• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.114-120
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• 2000

Friction forces of piston rings for a typical SI engine were independently measured while excluding the effects of cylinder pressure, oil starvation and piston secondary motion using a floating liner system. Friction patterns, represented by the measured friction forces, were classified into five frictional modes with regard to the combination of predominant lubrication regimes(boundary, mixed and hydrodynamic lubrication) and stroke regions(mid-stroke and dead centers). The modes were identified on the Stribeck diagram of the dimensionless bearing parameter and friction coefficients which were evaluated at the mid-stroke and at the dead centers. And the frictional modes were estimated to the full operation range. The compression rings behave in the mode where hydrodynamic lubrication is dominant at the mid-stroke and mixed lubrication is dominant at the dead centers under steady operating conditions. However, the oil control ring behave in the mode where mixed lubrication is dominant throughout the entire stroke.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.106-113
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• 2000

A pump which is a fundamental device in a hydraulic system affects on overall system performance to a great deal. Such problems as leakage and solid friction loss become important in field applications, especially for the case of operation under high pressure and at high speed. So the research on this kind of subjects is necessary to improve the performance of hydraulic devices. A high pressure radial piston pump is analyzed here, which has a stationary cylinder block. It pumps hydraulic fluid by letting camring push a piston in a cylinder. Fluid leaks between the piston and cylinder so that it deteriorates the pump efficiency. Furthermore, the piston happens to touch the cylinder wall to increase the friction loss and wear. In this research, by means of FDM, volumetric, mechanical and overall efficiencies are observed by varying several design Parameters and operation conditions. Design values or their trends are presented to improve these efficiencies.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.75-78
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• 2004

Engine power cylinder parts are faced with more severe wear and friction environment. For instance, emission gas recirculation (EGR), one of the most valid technologies related to emission legislation, is known to accelerate wear of piston ring and cylinder liner. Therefore, advanced materials and surface treatments have been developed and adopted successively so that a need exists for an accurate and repeatable friction and wear bench test for various combination of piston ring and cylinder liner that more closely relates to engine test result. This paper introduces accelerative bench wear test method for piston ring and cylinder liner, presents the experimental result of friction and wear properties of piston ring surface treatments that noticed in substitution for hard chrome plating.

• Tribology and Lubricants
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• v.16 no.4
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• pp.259-265
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• 2000

Pump which is the fundamental device in the hydraulic system affects on overall system performance to a great deal. Such problems as leakage and solid friction loss become important in field applications, especially for the case of operation under high pressure and at high speed. So the research on this kind of subjects is necessary to improve the performance of hydraulic devices. A high pressure radial piston pump is analyzed here, which has a stationary cylinder block. It pumps hydraulic fluid by letting camring push a piston in a cylinder. Fluid leaks between the piston and cylinder so that it deteriorates the pump efficiency. Furthermore, the piston happens to touch the cylinder wall to increase the friction loss and wear. In this research, by means of FDA, volumetric, mechanical and overall efficiencies are observed by varying several design parameters and operation conditions. Design values or their trends are presented to improve these effciencies.

• KSTLE International Journal
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• v.1 no.2
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• pp.83-90
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• 2000

The surface roughness between a piston ring pack and a cylinder liner directly affects the fuel economy, the oil consumption, and the emission of the engine so that it is very important to clarify the surface roughness effects on the lubrication characteristics. The friction characteristics of the piston ring during engine operations are known to as mixed lubrication experimentally. In this study to simulate the effects of the surface roughness of the piston ring pack on the lubrication characteristics, the mixed lubrication analysis of piston rings was performed using the simplified average Reynolds equation. From the results the surface roughness was found be considerably affects minimum oil film thickness as well as FMEP(Friction Mean Effective Pressure). Especially, the oil ring was the most sensitive on the surface roughness.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.99-104
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• 2010

Nonlinear seal friction in pneumatic cylinders can impede the performance of pneumatic systems designed for high precision positioning with favorable high speed actuation. The behaviour of an elastomeric piston seal in high speed pneumatic cylinders is analysed by nonlinear finite element analysis using ABAQUS. The contact pressures, stress and strain distributions and frictional forces of the piston seal are simulated with variation of interference fits, supply pressures, friction coefficients and piston rod velocities. The nonlinear finite element model of the piston seal is used to predict deformation of a seal, friction force and contact pressure distributions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.207-207
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• 2000

Fuel consumption of a modern combustion engine is significantly influenced by the mechanical friction losses. The reduction of the engine friction losses offers a remarkable potential in emission and fuel consumption reduction. The analysis of the engine friction distribution of modern engines shows that the piston and the cylinder have a high share at total engine friction. The present study uses PISDYN(by Ricardo) software to analyze the friction losses. The design parameters such as skirt profile, center of mass of the piston are shown to have key influences on the friction losses.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1548-1553
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• 2003

The design of a high speed axial piston pump for hydrostatic transmission systems requires specific understanding on where and how much its internal frictional and flow losses are generated. In this study, the frictional loss of a bentaxis type hydraulic piston pump was analyzed in order to find out which design factors influence the mechanical efficiency most significantly. To this end, the friction coefficients of the sliding components were experimentally identified by a specially constructed tribometer. Applying them to the three-dimensional dynamic model of the pump presented by Doh and Hong [1], the friction torques generated by the sliding components such as piston head , bearing and valve plate were theoretically computed. The accuracy of the computed results was confirmed by the comparison with the experimentally measured mechanical efficiency. In this paper, it is shown that the viscous friction on the valve plate and the drive shaft bearing is the primary sources of the frictional losses of the bent-axis type pump, while the friction forces on the piston contribute to them only slightly.

• Transactions of Materials Processing
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• v.18 no.6
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• pp.465-470
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• 2009

The frictional behaviors of Cermets/Cr-Ceramics and Cu-Al coatings of piston ring were investigated. Friction tests were carried out by pin-on-disk test and materials properties of coating layer were analyzed by nano indentation tester. The effect of surface roughness of cylinder liner on the friction coefficient was analyzed. This study provided tribological data of hard and soft piston ring coatings against cylinder liner. The surface roughness does exert an influence on the average friction coefficient, with smoother surfaces generally yielding lower friction coefficients. In case of hard-coating, the scratch depth, width and pile-up height had close relationship with hardness. So the scratch width, depth and pile-up height increases with decreasing friction coefficient. But in case of soft-coating, the friction coefficients are strongly dependent on the morphological characteristics such as, scratch depth, width, pile-up height and elastic modulus.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.36-43
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• 2008

This research is tendencious to manufacture solid piston-rod of shock absorber as hollow piston-rod using friction welding. The SM45C has been welded to the SM45C-pipe in order to investigate the effect of upset pressure on friction weldability. The friction time and upset pressure was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied of friction weld, and so the results were as follows. When the upset pressure is sufficient, gets the high tensile strength. The optimal welding conditions were n=2,000rpm, $P_1$=55MPa, $P_2$=95MPa, $t_1$=1.5sec, $t_2$=2.0sec when the total upset length is 4.5mm.