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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korean Society of Tribologists and Lubrication Engineers
Journal Basic Information
Journal DOI :
The Korean Society of Tribologists and Lubrication Engineers
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Volume & Issues
Volume 21, Issue 6 - Dec 2005
Volume 21, Issue 5 - Oct 2005
Volume 21, Issue 4 - Aug 2005
Volume 21, Issue 3 - Jun 2005
Volume 21, Issue 2 - Apr 2005
Volume 21, Issue 1 - Feb 2005
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Micro/Nano Adhesion and Friction Properties of SAMs with Different Head and Functional Group according to the Coating Methods
Yoon Eui-Sung ; Oh Hyun-Jin ; Han Hung-Gu ; Kong Hosung ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 21, issue 3, 2005, Pages 107~113
Micro/nano adhesion and friction properties of self-assembled monolayers (SAMs) with different head- and end-group were experimentally studied according to the coating methods. Various kinds of SAM having different spacer chains (C10 and C18), head-group and end-group were deposited onto Si-wafer by dipping and chemical vapour deposition (CVD) methods under atmospheric pressure, where the deposited SAM resulted in the hydrophobic nature. The adhesion and friction properties between tip and SAM surfaces under nano scale applied load were measured using an atomic force microscope (AFM) and also those under micro scale applied load were measured using a ball-on-flat type micro-tribotester. Surface roughness and water contact angles were measured with SPM (scanning probe microscope) and contact anglemeter respectively. Results showed that water contact angles of SAMs with the end-group of fluorine show higher relatively than those of hydrogen. SAMs with the end-group of fluorine show lower nano-adhesion but higher micro/nanofriction than those with hydrogen. Water contact angles of SAMs coated by CVD method show high values compared to those by dipping method. SAMs coated by CVD method show the increase of nano-adhesion but the decrease of nano-friction. Nano-adhesion and friction mechanism of SAMs with different end-group was proposed in a view of size of fluorocarbon molecule.
Study on the Air Foil Bearings of the Turbo-Expander for Fuel Cell System
Lee Yong-Bok ; Park Dong-Jin ; Kim Chang-Ho ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 21, issue 3, 2005, Pages 114~121
As fuel cell system is environmental friendly generator, its performance depends on its air supply system. Because, fuel cell stack generates electrical energy by electron and the electron is generated by reacting between air and hydrogen. So, more and more compressed air is supplied, more and more the energy can be obtained. In this study, turbo-expander supported by air foil bearing is introduced as the air supply system used by fuel cell systems. The turbo-expander is a turbo machine which operates at high speed, so air foil bearings suit its purpose for the bearing elements. Analysis for confirming the stability and endurance is conducted. Based on FDM and Newton-Raphson method, characteristics of air foil bearing, dynamic coefficients, pressure field and load capacity, are obtained. Using the characteristics of air foil bearing, the rotordynamic analysis is performed by finite element method. The analysis (stability analysis and critical speed map) shows that turbo-expander is stability at running speed. After the analysis, the test process and results are presented. The goals of test are running up to 90,000 RPM, flow rate of 150
and pressure ratio of 1.15. The test results show that the aerodynamic performance and stability of turbo-expander are satisfied to the primary goals.
Analysis of Response of Floating Ring for High Pressure Floating Ring Seal in Turbo Pump
Ha, Tae-Woong ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 21, issue 3, 2005, Pages 122~129
The floating ring seal has the ability of minimizing clearance without rubbing phenomenon. However, the seal ring can be unstable due to extremely high lock-up eccentricity ratio arisen from the poor design of height and surface finish of the ring. The exact prediction of the lock-up position of the floating ring is necessary to design the floating ring properly. The governing equations are developed and solved numerically. The test facility for the measurement of the boundary-lubrication-friction coefficient of the ring‘s surface has been established. Based on the results of analysis, the geometric conditions of the floating ring seal are suggested for operating at a low lock-up eccentricity ratio.
The Effects of Surface Roughness on Wear-life of DLC Coating in Dry Sliding
Lee Young-Ze ; Shin Kyung-Seob ; Cho Chung-Woo ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 21, issue 3, 2005, Pages 130~135
Dry sliding wear resistance of DLC coated silicon disk with different surface roughness has been evaluated using a ball-on-disk sliding tester. It was found that the transfer layer formed on steel ball produced a low friction regime and the formation of transfer layer was more active with increasing the substrate surface roughness. Wear life of DLC coating was increased as increasing the real area of contact.
The Contact Fatigue Life Analysis of Rough Surfaces
Chu Hyo-Jun ; Lee San-Don ; Cho Yong-Joo ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 21, issue 3, 2005, Pages 136~141
Analytical model to calculate the contact fatigue life of rough surface is presented in this paper. The effect of surface roughness can be calculated by this model. Computational method and the theoretical basis are also discussed. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions; the subsurface stress field is obtained using rectangular patch solutions. Mesoscopic multiaxial fatigue criterion which can yield satisfactory results for non-proportional loading is then applied to predict fatigue damage. Suitable counting method and damage rule were used to calculate the fatigue life of random loading caused by rough surface. As a result of analysis the relationship between the life and the roughness as well as the most probable depth of the crack initiation is calculated.
A Study for Effects of Automatic Transmission Fluid on Fuel Economy
Cha, Sang-Yeob ; Yang, Si-Won ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 21, issue 3, 2005, Pages 142~148
In order to improve the fuel economy by design change of automatic transmission, various technologies such as increased shift stages, slip control of lock-up clutch and compact and low-weight design have been developed. And also many OEMs have developed their own ATFs as a part of these automatic transmissions. In this study, to investigate the effects of ATF characteristics on fuel economy, we got the worldwide OEM ATFs and made some reference fluids. And physical properties, frictional characteristics and fuel economy using dynamometer test for these fluids were evaluated. From the investigation, it was found that viscosities of ATFs are correlated with fuel economy in dynamometer test and reducing the viscosities made it possible to obtain fuel economy.