Lubricated Rolling/Sliding Line Contacts

1991 ◽  
Vol 113 (1) ◽  
pp. 174-181 ◽  
Author(s):  
P. C. Sui ◽  
F. Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Numerical Model ◽  
Film Thickness ◽  
Thermal Stresses ◽  
Shear Stresses ◽  
Ehd Lubrication ◽  
Line Contacts ◽  
Thermoelastic Effects ◽  
Machine Elements ◽  
Thermoelastic Displacement

A numerical model was developed to investigate the subsurface mechanical and thermal stresses in rolling/sliding machine elements operating under elasto-hydrodynamic (EHD) lubrication of line contacts. A thermal non-Newtonian EHD lubrication model was modified to include the thermoelastic displacement of the solids. The pressure, film thickness, and temperature distribution obtained from the model were used to calculate the subsurface mechanical and thermal stresses within the rolling/sliding machine elements. The thermoelastic effects on the magnitude and location of the maximum shear stresses are presented.

The Effects of Surface Irregularities on the Elastohydrodynamic Lubrication of Sliding Line Contacts. Part I—Single Irregularities

1984 ◽  
Vol 106 (1) ◽  
pp. 104-112 ◽  
Author(s):  
P. R. Goglia ◽  
T. F. Conry ◽  
C. Cusano
Keyword(s):  
Shear Stress ◽  
Film Thickness ◽  
Smooth Surface ◽  
Maximum Stress ◽  
Elastohydrodynamic Lubrication ◽  
Maximum Value ◽  
Ehd Lubrication ◽  
Line Contacts ◽  
Surface Irregularities ◽  
Octahedral Shear Stress

A full line contact solution, under isothermal conditions, is obtained in which the effects of single stationary surface irregularities on the EHD lubrication process are studied under pure sliding conditions. The irregularities studied are furrows, furrows with built-up edges, and asperities. The effects of these irregularities on film thickness, pressure, and subsurface octahedral shear stress are presented. The pressure and film thickness resulting from such surface irregularities are significantly changed from their smooth surface values. These changes alter the state of stress in the subsurface region by increasing the maximum value of octahedral shear stress and bringing the location of this maximum stress closer to the surface. The film thickness in the contact is significantly changed from the smooth surface value only when the irregularities are located in the inlet region while the maximum value of the octahedral shear stress increases to the greatest extent when the irregularities are located in the outlet half of the contact.

Influence of Different Viscosity Lubricant to Finite Line Contacts on Elastohydrodynamic Lubrication (EHL) under Oscillating

2012 ◽  
Vol 538-541 ◽  
pp. 1939-1944
Author(s):  
Yan Fei Wang ◽  
Tong Shu Hua ◽  
Hao Yang Sun
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Oil Film ◽  
Entrainment Velocity ◽  
Finite Line Contact ◽  
Line Contacts ◽  
Finite Line ◽  
Contact Roller ◽  
Two Parameters ◽  
Experimental Rig

To make further researches into the elastohydrodynamic lubrication properties of a finite line contact roller, oscillating experiments were carried out on made overload experimental rig for oil film measurement using optical interference technique. Film thickness and shape were measured in two kinds of viscosity polyisobutylene. This study indicates that both lubricant viscosity and roller entrainment velocity play an important role on EHL of finite line contacts. On motion, the more increase in viscosity or speed, the thicker the oil film thickness, simultaneity edge effect is distinctly intensified and film thickness increases less on roller end, difference of the film thickness is increased between roller end and the central. Above two parameters are significant for logarithmic profile roller in crowning design.

Film thickness fluctuations in time-varying normal loading of rolling elastohydrodynamically lubricated contacts

2010 ◽  
Vol 224 (12) ◽  
pp. 2559-2567 ◽  
Author(s):  
A Félix-Quiñonez ◽  
G E Morales-Espejel
Keyword(s):  
Analytical Solution ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Squeeze Film ◽  
Contact Radius ◽  
Time Varying ◽  
Normal Loading ◽  
Lubricated Contacts ◽  
Approach Problem

A simplified semi-analytical solution for the film thickness fluctuations in the normal-approach problem of elastohydrodynamic lubrication (EHL) contacts has been obtained. The model is based on an inlet analysis to include squeeze-film effects together with the variation of lubricant entrainment speed that is induced by the changes of contact radius as the load oscillates. The results obtained are in excellent agreement with numerical solutions and suggest that the fluctuations in entrainment speed are the main cause for the observed film modulations. The modified semi-analytical solution seems applicable in many practical cases. The amplitude of the film thickness fluctuations produced by fluctuations in the load is in this way related to a single parameter.

