scholarly journals Closure to “Discussion of ‘Micro Elastohydrodynamic Lubrication of an Elliptical Contact With Transverse and Three Dimensional Sinusoidal Roughness’” (1990, ASME J. Tribol., 112, pp. 741–742)

1990 ◽  
Vol 112 (4) ◽  
pp. 742-742
Author(s):  
C. C. Kweh ◽  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Elliptical Contact

Micro-Elastohydrodynamic Lubrication of an Elliptical Contact With Transverse and Three-Dimensional Sinusoidal Roughness

1989 ◽  
Vol 111 (4) ◽  
pp. 577-584 ◽  
Author(s):  
C. C. Kweh ◽  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Surface Roughness ◽  
High Temperature ◽  
High Speed ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Two Dimensional ◽  
Direction Transverse ◽  
Ehd Lubrication ◽  
Elliptical Contact

The paper describes the results of the analysis of elastohydrodynamic (EHD) lubrication of an elliptical contact between a rough, stationary surface and a smooth, moving surface. Roughness takes the form of sinusoidal grooves aligned in the direction transverse to that of lubricant entrainment. The conditions analyzed are chosen to correspond to the operating conditions of a high speed, high temperature disk machine. The main feature of the results is the almost complete flattening of the roughness that occurs, accompanied by a corresponding ripple in the pressure distribution. A contact with three-dimensional roughness has also been analyzed, and this shows that in comparison with the two-dimensional case, the longitudinal grooves tend to persist.

Simulation of Plasto-Elastohydrodynamic Lubrication in Line Contacts of Infinite and Finite Length

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Tao He ◽  
Jiaxu Wang ◽  
Zhanjiang Wang ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Finite Length ◽  
3D Model ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Axial Direction ◽  
Contact Length ◽  
Line Contact ◽  
Line Contacts ◽  
3D Surface Topography

Line contact is common in many machine components, such as various gears, roller and needle bearings, and cams and followers. Traditionally, line contact is modeled as a two-dimensional (2D) problem when the surfaces are assumed to be smooth or treated stochastically. In reality, however, surface roughness is usually three-dimensional (3D) in nature, so that a 3D model is needed when analyzing contact and lubrication deterministically. Moreover, contact length is often finite, and realistic geometry may possibly include a crowning in the axial direction and round corners or chamfers at two ends. In the present study, plasto-elastohydrodynamic lubrication (PEHL) simulations for line contacts of both infinite and finite length have been conducted, taking into account the effects of surface roughness and possible plastic deformation, with a 3D model that is needed when taking into account the realistic contact geometry and the 3D surface topography. With this newly developed PEHL model, numerical cases are analyzed in order to reveal the PEHL characteristics in different types of line contact.

scholarly journals On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 78 ◽  
Author(s):  
Gregory de Boer ◽  
Andreas Almqvist
Keyword(s):  
Surface Topography ◽  
Load Capacity ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Multiscale Methods ◽  
Operating Conditions ◽  
Real Surface ◽  
Micro Scale ◽  
Macro Scale ◽  
Heterogeneous Multiscale

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies.

scholarly journals Elastohydrodynamics of a Worm Gear Contact

2000 ◽  
Vol 123 (2) ◽  
pp. 268-275 ◽  
Author(s):  
S. Kong ◽  
K. Sharif ◽  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Film Thickness ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Worm Gear ◽  
Simulation Technique ◽  
Elastic Contact ◽  
Gear Teeth ◽  
Film Forming ◽  
Worm Gears ◽  
Gear Contact

The paper is concerned with prediction of elastic contact and elastohydrodynamic film thickness in worm gears. Using the undeformed geometry of the gap between gear teeth in contact a three-dimensional elastic contact simulation technique has been developed for calculation of the true area of elastic contact under load relative to the wheel and worm surfaces. A parallel investigation of elastohydrodynamic lubrication effects has been carried out using a special non-Newtonian, thermal solver which takes account of the nonsymmetrical and spin aspects of worm contacts. An interesting feature of the results obtained is the discovery of regions of poor film forming due to entrainment failure at the edges of the contact.

Plasto-Elastohydrodynamic Lubrication in Point Contacts for Surfaces With Three-Dimensional Sinusoidal Waviness and Real Machined Roughness

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Tao He ◽  
Ning Ren ◽  
Dong Zhu ◽  
Jiaxu Wang
Keyword(s):  
Plastic Deformation ◽  
Rough Surface ◽  
Mechanical Design ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Von Mises Stress ◽  
Asperity Contacts ◽  
Lubrication Characteristics ◽  
Von Mises

Efficiency and durability are among the top concerns in mechanical design to minimize environmental impact and conserve natural resources while fulfilling performance requirements. Today mechanical systems are more compact, lightweight, and transmit more power than ever before, which imposes great challenges to designers. Under the circumstances, some simplified analyses may no longer be satisfactory, and in-depth studies on mixed lubrication characteristics, taking into account the effects of 3D surface roughness and possible plastic deformation, are certainly needed. In this paper, the recently developed plasto-elastohydrodynamic lubrication (PEHL) model is employed, and numerous cases with both sinusoidal waviness and real machined roughness are analyzed. It is observed that plastic deformation may occur due to localized high pressure peaks caused by the rough surface asperity contacts, even though the external load is still considerably below the critical load determined at the onset of plastic deformation in the corresponding smooth surface contact. It is also found, based on a series of cases analyzed, that the roughness height, wavelength, material hardening property, and operating conditions may all have significant influences on the PEHL performance, subsurface von Mises stress field, residual stresses, and plastic strains. Generally, the presence of plastic deformation may significantly reduce some of the pressure spikes and peak values of subsurface stresses and make the load support more evenly distributed among all the rough surface asperities in contact.

A Model for Elastohydrodynamic Film Failure in Contacts Between Rough Surfaces Having Transverse Finish

1996 ◽  
Vol 118 (4) ◽  
pp. 847-857 ◽  
Author(s):  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Physical Mechanism ◽  
Elastohydrodynamic Lubrication ◽  
Significant Loss ◽  
Complete Loss ◽  
Finite Width ◽  
Real Contact ◽  
Asperity Contacts ◽  
Conventional Grinding ◽  
Elliptical Contact ◽  
Failure Models

The paper describes an elastohydrodynamic lubrication (EHL) model for collapse of the film in a contact of finite width between surfaces which have roughness aligned transverse to that of lubricant entrainment. The failure mechanism proposed is that of sideways leakage of the lubricant in the gaps that are present between the surfaces due to the valley features of the surface roughness. Under typical high temperature conditions with surfaces finished by conventional grinding, it is shown that the gap between the surfaces when lubricated is almost identical to that between the same dry surfaces in contact with the addition of a small land clearance equivalent to the nominal EHL film thickness. Analysis of idealized valley geometries leads to criteria for complete cavitation or significant loss of pressure between asperity contacts, but application of these criteria to a real contact suggests that scuffing occurs under conditions which are less severe than predicted by either of these simple failure models. Detailed analysis of leakage from the valley features in the transverse direction at the edges of a real elliptical contact shows that this can explain the complete loss of the film in a real contact, and this suggests a physical mechanism of scuffing.

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.

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