Contact ratio of rough surfaces with multiple asperities in mixed lubrication at high pressures

2012 ◽  
Vol 258 (8) ◽  
pp. 3888-3896 ◽  
Author(s):  
Huaping Xiao ◽  
Dan Guo ◽  
Shuhai Liu ◽  
Guoshun Pan ◽  
Xinchun Lu
Keyword(s):  
High Pressures ◽  
Rough Surfaces ◽  
Mixed Lubrication ◽  
Contact Ratio

A Mixed Elastohydrodynamic Lubrication Model With Asperity Contact

1999 ◽  
Vol 121 (3) ◽  
pp. 481-491 ◽  
Author(s):  
Xiaofei Jiang ◽  
D. Y. Hua ◽  
H. S. Cheng ◽  
Xiaolan Ai ◽  
Si C. Lee
Keyword(s):  
Contact Pressure ◽  
Contact Area ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Load Ratio ◽  
Mixed Lubrication ◽  
Successful Implementation ◽  
Asperity Contact ◽  
Contact Ratio ◽  
Lubrication Performance

Most machine elements, such as gears and bearings, are operated in the mixed lubrication region. To evaluate lubrication performance for these tribological components, a contact model in mixed elastohydrodynamic lubrication is presented. This model deals with the EHL problem in the very thin film region where the film is not thick enough to separate the asperity contact of rough surface. The macro contact area is then divided into the lubricated area and the micro asperity contact areas by the contacted rough surfaces. In the case when asperity to asperity contact is present, Reynolds equation is only valid in the lubricated areas. Asperity contact pressure is determined by the interaction of two mating surfaces. The applied load is carried out by the lubricant film and the contacted asperities. FFT techniques are utilized to calculate the surface displacement (forward problem) by convolution and the asperity contact pressure (inverse problem) by deconvolution for non-periodic surfaces. With the successful implementation of FFT and multigrid methods, the lubricated contact problem can be solved within hours on a PC for the grids as large as one million nodes. This capability enables us to simulate random rough surfaces in a dense mesh. The load ratio, contact area ratio and average gap are introduced to characterize the performance of mixed lubrication with asperity contacts. Discussions are given regarding the asperity orientation as well as the effect of rolling-sliding condition. Numerical results of real rough topography are illustrated with effects of velocity parameter on load ratio, contact ratio, and average gap.

The investigation of contact ratio in mixed lubrication

2006 ◽  
Vol 39 (5) ◽  
pp. 409-416 ◽  
Author(s):  
J.B. Luo ◽  
S. Liu
Keyword(s):  
Mixed Lubrication ◽  
Contact Ratio

scholarly journals An Assessment of Quantitative Predictions of Deterministic Mixed Lubrication Solvers

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Yuechang Wang ◽  
Abdel Dorgham ◽  
Ying Liu ◽  
Chun Wang ◽  
Mark C. T. Wilson ◽  
...  
Keyword(s):  
Reynolds Equation ◽  
Thickness Distribution ◽  
Computation Time ◽  
Simulation Method ◽  
Coefficient Matrix ◽  
Mixed Lubrication ◽  
Contact Ratio ◽  
Lubricated Contacts ◽  
Discretization Schemes ◽  
Parametric Studies

Abstract The ability to simulate mixed lubrication problems has greatly improved, especially in concentrated lubricated contacts. A mixed lubrication simulation method was developed by utilizing the semi-system approach which has been proven to be highly useful for improving stability and robustness of mixed lubrication simulations. Then different variants of the model were developed by varying the discretization schemes used to treat the Couette flow terms in the Reynolds equation, varying the evaluation of density derivatives and varying the contribution of terms in the coefficient matrix. The resulting pressure distribution, film thickness distribution, lambda ratio, contact ratio, and the computation time were compared and found to be strongly influenced by the choice of solution scheme. This indicates that the output from mixed lubrication solvers can be readily used for qualitative and parametric studies, but care should be taken when making quantitative predictions.

