Film Thickness and Pressure Distribution in Elastohydrodynamic Lubrication

2001 ◽  
pp. 169-224
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Elastohydrodynamic Lubrication

Effect of changing geometrical characteristics for different shapes of a single ridge passing through elastohydrodynamic of point contacts

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohamed Abd Alsamieh
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Reynolds Equation ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Time Step ◽  
Content Type ◽  
Geometrical Characteristics ◽  
Different Shapes

Purpose The purpose of this paper is to study the behavior of a single ridge passing through elastohydrodynamic lubrication of point contacts problem for different ridge shapes and sizes, including flat-top, triangular and cosine wave pattern to get an optimal ridge profile. Design/methodology/approach The time-dependent Reynolds’ equation is solved using Newton–Raphson technique. Several shapes of surface feature are simulated and the film thickness and pressure distribution are obtained at every time step by simultaneous solution of the Reynolds’ equation and film thickness equation, including elastic deformation. Film thickness and pressure distribution are chosen to be the criteria in the comparisons. Findings The geometrical characteristics of the ridge play an important role in the formation of lubricant film thickness profile and the pressure distribution through the contact zone. To minimize wear, friction and fatigue life, an optimal ridge profile should have smooth shape with small ridge size. Obtained results are compared with other published numerical results and show a good agreement. Originality/value The study evaluates the performance of different surface features of a single ridge with different shapes and sizes passing through elastohydrodynamic of point contact problem in relation to film thickness and pressure profile.

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.

Non-Newtonian behaviour in elastohydrodynamic lubrication

1974 ◽  
Vol 337 (1608) ◽  
pp. 101-121 ◽  
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Critical Stress ◽  
Elastohydrodynamic Lubrication ◽  
Critical Factor ◽  
Molecular Size ◽  
High Speeds ◽  
Oil Films

The relation between shear stress and shear rate has been determined for elastohydrodynamic oil films. At low values the rate of shear is directly proportional to the shear stress, but at higher values the shear rate increases more rapidly than the stress. It is shown that the critical factor is the magnitude of the shear stress, not the shear rate, and that this critical magnitude depends upon the pressure and the molecular size. Above the critical stress, in the non-Newtonian region, the shape of the curve relating the stress to the rate of shear depends upon the distribution of the sizes of the molecules in the oil. It is shown that in elastohydrodynamic conditions the limits of Newtonian behaviour are frequently exceeded and that this is liable to influence the pressure distribution, the magnitude of the traction, the generation of heat, and, at high speeds, the value of the film thickness.

Inverse Solution of Reynolds’ Equation of Lubrication Under Point-Contact Elastohydrodynamic Conditions

1981 ◽  
Vol 103 (4) ◽  
pp. 539-546 ◽  
Author(s):  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Reynolds Equation ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Inverse Solution ◽  
Heavy Loads

The paper describes a technique for solving the inverse lubrication problem under point contact elastohydrodynamic conditions, i.e. the calculation of a film thickness and shape corresponding to a given hydrodynamic pressure distribution by an inverse solution of Reynolds’ equation. The effect of compressibility and influence of pressure upon viscosity are included in the analysis. The technique will be of use in solving the point contact elastohydrodynamic lubrication problem at heavy loads.

Analysis of elastohydrodynamic lubrication in a novel metal-on-metal hip joint replacement

2002 ◽  
Vol 216 (3) ◽  
pp. 185-193 ◽  
Author(s):  
M Jagatia ◽  
Z M Jin
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Contact Pressure ◽  
Elastohydrodynamic Lubrication ◽  
Metal On Metal ◽  
Minimum Film Thickness ◽  
Acetabular Components ◽  
Cobalt Chrome Alloy ◽  
Cobalt Chrome

Elastohydrodynamic lubrication (EHL) analysis was carried out in this study for a novel metal-on-metal hip prosthesis, which consists of a cobalt-chrome alloy femoral head articulating against a cobalt-chrome alloy acetabular insert connected to a titanium fixation shell through a taper. Finite element models were developed to investigate the effect of the pelvic bone and the load on the predicted contact pressure distribution between the two bearing surfaces under dry conditions. The finite element method was used to develop elasticity models for both the femoral and the acetabular components; it was found that the elastic deformation of the acetabular insert was mainly dependent on the load, rather than the detailed pressure distribution. A modified solution methodology was accordingly developed to couple the elasticity models for both the femoral and the acetabular surfaces with the Reynolds equation and to solve these numerically by the finite difference method. It was found that a load increase from 500 to 2500 N had a negligible effect on the predicted maximum contact pressure and the minimum film thickness, due to the relatively flexible and accommodating structure of the acetabular insert. Furthermore, the predicted minimum film thickness was shown to be significantly greater than the simple estimation based on the assumption of semi-infinite solids (mono-block design) using the Hamrock and Dowson formula. The effects of the viscosity of the lubricant and the radial clearance between the femoral and the acetabular components on the predicted lubricating film thickness were investigated under both in vitro simulator testing and in vivo walking conditions.