The Elastohydrodynamic Lubrication of Heavily Loaded Contacts

1977 ◽  
Vol 19 (4) ◽  
pp. 149-156 ◽  
Author(s):  
C. J. Hooke
Keyword(s):  
Analytical Solution ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Dimensional Parameter ◽  
Effect Of Pressure ◽  
General Line ◽  
Minimum Film Thickness ◽  
Line Contacts

An analytical solution is presented to the problem of the lubrication of highly deformed contacts, including the effect of pressure on viscosity. It is shown that the character of the lubrication process depends on the value of a single non-dimensional parameter, and that for each value of this parameter there is a unique non-dimensional value for minimum film thickness. Results are presented for general line contacts and for cylindrical contacts.

The Minimum Film Thickness in Lubricated Line Contacts during a Reversal of Entrainment—Piezoviscous Behaviour

1992 ◽  
Vol 206 (6) ◽  
pp. 417-424 ◽  
Author(s):  
C J Hooke
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Lubrication Theory ◽  
Rate Of Change ◽  
Operating Conditions ◽  
Entrainment Velocity ◽  
Residual Film ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Important Exception

In many line contacts the operating conditions, such as load, entrainment velocity and contact radii, vary with time. Generally, the results from standard elastohydrodynamic lubrication theory, derived for constant conditions, can be used to obtain a quasi-steady prediction of film thickness that is sufficiently accurate for design purposes. An important exception to this is where the entrainment direction changes because, under those conditions, the quasi-steady approach predicts that there will be no clearance between the surfaces while in practice a residual film will persist. A previous paper showed that the minimum film thickness during entrainment reversal depends primarily on the rate of change of entrainment velocity. Limit expressions for the minimum clearance in the four regimes of lubrication were obtained. The present paper is part of a programme to develop a minimum film thickness chart for entrainment reversal and deals with the transition between the rigid-piezoviscous and the elastic-piezoviscous regimes.

Thermal EHL of Rough Rolling/Sliding Line Contacts Using a Mixture of Two Fluids at Dynamic Loads

2002 ◽  
Vol 124 (4) ◽  
pp. 709-715 ◽  
Author(s):  
Punit Kumar ◽  
S. C. Jain ◽  
S. Ray
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Dynamic Loading ◽  
Coefficient Of Friction ◽  
Contact Region ◽  
Dynamic Loads ◽  
Maximum Pressure ◽  
Moving Surface ◽  
Line Contacts ◽  
Rough Rolling

The behavior of the thermal elastohydrodynamic lubrication film in rough rolling/sliding line contacts at dynamic loads is investigated numerically. The lubricant is assumed to be a mixture of Newtonian and Ree-Eyring fluids. The results show that the maximum pressure in the contact region undergoes a noteworthy change with time due to dynamic loading and the effect of moving surface roughness. The variation of minimum film thickness and coefficient of friction with the composition of the lubricant is found to be dependent upon the reference viscosity ratio. The superposition of the effects of moving surface roughness and dynamic loading is shown to determine the behavior of time dependent film thickness and coefficient of friction.

A Reynolds-Eyring Equation for Elastohydrodynamic Lubrication in Line Contacts

1987 ◽  
Vol 109 (4) ◽  
pp. 648-654 ◽  
Author(s):  
T. F. Conry ◽  
S. Wang ◽  
C. Cusano
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Newtonian Flow ◽  
Line Contacts ◽  
Different Temperatures ◽  
Eyring Model ◽  
Eyring Theory ◽  
New Equation

A new Reynolds equation, based on the Eyring theory of non-Newtonian flow, is derived for flow in one dimension. It is shown that this new equation reduces to the traditional Reynolds equation as the Eyring model approaches the Newtonian model in the limit. Numerical solutions are presented for a selected oil at two different temperatures. The central film thickness decreases with increasing dimensionless viscosity parameter and slide/roll ratios. A transition zone is noted through which the ratio of minimum to central film thickness passes as the pressure distribution goes from near Hertzian to a distribution that appreciably deviates from Hertzian.

The Minimum Film Thickness in Lubricated Line Contacts during a Reversal of Entrainment—Isoviscous Behaviour

1992 ◽  
Vol 206 (5) ◽  
pp. 337-345 ◽  
Author(s):  
C J Hooke
Keyword(s):  
Film Thickness ◽  
Transition Zone ◽  
Static Analysis ◽  
Rate Of Change ◽  
Entrainment Velocity ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Static Approach ◽  
The One

In most line contacts, the film thickness can be adequately determined using a quasi-static analysis. The one exception appears to occur when the direction of entrainment changes. Here, the quasi-static approach predicts that the film will fall to zero while, in practice, there will always be a finite clearance between the surfaces. It was shown in a previous paper that this minimum clearance depends upon the rate of change of entrainment velocity, and limit expressions for the film thicknesses in the four regimes of lubrication were developed. The present paper examines the transition between the rigid-isoviscous and the elastic-isoviscous regimes and determines how the minimum film thickness behaves in this transition zone.

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