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Article
Publication date: 1 October 2005

Y. Zhang

To form and develop a new mode of mixed elastohydrodynamic lubrication (mixed EHL) which is more realistic and of more application values to a practical elastohydrodynamic…

Abstract

Purpose

To form and develop a new mode of mixed elastohydrodynamic lubrication (mixed EHL) which is more realistic and of more application values to a practical elastohydrodynamic contact on gears, cams and roller bearings than the previous and current existing mixed EHL models.

Design/methodology/approach

The representative theoretical and experimental studies on elastohydrodynamic lubrication (EHL) and mixed EHL carried out in the previous and recent time, including those of the author, are reviewed. The obtained results on EHL and mixed EHL in those studies and the viewpoints on the mode of mixed EHL based on those results developed in those studies are compared and evaluated. Strong proves are formed on the new mode of mixed EHL proposed in the present paper based on these comparisons and evaluations.

Findings

Strong viewpoints are formed on the mode of the occurrence of dry contact in EHL in a practical concentrated contact. A new mode of mixed EHL is proposed by incorporating this mode of the occurrence of dry contact in EHL. Also, comments and evaluations on the previous researches on mixed EHL are made.

Practical implications

A very useful material for the engineers who are engaged in the design of EHL on gears, cams and roller bearings, and for the tribology scientists who thrust efforts in studying EHL and mixed EHL both by theoretical modeling and by experiments.

Originality/value

A new mode of mixed EHL is originally proposed by incorporating the finding of a more realistic mode of the occurrence of dry contact in EHL. This new mode of mixed EHL should become the direction of the theoretical research of mixed EHL in the future time. It provides a clearer way to this research.

Details

Industrial Lubrication and Tribology, vol. 57 no. 5
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 8 January 2018

Zhenhua Zhang, Jiaxu Wang, Guangwu Zhou and Xin Pei

This paper aims to solve the lubrication failures in the turning arm bearing of RV reducer, give some help in perfecting the bearing structure design and provide…

Abstract

Purpose

This paper aims to solve the lubrication failures in the turning arm bearing of RV reducer, give some help in perfecting the bearing structure design and provide theoretical basis for the reducer’s performance improvement.

Design/methodology/approach

The paper establishes a mixed lubrication analysis model to study performance parameters. According to the discretization of parameters and iteration of equations, numerical simulation and theoretical analysis are achieved in computational process.

Findings

Considering influences of contact load, real rough surface and realistic geometry of RV reducer turning arm roller bearing, the mixed lubrication analysis model is established to study the ratio of oil film thickness, pressure distribution and maximum von Mises stress in different speeds, temperatures and fillets. The results of mixed lubrication show that reasonable round corner modification, increase in temperature and speed, decrease of surface roughness and lubricant types can improve the lubrication performance.

Originality/value

The mixed lubrication analysis model is established to study the influences of contact load, real rough surface and realistic geometry of RV reducer turning arm roller bearing. Different speed, temperature, lubricant and fillet modification are also considered in the research to analyze oil film thickness, pressure distribution and maximum von Mises stress. These studies can optimize structural design of bearing and direct engineer operations.

Details

Industrial Lubrication and Tribology, vol. 70 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 8 January 2018

Yanzhong Wang, Chao Guo, Yuan Li and Guoxing Li

This study aims to establish a friction coefficient model relative to the rotation speed of a wet clutch engagement, which can predict friction coefficient under different…

Abstract

Purpose

This study aims to establish a friction coefficient model relative to the rotation speed of a wet clutch engagement, which can predict friction coefficient under different stages of slipping velocity and different load pressures. In particular, the model has been improved by accounting the speed effect for the perdition of wet friction-element boundary friction, which is significant for understanding the friction mechanisms and for supporting the development of more efficient and related products.

Design/methodology/approach

This research investigated the mechanism of wet friction in a wet clutch engagement. A mixed friction model is established based on the asperity model and Newton’s law of viscosity. To obtain a friction coefficient computed by the model, the normal load shared by both asperities and lubrication fluid needs to be determined. Therefore, rough surface contact mechanism is analysed; a surface topography model is established; and surface parameters are obtained by means of surface topography measurement and reconstruction. Finally, verification of the mixed friction model is achieved.

