Observation of Wall Slip in Elastohydrodynamic Lubrication

1990 ◽  
Vol 112 (3) ◽  
pp. 447-452 ◽  
Author(s):  
M. Kaneta ◽  
H. Nishikawa ◽  
K. Kameishi
Keyword(s):  
Experimental Technique ◽  
Elastohydrodynamic Lubrication ◽  
Wall Slip ◽  
Optical Interferometry ◽  
Stepping Motor ◽  
Ehd Lubrication ◽  
Pure Rolling ◽  
Direct Indication ◽  
Contact Surfaces ◽  
Oil Films

A new experimental technique using optical interferometry has been developed to obtain a direct indication of non-Newtonian response of an oil film under conditions of elastohydrodynamic (EHD) lubrication. A glass disk or a steel ball has been driven by a stepping motor so that crescent-shaped thick oil films with undulation in thickness along the direction of motion have been generated. The experiments have been carried out under pure rolling and pure sliding conditions. It has been found that the oil in an EHD contact behaves like a solid and slips at or near the contact surfaces.

Effects of a Single Bump or Dent in Time Dependent Thermal Line EHD Lubrication

1994 ◽  
Vol 116 (1) ◽  
pp. 9-20 ◽  
Author(s):  
Farshid Sadeghi ◽  
Kyung-Hoon Kim
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Transient Behavior ◽  
Time Dependent ◽  
Line Contact ◽  
Temperature Distributions ◽  
Ehd Lubrication ◽  
Pure Rolling ◽  
Energy Equations ◽  
Thermal Line

A time-dependent thermal compressible elastohydrodynamic lubrication of line contact model has been developed to investigate the effects of a single bump or dent in heavily loaded rolling/sliding contacts. The results illustrate the transient behavior of the film thickness, pressure and temperature distributions as a bump or a dent travels through the contact. The multigrid multilevel technique was used to simultaneously solve the discretized time dependent Reynolds, elasticity and energy equations. The effects of various loads and speeds have been investigated. Results are presented for the nondimensional loads of W = 1.3 × 10−4, 2.3 × 10−4 and nondimensional speeds ranging from U = 1 × 10−11 to U = 10−10 under pure rolling and rolling/sliding conditions.

Effects of Asperities in Elastohydrodynamic Lubrication

1980 ◽  
Vol 102 (3) ◽  
pp. 374-378 ◽  
Author(s):  
M. Kaneta ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Glass Plate ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Critical Value ◽  
Optical Interferometry ◽  
Asperity Height ◽  
Height Ratio ◽  
Pure Rolling

Optical interferometry was used to study rough surfaces under lubricated point contact. Three dimensional “asperities” of chromium were sputtered onto a steel ball which was run against a smooth glass plate under both rolling and sliding. The experimental results were compared with the various published theories. The film thicknesses found in sliding are different from those observed in pure rolling, which are nearly equal to the theoretical values. Film thickness collapse occurred when the central film thickness/half asperity height ratio (λ ratio) reached a critical value.

Elastohydrodynamic Lubrication of a Line Contact

1974 ◽  
Vol 188 (1) ◽  
pp. 221-238 ◽  
Author(s):  
D. G. Wymer ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Central Region ◽  
Glass Plate ◽  
Elastohydrodynamic Lubrication ◽  
Optical Interferometry ◽  
Optical Measurements ◽  
Line Contact ◽  
Electrical Measurements ◽  
Oil Film ◽  
Pure Rolling

In Part 1, optical interferometry is used to study an elastohydrodynamically lubricated line contact between a taper roller and a glass plate under pure rolling conditions. The results give detailed information on film profiles and show the effects of end blending, lubricant starvation, deep scratches and static oil entrapments. In Part 2, oil film thicknesses in an elastohydrodynamic line contact are measured using optical interferometry and compared with theory. Two empirical formulae are derived for film thickness in the central region and at the exit constriction. In addition to the optical measurements, electrical measurements (resistance and capacitance) are made simultaneously, enabling a direct comparison to be made.

Numerical Modeling of Mixed Lubrication and Flash Temperature in EHL Elliptical Contacts

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Neelesh Deolalikar ◽  
Farshid Sadeghi ◽  
Sean Marble
Keyword(s):  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Lubrication Regime ◽  
Predicting Performance ◽  
Pure Rolling ◽  
Rolling Element ◽  
Contact Pressures ◽  
Film Lubrication

Highly loaded ball and rolling element bearings are often required to operate in the mixed elastohydrodynamic lubrication regime in which surface asperity contact occurs simultaneously during the lubrication process. Predicting performance (i.e., pressure, temperature) of components operating in this regime is important as the high asperity contact pressures can significantly reduce the fatigue life of the interacting components. In this study, a deterministic mixed lubrication model was developed to determine the pressure and temperature of mixed lubricated circular and elliptic contacts for measured and simulated surfaces operating under pure rolling and rolling/sliding condition. In this model, we simultaneously solve for lubricant and asperity contact pressures. The model allows investigation of the condition and transition from boundary to full-film lubrication. The variation of contact area and load ratios is examined for various velocities and slide-to-roll ratios. The mixed lubricated model is also used to predict the transient flash temperatures occurring in contacts due to asperity contact interactions and friction. In order to significantly reduce the computational efforts associated with surface deformation and temperature calculation, the fast Fourier transform algorithm is implemented.

