A Study of Elastohydrodynamic Lubrication of Rough Surfaces

1991 ◽  
Vol 113 (1) ◽  
pp. 110-115 ◽  
Author(s):  
L. Chang ◽  
M. N. Webster
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Rough Surface ◽  
Contact Zone ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Micro Deformation ◽  
Sinusoidal Functions ◽  
Sensitive Parameters ◽  
Pressure Perturbations

This paper reports some results of rough-surface, elastohydrodynamically lubricated (EHD) contacts obtained using a previously developed transient EHD model. The surface roughness is modeled with sinusoidal functions of small wavelength compared to the contact zone. Results are presented showing how the operating conditions affect the film thickness, micro-deformation of the roughness, and the pressure perturbations due to motion and interaction of roughness within the contact. This preliminary work suggests that the entraining velocity and the slide-to-roll ratio are the most sensitive parameters influencing the lubrication process of rough-surface EHD contacts.

A Starved Mixed Elastohydrodynamic Lubrication Model for the Prediction of Lubrication Performance, Friction and Flash Temperature With Arbitrary Entrainment Angle

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Wei Pu ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Flash Temperature ◽  
Machined Surface ◽  
Lubrication Performance ◽  
Wide Range ◽  
Starved Lubrication

In this study, a modified mixed lubrication model is developed with consideration of machined surface roughness, arbitrary entraining velocity angle, starvation, and cavitation. Model validation is executed by means of comparison between the obtained numerical results and the available starved elastohydrodynamic lubrication (EHL) data found from some previous studies. A comprehensive analysis for the effect of inlet oil supply condition on starvation and cavitation, mixed EHL characteristics, friction and flash temperature in elliptical contacts is conducted in a wide range of operating conditions. In addition, the influence of roughness orientation on film thickness and friction is discussed under different starved lubrication conditions. Obtained results reveal that inlet starvation leads to an obvious reduction of average film thickness and an increase in interasperity cavitation area due to surface roughness, which results in significant increment of asperity contacts, friction, and flash temperature. Besides, the effect of entrainment angle on film thickness will be weakened if the two surfaces operate under starved lubrication condition. Furthermore, the results show that the transverse roughness may yield thicker EHL films and lower friction than the isotropic and longitudinal if starvation is taken into account. Therefore, the starved mixed EHL model can be considered as a useful engineering tool for industrial applications.

On the Pressure Rippling and Roughness Deformation in Elastohydrodynamic Lubrication of Rough Surfaces

1993 ◽  
Vol 115 (3) ◽  
pp. 439-444 ◽  
Author(s):  
L. Chang ◽  
M. N. Webster ◽  
A. Jackson
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Thermal Effects ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Isothermal Conditions ◽  
Large Pressure ◽  
Shear Heating ◽  
Micro Deformation

The objective of this paper is to conduct a qualitative analysis on the effects of lubricant shear thinning, lubricant shear heating and the roughness-induced transients on the pressure rippling and roughness deformation that occurs under elastohydrodynamic lubrication (EHL) conditions. To facilitate the analysis, the numerical solutions to an example problem of EHL line contact between a perfectly smooth surface and a sinusoidal rough surface are presented. This micro-EHL problem is first solved using the conventional model of a Newtonian lubricant and a stationary rough surface under isothermal conditions. It is then solved by including the non-Newtonian effects, the roughness-induced transients and the thermal effects in sequence, so that the changes in the results brought about by each of these elements can be clearly observed and then analyzed. The analysis, which is not limited to the model problem solved in this paper, suggests that misleading results of large pressure rippling and flattened surface roughness are obtained using the Newtonian lubricant models under steady-state, isothermal conditions. Much less micro-deformation of the surface roughness is actually produced because the magnitude of the pressure ripples is greatly limited by either the lubricant non-Newtonian shear thinning and shear heating or the roughness-induced transients.

