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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 29, Issue 6 - Dec 2013
Volume 29, Issue 5 - Oct 2013
Volume 29, Issue 4 - Aug 2013
Volume 29, Issue 3 - Jun 2013
Volume 29, Issue 2 - Apr 2013
Volume 29, Issue 1 - Feb 2013
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Fabrication of Tungsten Probe Tips for AFM using Electrochemical Etching
Han, Gue-Bum ; Jang, Hyuna ; Ahn, Hyo-Sok ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 4, 2013, Pages 213~217
DOI : 10.9725/kstle-2013.29.4.213
As commercial atomic force microscopy (AFM) probes made of Si and
have low stiffness, it is difficult to induce sufficient elastic deformation on the surface of a specimen in a tapping mode. Therefore, high-guality phase contrast images can not obtained. On the other hand, a tungsten AFM probe has relatively higher stiffness than a commercial AFM probe. Accordingly, it is expected to provide an enhanced phase contrast image, which is an effective tool for achieving a better understanding of the micromechanical properties of worn surfaces and wear mechanisms. In this study, on electrochemical etching method was optimized to fabricate tungsten probe tips for an AFM. Electrochemical etching was performed by applying pulse waves with a 20% duty cycle at various voltages instead of only a DC voltage, which has been commonly used.
CFD-Based Flow Analysis of Rolling Elements in Water-Lubricated Ball Bearings
Jo, Jun Hyeon ; Kim, Choong Hyun ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 4, 2013, Pages 218~222
DOI : 10.9725/kstle-2013.29.4.218
Water-lubricated ball bearings consist of rolling elements, an inner raceway, an outer raceway, a retainer, and an operating lubricant. In the water environment, ball bearings are required to sustain high loads at high speeds under poorly lubricated conditions. For the analysis of bearing behavior, friction torque is considered as the main factor at various flow rates, rotating speeds, and roughnesses between the rolling element and raceways. When the bearing operates at high rotating speeds, the friction torque between the raceway and rolling elements increases considerably. This frictional torque is an important factor affecting bearing reliability and life cycle duration. For understanding the flow conditions in the inner part of the bearing, this study focuses on the flow around the rotating and revolving rolling elements. A simple model of fluid flow inside the ball bearing is designed using the commercial CFD program ANSYS.
Research on Friction Characteristics of Constant Velocity Joint Grease
Lee, Sung Uk ; Bae, Dae Yoon ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 4, 2013, Pages 223~227
DOI : 10.9725/kstle-2013.29.4.223
A GAF (generated axial force) is produced at a plunging-type CVJ (constant velocity joint). A high GAF can cause vibrations in a vehicle. Grease is used to reduce friction between the roller and the track of the outer case of a CVJ. The grease performance depends on the surface conditions and operating temperature. The surface of the outer case is extremely rough and hard. In recent times, the maximum operating temperature of CVJs has crossed
, because the exhaust line is now located close to the CVJ. In this study, we examined the friction characteristics of friction additives at
and determined an optimal formulation with a low friction coefficient. This formulation can be used to develop low-friction grease that can reduce the GAF produced at a CVJ by approximately 7-26%.
EHL Analysis of Ball Bearing Considering Surface Roughness
Lee, Hyang ; Cho, Yongjoo ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 4, 2013, Pages 228~234
DOI : 10.9725/kstle-2013.29.4.228
This paper presents analysis of elastohydrodynamic lubrication (EHL) of ball bearings, in which surface roughness is considered. A lot of time is required to obtain a solution in the case of EHL analysis where surface roughness is considered, because the analysis requires a variety of analytic nodes. To save time, we use the full approximation scheme (FAS) among multilevel methods. We analyze the results of EHL and contact analyses in terms of pressure. We also compare the results for smooth and rough surfaces with respect to film thickness. We confirm that the film pressure decreases as compared to contact pressure because of the presence of lubricants between the ball and the raceway. Furthermore, in the case when surface roughness is considered, the film pressure increases because of contact asperities. Therefore, surface roughness should be considered when designing ball bearings.
Tribological Characteristics of Dental Metal Alloys
Kim, J.H. ; Choi, W.S. ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 4, 2013, Pages 235~241
DOI : 10.9725/kstle-2013.29.4.235
The tribological characteristics of dental metal alloys and zirconia were studied by carrying out a friction and wear performance test. In this study, a pin-on-disk-type tester was used and dead weight was employed as the normal load applied to the test specimen. The friction coefficient of dental metal alloys was investigated in terms of their weight and sliding velocity. Microscopic observations were carried out on worn surfaces of specimens. The results indicated that among all metal alloys, Super-A had the highest friction coefficient. Super-A had the lowest amount of wear among all metal alloys, and the amount of wear increased in the following order: Crown & Bridge, Porcelain, and Partial. Crown & Bridge had the best friction coefficient, but the hardness of Crown & Bridge was lower than that of Porcelain and Partial. Experimental measurement results indicated that the disk weight before and after the experiment was the same.
Study on Dependence of Friction Characteristics of Sintered Brake Friction Materials on Graphite Shape and Ratio with regard to Speeding up Rapid Transit System
Kim, Young Kyu ; Lee, Hi Sung ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 4, 2013, Pages 242~247
DOI : 10.9725/kstle-2013.29.4.242
This study aims to establish the fundamental basis for the design of materials used in high-speed trains, by using a lab-scale dynamometer to evaluate the characteristic behavior of metallic sintered friction materials in relation to the shape of graphite. The test results clearly demonstrate that when flake graphite and granular graphite are added equivalently, the average coefficient of friction is much lower, and it is less influenced by speed variation; moreover, friction wear is observed to be insignificantly low. Adding flake graphite increases the coefficient of friction, which leads to higher friction wear. In addition, the roughness of the disc surface was equivalent regardless of the shape of the graphite.
Dynamic Analysis of Effect of Number of Balls on Rotor-Bearing System
Hwang, Pyung ; Nguyen, Van Trang ;
Journal of the Korean Society of Tribologists and Lubrication Engineers, volume 29, issue 4, 2013, Pages 248~254
DOI : 10.9725/kstle-2013.29.4.248
This paper presents a numerical model for investigating the structural dynamic response of an unbalanced rotor system supported on deep groove ball bearings. The aim of this work is to develop a numerical model for investigating the effect of the number of balls on the dynamic characteristics of the rotor ball bearing system. The fourth-order Runge-Kutta numerical integration technique has been applied. The results are presented in the form of time displacement responses and frequency spectra. The analysis demonstrates that the model can be used as a tool for predicting the nonlinear dynamic behavior of the rotor ball bearing system under different operating conditions. Moreover, the study may contribute to a further understanding of the nonlinear dynamics of rotor bearing systems.