A Line-Contact Micro-EHL Model With Three-Dimensional Surface Topography

1994 ◽  
Vol 116 (1) ◽  
pp. 21-28 ◽  
Author(s):  
L. Chang ◽  
M. N. Webster ◽  
A. Jackson
Keyword(s):  
Surface Topography ◽  
Surface Deformation ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Asperity Contact ◽  
Contact Conditions ◽  
Physical Problems ◽  
Mixed Lubrication Regime ◽  
Side Flow ◽  
Local Side

A mathematical model is presented in this paper that can be used to analyze the effect of 3-D surface topography on the thermal, transient micro-elastohydrodynamic lubrication (EHL). The model efficiently incorporates the surface deformation due to the 3D pressure rippling and the lubricant side flow around the asperities. The resulting computer implementation requires little additional storage space and does not reduce computational efficiency from its 2-D counterpart. The model is shown to sensibly describe the physical problems. The results presented in this paper and in a separate paper (Chang et al., 1993c) show that the lubricant local side flow significantly affects the contact conditions of the EHL of rough surfaces, especially under high sliding. The work reported thus far represents the authors’ continuing effort to develop an analytical/computational model for tribo-systems operating in the micro-EHL/mixed-lubrication regime. Work in the future will model and integrate the asperity contact mechanics and lubricant-surface tribo-chemistry in the micro-EHL environment.

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.

Numerical Modeling of Mixed Lubrication and Flash Temperature in EHL Elliptical Contacts

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Neelesh Deolalikar ◽  
Farshid Sadeghi ◽  
Sean Marble
Keyword(s):  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Lubrication Regime ◽  
Predicting Performance ◽  
Pure Rolling ◽  
Rolling Element ◽  
Contact Pressures ◽  
Film Lubrication

Highly loaded ball and rolling element bearings are often required to operate in the mixed elastohydrodynamic lubrication regime in which surface asperity contact occurs simultaneously during the lubrication process. Predicting performance (i.e., pressure, temperature) of components operating in this regime is important as the high asperity contact pressures can significantly reduce the fatigue life of the interacting components. In this study, a deterministic mixed lubrication model was developed to determine the pressure and temperature of mixed lubricated circular and elliptic contacts for measured and simulated surfaces operating under pure rolling and rolling/sliding condition. In this model, we simultaneously solve for lubricant and asperity contact pressures. The model allows investigation of the condition and transition from boundary to full-film lubrication. The variation of contact area and load ratios is examined for various velocities and slide-to-roll ratios. The mixed lubricated model is also used to predict the transient flash temperatures occurring in contacts due to asperity contact interactions and friction. In order to significantly reduce the computational efforts associated with surface deformation and temperature calculation, the fast Fourier transform algorithm is implemented.

A Three-Dimensional Model of Line-Contact Elastohydrodynamic Lubrication for Heterogeneous Materials with Inclusions

2016 ◽  
Vol 08 (02) ◽  
pp. 1650014 ◽  
Author(s):  
Kun Zhou ◽  
Qingbing Dong
Keyword(s):  
Film Thickness ◽  
Half Space ◽  
Surface Deformation ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Line Contact ◽  
Lubricant Film Thickness ◽  
Equivalent Inclusion Method ◽  
Surface Contact

This paper develops a three-dimensional (3D) model for a heterogeneous half-space with inclusions distributed periodically beneath its surface subject to elastohydrodynamic lubrication (EHL) line-contact applied by a cylindrical loading body. The model takes into account the interactions between the loading body, the fluid lubricant and the heterogeneous half-space. In the absence of subsurface inclusions, the surface contact pressure distribution, the half-space surface deformation and the lubricant film thickness profile are obtained through solving a unified Reynolds equation system. The inclusions are homogenized according to Eshelby’s equivalent inclusion method (EIM) with unknown eigenstrains to be determined. The disturbed half-space surface deformations induced by the subsurface inclusions or eigenstrains are iteratively introduced into the lubricant film thickness until the surface deformation finally converges. Both time-independent smooth surface contact and time-dependent rough surface contact are considered for the lubricated contact problem.

