scholarly journals STRIBECK AND TRACTION CURVES FOR ELLIPTICAL CONTACTS: ISOTHERMAL FRICTION MODEL

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
R.I. Popovici ◽  
D.J. Schipper
Keyword(s):  
Film Thickness ◽  
Rough Surface ◽  
Boundary Lubrication ◽  
Friction Model ◽  
Mixed Lubrication ◽  
Rigid Surface ◽  
Volume Conservation ◽  
Line Contacts ◽  
Highly Loaded ◽  
Model Approach

This paper deals with the prediction of the Stribeck and traction curves, by proposing a mixed lubrication model for highly loaded elliptical contacts. The model represents an extension on the mixed lubrication model of Gelinck and Schipper and comprehends both the asperity component or the so called boundary lubrication component (BL) and the elastohydrodynamic component (EHL). The asperity component is calculated from a fully deterministic contact perspective, where an equivalent rough surface is in contact with a smooth and rigid surface. In EHL regime, the film thickness is calculated according to Nijenbanning et al. and the separation for the asperity component is derived from Johnson, with a small adaptation, which was possible due to the deterministic contact model approach. In this way, the separation is calculated from the volume conservation theory of Johnson and even if this can be negative, the film thickness remains above zero permitting the calculation of highly loaded contacts. For the traction curve calculation, an elastic-plastic approximation for BL micro-contacts as proposed by Gelinck and Schipper for line contacts is used.

Stribeck Curve for Starved Line Contacts

2006 ◽  
Vol 129 (1) ◽  
pp. 181-187 ◽  
Author(s):  
I. C. Faraon ◽  
D. J. Schipper
Keyword(s):  
Film Thickness ◽  
Layer Thickness ◽  
Boundary Lubrication ◽  
Numerical Data ◽  
Contact Model ◽  
Stribeck Curve ◽  
Lubrication Regime ◽  
Straight Line ◽  
Line Contacts ◽  
Good Agreement

This paper discusses a mixed lubrication model in order to predict the Stribeck curve for starved lubricated line contacts. This model is based on a combination of the contact model of Greenwood and Williamson and the elastohydrodynamic (EHL) film thickness for starved line contacts. The starved solution to be implemented in the EHL component is obtained by using numerical data of Wolveridge, who computed the starved film thickness for smooth line contacts. Calculations are presented for different oil supply layer thickness over roughness values (hoil∕σs). For values of the oil layer thickness over roughness ratio larger than approximately 6, the Stribeck curve and separation between the rough surfaces do not change compared to the fully flooded situation. If the oil layer thickness over roughness ratio is in the range of 6 down to 0.7, friction starts to increase and the film thickness decreases. When the oil layer thickness over roughness ratio is less than approximately 0.7, the Stribeck curve tends to transform into a straight line and separation stays at the same value as in the boundary lubrication regime. Comparison between measurements and calculations is made and a good agreement is found.

scholarly journals Friction coefficient in mixed lubrication: A simplified analytical approach for highly loaded non-conformal contacts

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770626 ◽  
Author(s):  
Javier Echávarri Otero ◽  
Eduardo de la Guerra Ochoa ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Thermal Effects ◽  
Mixed Lubrication ◽  
Good Precision ◽  
Experimental Conditions ◽  
Lubrication Regime ◽  
Line Contacts ◽  
Mixed Lubrication Regime ◽  
Lubrication Conditions ◽  
Highly Loaded

This article presents an analytical model for predicting friction in mixed lubrication regime. The calculations consider load shared between roughness asperities and the lubricant film, as well as the appearance of thermal effects in the contact and the influence of the lubricant rheology. Tests using tribometers have been performed to measure the friction coefficient in non-conformal surfaces for both point and line contacts. This allows verifying the results of the model under a broad range of experimental conditions with an influence on the lubrication conditions. Reasonably good precision has been found in the results obtained, which combined with a simplicity of use confers the model a high practical utility for rough estimates of the friction coefficient under mixed lubrication.

