• Title/Summary/Keyword: Tribology

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An Experimental Study on the Wear and Vibrational Characteristics Resulted from Rotordynamics System Failure(I) (회전기계 파손에 따른 마멸 및 진동 특성(I))

  • Kang, Ki-Hong;Yoon, Eui-Sung;Chang, Rae-Hyuk;Kong, Ho-Sung;Kim, Seong-Jong;Lee, Yong-Bok;Kim, Chang-Ho
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2001.11a
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    • pp.43-52
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    • 2001
  • Condition monitoring plays a vital role since it sustains the reliable operation of industrial plant and machinery in the pursuit of economic whole life operation. In order to achieve this goal, it is needed to monitor various parameters of mechanical system such as vibration, wear, temperature, and etc., and finally to diagnosis the root causes of any possible abnormal machine condition. In this work, we constructed a rotor system where various types of functional machine failures occurred frequently in industry were induced. Characteristics of the machine failure were monitored simultaneously by the on-line measurement of vibration, wear and temperature. Result showed that these parameters responded differently to the induced functional machine failure. The availability of each parameter on effective condition monitoring was discussed in this work.

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A New Method for Lateral Force Calibration in Atomic Force Microscope (원자현미경(AFM)에서 마찰력 측정을 위한 새로운 보정 기술 연구)

  • Yoon Eui-Sung;Kim Hong Joon;Wang Fei;Kong Hosung
    • Tribology and Lubricants
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    • v.21 no.5
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    • pp.221-226
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    • 2005
  • A new calibration method for exact measurement of friction force in atomic force microscope (AFM) is presented. A new conversion factor involves a contact factor affected by tip, cantilever and contact stiffness. Especially the effect of contact stiffness on the conversion factor between lateral force and lateral signal is considered. Conventional conversion factor and a new modified conversion factor were experimentally compared. Results showed that a new calibration method could minimize the effect of normal load on friction force and improve the conventional method. A new method could be applied to the specimens with different physical properties.

RECENT AND CURRENT TRENDS IN BASIC TRIBOLOGY RESEARCH

  • LARSEN-BASSE, J
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.11-12
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    • 2002
  • Tribology research is constantly changing focus as new drivers for the research emerge. They include new industrial needs and barriers to performance, new possibilities brought about by new observation and modeling tools, and new people with different backgrounds. We outline the changes in basic academic tribology research over the past 15-20 years, as it is reflected in the research portfolio of the US National Science Foundation. While independent tribology programs may be a thing of the past there is a clear tendency for tribology research to continue as part of other activites, such as nano- and biotechnology and computational materials research.

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Nanotribological Properties of Hydrophobic Surfaces Using an Atomic Force Microscope

  • Yoon, Eui-Sung;Yang, Seung-Ho;Oh, Hyun-Jin;Han, Hung-Gu;Kong, Ho-Sung;Lee, Hae-Seong
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.55-56
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    • 2002
  • Nanotribological characteristics of hydrophobic surfaces were studied experimentally using an atomic force microscope (AFM). Two kinds of thiolic self-assembled monolayers (SAM) having different spacer chains and their mixture were deposited onto gold-coated mica, where the deposited SAM resulted in the hydrophobic nature. Results showed that the mixed thiolic SAMs resulted in low adhesion and friction in nano-scale contact. It was argued that the water wetting characteristics played a central role on nano-scale adhesion and friction. Also the effect of mixing the thiolic SAMs were discussed on the basis of real area on contact and the stiffness of the SAM layers.

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Experimental study of Braking characteristics of Disk brake (디스크 브레이크의 제동특성에 관한 실험적 연구)

  • Han Joohyun;Cho Seunghyun;Kim Hangoo;Lee Boungkwan;Kim Chungkyun;Lee Ilkwon
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2004.11a
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    • pp.241-244
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    • 2004
  • In this paper wear ratio, hardness and microstructure were experimented for study of friction wear characteristic of automotive disk brake considering running distance. In this work.4 specimens were employed for test of the friction&wear tester as a function running distance. Despite the fact that brakes must operate under a variety of environmental conditions. most research has worked in laboratory with ideal condition.

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A Comparison of Friction Force Calibration in Lateral Force Microscope

  • Wang Yuli-Ang;Kim Hong-Joon;Kong Ho-Sung;Zhao Xu-Zheng;Yoon Eui-Sung
    • KSTLE International Journal
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    • v.7 no.1
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    • pp.5-9
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    • 2006
  • The main principle of two widely used methods which were proposed by Ruan and Bhushan, and by Ogletree and Carpick are introduced. Experiments were conducted using the two methods to measure friction force between AFM probe and silicon sample quantitatively. To characterize the frictional properties, the conversion factors of the two methods by which lateral electronic signal is converted into actual friction force were calculated. The experimental results show that that the conversion factors were extraordinarily different from each other. Further research should be done to identity the reasons for these differences.

Wear Debris Analysis using the Color Pattern Recognition

  • Chang, Rae-Hyuk;Grigoriev, A.Y.;Yoon, Eui-Sung;Kong, Hosung;Kang, Ki-Hong
    • KSTLE International Journal
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    • v.1 no.1
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    • pp.34-42
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    • 2000
  • A method and results of classification of four different metallic wear debris were presented by using their color features. The color image of wear debris was used far the initial data, and the color properties of the debris were specified by HSI color model. Particles were characterized by a set of statistical features derived from the distribution of HSI color model components. The initial feature set was optimized by a principal component analysis, and multidimensional scaling procedure was used fer the definition of a classification plane. It was found that five features, which include mean values of H and S, median S, skewness of distribution of S and I, allow to distinguish copper based alloys, red and dark iron oxides and steel particles. In this work, a method of probabilistic decision-making of class label assignment was proposed, which was based on the analysis of debris-coordinates distribution in the classification plane. The obtained results demonstrated a good availability for the automated wear particle analysis.

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Micro/Nano Adhesion and Friction Properties of Mixed Self-assembled Monolayer (혼합 자기 조립 단분자막의 마이크로/나노 응착 및 마찰 특성)

  • Yoon Eui-Sung;Oh Hyun-Jin;Han Hung-Gu;Kong Hosung;Jhang Kyung Young
    • Tribology and Lubricants
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    • v.20 no.2
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    • pp.51-57
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    • 2004
  • Micro/nano adhesion and friction properties of mixed self-assembled monolayer (SAM) with different chain length for MEMS application were experimentally studied. Many kinds of SAM having different spacer chains(C6, C10 and C18) and their mixtures (1:1) were deposited onto Si-wafer, 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 under micro scale applied load were measured using ball-on-flat type micro-tribotester. Surface roughness and water contact angles were measured with SPM (scanning probe microscope) and contact anglemeter. Results showed that water contact angles of mixed SAMs were similar to those of pure SAMs. The morphology of coating surface was roughened as mixing of SAM. Nano adhesion and nano friction decreased as increasing of the spacer chain length and mixing of SAM. Micro friction was decreased as increasing of the spacer chain length, but micro friction of mixed SAM showed the value between pure SAMs. Nano adhesion and friction mechanism of mixed SAM was proposed in a view of stiffness of spacer chain modified chemically and topographically.