• Title/Summary/Keyword: Micro-tribology

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Evaluation of Antiwear Performance of Mono/multilayer LB Molecular Films (단층/다층 LB 분자막의 내마멸 성능 평가)

  • ;;G.K. Zhavnerko
    • Tribology and Lubricants
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    • v.19 no.6
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    • pp.329-334
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    • 2003
  • The antiwear properties of amphiphilic monolayers and composite multilayer on silicon surface were investigated using micro­tribometer and Auger Electron Spectroscopy. Langmuir­Blodgett (LB) monolayers from behenic acid, 2,4­heneicosanedione(HD) and its lopper complex((HD)$_2$Cu) were fabricated on silicon surface and the composite multilayer of 5­bilayer of (HD)$_2$Cu was fabricated on the surface of octadecyltrichlorosilane (OTS) self­assembled monolayer (SAM). We observed that LB monolayers and the composite multilayer exhibited a steady and excellent friction response when compared with the OTS SAM. These LB mono and multilayer also showed much higher wear­resistance than the OTS SAM.

A Study on Clearance Behaviors with Micro Scaled Lubricant Aeration under the Dynamically-Loaded Condition (동하중 조건에서 마이크로 크기의 공기 혼입 윤활유의 틈새 거동 연구)

  • Jang, Si-Youl
    • Tribology and Lubricants
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    • v.22 no.1
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    • pp.26-32
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    • 2006
  • This work analyzes the behaviors of aerated lubricant in the gap between con-rod bearing and journal. Aerated lubricant influences two major factors on the film formation. One is the density characteristics of the lubricant due to the volume change by the bubbles and the other is the viscosity characteristics of the lubricant due to the surface tension of the bubble. Those two major factors surprisingly increase the load capacity in certain ranges of bubble sizes and densities. Modified Reynolds' equation is developed with the consideration of aerated ratio in the lubricant and journal locus is computed with the Mobility method after the computation of two dimensional pressure distributions over the bearing area.

A study on the Nano adhesion and Friction at Different Contact Conditions using SPM (SPM을 이용한 접촉조건 변화에 따른 미소응착 및 마찰특성에 관한 연구)

  • 윤의성;박지현;양승호;공호성
    • Tribology and Lubricants
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    • v.17 no.3
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    • pp.191-197
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    • 2001
  • Nano adhesion and friction characteristics between SPM(scanning electron microscope) tips and flat plates of different materials were experimentally studied. Tests were performed to measure adhesion and friction in AFM(atomic force microscope) and LFM(lateral force microscope) modes in different conditions of relative humidity. Three different Si$_3$N$_4$ tips (rdaii : 15nm, 22nm and 50 nm) and three different flat plates of Si-wafer(100), W-DLC(tungsten-incorporated diamond-like carbon) and DLC were used. Results generally showed that adhesion and friction increased with the tip radius, and W-DLC and DLC surfaces were superior to Si-wafer. But the adhesion force of Si-wafer showed non linearity with the tip radius while W-DLC and DLC surfaces showed good correlation to the “JKR model”. It was found that high adhesion force between Si-wafer and a large radius of tip was caused by a capillary action due to the condensed water.

Thin Film Elastohydrodynamcic Lubrication of Nanometer Scale (나노 미터 크기 유막에서의 탄성유체윤활)

  • 장시열
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1997.10a
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    • pp.173-182
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    • 1997
  • In many practical lubricated contacts such as a rough concentrated contact on the sliding of nominally flat surfaces, the fluid may be of molecular (nanometer) scale owing to the asperity interactions on the surfaces. Under this condition, there is insufficient lubricant on the concentrated contact spot to maintain a realistic continuum. Rheological behavior for this kind of concentrated contact was studied to know whether the application of viscous fluid model is appropriate. The interaction of two rough surfaces is simplified as perfectly flat-rough surfaces contact under certain conditions by "composite topography" and for a nanometer scale fluid film, three kinds of rheological fluid behavior are analyzed in elastohydrodynamic asperity point contact.t contact.

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Application of Biomimetic Surfaces for MEMS Tribology

  • Singh, R.Arvind;Pham, Duc-Cuong;Yoon, Eui-Sung
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1556-1557
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    • 2008
  • "Biomimetics" is the study and simulation of biological systems with desired properties. In recent times, biomimetic surfaces have emerged as novel solutions for tribological applications in micro-electromechanical systems (MEMS). These biomimetic surfaces are attractive for MEMS application as they exhibit low adhesion/friction and wear properties at small-scales. In this paper, we present some of the examples of biomimetic surfaces that have potential application in small-scale devices.

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Investigation of Head-Disk Impact for Development of Ultra-Low Flying HDI (극저부상 HDI 개발을 위한 Head-Disk Impact 연구)

  • 조언정;박노열
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2001.06a
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    • pp.122-126
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    • 2001
  • Magnetic hard disk drive is continually being pushed to reduce head-disk spacing for higher recording densities. The current minimum spacing between the air-bearing slider and disk has been reduced to under 15 nm. In this work, it was investigated if flying height could be lowered under the height of laser bumps. With the reduction of the spinning speed, the flying height was decreased under the height of laser bumps. When a head swept between landing zone and data zone, the head-disk impact was monitored using AE and friction signals. It is demonstrated that magnetic hard disk drive could be operated without tribological failures under the height of laser bumps.

