Mixed Lubrication Analyses by a Macro-Micro Approach and a Full-Scale Mixed EHL Model

2004 ◽  
Vol 126 (1) ◽  
pp. 81-91 ◽  
Author(s):  
Q. Jane Wang ◽  
Dong Zhu ◽  
Herbert S. Cheng ◽  
Tonghui Yu ◽  
Xiaofei Jiang ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Numerical Experiments ◽  
Flow Model ◽  
Elastohydrodynamic Lubrication ◽  
Full Scale ◽  
Asperity Contact ◽  
Average Pressure ◽  
Average Flow ◽  
Simplified Approach ◽  
Average Flow Model

This paper presents an improvement of a simplified approach, namely, the macro-micro approach, used to model the mixed elastohydrodynamic lubrication problems in counterformal contacts, and its comparison with Zhu and Hu’s full-scale mixed-EHL model. In this approach, Patir and Cheng’s average flow model is employed to obtain the distribution of piecewise average pressure. A contact-embedment method that incorporates the detail of asperity contact pressure into the overall pressure distribution is utilized to reveal the severity of surface interaction. Numerical experiments are conducted, and the results are compared with those obtained by means of the full-scale mixed-EHL. The regime of the application of this macro-micro approach is explored.

Initial Pressure Influence on Pressure Flow Factor Used in Mixed-Lubrication Model

2011 ◽  
Vol 86 ◽  
pp. 65-69
Author(s):  
Fan Ming Meng ◽  
Yuan Pei Chen
Keyword(s):  
Analytical Solution ◽  
Pressure Distribution ◽  
Flow Model ◽  
Initial Pressure ◽  
Mixed Lubrication ◽  
Average Pressure ◽  
Pressure Flow ◽  
Average Flow ◽  
Flow Factor ◽  
Average Flow Model

The average flow model proposed by Patir and Cheng offers a great convenience for the mixed-lubrication analysis of rough surfaces. The pressure flow factor introduced by Patir and Cheng helps to analyze the influence of roughness on the average pressure and average flow of a lubricant between surfaces. This paper reports how to reasonably choose initial pressure in computing the pressure flow factor. The numerical results show that the pressure distribution and further pressure flow factor value are sensitive to an initial pressure in solving the pressure flow factor, and the initial pressure of a constant value is not suitable for the pressure flow factor calculation for a measured surface with many sample points. Meanwhile, the pressure flow code is demonstrated by the comparison of the pressure obtained numerically with the analytical solution of pressure.

Load-Bearing Capacity Investigation of Friction Pairs in Hydro-Viscous Drive Based on Fractal Contact Theory

2021 ◽  
Vol 143 (12) ◽  
Author(s):  
Hong-Wei Cui ◽  
Yu-Yu Jiang ◽  
Qi-Liang Wang
Keyword(s):  
Film Thickness ◽  
Bearing Capacity ◽  
Flow Model ◽  
Thickness Ratio ◽  
Contact Model ◽  
Asperity Contact ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Average Flow ◽  
Average Flow Model

Abstract Hydro-viscous drive has gained extensive application in fans, pumps, belt conveyors, and scraper conveyors for step-less speed regulating, soft starting, and overload protection. In the mixed friction stage, the state of contact and load-bearing capacity are always changing with the pressure of control oil. In order to predict the load-bearing capacity of friction pairs, a description of the frictional and hydrodynamic lubrication states was first made. Oil film’s pressure distribution and load-bearing capacity were analyzed with the average flow model. The fractal contact model of the asperity surface was proposed for simulating mutual contact state and contact load between the asperities. The influences of fractal parameters on the contact performance of friction pairs were conducted. Eventually, test rig of load-bearing capacity was established. As indicated by the experiment, asperity contact area and load-bearing capacity of the asperity contact increase slowly at first and then rapidly with reduced film thickness ratio. Correspondingly, oil film load-bearing capacity progressively reduces. Due to the reduction of film thickness ratio, friction pairs’ load-bearing capacity increases gradually. The load-bearing capacity of friction pairs is affected by the fractal dimension and scale factor. Results of the experiment well conform to the theoretical values, which illustrates that friction pairs’ load-bearing capacity can be accurately predicted and computed using the average flow model and M-B fractal contact model. The calculation offers a theoretical reference to the survey about friction and torque properties of the hydro-viscous drive.