Findings

Friction will be generated by both the asperity contact and the lubrication film shear relative to the rotation speed. And, the higher the relative speed, the larger the shearing power of lubrication film. It is caused by decrease in contact area of asperity. Surface morphology of a sintered bronze friction disk was obtained by a Laser-Micro-Test. The predicted results by the established model show that the total friction coefficient slightly reduced and then increased suddenly with speed. The surface topography model is responsible for the nonlinear behaviour of the asperity friction. Results of the simulation model are in agreement with those of the wet clutch engagement experiments.

Originality/value

This research is original and it is supported by the national defence project. The wet friction element which is applied on tracked vehicles is analysed for the first time. Through the model, the trend of the friction coefficient can be more accurately predicted. The problem of the wet friction plate modelling difficult is solved by using the mixed friction model.

Details

Industrial Lubrication and Tribology, vol. 70 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 24 November 2021

Junru Wang, Quandai Wang, Yueyan Li, Meiling Guo, Pengyang Li and Yan Li

The purpose of this paper is to investigate the effects of surface texture with roughness orientation considered on tribological properties under a mixed lubrication state…

Abstract

Purpose

The purpose of this paper is to investigate the effects of surface texture with roughness orientation considered on tribological properties under a mixed lubrication state numerically and experimentally.

Design/methodology/approach

Based on the average Reynolds equation and asperity contact model, the impacts of surface texture parameters and roughness orientation on lubrication properties have been calculated using finite difference method. Tin–bronze samples with various prescribed surface texture geometric parameters and roughness orientation were fabricated by laser surface texturing technique, and the tribology performance of the textured surface was studied experimentally.

Findings

The effects of surface geometric parameters and roughness orientation parameters have been discerned. The experimental observations are in good agreement with the numerical prediction, which suggests that the numerical scheme adopted in this work is suitable in capturing the surface texture and roughness effect under mixed lubrication state.

Originality/value

By meticulously controlling the surface roughness and surface texture geometric characteristics based on the laser surface texturing process, samples with prescribed surface texture parameters and roughness orientation consistent with that in theoretical studies were fabricated and the theoretical model and results were verified experimentally.

Details

Industrial Lubrication and Tribology, vol. 73 no. 10
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 14 March 2016

De-Liang Liu, Shu-hua Cao, Shi-feng Zhang and Jiu-jun Xu

The purpose of this study is to solve this problem. Different lubrication states play a huge role in friction, wear and service life of parts. To ensure the reliability…

Abstract

Purpose

The purpose of this study is to solve this problem. Different lubrication states play a huge role in friction, wear and service life of parts. To ensure the reliability and power of the internal combustion engine, it is necessary to ensure that the friction pair has been in the best lubrication state. One of the key problems of lubrication state and transformation characteristics is to achieve real-time measurement of lubrication state.

Design/methodology/approach

Previous studies show that the contact resistance method is very effective in the qualitative analysis of lubrication state test. The circuit is simple and does not require expensive test equipment. But this method could not accurately reflect the film thickness ratio. Through a combination of experimental and theoretical analysis methods, the limitation of the contact resistance method could be overcome.

Findings

The relationship between the point contact film-thickness ratio and contact resistance was established, then the film-thickness ratio could be obtained through the contact resistance, thus providing the basis for determining the point contact lubrication state.

Research limitations/implications

According to existing research, the lubrication state of the friction pair mainly was determined through two methods, the friction coefficient and film-thickness ratio. But there are limitations on either using Stribeck curves or optical interference methods. The method used in this paper not only provides a verified way of design theory and model, but is also beneficial to the formation of a new design theory.

Originality/value

A new real-time measurement method of lubrication state based on contact resistance is established and its practicability and veracity are verified by series experiments.

Details

Industrial Lubrication and Tribology, vol. 68 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 27 July 2021

Jiang Zhao, Zhengminqing Li, Hong Zhang and Rupeng Zhu

The purpose of this paper is to use a combination of numerical simulation and experiment to evaluate the performance of laser surface texturing (LST) in the field of gear…

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Abstract

Purpose

The purpose of this paper is to use a combination of numerical simulation and experiment to evaluate the performance of laser surface texturing (LST) in the field of gear lubrication, and to more accurately predict the lubrication characteristics of different surfaces.