Numerical Solution of Mixed Thermal Elastohydrodynamic Lubrication in Point Contacts With Three-Dimensional Surface Roughness

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Xiaopeng Wang ◽  
Yuchuan Liu ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Thickness Variation ◽  
Wide Range ◽  
Film Lubrication

Elastohydrodynamic lubrication (EHL) is a common mode of fluid-film lubrication in which many machine elements operate. Its thermal behavior is an important concern especially for components working under extreme conditions such as high speeds, heavy loads, and surfaces with significant roughness. Previous thermal EHL (TEHL) studies focused only on the cases with smooth surfaces under the full-film lubrication condition. The present study intends to develop a more realistic unified TEHL model for point contact problems that is capable of simulating the entire transition of lubrication status from the full-film and mixed lubrication all the way down to boundary lubrication with real machined roughness. The model consists of the generalized Reynolds equation, elasticity equation, film thickness equation, and those for lubricant rheology in combination with the energy equation for the lubricant film and the surface temperature equations. The solution algorithms based on the improved semi-system approach have demonstrated a good ability to achieve stable solutions with fast convergence under severe operating conditions. Lubricant film thickness variation and temperature rises in the lubricant film and on the surfaces during the entire transition have been investigated. It appears that this model can be used to predict mixed TEHL characteristics in a wide range of operating conditions with or without three-dimensional (3D) surface roughness involved. Therefore, it can be employed as a useful tool in engineering analyses.

Transient Thermo-Elastohydrodynamic Lubrication of Rough Surface in Soft Material

2013 ◽  
Vol 651 ◽  
pp. 505-510 ◽  
Author(s):  
Khanittha Wongseedakaew
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Film Thickness ◽  
Rough Surface ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Soft Material ◽  
Pressure Profiles ◽  
Finite Different Method ◽  
Raphson Method

This paper presents the effects of transient rough surface thermo-elastohydrodynamic lubrication (TEHL) of rollers for soft material with non-Newtonian fluid base on power law model. The time independent modified Reynolds equation, energy equation and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel method to obtain the film pressure profiles, film thickness profiles and friction coefficient in the contact region. The simulation results show surface roughness has effect on film thickness but its effect on film temperature is insignificant. The minimum film thickness decreases while the coefficient increases when the amplitude of surface roughness increases. Meanwhile, increasing applied loads causes the friction coefficient to decrease.

Transient Air-Soft EHL of Rough Surface with Impact Sudden Load

2013 ◽  
Vol 394 ◽  
pp. 96-100
Author(s):  
Khanittha Wongseedakaew
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Rough Surface ◽  
Contact Region ◽  
Load Condition ◽  
Elastohydrodynamic Lubrication ◽  
Film Pressure ◽  
Pressure Profiles ◽  
The Impact ◽  
Sudden Load

This paper presents the effects of transient rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material. The time independent modified Reynolds equation, and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel method to obtain the film pressure profiles and film thickness in the contact region. The effects of overload, surface roughness and time period are examined. The simulation results show surface roughness has effect on film thickness. The impact of sudden load condition is that the air film pressure increases but film thickness decreases. The minimum film thickness decreases when the amplitude of surface roughness increases. Increasing of impact from sudden loads resulted in minimal film thickness decrease.

Rough Air-Soft Elastohydrodynamic Lubrication

2013 ◽  
Vol 420 ◽  
pp. 30-35
Author(s):  
Khanittha Wongseedakaew ◽  
Jesda Panichakorn
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Modulus Of Elasticity ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Multilevel Methods ◽  
Inlet Temperature ◽  
Film Pressure ◽  
Air Inlet ◽  
Air Film

This paper presents the effects of rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material under the effect of air molecular slip. The time independent modified Reynolds equation and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel methods were used to obtain the film pressure profiles and film thickness in the contact region. The effects of amplitude of surface roughness, modulus of elasticity and air inlet temperature are examined. The simulation results showed surface roughness has effect on film thickness but it little effect to air film pressure. When the amplitude of surface roughness and modulus of elasticity increased, the air film thickness decreased but air film pressure increased. However, the air inlet temperature increased when the air film thickness increased.

Effect of Rolling Velocity and Maximum Hertzian Pressure on Fluid Film in Steady State EHL Line Contact with Rough Surface and Linear Piezoviscosity

2014 ◽  
Vol 592-594 ◽  
pp. 1371-1375
Author(s):  
Nitesh Talekar ◽  
Punit Kumar
Keyword(s):  
Surface Roughness ◽  
Steady State ◽  
Film Thickness ◽  
Rough Surface ◽  
Computer Code ◽  
Fluid Film ◽  
Line Contact ◽  
Rolling Velocity ◽  
Load Carrying ◽  
Lubricated Contact

