Search results

1 – 10 of 359
Article
Publication date: 22 June 2010

Li‐Ming Chu

The purpose of this paper is to explore the pure squeeze thin film elastohydrodynamic lubrication (TFEHL) motion of circular contacts with adsorption layers attached to…

Abstract

Purpose

The purpose of this paper is to explore the pure squeeze thin film elastohydrodynamic lubrication (TFEHL) motion of circular contacts with adsorption layers attached to each surface under constant load condition. The proposed model can reasonably calculate the pressure distributions, film thicknesses, normal squeeze velocities, and effective viscosities during the pure squeeze process under thin film lubrication.

Design/methodology/approach

The transient modified Reynolds equation is derived in polar coordinates using viscous adsorption theory. The finite difference method and the Gauss‐Seidel iteration method are used to solve the transient modified Reynolds equation, the elasticity deformation equation, load balance equation, and lubricant rheology equations simultaneously.

Findings

The simulation results reveal that the thickness of the adsorption layer and the viscosity ratio significantly influence the lubrication characteristics of the contact conjunction in the thin film regime. In additional, the turning points in the film thickness which distinguish thin film lubrication from elastohydrodynamic lubrication curve is found. In thin film region, the effective viscosity predicted by present model is better than that predicted by traditional elastohydrodynamic theory.

Originality/value

The paper develops a numerical method for general applications with adsorption layers attached to each surface to investigate the pure squeeze action in a TFEHL spherical conjunction under constant load condition.

Details

Industrial Lubrication and Tribology, vol. 62 no. 4
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 10 June 2021

Hongyu Duan, Qingtao Yu and Zhijian Wang

The purpose of this paper is to study the film-forming capacity of logarithmic crowned roller for tapered roller bearing (TRB) and to design a tapered roller profile based…

Abstract

Purpose

The purpose of this paper is to study the film-forming capacity of logarithmic crowned roller for tapered roller bearing (TRB) and to design a tapered roller profile based on an elastohydrodynamic lubrication model.

Design/methodology/approach

A coupled model, incorporating a quasi-static model of TRBs and an elastohydrodynamic lubrication model was developed to investigate the load distribution of TRB and to evaluate the lubrication state of tapered roller/raceway contact.

Findings

The model is verified with published literature results. Parametric analysis is conducted to investigate the effect of crown drop on azimuthal load distribution of the roller, film thickness and pressure distribution in the contact area. The result shows that crown drop has little influence on the azimuthal load distribution; also, the film thickness and the pressure distribution are asymmetric. When the tapered roller is designed and manufactured, the crown drop of the small end should be larger than that in the large end.

Originality/value

Precise roller profile design is conducive to improve the fatigue life of TRBs. Currently, most crown design methods neglect the influence of lubrication, which can lead to a non-suitable roller profile. Therefore, the present work is undertaken to optimize roller profiles based on lubrication theory.

Details

Industrial Lubrication and Tribology, vol. 73 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 April 2004

Y. Zhang

This paper studies elastohydrodynamic lubrication (EHL) of line contacts for the slide‐roll ratios 0‐2 based on the assumptions of interfacial shear strength and…

Abstract

This paper studies elastohydrodynamic lubrication (EHL) of line contacts for the slide‐roll ratios 0‐2 based on the assumptions of interfacial shear strength and interfacial slip. It is shown that the viscoelastic, viscoplastic and non‐continuum fluids distribute from the inlet zone to the Hertzian contact zone in order for a given operating condition when the load and rolling speed exceed critical values. For the rolling speed below the critical, the distributing fluids from the inlet zone to the Hertzian contact zone in order are viscoelastic and non‐continuum when the load exceeds a critical value. These show a multirheological behavior EHL film, formed in a contact, which may represent a mode of mixed lubrication. For this mode of lubrication, the fluid model should handle both inlet and Hertzian contact zones where the fluids are, respectively, continuum and non‐continuum. A new EHL analysis and theory, therefore needs to be established.

Details

Industrial Lubrication and Tribology, vol. 56 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 8 January 2018

Ye Zhou, Degong Chang and Songmei Li

This paper aims to improve the grease thermal elastohydrodynamic lubrication (TEHL) properties of the tripod sliding universal coupling (TSUC) under automotive practical…

Abstract

Purpose

This paper aims to improve the grease thermal elastohydrodynamic lubrication (TEHL) properties of the tripod sliding universal coupling (TSUC) under automotive practical conditions. For this purpose, the effect of effective radius was theoretically investigated.

Design/methodology/approach

Based on the simplified geometric model, the effect of effective radius on the pressure distribution, film thickness and temperature distribution of the TSUC was theoretically investigated using the multigrid and stepping methods. The TEHL properties were compared with the results obtained using the isothermal calculation method.

Findings

The results show that the thermal effect has a great impact on the film thickness and the pressure distribution of grease lubrication properties. Moreover, larger effective radius results in a wider but lower pressure distribution, a wider and thicker lubricating film and a lower temperature distribution.

Originality/value

The TSUC can be widely used in the front drive automotive transmission because it can transmit larger torque than before. The effect of effective radius on the thermal grease lubrication properties under automotive practical conditions provides a new direction for designing it.

Details

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

Keywords

Article
Publication date: 21 June 2019

Ömer Özdemir, Felix Fischer, Adrian Rienäcker and Katharina Schmitz

The purpose of this paper is to show these effects in an abstracted micro gap test bench. Because of stronger emission laws, the ambition to raise the rail pressure in…

Abstract

Purpose

The purpose of this paper is to show these effects in an abstracted micro gap test bench. Because of stronger emission laws, the ambition to raise the rail pressure in common-rail systems from the current 2500 bar to 3000 bar is a given. The pressure increase will allow fine atomization of fuel and therefore more efficient combustion. But within the technical system of the high-pressure pump, stronger thermal stresses of the piston–cylinder contact are expected. A pressure drop from such a high level causes high temperature gradients due to energy dissipation.