Elasto-plastic contact of rough surfaces: a mixed-lubrication model for the textured surface analysis

Meccanica ◽  
2016 ◽  
Vol 52 (7) ◽  
pp. 1541-1559 ◽  
Author(s):  
Xianghui Meng ◽  
Chunxing Gu ◽  
Youbai Xie
Keyword(s):  
Surface Analysis ◽  
Rough Surfaces ◽  
Mixed Lubrication ◽  
Textured Surface

scholarly journals Understanding the Mechanism of Load-Carrying Capacity between Parallel Rough Surfaces through a Deterministic Mixed Lubrication Model

Lubricants ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 12
Author(s):  
Yuechang Wang ◽  
Abdullah Azam ◽  
Gaolong Zhang ◽  
Abdel Dorgham ◽  
Ying Liu ◽  
...  
Keyword(s):  
Carrying Capacity ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Stribeck Curve ◽  
Future Research ◽  
Load Carrying Capacity ◽  
Proposed Model ◽  
Load Carrying ◽  
Lift Off

Experimental results have confirmed that parallel rough surfaces can be separated by a full fluid film. However, such a lift-off effect is not expected by the traditional Reynolds theory. This paper proposes a deterministic mixed lubrication model to understand the mechanism of the lift-off effect. The proposed model considered the interaction between asperities and the micro-elastohydrodynamic lubrication (micro-EHL) at asperities within parallel rough surfaces for the first time. The proposed model is verified by predicting the measured Stribeck curve taken from literature and experiments conducted in this work. The simulation results highlight that the micro-EHL effect at the asperity scale is critical in building load-carrying capacity between parallel rough surfaces. Finally, the drawbacks of the proposed model are addressed and the directions of future research are pointed out.

scholarly journals A mixed lubrication analysis of a thrust bearing with fractal rough surfaces

2019 ◽  
Vol 234 (4) ◽  
pp. 608-621
Author(s):  
Xiaohan Zhang ◽  
Yang Xu ◽  
Robert L Jackson
Keyword(s):  
Fractal Dimension ◽  
Roughness Length ◽  
Thrust Bearing ◽  
Rough Surfaces ◽  
Mixed Lubrication ◽  
Bearing Surface ◽  
Fractal Surfaces ◽  
Lubrication Regime ◽  
Surface Data ◽  
Mixed Lubrication Regime

Fractal descriptions of rough surfaces are widely used in tribology. The fractal dimension, D, is an important parameter which has been regarded as instrument and scale independent, although recent findings bring this into question. A thrust bearing is analyzed in the mixed lubrication regime while considering the fractal nature. Surface data obtained from a thrust bearing surface are characterized and used to calculate the fractal dimension value by the roughness-length method. Then these parameters are used to generate different rough surfaces via a filtering algorithm. By comparing the predicted performance between the measured surface and generated fractal surfaces, it is found that the fractal dimension must be used carefully when characterizing the tribological performance of rough surfaces, and other parameters need to be found.

Development of Theoretical Contact Width Formulas and a Numerical Model for Curved Rough Surfaces

2007 ◽  
Vol 129 (4) ◽  
pp. 735-742 ◽  
Author(s):  
Shao Wang
Keyword(s):  
Rough Surfaces ◽  
Contact Region ◽  
Roughness Parameter ◽  
Load Parameter ◽  
Traditional Theory ◽  
Contact Ratio ◽  
Contact Parameter ◽  
Contact Width ◽  
General Power ◽  
Truncated Gaussian

The apparent contact area of curved rough surfaces can be larger than that predicted by the Hertz theory due to asperity interaction outside the Hertzian region. In the present study, simple theoretical formulas for the contact semi-width and radius for Gaussian and truncated Gaussian height distributions were derived, and a numerical contact model was developed based on a general power-law relationship between the local apparent pressure and real-to-apparent contact ratio. Numerical results of the contact semi-width agree well with the prediction of the formula. The apparent contact region becomes increasingly larger than the Hertzian region as a dimensionless roughness parameter increases or as a dimensionless load parameter decreases. The ratio of the contact semi-width to the Hertzian semi-width and the apparent pressure distribution are completely determined by a dimensionless contact parameter and the dimensionless roughness parameter, which are both independent of the instrument resolution, thus providing a long awaited solution to the problem of instrument dependency in a traditional theory. An application to fractal-regular surfaces indicates that the influence of the fractal dimension on the contact behavior is due to its effects on both the area-load coefficient and the load exponent.

Mixed Lubrication with Rough Surfaces

2019 ◽  
pp. 251-297
Author(s):  
Q. Jane Wang ◽  
Dong Zhu
Keyword(s):  
Rough Surfaces ◽  
Mixed Lubrication
Sign in / Sign up

Export Citation Format

Share Document