Design/methodology/approach

The method used in this paper is developed on the basis of the deterministic solution of the three-dimensional (3D) mixed elasto-hydrodynamic lubrication (EHL) model and the model parameters are corrected by friction test. The film pressure, film thickness and friction coefficient of different micro-textured tooth surfaces are predicted on the basis of accurate 3D mixed EHL models.

Findings

The results demonstrate that the micro-texture structure of the tooth surface can increase the local film thickness and enhance the lubricating performance of the tooth surface without drastically reducing the contact fatigue life. The stress distribution and friction characteristics of the tooth surface can be optimized by adjusting the micro-texture arrangement and the size of the micro-textures.

Originality/value

A new evaluation method using a 3D hybrid EHL model and friction test to predict the lubrication characteristics of LST is proposed, which can effectively improve the processing economy and save time.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2020-0423

Details

Industrial Lubrication and Tribology, vol. 73 no. 9
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 12 March 2018

Wei Pu, Jiaxu Wang, Guangwu Zhou, Ke Xiao and Junyang Li

The purpose of this study is to describe and observe the effect of surface topography associated with arbitrary directions of rolling and sliding velocities on the…

Abstract

Purpose

The purpose of this study is to describe and observe the effect of surface topography associated with arbitrary directions of rolling and sliding velocities on the performance of lubricating films in elliptical contacts.

Design/methodology/approach

The most recently published mixed elastohydrodynamic (EHL) model by Pu and Zhu is used. Three different machined rough surfaces are discussed and the correlated inclined angle of surface velocity varies from 0° to 90° in the analyzed cases. These cases are carried out in a wide range of speeds (five orders of magnitude) while the simulated lubrication condition covers full-film and mixed EHL down to the boundary lubrication.

Findings

The results indicate that the variation of the average film thickness corresponding to different entrainment angles is distinct from those without considering surface roughness. In addition, the surface topography appears to have an immense effect on the lubrication film thickness in the exceptive situation.

Originality/value

This paper has not been published previously. Surface roughness has attracted much attention for many years owing to the significant influence on lubricating property. However, previous studies mainly focus on the counterformal contact with the same direction between surface velocity and principal axis of the contact zone. Little attention has been paid to the specific condition with the arbitrary direction of rolling and sliding velocities found in hypoid gears and worm, and some other components. The purpose of this study is to describe and observe the effect of surface topography associated with arbitrary directions of rolling and sliding velocities on the performance of lubricating films in elliptical contacts based on the most recently published mixed EHL model by Pu and Zhu.

Details

Industrial Lubrication and Tribology, vol. 70 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 4 March 2020

Hua Zhang, Guangwu Zhou, Ping Zhong, Kepeng Wu and Xingwu Ding

The purpose of this paper is to study the influence of friction coefficient of materials with different elastic modulus on the variation of velocity and load under water…

Abstract

Purpose

The purpose of this paper is to study the influence of friction coefficient of materials with different elastic modulus on the variation of velocity and load under water lubrication and oil lubrication conditions.

Design/methodology/approach

Low-viscosity lubricating oil and water were used as lubricants to test the friction performance of the ball-disc contact friction pair in the lubrication state on the universal micro-tribometer multi-functional friction and wear test system.

Findings

In the same speed range, the lubrication states from soft to rigid materials are not necessarily similar to each other. Generally, the material with low elastic modulus is suitable in low-viscosity lubricant environments, while the material with high elastic modulus has relatively smaller friction coefficients in oil-lubricated environments compared with water lubrication. However, the coefficients of polyethylene, polytetrafluoroethylen and polyoxymethylene are exceeded by rubber’s coefficients under water lubrication in the same experiment environments, and their lubrication states are not affected by lubricants. The friction coefficient of the friction pair decreases with the increase of loads; however, it does not apply to all materials. The friction coefficients of materials with smaller elastic modulus such as rubber under high loads are rather large. Therefore, the elastic modulus of the material under high loads is a factor to be considered.

