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Article
Publication date: 2 July 2018

Xianghui Meng, Changya Yu, Youbai Xie and Benfu Mei

This paper aims to investigate the lubrication performance of cam/tappet contact during start up. Especially, the thermal insulation effects of coating on the lubrication…

Abstract

Purpose

This paper aims to investigate the lubrication performance of cam/tappet contact during start up. Especially, the thermal insulation effects of coating on the lubrication performance during cold start up process and warm start up process are studied.

Design/methodology/approach

A numerical model for the analysis of thermal elastohydrodynamic lubrication of coated cam/tappet contact is presented. In this model, the Reynolds equation and the energy equations are discretized by the finite difference method and solved jointly.

Findings

During start up, the contact force at cam nose-to-tappet contact decreases with increasing time, while the absolute entrainment velocity has the upward trend. The minimum film thickness, maximum average temperature and friction power loss increase with increasing time, while the coefficient of friction decreases during start up. Because of the thermal insulation effect, the coating can significantly increase the degree of temperature rise. Compared with the uncoated case, the coated cam/tappet results in a lower friction power loss. Generally, the friction power loss in the cold start up process is much higher than that in the warm start up process.

Originality/value

By this study, the lubrication performance and the kinematics and the dynamics of the cam/tappet during start up process are investigated. Meanwhile, the thermal insulation effect of coating is also illustrated. The difference of lubrication performance between cold start up process and warm start up process is analyzed. The results and thermal elastohydrodynamic lubrication method presented in this study can be a guidance in the design of the coated cam/tappet.

Details

Industrial Lubrication and Tribology, vol. 70 no. 6
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 13 March 2017

Yang Hu, Xianghui Meng, Youbai Xie and Jiazheng Fan

During running-in, the change in the honed cylinder liner surface alters the performance and efficiency of the piston ring-pack system. The present paper, thus, aims to…

Abstract

Purpose

During running-in, the change in the honed cylinder liner surface alters the performance and efficiency of the piston ring-pack system. The present paper, thus, aims to investigate the surface topography and wear and friction evolution of a cylinder liner surface during the running-in tests on a reciprocating ring–liner tribometer under a mixed lubrication regime. After an initial period of rapid wear termed “running-in wear”, a relatively long-term steady-state surface topography can emerge. A numerical model is developed to predict the frictional performance of a piston ring-pack system at the initial and steady-state stages.

Design/methodology/approach

The liner surfaces are produced by slide honing (SH) and plateau honing (PH). The bearing area parameter (Rk family), commonly used in the automotive industry, is used to quantitatively characterize the surface topography change during the running-in process. A wear volume-sensitive surface roughness parameter, Rktot, is used to show the wear evolution.

Findings

The experimental results show that a slide-honed surface leads to reduced wear, and it reduces the costly running-in period compared to the plateau-honed surface. The simulation results show that running-in is a beneficial wear process that leads to a reduced friction mean effective pressure at the steady-state.

Originality/value

To simulate the mixed lubrication performance of a ring–liner system with non-Gaussian roughness, a one-dimensional homogenized mixed lubrication model was established. The real surface topography instead of its statistical properties is taken into account.

Details

Industrial Lubrication and Tribology, vol. 69 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 13 March 2017

Jun Liu, Zhinan Zhang, Zhe Ji and Youbai Xie

This paper aims to investigate the effects of reciprocating frequency, large normal load on friction and wear behavior of hydrogenated diamond-like carbon (H-DLC) coating…

Abstract

Purpose

This paper aims to investigate the effects of reciprocating frequency, large normal load on friction and wear behavior of hydrogenated diamond-like carbon (H-DLC) coating against Ti-6Al-4V ball under dry and lubricated conditions.

Design/methodology/approach

The friction and wear mechanisms are analyzed by scanning electron microscope, energy dispersive spectroscopy and Raman spectroscopy.

Findings

The results show that as reciprocating frequency increases under lubricated conditions, the friction coefficient decreases first and then increases. When the reciprocating frequency is 2.54 Hz, the value of friction coefficient reaches the minimum. The friction reduction is because of the transformation from sp3 to sp2, the formation of transfer layer on Ti-6Al-4V ball and the reduction in viscous friction, whereas the increase of friction coefficient is related to wear. In dry conditions, the friction coefficient is between 0.06 and 0.1. And, the service life of H-DLC coating decreases with the increase in reciprocating frequency and normal load.

Research limitations/implications

It is confirmed that adding the lubricant could prolong the service life of H-DLC coating and reduce friction and wear efficiently. And, the wear mechanisms under dry and lubricated conditions encompass abrasive wear and adhesive wear.

Originality/value

The results are helpful for application of diamond-like carbon coating.

Details

Industrial Lubrication and Tribology, vol. 69 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 10 August 2015

Jun Cheng, Xianghui Meng, Youbai Xie and Wenxiang Li

The purpose of this paper is to study the real-time change of surface roughness at different small regions of piston rings during running-in process. Meanwhile, the…

Abstract

Purpose

The purpose of this paper is to study the real-time change of surface roughness at different small regions of piston rings during running-in process. Meanwhile, the effects of real-time change of the rough surface topography on the lubrication and friction of piston rings are investigated.

Design/methodology/approach

An uneven wear model has been developed to research the running-in behavior at the different small regions of piston rings. The model is verified by comparing the simulation results with the experimental results on a reciprocating friction and wear test rig.

Findings

This research shows that the wear process of piston ring surface is uneven during running-in. At most time of the operating cycle except the vicinity of top dead center and bottom dead center, the minimum oil film thickness ratio increases while the friction force and power loss decrease after the running-in period.

Originality/value

Through this research, the running-in behavior of piston rings is investigated in detail. The interaction between the running-in and the lubrication and friction of piston rings is understood more deeply.

Details

Industrial Lubrication and Tribology, vol. 67 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

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Article
Publication date: 14 March 2016

Ridha Mazouzi, Ahmed Kellaci and Abdelkader Karas

– This paper aims to study the effect of piston skirt design parameters on the dynamic characteristics of a piston–cylinder contact.

Abstract

Purpose

This paper aims to study the effect of piston skirt design parameters on the dynamic characteristics of a piston–cylinder contact.

Design/methodology/pproach

This paper focuses on an analysis of the piston dynamic response. The oil-film pressure and the structural deformation were approximated, respectively, by finite difference method and finite element method.

Findings

The results show that the design parameters such as clearance, offset and the axial location of piston pin have a great influence on the dynamics of the piston and hence on the piston slap phenomenon and the frictional power loss.

Originality/value

All the results mainly focus on the slap noise of the engine and can be used in the piston–liner development at the development of the engine.

Details

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

Keywords

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