Friction coefficient in mixed lubrication: A simplified analytical approach for highly loaded non-conformal contacts

Otero, Javier Echávarri; Ochoa, Eduardo de la Guerra; Tanarro, Enrique Chacón; López, Benito del Río

doi:10.1177/1687814017706266

Cited by 10 publications

(14 citation statements)

References 39 publications

(91 reference statements)

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“…The thermal effect is also considered in the central film thickness (H c ) by incorporating thermal correction factor (f th ). The expression for the thermal correction factor is given in equation (6) [39].…”

Section: Hydrodynamic Lubrication Modelmentioning

confidence: 99%

“…To incorporate the shear-thinning effect in the lubricant film thickness, a shear-thinning correction factor (f NE ) is used in this work. The expression for a shear-thinning correction factor is given in equation ( 7) [39].…”

Section: Hydrodynamic Lubrication Modelmentioning

confidence: 99%

“…They proposed a new equation as a function of the lambda ratio to generate an S-curve and suggested that rough surface contact modelling should be treated as a growth/ decay process. Few studies on the effect of non-Newtonian lubricant rheology on the mixed-EHL traction coefficient have also been reported [38,39]. The surface roughness values (S q = 50 nm, 200 nm) considered in these studies were low enough, even then significant asperity contacts was observed.…”

Section: Introductionmentioning

confidence: 99%

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A numerical study on the impact of lubricant rheology and surface topography on heavily loaded non-conformal contacts

Prajapati

Ahmad

Katiyar

et al. 2023

Surf. Topogr.: Metrol. Prop.

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The increasing requirement of high-power density (power throughput/ weight) in modern day machines lead to thin film lubrication condition in various machine components (rolling element bearings, gears, cams, etc.,) due to severe loading conditions. Surface roughness features and lubricant rheology plays a vital role in thin film lubrication, and significantly affects the lubrication performance and lifetime of machine components. The present work demonstrates surface topography and lubricant rheology effects on the traction coefficient for heavily loaded non-conformal contacts. The load-sharing concept considering elastic-plastic deformation of asperities, and Carreau shear-thinning rheological model is employed to describe the dry rough contacts and non-Newtonian behavior of lubricant. An influence of surface topography parameters such as roughness, skewness, kurtosis, and pattern ratio on the traction coefficient is discussed. From results, it is found that among different surface topographies, negatively skewed surfaces having isotropic surface pattern exhibit minimum traction coefficient. The load share function and the critical rolling speed are determined for various surface topographies which provides further insights into the surface topography effect on traction coefficient. The findings of present study are noteworthy as they provide a theoretical basis for an assessment of the lubrication performance of heavily loaded non-conformal contacts.

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Section: Hydrodynamic Lubrication Modelmentioning

confidence: 99%

Section: Hydrodynamic Lubrication Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A numerical study on the impact of lubricant rheology and surface topography on heavily loaded non-conformal contacts

Prajapati

Ahmad

Katiyar

et al. 2023

Surf. Topogr.: Metrol. Prop.

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“…This can be resolved to some extent by using machine learning models to predict the traction coefficient for different surface topographies of non-conformal contacts. Earlier, a simplified method and expressions have been developed for the prediction of the traction coefficient, the asperity load ratio, the film thickness for different RMS roughness ( S q ) and operating conditions (Otero et al , 2017; Masjedi and Khonsari, 2015). This work demonstrates the prediction of mixed-EHL parameters using various topography parameters such as skewness, kurtosis and pattern ratio as an input in the ML model (supervision-based machine learning model).…”

Section: Introductionmentioning

confidence: 99%

Machine learning approach for the prediction of mixed lubrication parameters for different surface topographies of non-conformal rough contacts

Prajapati,

Katiyar,

Prakash

2023

ILT

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Purpose This study aims to use a machine learning (ML) model for the prediction of traction coefficient and asperity load ratio for different surface topographies of non-conformal rough contacts. Design/methodology/approach The input data set for the ML model is generated using a mixed-lubrication model. Surface topography parameters (skewness, kurtosis and pattern ratio), rolling speed and hardness are used as input features in the multi-layer perceptron (MLP) model. The hyperparameter tuning and fivefold cross-validation are also performed to minimize the overfitting. Findings From the results, it is shown that the MLP model shows excellent accuracy (R2 > 90%) on the test data set for making the prediction of mixed lubrication parameters. It is also observed that engineered rough surfaces with high negative skewness, low kurtosis and isotropic surface patterns exhibit a significant low traction coefficient. It is also concluded that the MLP model gives better accuracy in comparison to the random forest regression model based on the training and testing data sets. Originality/value Mixed lubrication parameters are predicted by developing a regression-based MLP model. The machine learning model is trained using several topography parameters, which are vital in the mixed-EHL regime because of the lack of regression-fit expressions in previous works. The accuracy of MLP with random forest models is also compared.

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“…Echávarri Otero et al. 15 presented an analytical model that considered load shared between the roughness asperities and lubricant film to predict friction in a mixed lubrication regime. Ouyang et al.…”

Section: Introductionmentioning

confidence: 99%

Effects on lubrication characteristics of water-lubricated rubber bearings with journal tilting and surface roughness

2019

Proceedings of the Institution of Mechanical Engineers, Part J:

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To study the effect of surface roughness on the lubrication characteristics of water-lubricated rubber bearings (WLRBs) when the stern shaft is tilted, the surface roughness of the bearings was measured by a surface roughness measuring instrument. Considering the tilting stern shaft and surface roughness, a mathematical model was constructed and water film thickness equation was deduced. By adopting the finite difference method, the film thickness and pressure distribution of WLRBs with tilt angle and roughness were analysed. The effects of tilt angle on film thickness and pressure under different surface roughness amplitudes and wavelengths were studied, and the results were then compared with those of smooth surface bearings without tilt angle. Finally, the minimum film thickness and maximum film pressure were analysed. The results showed that when the tilt of rotor and surface roughness of bearing were considered simultaneously, the film thickness exhibited a jagged distribution in the circumferential direction and decreased gradually in the axial direction. The film pressure had slightly irregular fluctuations and a sharp pressure peak. The tilt angle and roughness reduced the minimum film thickness, and the film thickness difference increased. The film pressure increased rapidly and local pressure exhibited slight, sudden changes. The surface roughness amplitude and wavelength had a considerable influence on the water film thickness, and the roughness amplitude had a clear effect on the film pressure. As the roughness amplitude increased, the minimum film thickness gradually declined and film pressure peak fluctuation grew. As the roughness wavelength increased, the film thickness fluctuated irregularly within a certain range of magnitude, and the minimum film thickness was almost constant.

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Friction coefficient in mixed lubrication: A simplified analytical approach for highly loaded non-conformal contacts

Cited by 10 publications

References 39 publications

A numerical study on the impact of lubricant rheology and surface topography on heavily loaded non-conformal contacts

A numerical study on the impact of lubricant rheology and surface topography on heavily loaded non-conformal contacts

Machine learning approach for the prediction of mixed lubrication parameters for different surface topographies of non-conformal rough contacts

Effects on lubrication characteristics of water-lubricated rubber bearings with journal tilting and surface roughness

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