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Lubrication Characteristics of Laser Textured Parallel Thrust Bearing : Part 3 - Effect of Number of Dimples (Laser Texturing한 평행 스러스트 베어링의 윤활특성 : 제3보 - 딤플 수의 영향)

  • Park, Tae-Jo
    • Tribology and Lubricants
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    • v.27 no.6
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    • pp.302-307
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    • 2011
  • Laser surface texturing (LST) methods are widely applied recently to reduce friction and improve reliability of machine components such as thrust bearings, mechanical face seals and piston rings, etc. In this paper, numerical analysis is carried out to investigate the effect of number of dimples on the lubrication characteristics of parallel thrust bearing using a commercial computational fluid dynamics (CFD) code, FLUENT. Pressure distributions of present analysis are physically consistent than those obtained from numerical analysis of Reynolds equation. The overall lubrication characteristics are highly affected by number of dimples and their locations. The results can be use in design of optimum dimple characteristics to improve thrust bearing performance and further researches are required.

Lubrication Characteristics of Laser Textured Parallel Thrust Bearing : Part 4 - Effect of Dimple Shape (Laser Texturing한 평행 스러스트 베어링의 윤활특성 : 제4보 - 딤플 형상의 영향)

  • Park, Tae-Jo
    • Tribology and Lubricants
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    • v.27 no.6
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    • pp.338-343
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    • 2011
  • Laser surface texturing (LST) methods are widely applied now to reduce friction and improve reliability of machine components such as thrust bearings, mechanical face seals and piston rings, etc. In this paper, the effect of dimple shapes on the lubrication characteristics of parallel thrust bearing are studied using a commercial computational fluid dynamics (CFD) code, FLUENT. Pressure and streamline distributions, variations of supporting load, leakage flow rate and friction force, are compared for three different dimple sectional shapes such as circle, pyramid and rectangle type. The lubrication characteristics are highly affected by dimple shapes and number of dimples. The pyramid type dimple shape can support the highest load while the rectangle type is the best in friction reduction.

Micro/Nanotribology and Its Applications

  • Bhushan, Bharat
    • Tribology and Lubricants
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    • v.11 no.5
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    • pp.128-135
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    • 1995
  • Atomic force microscopy/friction force microscopy (AFM/FFM) techniques are increasingly used for tribological studies of engineering surfaces at scales, ranging from atomic and molecular to microscales. These techniques have been used to study surface roughness, adhesion, friction, scratching/wear, indentation, detection of material transfer, and boundary lubrication and for nanofabrication/nanomachining purposes. Micro/nanotribological studies of single-crystal silicon, natural diamond, magnetic media (magnetic tapes and disks) and magnetic heads have been conducted. Commonly measured roughness parameters are found to be scale dependent, requiring the need of scale-independent fractal parameters to characterize surface roughness. Measurements of atomic-scale friction of a freshly-cleaved highly-oriented pyrolytic graphite exhibited the same periodicity as that of corresponding topography. However, the peaks in friction and those in corresponding topography were displaced relative to each other. Variations in atomic-scale friction and the observed displacement has been explained by the variations in interatomic forces in the normal and lateral directions. Local variation in microscale friction is found to correspond to the local slope suggesting that a ratchet mechanism is responsible for this variation. Directionality in the friction is observed on both micro- and macro scales which results from the surface preparation and anisotropy in surface roughness. Microscale friction is generally found to be smaller than the macrofriction as there is less ploughing contribution in microscale measurements. Microscale friction is load dependent and friction values increase with an increase in the normal load approaching to the macrofriction at contact stresses higher than the hardness of the softer material. Wear rate for single-crystal silicon is approximately constant for various loads and test durations. However, for magnetic disks with a multilayered thin-film structure, the wear of the diamond like carbon overcoat is catastrophic. Breakdown of thin films can be detected with AFM. Evolution of the wear has also been studied using AFM. Wear is found to be initiated at nono scratches. AFM has been modified to obtain load-displacement curves and for nanoindentation hardness measurements with depth of indentation as low as 1 mm. Scratching and indentation on nanoscales are the powerful ways to screen for adhesion and resistance to deformation of ultrathin fdms. Detection of material transfer on a nanoscale is possible with AFM. Boundary lubrication studies and measurement of lubricant-film thichness with a lateral resolution on a nanoscale have been conducted using AFM. Self-assembled monolyers and chemically-bonded lubricant films with a mobile fraction are superior in wear resistance. Finally, AFM has also shown to be useful for nanofabrication/nanomachining. Friction and wear on micro-and nanoscales have been found to be generally smaller compared to that at macroscales. Therefore, micro/nanotribological studies may help def'me the regimes for ultra-low friction and near zero wear.

A Study on the Surfaces Modification of Tool Steel by YAG LASER (YAG LASER에 의한 공구강의 표면개질에 관한 연구)

  • 옥철호;강형식;이광영;박홍식;전태옥
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1998.04a
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    • pp.292-299
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    • 1998
  • Case hardening behavior of tool steel(SK5) was investigated after YAG laser irradiation. In the case of beam passes, martensite formed in the melt zone and in former pearlite regions of the austenization zone exhibited very high Vickers Hardness values. The molten depth and radius, micro structure, hardness were investigated as a function of defocusing distance, pulse width, and power density.

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