scholarly journals Non-Newtonian Fluid Model Incorporated Into Elastohydrodynamic Lubrication of Rectangular Contacts

1984 ◽  
Vol 106 (2) ◽  
pp. 275-282 ◽  
Author(s):  
B. O. Jacobson ◽  
B. J. Hamrock
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Film Thickness ◽  
Numerical Solution ◽  
Newtonian Fluid ◽  
Fluid Model ◽  
Elastohydrodynamic Lubrication ◽  
Sliding Velocity ◽  
Minimum Film Thickness ◽  
Limiting Value

A procedure is outlined for the numerical solution of the complete elastohydrodynamic lubrication of rectangular contacts incorporating a non-Newtonian fluid model. The approach uses a Newtonian model as long as the shear stress is less than a limiting shear stress. If the shear stress exceeds the limiting value, the shear stress is set equal to the limiting value. The numerical solution requires the coupled solution of the pressure, film shape, and fluid rheology equations from the inlet to the outlet. Isothermal and no-side-leakage assumptions were imposed in the analysis. The influence of dimensionless speed U, load W, materials G, and sliding velocity U* and limiting-shear-strength proportionality constant γ on dimensionless minimum film thickness Hmin was investigated. Fourteen cases were investigated for an elastohydrodynamically lubricated rectangular contact incorporating a non-Newtonian fluid model. The influence of sliding velocity (U*) and limiting shear strength (γ) on minimum film thickness was observed to be small. Hence the film thickness equation obtained for a Newtonian fluid is sufficient for calculations considering non-Newtonian effects. Computer plots are also presented that indicate in detail pressure distribution, film shape, shear stress at the surfaces, and flow throughout the conjunction.

A Circular Non-Newtonian Fluid Model: Part I—Used in Elastohydrodynamic Lubrication

1990 ◽  
Vol 112 (3) ◽  
pp. 486-495 ◽  
Author(s):  
Rong-Tsong Lee ◽  
B. J. Hamrock
Keyword(s):  
Shear Strength ◽  
Newtonian Fluid ◽  
Reynolds Equation ◽  
Fluid Model ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Load Parameter ◽  
Viscosity Term ◽  
Pure Rolling ◽  
The Coefficient Of Friction

A circular non-Newtonian fluid model associated with the limiting shear strength was considered. Using this model a modified Reynolds equation was developed which is almost the same as the classical Reynolds equation except for the viscosity term. Results show that the calculation of the central and minimum film thicknesses from the classical Reynolds equation is still valid for pure rolling conditions. The effects on performance of dimensionless load parameter, dimensionless speed parameter, slide/roll ratio, different oils, the limiting shear strength proportionality constant were studied. Such parameters as the pressure profile, the film shape, the coefficient of friction, the dimensionless shear stress at surface a, and the velocitiy contour in the conjunction were considered.

Non-Newtonian Thermal Elastohydrodynamic Lubrication

1991 ◽  
Vol 113 (2) ◽  
pp. 390-396 ◽  
Author(s):  
P. C. Sui ◽  
F. Sadeghi
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Reynolds Equation ◽  
Fluid Model ◽  
Traction Force ◽  
Elastohydrodynamic Lubrication ◽  
Simultaneous System ◽  
Energy Equations ◽  
Rheology Model ◽  
Generalized Reynolds Equation

A numerical solution to the problem of thermal and non-Newtonian fluid model in elastohydrodynamic lubrication is presented. The generalized Reynolds equation was modified by the Eyring rheology model to incorporate the non-Newtonian effects of the fluid. The simultaneous system of modified Reynolds, elasticity and energy equations were numerically solved for the pressure, temperature and film thickness. Results have been presented for loads ranging from W = 7 × 10−5 to W = 2.3 × 10−4 and the speeds ranging from U* = 2 × 10−11 to U* = 6 × 10−11 at various slip conditions. Comparison between the isothermal and thermal non-Newtonian traction force has also been presented.

Influence of Surface Waviness on the Thermal Elastohydrodynamic Lubrication of an Eccentric-Tappet Pair

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
J. Wang ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Surface Waviness ◽  
Film Pressure ◽  
Oil Film ◽  
Working Cycle ◽  
Temperature Oscillations ◽  
Minimum Film Thickness ◽  
Traction Coefficient ◽  
Oil Film Pressure

The effect of single-sided and double-sided harmonic surface waviness on the film thickness, pressure, and temperature oscillations in an elastohydrodynamically lubricated eccentric-tappet pair has been investigated in relation to the eccentricity and the waviness wavelength. The results show that, during one working cycle, the waviness causes significant fluctuations of the oil film, pressure, and temperature, as well as a reduction in minimum film thickness. Smaller wavelength causes more dramatic variations in oil film. The fluctuations of the pressure, film thickness, temperature, and traction coefficient caused by double-sided waviness are nearly the same compared with the single-sided waviness, but the variations are less intense.

Film thickness in elastohydrodynamically lubricated slender elliptic contacts: Part I – numerical studies of central film thickness

2021 ◽  
pp. 135065012110477
Author(s):  
Marius Wolf ◽  
Sergey Solovyev ◽  
Fatemi Arshia
Keyword(s):  
Film Thickness ◽  
State Of The Art ◽  
Experimental Studies ◽  
Elastohydrodynamic Lubrication ◽  
Large Parameter ◽  
Numerical Studies ◽  
Minimum Film Thickness ◽  
Subsequent Publication ◽  
New Formula ◽  
Increasing Load

In this paper, analytical equations for the central film thickness in slender elliptic contacts are investigated. A comparison of state-of-the-art formulas with simulation results of a multilevel elastohydrodynamic lubrication solver is conducted and shows considerable deviation. Therefore, a new film thickness formula for slender elliptic contacts with variable ellipticity is derived. It incorporates asymptotic solutions, which results in validity over a large parameter domain. It captures the behaviour of increasing film thickness with increasing load for specific very slender contacts. The new formula proves to be significantly more accurate than current equations. Experimental studies and discussions on minimum film thickness will be presented in a subsequent publication.

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.

The Effects of Surface Irregularities on the Elastohydrodynamic Lubrication of Sliding Line Contacts. Part II—Wavy Surfaces

1984 ◽  
Vol 106 (1) ◽  
pp. 113-119 ◽  
Author(s):  
P. R. Goglia ◽  
C. Cusano ◽  
T. F. Conry
Keyword(s):  
Shear Stress ◽  
Film Thickness ◽  
Smooth Surface ◽  
Wave Amplitude ◽  
Elastohydrodynamic Lubrication ◽  
Wavy Surface ◽  
Line Contacts ◽  
Surface Irregularities ◽  
Wavy Surfaces ◽  
Octahedral Shear Stress

The micro-EHD effects caused by wavy surfaces have been analytically investigated. The investigation includes the effects of phase, wavelength, and wave amplitude on film thickness, pressure distribution and subsurface octahedral shear stress field. The presence of a wavy surface with a given wavelength produces pressure oscillations of the same wavelength. With increasing wave amplitude and decreasing wavelength, the micro-EHD action increases. This results in a maximum value of the octahedral shear stress which is greater in magnitude and closer to the surface than the corresponding smooth surface case. The slope of the wavy surface in the inlet region determines whether the average film thickness is smaller or larger than the smooth surface value.

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.

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