Numerical study on the interaction of transversely oriented ridges in thermal elastohydrodynamic lubrication point contacts using the Eyring shear-thinning model

2016 ◽  
Vol 231 (1) ◽  
pp. 93-106 ◽  
Author(s):  
Jinlei Cui ◽  
Peiran Yang ◽  
Motohiro Kaneta ◽  
Ivan Krupka
Keyword(s):  
Friction Coefficient ◽  
Numerical Study ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Solid Surfaces ◽  
Point Contacts ◽  
Transient Behaviour ◽  
Contact Surfaces ◽  
Thinning Effect

Transient behaviour of tribo-characteristics caused by transversely oriented ridges on point contact surfaces was investigated based on a thermal elastohydrodynamic lubrication analysis. The ridges were assumed to exist on both the contact surfaces with different velocities. Results show that the interaction of ridges gives a large influence on the local film thickness, pressure, friction coefficient, temperatures on both the solid surfaces and temperature in the oil film. It is also pointed out that the size of the contact bodies brings strong effect on the temperature distribution and shear rate as well as on the friction coefficient. Furthermore, it is revealed that under rolling-sliding conditions, the shear-thinning property of the lubricant is negligible when the size of the contact body is large enough. However, shear-thinning effect plays an important role when the size is extremely small.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

Numerical Study on Effect of Dimples on Tribo-Characteristics in Non-Newtonian Thermal Elastohydrodynamic Lubrication Point Contacts With Different Mechanical and Thermal Properties

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Jing Wang ◽  
Peiran Yang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Numerical Study ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Transient Behavior ◽  
Mechanical And Thermal Properties ◽  
Smooth Surfaces ◽  
Contact Surfaces ◽  
Micro Dimples

Abstract The transient behavior of tribo-characteristics caused by micro-dimples on point contact surfaces with different mechanical and thermal properties was investigated based on non-Newtonian thermal elastohydrodynamic lubrication (EHL) analysis. The dimples were assumed to exist on both contact surfaces and the surface shapes of the contact bodies were evaluated separately. It is pointed out that surface texturing due to the micro-dimples is not necessarily beneficial in EHL contacts under fully flooded conditions since the micro-dimples provide a high pressure and a thin minimum film thickness as compared with the case of contacts with smooth surfaces, although the friction coefficient of surfaces with micro-dimples is always lower than that of the smooth surfaces. In order to obtain relatively good tribo-characteristics, the velocity of the surface with low thermal conductivity should be faster than that with high thermal conductivity, and the wavelengths of micro-dimples in the direction of motion on both surfaces should be different.

Numerical Study on Effect of Thermal Conductivity in Point Contacts With Longitudinal Roughness on Abnormal Pressure Distribution

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Jing Wang ◽  
Peiran Yang
Keyword(s):  
Thermal Conductivity ◽  
Numerical Study ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Variation ◽  
Point Contacts ◽  
Contact Materials ◽  
Opposite Case ◽  
Abnormal Pressure ◽  
Longitudinal Roughness

Abstract In order to clarify the effect of thermal conductivity on non-Newtonian thermal elastohydrodynamic lubrication (EHL) in the point contact with longitudinal roughness on one surface or on both surfaces, numerical calculations are carried out. The contact is formed by ceramics and steel. The surface shapes of both contact solids are investigated separately. It was found that the pressure at ridges shows lower than that at grooves when the speed of a material with low thermal conductivity is faster than that of a material with high thermal conductivity. In the opposite case, such a phenomenon never occurs. This abnormal pressure variation is largely affected by the combination of contact materials and running conditions.

Experimental and numerical study on cavitation under elastohydrodynamic lubrication point contact

2021 ◽  
pp. 135065012110527
Author(s):  
Mingfei Ma ◽  
Wen Wang ◽  
Wenxun Jiang
Keyword(s):  
Contact Area ◽  
Numerical Study ◽  
Ambient Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hertzian Contact ◽  
Pressure Area ◽  
Cavitation Pressure ◽  
Experimental Researches ◽  
State 1

As a common phenomenon in elastohydrodynamic lubrication, cavitation has an effect on the completeness of the oil film in the contact area. Many studies have therefore been conducted on cavitation. Experimental researches on cavitation usually rely on optical interference observation, which offers a limited resolution and observation range. In this paper, an infrared thermal camera is used to observe the cavity bubbles on a ball-on-disc setup under sliding/rolling conditions. The results show that the cavity length increases with an increases of the entrainment speed and the viscosity of the lubricants. These observations are explained by a numerical model based on Elrod's algorithm. Effects of entrainment speed and lubricant viscosity on the breakup of cavitation bubbles and the cavitation states are investigated. Both the simulation and experimental results show that a negative pressure area is present behind the Hertzian contact area. The ambient pressure plays a role in maintaining cavitation state 1. The cavitation pressure is close to the vacuum pressure when the entrainment speed is low and to the ambient pressure instead when the entrainment speed is high.

Scale Effects in Generalized Newtonian Elastohydrodynamic Films

2008 ◽  
Author(s):  
I. I. Kudish ◽  
P. Kumar ◽  
M. M. Khonsary ◽  
S. Bair
Keyword(s):  
Film Thickness ◽  
Scale Effects ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Shear Thinning ◽  
Effective Pressure ◽  
Practical Advantage ◽  
Inlet Zone ◽  
Real Machine

The prediction of elastohydrodynamic lubrication (EHL) film thickness requires knowledge of the lubricant properties. Today, in many instances, the properties have been obtained from a measurement of the central film thickness in an optical EHL point contact simulator and the assumption of a classical Newtonian film thickness formula. This technique has the practical advantage of using an effective pressure-viscosity coefficient which compensates for shear-thinning. We have shown by a perturbation analysis and by a full EHL numerical solution that the practice of extrapolating from a laboratory scale measurement of film thickness to the film thickness of an operating contact within a real machine may substantially overestimate the film thickness in the real machine if the machine scale is smaller and the lubricant is shear-thinning in the inlet zone.

Theoretical and experimental studies of the oil film in lubricated point contact

1966 ◽  
Vol 291 (1427) ◽  
pp. 520-536 ◽  
Keyword(s):  
Surface Layer ◽  
Film Thickness ◽  
Strong Evidence ◽  
Experimental Studies ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Point Contacts ◽  
Previous Theory ◽  
Oil Film

A technique using Newton’s rings for mapping the oil film of lubricated point contacts is described. A theoretical value for the film thickness of such contacts in elastohydrodynamic lubrication is derived. The experimental results give the exit constriction predicted by previous theory but never shown in detail. The comparison of theoretical and experimental oil film thicknesses, which is satisfactorily accurate, gives strong evidence for a viscous surface layer some 1000Å thick. This film agrees with the known ‘lubricating power’ of the various oils tested.

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.

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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