Elastohydrodynamic Film Thickness in Elliptical Contacts With Spinning and Rolling

1999 ◽  
Vol 121 (4) ◽  
pp. 686-692 ◽  
Author(s):  
Qian Zou ◽  
Changhua Huang ◽  
Shizhu Wen
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Computing Time ◽  
Elastohydrodynamic Lubrication ◽  
Low Complexity ◽  
Numerical Results ◽  
Analysis And Design ◽  
Pure Rolling ◽  
Thickness Prediction ◽  
Ellipticity Ratio

In this paper, a theoretical model for the film thickness prediction of elastohydrodynamic lubrication of elliptical contacts with spinning and rolling/sliding motions is presented, in which 1) an effective ellipticity ratio ke is introduced to present the ellipse feature instead of the normal ellipticity ratio k in case of that the entraining velocity at the center of contact ellipse is at an angle with minor axis, 2) Roelands and Dowson-Higginson’s equations are adopted to express the influence of pressure upon lubricant viscosity and density, 3) multilevel/multigrid techniques, with low complexity and good stability, are used for the purpose of reducing computing time in the complex numerical analysis. With this model the characteristics of film shape and pressure distribution of elastohydrodynamic lubrication of elliptical concentrated contacts with spinning and rolling/sliding were discussed. The results showed that the spinning motion has significant influence on the film shape and pressure distribution. Based on a large number of numerical results of elastohydrodynamic lubrication analysis of elliptical concentrated contacts with spinning and rolling/sliding, new expressions for the minimum and central film thickness prediction were regressed. Their accuracy was analyzed by comparisons with numerical results of an evaluation set and others’ expressions under pure rolling and/or sliding condition. The comparisons showed that the two new expressions have satisfactory accuracy and potential application to engineering analysis and design.

The elastohydrodynamic behaviour of polyphenyl ether

1975 ◽  
Vol 344 (1638) ◽  
pp. 403-426 ◽  
Keyword(s):  
Shear Stress ◽  
Viscous Fluid ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Critical Stress ◽  
Elastohydrodynamic Lubrication ◽  
Elastic Fluid ◽  
Polyphenyl Ether ◽  
Mineral Oils ◽  
Non Linear

The paper describes measurements of the film thickness and traction given in elastohydrodynamic lubrication by polyphenyl ether. The film thickness is well below the theoretical value and very sensitive to temperature but its variation with load is of the theoretical magnitude. The tractional behaviour is more complex than that of mineral oils and this is thought to be due to the variation of the pressure distribution with speed and load. The results indicate that the fluid behaves elastically when the slip is small, even at the lowest load. Above a critical stress the relation between the shear stress and the rate of shear becomes non-linear. The non-Newtonian characteristics of this ’elastic’ fluid then become similar to those of a ‘viscous’ fluid.

EFFECTS OF SURFACE FORCES ON SQUEEZE EHL MOTION BETWEEN ELASTIC BALL AND ELASTIC COATED SURFACE

2016 ◽  
Vol 40 (5) ◽  
pp. 821-833
Author(s):  
Li-Ming Chu ◽  
Jaw-Ren Lin ◽  
Hsiang-Chen Hsu ◽  
Yuh-Ping Chang
Keyword(s):  
Elastic Modulus ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Contact Region ◽  
Load Condition ◽  
Elastohydrodynamic Lubrication ◽  
Surface Force ◽  
Surface Forces ◽  
Operating Conditions ◽  
Transient Pressure

The effects of surface forces (SF) and coated layers (CL) on pure squeeze elastohydrodynamic lubrication (EHL) motion of circular contacts are explored under constant load condition by using the finite difference method (FDM) and the Gauss–Seidel iteration method. The transient pressure profiles, surface force, film shapes, and elastic deformation during the pure squeeze process under various operating conditions in the TFEHL regime are discussed. The simulation results reveal that the difference between SFEHL model and EHL model is apparent as the film thickness is thinner than 5 nm. The oscillation phenomena in pressure and film thickness come mainly from the action of solvation forces. At contact region, the greater elastic modulus and smaller coating thicknesses, the greater pressure distribution, and the smaller film thickness. The film thicknesses are found reverse at outside the contact zone. At the exit region, i.e. the minimum film thickness region, it is valid that the greater the elastic modulus and the smaller the coating thicknesses, the greater the solvation pressure distribution. The effects of surface forces become significant as the film thickness becomes thinner.

Regimes of Elastohydrodynamic Lubrication

1970 ◽  
Vol 12 (1) ◽  
pp. 9-16 ◽  
Author(s):  
K. L. Johnson
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Elastic Deformation ◽  
Variable Viscosity ◽  
Elastohydrodynamic Lubrication ◽  
Single Parameter ◽  
Relative Importance ◽  
Light Load

The different regimes of behaviour in the elastohydrodynamic lubrication of rollers are displayed on a chart whose rectangular co-ordinates express the influence of elasticity of the solids and variation of viscosity of the lubricant with pressure respectively. At small values of these co-ordinates, i.e. at a very light load, the behaviour is effectively rigidisoviscous. At high loads the relative importance of elastic deformation and variable viscosity is shown to depend upon a single parameter suggested by Archard. Approximate boundaries for the various regimes are suggested. Using the computer solutions which are available, the variations in film thickness and pressure distribution in the different regimes are examined.

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