Consideration of surface roughness in steady state EHL line contact is the first step towards understanding the lubrication of rough surface problem. Current paper investigates the use of sinusoidal waviness in the contact; more precisely it gives performance of real fluid in EHL line contact. The effect of various parameters like rolling velocity (U) and maximum Hertzian pressure (ph) on surface roughness by using properties of linear and exponential piezo-viscosity is taken into consideration to evaluate behavior of pressure distribution of load carrying fluid film and film thickness. Full isothermal, Newtonian simulation of EHL problem gives described effects. Spiking or fluctuation of pressure and film thickness curves is expected to show presence of irregularities on the surface chosen and amount of fluctuation depends on certain parameters and intensity of irregularities present. Rolling side domain of-4.5 ≤ X ≤ 1.5 with grid size ∆X=0.01375 is selected. A computer code is developed to solve Reynolds equation, which governs the generation of pressure in the lubricated contact zone is discritized and solved along with load balance equation using Newton-Raphson technique.

Report Paper 3: Elastohydrodynamic Lubrication of ‘O’ Ring Seals

1969 ◽  
Vol 184 (12) ◽  
pp. 197-200
Author(s):  
I. A. Gibson ◽  
C. J. Hooke ◽  
J. P. O'Donoghue
Keyword(s):  
Theoretical Analysis ◽  
Film Thickness ◽  
Pressure Gradient ◽  
Contact Zone ◽  
Elastohydrodynamic Lubrication ◽  
Iterative Solution ◽  
Contact Conditions ◽  
Dry Contact

This report gives details of a theoretical analysis of the lubrication of ‘O’ ring seals. Under dry contact conditions the pressure gradient at inlet to the contact zone is infinite, and an iterative solution has been developed to determine the inlet sweep of pressure under conditions of elastohydrodynamic lubrication. The exit film thickness and pressures have also been determined for conditions of variable outlet viscosity and pressure gradient. Typical results for an ‘O’ ring are given for a standard seal section.

Roughness Amplitude Reduction Under Non-Newtonian EHL Conditions

2005 ◽  
Author(s):  
A. D. Chapkov ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Pressure Fluctuations ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Quantitative Prediction ◽  
Point Contacts ◽  
Minimum Film Thickness ◽  
Roughness Amplitude ◽  
Average Film Thickness ◽  
Ehl Contact

The influence of surface roughness on the performance of bearings and gears operating under ElastoHydrodynamic Lubrication (EHL) conditions has become increasingly important over the last decade, as the average film thickness decreased due to various influences. Surface features can reduce the minimum film thickness and thus increase the wear. They can also increase the temperature and the pressure fluctuations, which directly affects the component life. In order to describe the roughness geometry inside an EHL contact, the amplitude reduction of harmonic waviness has been studied over the last ten years. This theory currently allows a quantitative prediction of the waviness amplitude and includes the influence of wavelength and contact operating conditions. However, the model assumes a Newtonian behaviour of the lubricant. The current paper makes a first contribution to the extension of the roughness amplitude reduction for EHL point contacts including non-Newtonian effects.

scholarly journals Analysis of Line Contact Elastohydrodynamic Lubrication with the Particles under Rough Contact Surface

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Keying Chen ◽  
Liangcai Zeng ◽  
Juan Chen ◽  
Xianzhong Ding
Keyword(s):  
Film Thickness ◽  
Rough Surface ◽  
Thickness Distribution ◽  
Traction Force ◽  
Elastohydrodynamic Lubrication ◽  
Equation System ◽  
Line Contact ◽  
Equivalent Inclusion Method ◽  
Equivalent Inclusion ◽  
The Matrix

A numerical solution for line contact elastohydrodynamic lubrication (EHL) occurring on the rough surface of heterogeneous materials with a group of particles is presented in this study. The film thickness disturbance caused by particles and roughness is considered into the solution system, and the film pressure between the contact gap generated by the particles and the surface roughness is obtained through a unified Reynold equation system. The inclusions buried in the matrix are made equivalent to areas with the same material as that of the matrix through Eshelby’s equivalent inclusion method and the roughness is characterized by related functions. The results present the effects of different rough topographies combined with the related parameters of the particles on the EHL performance, and the minimum film thickness distribution under different loads, running speeds, and initial viscosities are also investigated. The results show that the roughness morphology and the particles can affect the behavior of the EHL, the traction force on a square rough surface is smaller, and the soft particles have more advantages for improving the EHL performance.

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