Originality/value

The Stribeck curves study of the ball-disk contact friction pair comprising soft and rigid materials, whose elastic modulus is from hundreds of GPa to a few of MPa, was carried out. The influence of different speeds, loads and lubricants on the friction coefficient of the friction pair was revealed, which provided a research basis for the selection and matching of friction pair materials.

Details

Industrial Lubrication and Tribology, vol. 72 no. 6
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 9 January 2017

Anastasios Zavos and Pantelis Nikolakopoulos

Compression rings are the main sources of frictional losses in internal combustion engines. The present paper aims to present a thermo-mixed hydrodynamic analysis for…

Abstract

Purpose

Compression rings are the main sources of frictional losses in internal combustion engines. The present paper aims to present a thermo-mixed hydrodynamic analysis for coated top compression rings. To understand the coating effects, the main tribological parameters are investigated into a ring-cylinder conjunction in a motorbike engine. Furthermore, flow simulations have been carried out on how different worn profiles on the cylinder inner liner affects friction, lubricant film and localized contact deformation of the coated compression rings.

Design/methodology/approach

In this paper, the basic geometrical dimensions of the top compression ring-cylinder system are obtained from a real motorbike engine. A 2D axisymmetric CFD/FLOTRAN model is created for coated compression rings. Flow simulations are performed by solving the Navier-Stokes and the energy equations. The load capacity of the asperities is also taken into account by Greenwood and Tripp contact model. Realistic boundary conditions are imposed to simulate the in-plane ring motion. The simulation model is validated with analytical and experimental data from the literature. Under thermal considerations, the contribution of worn cylinder profiles in conjunction with different coated compression rings is presented.

Findings

This research shows that because of thermal effects, the boundary friction is higher at reversals and the viscous friction is lower because of reduced oil viscosity. As regards to the isothermal case, the viscous friction is greater because of a higher lubricant viscosity. In the case of chromium-plated ring, boundary friction was 16 per cent lower than a grey cast iron ring taking into account thermal effects. Regarding the localized contact deformation, the coated compression rings showed lower values under different worn cylinder shapes. In particular, hard wear-resistant (Ni-Cr-Mo) coating showed the slighter local deformation. Therefore, the worn cylinder profiles promote boundary/mixed lubrication regime, whereas the lobed profile of cylinder inner liner becomes more wavy.

Originality/value

The solution of the thermo-mixed lubrication model, concerning the piston ring and worn cylinder tribo pair by taking into account the coating of the top compression ring.

Details

Industrial Lubrication and Tribology, vol. 69 no. 1
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 10 August 2018

Dong Guan, Harry H. Hilton, Zhengwei Yang, Li Jing and Kuan Lu

This paper aims to investigate the lubrication regime in spherical pump, especially under different structural parameters and operational conditions.

Abstract

Purpose

This paper aims to investigate the lubrication regime in spherical pump, especially under different structural parameters and operational conditions.

Design/methodology/approach

A ball-on-plane configuration is adopted to represent the contact model between spherical piston and cylinder cover. The governing equations, which include the Reynolds and elasticity equations, are solved and validated by Jin–Dowson model. Both minimum film thickness and lambda ratio (ratio of minimum fluid film thickness to combined surface roughness of the piston and cylinder cover) of the equivalent model are obtained using an established model.

Findings

The results indicate that piston diameter and radial clearance are the two main factors affecting the pump lubrication regime. Other related parameters such as rotation speed of the piston, load, viscosity of working medium, material matching and surface roughness of piston and cylinder cover also have different impacts on the lubrication regime of the spherical pump.

Originality/value

These results emphasize the importance of the design and manufacturing parameters on the tribological performance of spherical pumps and these are also helpful in improving the spherical pump lubrication regime and enlarging its life cycle. This is to certify that to the best of the authors’ knowledge, the content of this manuscript is their own work. This manuscript has only been submitted to this journal and never been published elsewhere. The authors certify that the intellectual content of this manuscript is the product of their own work and that all the assistance received in preparing this manuscript and sources has been acknowledged.

Details

Industrial Lubrication and Tribology, vol. 70 no. 8
Type: Research Article
ISSN: 0036-8792

Keywords

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