Three-Dimensional Plasto-Elastohydrodynamic Lubrication (PEHL) for Surfaces with Irregularities

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Ning Ren ◽  
Dong Zhu ◽  
Q. Jane Wang
Keyword(s):  
Plastic Deformation ◽  
Work Hardening ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Continuous Variable ◽  
External Loading ◽  
Surface Irregularity ◽  
Asperity Contact ◽  
Stress Concentrations ◽  
Subsurface Stress

Elastohydrodynamic lubrication (EHL) is one of the most common types of lubrication, which widely exists in many machine elements such as gears, rolling bearings, cams and followers, metal rolling tools, and continuous variable transmissions. These components often transmit substantial power under heavy loading conditions that may possibly induce plastic deformation of contacting surfaces. Moreover, the roughness of machined surfaces is usually of the same order of magnitude as, or greater than, the average EHL film thickness. Consequently, most components operate in mixed lubrication with considerable asperity contacts, which may result in localized pressure peaks much higher than the Hertzian pressure, causing subsurface stress concentrations possibly exceeding the material yield limit. Plastic deformation, therefore, often takes place, which not only permanently changes the surface profiles and contact geometry, but alters material properties through work-hardening as well. Available mixed EHL models, however, do not consider plastic deformation, often yielding unrealistically high pressure spikes and subsurface stresses around asperity contact locations. Recently, a three-dimensional (3D) plasto-elastohydrodynamic lubrication (PEHL) model has been developed for investigating the effects of plastic deformation and material work-hardening on the EHL characteristics and subsurface stress/strain fields. The present paper is a continuation of the previous work done by Ren et al. (2010, “PEHL in point contacts,” ASME J. Tribol., 132(3), pp. 031501) that focused on model development and validation, as well as investigation of fundamental PEHL mechanisms in smooth surface contacts. This part of the study is mainly on the PEHL behavior involving simple surface irregularities, such as a single asperity or dent, which can be considered as basic elements of more complicated surface roughness. It is found that considerable plastic deformation may occur due to the pressure peaks caused by the surface irregularity, even though sometimes external loading is not heavy and the irregularity is concave. The plastic deformation may significantly affect contact and lubrication characteristics, resulting in considerable reductions in peak pressure and maximum subsurface stresses.

A Full Numerical Solution to the Mixed Lubrication in Point Contacts

1999 ◽  
Vol 122 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Yuan-Zhong Hu ◽  
Dong Zhu
Keyword(s):  
Numerical Solution ◽  
Reynolds Equation ◽  
Surface Deformation ◽  
Full Range ◽  
Computing Time ◽  
Numerical Procedure ◽  
Elastohydrodynamic Lubrication ◽  
Asperity Contact ◽  
Point Contacts ◽  
Severe Condition

A full numerical solution for the mixed elastohydrodynamic lubrication (EHL) in point contacts is presented in this paper, using a new numerical approach that is simple and robust, capable of handling three-dimensional measured engineering rough surfaces moving at different rolling and sliding velocities. The equation system and the numerical procedure are unified for a full coverage of all the lubrication regions including the full film, mixed and boundary lubrication. In the hydrodynamically lubricated areas the Reynolds equation is used. In the asperity contact areas, where the film thickness is zero, the Reynolds equation is reduced to an expression equivalent to the mathematical description of dry contact problem. In order to save computing time, a multi-level integration method is used to calculate surface deformation. Sample cases under severe condition show that this approach is capable of analyzing different cases in a full range of λ ratio, from infinitely large down to nearly zero (less than 0.03). [S0742-4787(00)00101-6]

Sliding Contact Analysis of Layered Elastic/Plastic Solids With Rough Surfaces

2001 ◽  
Vol 124 (1) ◽  
pp. 46-61 ◽  
Author(s):  
Wei Peng ◽  
Bharat Bhushan
Keyword(s):  
Surface Deformation ◽  
Rough Surfaces ◽  
Normal Load ◽  
Three Dimensional ◽  
Sliding Contact ◽  
Fast Fourier Transformation ◽  
Maximum Pressure ◽  
Asperity Contact ◽  
Elastic Plastic ◽  
Von Mises

A three-dimensional numerical model is presented to investigate the quasi-static sliding contact behavior of layered elastic/plastic solids with rough surfaces. The model is applicable for both single-asperity contact and multiple-asperity contacts. The surface deformation is obtained based on a variational principle. The surface and subsurface stresses in the layer and the substrate are determined with a Fast Fourier transformation (FFT) based scheme and von Mises and principal tensile stresses are computed accordingly. Contact statistics, such as fractional contact area, maximum pressure/E2 and relative meniscus force are predicted. The results are used to investigate the effect of the contact statistics on friction, stiction, and wear problems such as debris generation, brittle failure, and delamination of layered media. Optimum layer parameters are identified. It allows the specification of layer properties, according to the contact statistics, to reduce friction, stiction, and wear of materials. A normalization procedure is presented to apply the results on various combinations of surface roughness, material properties, and normal load.