scholarly journals An Average Flow Model of the Reynolds Roughness Including a Mass-Flow Preserving Cavitation Model

2005 ◽  
Vol 127 (4) ◽  
pp. 793-802 ◽  
Author(s):  
Guy Bayada ◽  
Sébastien Martin ◽  
Carlos Vázquez
Keyword(s):  
Mass Flow ◽  
Numerical Experiments ◽  
Reynolds Equation ◽  
Flow Model ◽  
Two Dimensional ◽  
Scale Analysis ◽  
Cavitation Model ◽  
Average Flow ◽  
One Dimensional ◽  
Average Flow Model

An average Reynolds equation for predicting the effects of deterministic periodic roughness, taking Jakobsson, Floberg, and Olsson mass flow preserving cavitation model into account, is introduced based upon the double scale analysis approach. This average Reynolds equation can be used both for a microscopic interasperity cavitation and a macroscopic one. The validity of such a model is verified by numerical experiments both for one-dimensional and two-dimensional roughness patterns.

An Evaluation of the Average Flow Model [1] for Surface Roughness Effects in Lubrication

1980 ◽  
Vol 102 (3) ◽  
pp. 360-366 ◽  
Author(s):  
J. L. Teale ◽  
A. O. Lebeck
Keyword(s):  
Surface Roughness ◽  
Flow Model ◽  
Two Dimensional ◽  
Roughness Effects ◽  
Important Conclusion ◽  
Average Flow ◽  
One Dimensional ◽  
Dimensional Flow ◽  
Two Dimensional Flow ◽  
Average Flow Model

The average flow model presented by Patir and Cheng [1] is evaluated. First, it is shown that the choice of grid used in the average flow model influences the results. The results presented are different from those given by Patir and Cheng. Second, it is shown that the introduction of two-dimensional flow greatly reduces the effect of roughness on flow. Results based on one-dimensional flow cannot be relied upon for two-dimensional problems. Finally, some average flow factors are given for truncated rough surfaces. These can be applied to partially worn surfaces. The most important conclusion reached is that an even closer examination of the average flow concept is needed before the results can be applied with confidence to lubrication problems.

An EHD-mixed lubrication analysis of main bearings for diesel engine based on coupling between flexible whole engine block and crankshaft

2015 ◽  
Vol 67 (2) ◽  
pp. 150-158 ◽  
Author(s):  
Lidui Wei ◽  
Haijun Wei ◽  
Shulin Duan ◽  
Yu Zhang
Keyword(s):  
Diesel Engine ◽  
Flow Model ◽  
Mixed Lubrication ◽  
Engine Block ◽  
Contact Theory ◽  
Asperity Contact ◽  
Block Model ◽  
Content Type ◽  
Oil Film ◽  
Average Flow Model

Purpose – The purpose of this paper is to develop a good calculation model to accurately predict the lubrication characteristic of main bearings of diesel engine and improve the service life. Design/methodology/approach – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the Component Mode Synthesis (CMS) method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an elastohydrodynamic (EHD)-mixed lubrication model of the main bearings for the diesel engine is developed and researched with the finite volume method and the finite element method. Findings – Obviously, the mixed lubrication of bearings is normal, while full hydrodynamic lubrication is transient. The results show that under the whole flexible block model, maximum oil film pressure, maximum asperity contact pressure and radial shell deformation decrease, while minimum oil film thickness increases. Oil flow over edge decreases, and so does friction loss. Therefore, coordination deformation ability of whole engine block is favorable to mean load. In the whole block model, friction contact happens on both upper shell and lower shell positions. In addition, average oil film fill ratio at the key position becomes smaller in the whole engine block model, and consequently increases the chances of cavitations erosion more. So, wearing resistance of both upper and lower shells and anti-cavitations erosion ability must be enhanced simultaneously. Originality/value – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the CMS method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an EHD-mixed lubrication model of the main bearings for the diesel engine is built, which can predict the lubrication of journal bearings more accurately.