A New Method for Measuring the Film Thickness of Mixed Lubrication in Line Contacts

1995 ◽  
Vol 38 (4) ◽  
pp. 869-874 ◽  
Author(s):  
Qian Zou ◽  
Fanrong Kong ◽  
Shizhu Wen
Keyword(s):  
Film Thickness ◽  
Mixed Lubrication ◽  
New Method ◽  
Line Contacts

Rubber–Road Contact: Comparison of Physics-Based Theory and Indoor Experiments

2016 ◽  
Vol 44 (3) ◽  
pp. 150-173 ◽  
Author(s):  
Mehran Motamedi ◽  
Saied Taheri ◽  
Corina Sandu
Keyword(s):  
Rough Surface ◽  
Practical Importance ◽  
Surface Profile ◽  
Surface Characteristics ◽  
Mechanical Analysis ◽  
Friction Model ◽  
Rubber Friction ◽  
Optical Profilometer ◽  
Viscoelastic Modulus ◽  
Longitudinal Slip

ABSTRACT For tire designers, rubber friction is a topic of pronounced practical importance. Thus, development of a rubber–road contact model is of great interest. In this research, to predict the effectiveness of the tread compound in a tire as it interacts with the pavement, the physics-based multiscale rubber-friction theories developed by B. Persson and M. Klüppel were studied. The strengths of each method were identified and incorporated into a consolidated model that is more comprehensive and proficient than any single, existing, physics-based approach. In the present work, the friction coefficient was estimated for a summer tire tread compound sliding on sandpaper. The inputs to the model were the fractal properties of the rough surface and the dynamic viscoelastic modulus of rubber. The sandpaper-surface profile was measured accurately using an optical profilometer. Two-dimensional parameterization was performed using one-dimensional profile measurements. The tire tread compound was characterized via dynamic mechanical analysis. To validate the friction model, a laboratory-based, rubber-friction test that could measure the friction between a rubber sample and any arbitrary rough surface was designed and built. The apparatus consisted of a turntable, which can have the surface characteristics of choice, and a rubber wheel in contact with the turntable. The wheel speed, as well as the turntable speed, could be controlled precisely to generate the arbitrary values of longitudinal slip at which the dynamic coefficient of friction was measured. The correlation between the simulation and the experimental results was investigated.

Simple Formulas for Performance Parameters Used in Elastohydrodynamically Lubricated Line Contacts

1989 ◽  
Vol 111 (2) ◽  
pp. 246-251 ◽  
Author(s):  
Ping Pan ◽  
B. J. Hamrock
Keyword(s):  
Film Thickness ◽  
Curve Fitting ◽  
Center Of Pressure ◽  
Operating Parameters ◽  
Performance Parameters ◽  
Practical Applications ◽  
Line Contacts ◽  
Pressure Spike

The film thickness and pressure in elastohydrodynamically lubricated conjunctions have been evaluated numerically for a rather complete range of operating parameters (dimensionless load, speed, and materials parameters) normally experienced in practical applications. From the film thickness and pressure throughout the conjunction a number of performance parameters were evaluated. By curve fitting the data, formulas were obtained that allow easy evaluation of the amplitude and location of the pressure spike, the minimum and central film thicknesses, the value of ρeHe, and the center of pressure.

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.

Analysis on sealing performance of VL seals based on mixed lubrication theory

2019 ◽  
Vol 71 (1) ◽  
pp. 54-60 ◽  
Author(s):  
Shixian Xu ◽  
Zhengtao Su ◽  
Jian Wu
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Finite Element Model ◽  
Friction Factor ◽  
Contact Pressure ◽  
Element Model ◽  
Mixed Lubrication ◽  
Content Type ◽  
Deformation Mechanics ◽  
The Finite Element Model

Purpose This paper aims to research the influence of pressure, friction factors, roughness and actuating speed to the mixed lubrication models of outstroke and instroke. Design/methodology/approach Mixed lubrication model is solved by finite volume method, which consists of coupled fluid mechanics, deformation mechanics and contact mechanics analyses. The influence of friction factor on the finite element model is also considered. Then, contact pressure, film thickness, friction and leakage have been studied. Findings It was found that the amount of leakage is sensitive to the film thickness. The larger the film thickness is, the greater the influence received from the friction factor, however, the effect of oil film on the friction is negligible. The friction is determined mainly by the contact pressure. The trend of friction and leakage influenced by actuating velocity and roughness is also obtained. Originality/value The influence of friction factor on the finite element model is considered. This can make the calculation more accurate.

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