Design/methodology/approach

For a detailed examination, the critical piston–cylinder contact has been investigated in an abstracted test bench with a flat parallel gap and an equivalent thermo-elastohydrodynamic simulation model.

Findings

The simulation results show good accordance to the measurements of pressures, temperatures and leakages for pressures up to 3000 bar. Comparison with elastohydrodynamic lubrication results outlines the need to consider temperature and pressure effects viscosity and solid deformation for the simulation and design of tribological contacts at high pressures.

Originality/value

This paper describes a simulation method with high accuracy to investigate tribological contacts considering temperature effects on solid structures and the fluid film. The thermo-elastohydrodynamic lubrication simulation method is valid not only for piston–cylinder contacts in high-pressure pumps but also for journal bearings in combustion engines.

Details

Industrial Lubrication and Tribology, vol. 71 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 12 March 2018

Li-Ming Chu, Jaw-Ren Lin and Cai-Wan Chang-Jian

The modified Reynolds equation for non-Newtonian lubricant is derived using the viscous adsorption theory for thin-film elastohydrodynamic lubrication (TFEHL) of circular…

Abstract

Purpose

The modified Reynolds equation for non-Newtonian lubricant is derived using the viscous adsorption theory for thin-film elastohydrodynamic lubrication (TFEHL) of circular contacts. The proposed model can reasonably calculate the phenomenon in the thin-film lubrication (TFL) unexplained by the conventional EHL model. The differences between classical EHL and TFEHL with the non-Newtonian lubricants are discussed.

Design/methodology/approach

The power-law lubricating film between the elastic surfaces is modeled in the form of three layers: two adsorption layers on each surface and one middle layer. The modified Reynolds equation with power-law fluid is derived for TFEHL of circular contacts using the viscous adsorption theory. The finite difference method and the Gauss–Seidel iteration method are used to solve the modified Reynolds equation, elasticity deformation, lubricant rheology equations and load balance equations simultaneously.

Findings

The simulation results reveal that the present model can reasonably calculate the pressure distribution, the film thickness, the velocity distribution and the average viscosity in TFL with non-Newtonian lubricants. The thickness and viscosity of the adsorption layer and the flow index significantly influence the lubrication characteristics of the contact conjunction.

Originality/value

The present model can reasonably predict the average viscosity, the turning point and the derivation (log film thickness vs log speed) phenomena in the TFEHL under constant load conditions.

Details

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

Keywords

Article
Publication date: 6 September 2021

Lu Chen, Chenchen Xu, Mingfei Ma, Wen Wang, Liang Guo and Patrick Wong

The cleaning of food production equipment using cleaning detergents may contaminate the lubricant of the bearings, thereby reducing the bearing service life. The purpose…

Abstract

Purpose

The cleaning of food production equipment using cleaning detergents may contaminate the lubricant of the bearings, thereby reducing the bearing service life. The purpose of this paper is to investigate the cause and mechanism of such damage of bearings lubricated by cleaning detergent/water-in-oil emulsions.

Design/methodology/approach

The emulsion was prepared by adding a mixture of cleaning detergent and water in one base oil. A self-designed ball-on-disc optical interference test rig was applied to examine the effect of emulsion on lubrication and wear of bearing contacts under pure sliding conditions.

Findings

The emulsion reduced lubricating film thickness at a relatively low-sliding speed but only when the water concentration (20%) in emulsion was high. Water droplets were trapped around the ball-on-disc contact area under static conditions because of a high capillary force. The emulsion can induce damages on the soft surface in the startup mainly due to the presence of water around the contact.

Originality/value

The basic lubrication behaviour of water/oil emulsions containing cleaning detergent under pure sliding was experimental studied and the mechanism of bearing damage in food production equipment was investigated. Based on the study, the solution to avoid such damage was proposed.

Details

Industrial Lubrication and Tribology, vol. 73 no. 7
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 12 September 2016

Li Ming Chu, Jaw-Ren Lin, Yuh-Ping Chang and Chung-Chun Wu

This paper aims to explore pure squeeze elastohydrodynamic lubrication (EHL) motion of circular contacts with micropolar lubricants under constant load. The proposed model…

Abstract

Purpose

This paper aims to explore pure squeeze elastohydrodynamic lubrication (EHL) motion of circular contacts with micropolar lubricants under constant load. The proposed model can reasonably calculate the pressure distributions, film thicknesses and normal squeeze velocities during the pure squeeze process.

Design/methodology/approach

The transient modified Reynolds equation is derived in polar coordinates using micropolar fluids theory. The finite difference method and the Gauss–Seidel iteration method are used to solve the transient modified Reynolds equation, the elasticity deformation equation, load balance equation and lubricant rheology equations simultaneously.

Findings

The simulation results reveal that the effect of the micropolar lubricant is equivalent to enhancing the lubricant viscosity. As the film thickness is enlarged, the central pressure and film thickness for micropolar lubricants are larger than those of Newtonian fluids under the same load in the elastic deformation stage. The greater the coupling parameter (N), the greater the maximum central pressure. However, the smaller the characteristic length (L), the greater the maximum central pressure. The time needed to achieve maximum central pressure increases with increasing N and L.

Originality/value

A numerical method for general applications was developed to investigate the effects of the micropolar lubricants at pure squeeze EHL motion of circular contacts under constant load.

Details

Industrial Lubrication and Tribology, vol. 68 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

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

Keywords

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

Keywords

1 – 10 of 359