Transient tribodynamic analysis of crankshaft-main bearing system during engines starting up

2017 ◽  
Vol 232 (5) ◽  
pp. 535-549 ◽  
Author(s):  
Ruichao Liu ◽  
Xianghui Meng ◽  
Peng Li
Keyword(s):  
Internal Combustion Engines ◽  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Viscous Friction ◽  
Friction Loss ◽  
Asperity Contact ◽  
Main Bearing ◽  
Start Up ◽  
Run Up ◽  
Bearing System

The starting-up process of internal combustion engines presents a great challenge to the tribodynamic performance of the crankshaft-main bearing system. In this study, a transient mixed elastohydrodynamic lubrication model is presented to investigate the transient process. In the model, the average Reynolds equation is adopted with considering the influences of surface deformation and starting temperature. Then the oil film and friction loss of the system and the journal center trajectory during engines starting up are analyzed. The results at different starting temperatures show that the asperity contact under the hot start-up condition is more serious. However, during the engine run-up and transition to idling phases, more viscous friction loss is generated under the cold start-up condition.

Scuffing Theory Modeling and Experimental Correlations

1991 ◽  
Vol 113 (2) ◽  
pp. 327-334 ◽  
Author(s):  
S. C. Lee ◽  
H. S. Cheng
Keyword(s):  
Preliminary Investigation ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Effects ◽  
Asperity Contact ◽  
Contact Conditions ◽  
Surface Profiles ◽  
Temperature And Pressure ◽  
Rough Surface Contact ◽  
Contact Pressures ◽  
Temperature And Pressure Effects

The scuffing behavior for contacts operating in the partial elastohydrodynamic lubrication regime is shown to be greatly affected by the asperity contact temperatures and the lubricant pressures inside the elastohydrodynamic lubrication conjunction. A scuffing model which takes into account the temperature and pressure effects for predicting the onset of scuffing failure has been developed. This model is based on the lubricant molecule physisorption theory and is capable of predicting the scuffing failures for general contact conditions including the boundary lubrication contacts and the elastohydrodynamic lubrication (ehl) contacts. A preliminary investigation into this model showed a good correlation existing between the theory and some scuffing experiment results conducted on a twin disk machine. However, more experimentation is necessary to further ascertain the validity of this new model. To validate the new scuffing theory, a method for calculating the asperity flash temperatures is formulated. The flash temperature calculations were performed using the actual digitized run-in surface profiles of the mating bodies. The necessary informations for calculating the flash temperatures such as, the real areas of contact and the asperity contact pressures were all determined using a recently developed rough surface contact simulation model.

Effects of Lubricant Rheology and Kinematic Conditions on Micro-Elastohydrodynamic Lubrication

1989 ◽  
Vol 111 (2) ◽  
pp. 344-351 ◽  
Author(s):  
L. Chang ◽  
C. Cusano ◽  
T. F. Conry
Keyword(s):  
Central Region ◽  
Surface Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Surface Irregularity ◽  
Experimental Measurements ◽  
Line Contact ◽  
Contact Conditions ◽  
Ehd Lubrication ◽  
Isothermal Line ◽  
Lubricant Rheology

The effects of lubricant rheology and surface kinematic conditions on micro-elastohydrodynamic (EHD) lubrication are analyzed under isothermal line-contact conditions. Micro-EHD lubrication is modeled by introducing a surface irregularity in the form of an asperity or a furrow into the contact zone. Under simple sliding conditions, the pressure generated in the vicinity of the irregularity and the resulting surface deformation depend strongly on the lubricant rheology. The surface kinematic conditions have profound effects on micro-EHD lubrication. In general, a stationary surface irregularity produces a relatively strong downstream effect when it is in the inlet region of the contact, and a moving surface irregularity produces a relatively strong upstream effect after it enters the Hertzian central region. The simulated results agree qualitatively with previous experimental measurements and observations.

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