CFD Prediction of the Effects of Surface Roughness on Elastohydrodynamic Lubrication under Rolling/Sliding Conditions

2012 ◽  
Vol 184-185 ◽  
pp. 86-89 ◽  
Author(s):  
Shian Gao ◽  
Sutthinan Srirattayawong
Keyword(s):  
Surface Roughness ◽  
Shear Stress ◽  
Fluid Dynamic ◽  
Flow Behavior ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Hertzian Contact ◽  
Pure Rolling ◽  
Large Fluctuations ◽  
Two Parameters

The surface roughness plays an important role in elastohydrodynamic lubrication (EHL). To improve the lubrication system the flow behavior and lubrication mechanism must be understood, especially in the thin film classification. The effects of surface roughness in the EHL problem are complicated and difficult to measure by experiment. Therefore numerical simulation using the computational fluid dynamic (CFD) approach is proposed in this research. The CFD model developed has taken the arbitrary surface roughness into consideration, and has been used to predict the characteristics of fluid flow, such as the pressure distribution, the minimal film thickness and the shear stress. The cylinder is considered to be under elastic deformation according to the theory of Hertzian contact and the surface of cylinder is defined to have an arbitrary roughness. The simulation results show that the surface roughness has significant effects on the pressure profile and shear stress, especially in the case of pure rolling, where the two parameters in the rough surface case show large fluctuations that are much higher than the corresponding smooth surface case.

Solution of the Non-Newtonian Elastohydrodynamic Problem for Circular Contacts Based on a Flow Continuity Method

1996 ◽  
Vol 210 (4) ◽  
pp. 247-258 ◽  
Author(s):  
C A Holt ◽  
H P Evans ◽  
R W Snidle
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Control Volume ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Theoretical Formulation ◽  
New Approach ◽  
Limiting Shear Stress ◽  
Pure Rolling ◽  
Stress Behaviour

The paper describes a numerical solution method for the point contact elastohydrodynamic lubrication (EHL) problem under non-Newtonian, isothermal conditions. The theoretical formulation of the non-Newtonian effect is general and may be applied to both shear thinning and limiting shear stress behaviour. The particular rheological model investigated in this work is the Eyring ‘sinh law’ relation. The numerical solution of the lubrication equations is based upon a control volume approach rather than the more usual methods that utilize a modified Reynolds equation. This new approach ensures that flow continuity is satisfied at the discretization level. Results are presented to show the effect of non-Newtonian behaviour on film thickness and pressure distribution in circular EHL contacts operating over a range of slide-roll ratios from 0 (pure rolling) to 1.5. Under conditions of pure rolling or low sliding there is found to be little effect of non-Newtonian behaviour, but at the highest degree of sliding the film thickness over the central, flattened area of the contact is reduced by up to 10 per cent at the highest rolling speed of 0.75 m/s.

The Effect of Piston Skirt Profile on EHD Lubrication in an Internal Combustion Engine

2013 ◽  
Vol 787 ◽  
pp. 704-710 ◽  
Author(s):  
Kellaci Ahmed ◽  
Khelidj Benyoucef ◽  
Mazouzi Redha ◽  
Lounis Mourad
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Elastic Equilibrium ◽  
Internal Combustion ◽  
Lubricant Film ◽  
Piston Skirt ◽  
Ehd Lubrication ◽  
Finite Differences Method

This investigation is concerned with the elastohydrodynamic lubrication of the piston skirt / cylinder link of an internal combustion engine. In such compliant structures, the thickness of the lubricant film depends not only on the elastic deformation elements of the mechanism but also on their profiles. We have developed a computer program to study the effect of the profile of the piston skirt on the lubricant film. This program is based on a two-dimensional description of the lubricant film flow and a three-dimensional deformation of solids. The Reynolds equation defines the behavior of hydrodynamic film of oil in the liaison piston skirt / cylinder, and the equations of static and elastic equilibrium quantify the behavior of the structure. These Equations are solved numerically by using the finite differences method.

A Quantitative Solution for the Full Shear-Thinning EHL Point Contact Problem Including Traction

2007 ◽  
Author(s):  
Yuchuan Liu ◽  
Q. Jane Wang ◽  
Scott Bair ◽  
Philippe Vergne
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
High Viscosity ◽  
Viscosity Models ◽  
Pure Rolling ◽  
Volume Viscosity ◽  
Traction Coefficient ◽  
Simulation And Experiment

We present a realistic elastohydrodynamic lubrication (EHL) simulation in point contact using a Carreau-like model for the shear-thinning response and the Doolittle-Tait free-volume viscosity model for the piezoviscous response. The liquid is a high viscosity polyalphaolefin which possesses a relatively low threshold for shear-thinning. As a result, the measured EHL film thickness is about one-half of the Newtonian prediction. We derived and numerically solved the two-dimensional generalized Reynolds equation for the modified Carreau model based on Greenwood [1]. Departing from many previous solutions, the viscosity models used for the pressure and shear dependence were obtained entirely from viscometer measurements. Truly remarkable agreement is found in the comparisons of simulation and experiment for traction coefficient and for film thickness in both pure rolling and sliding cases. This agreement validates the use of a generalized Newtonian model in EHL.

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