Pressure and Shear Flow in a Rough Hydrodynamic Bearing, Flow Factor Calculation

1997 ◽  
Vol 119 (3) ◽  
pp. 549-555 ◽  
Author(s):  
L. Lunde ◽  
K. To̸nder
Keyword(s):  
Finite Element Method ◽  
Surface Roughness ◽  
Finite Element ◽  
Shear Flow ◽  
Reynolds Equation ◽  
Flow Model ◽  
The Finite Element Method ◽  
Average Flow ◽  
Hydrodynamic Bearing ◽  
Average Flow Model

The lubrication of isotropic rough surfaces has been studied numerically, and the flow factors given in the so-called Average Flow Model have been calculated. Both pressure flow and shear flow are considered. The flow factors are calculated from a small hearing part, and it is shown that the flow in the interior of this subarea is nearly unaffected by the bearing part’s boundary conditions. The surface roughness is generated numerically, and the Reynolds equation is solved by the finite element method. The method used for calculating the flow factors can be used for different roughness patterns.

A Simple Method to Calculate Contact Factor Used in Average Flow Model

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Fanming Meng ◽  
Q. Jane Wang ◽  
Diann Hua ◽  
Shuangbiao Liu
Keyword(s):  
Density Distribution ◽  
Probability Density ◽  
Method Validation ◽  
Present Method ◽  
Flow Model ◽  
Probability Density Distribution ◽  
Simple Method ◽  
Average Flow ◽  
Non Gaussian ◽  
Average Flow Model

The average flow model proposed by Patir and Cheng offers a great convenience for the analysis of rough surfaces in lubrication. The contact factor introduced by Wu and Zheng helps to solve a difficulty in local film evaluation using the average flow model. This paper reports a simple method to calculate the contact factor. Method validation is demonstrated by the comparison of the contact factors for Gaussian surfaces obtained with the present method and the fitting formula of Wu and Zheng. The proposed method cannot only easily compute the contact factor values for Gaussian surfaces; it can also be used for those of non-Gaussian and measured surfaces, especially those with unknown probability density distribution of the roughness height.

Elastohydrostatic Lubrication of Circular Plate Thrust Bearings

1967 ◽  
Vol 89 (3) ◽  
pp. 237-242 ◽  
Author(s):  
D. Dowson ◽  
C. M. Taylor
Keyword(s):  
Pressure Distribution ◽  
Circular Plate ◽  
Thrust Bearing ◽  
Elastohydrodynamic Lubrication ◽  
Radial Pressure ◽  
Simplified Approach ◽  
Thrust Bearings ◽  
Low Modulus ◽  
Elastic Distortion ◽  
Equivalent Modulus

The subject of elastohydrodynamic lubrication has developed considerably in recent years and in the present paper the influence of elastic distortion upon the performance of a hydrostatic thrust bearing is considered. A circular plate hydrostatic thrust bearing is considered and one of the pads is assumed to be lined by a thin layer of elastic material. A simplified approach to the calculation of elastic displacements is used and an approximate analytical solution of the governing elastohydrostatic equations is presented. Theoretical solutions showing the influence of elastic distortion upon pressure distribution are presented. Experimental measurements of radial pressure distribution are recorded for bearings lined with low modulus nitrile and polyurethane rubber. Difficulties encountered in the measurement of the rubber properties prevented a strict comparison between experimental and theoretical results but the selection of an equivalent modulus enabled qualitative agreement to be demonstrated. Elastohydrostatic behavior is shown to have a beneficial effect upon bearing performance.

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