• Title/Summary/Keyword: Real Contact Area

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Estimation of Real Area of Contact and Lubrication Regimes using Electric Contact Resistance (전기 저항을 이용한 실접촉 면적과 윤활 영역의 예측)

  • 이홍철;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2000.11a
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    • pp.11-17
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    • 2000
  • The electric contact resistance between ball and disk was measured to estimate the real area of contact under dry and lubrication conditions. The results from the measured constriction resistance using the hypothesis of a single circular contact was compared with those of Hertzian contact theory and hardness. The resistance correlated well with the asperity contact area and friction when the ball slides on the flat disk spreaded with lubricant film. Therefore, the constriction resistance method was useful to identify the lubrication regimes with respect to various loads and speeds. The results of this work will aid in better prediction of lubrication regimes with respect to the operating conditions.

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Evaluation of Friction Properties According to Normal Force and Direction of Wood Grain in Real Contact Area

  • Park, Chun-Young;Kim, Chul-Ki;Kim, Hyung-Kun;Lee, Jun-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.39 no.5
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    • pp.437-443
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    • 2011
  • In Korea, there has been a traditional post and beam wood construction with large roof load. Because a large friction is generated in wooden joint or members, it is important to evaluate the friction between wood members according to wood direction. Because most of studies have been concerned with friction between wood and steel, excluding effect of real area of contact, there are a few studies on the friction between wood members. The object of this study was to evaluate friction or coefficient of friction according to normal force and real area of contact of wood. With Japanese larch (Larix kaempferi) test specimens, five steps of normal force and combinations of test were prepared. Results indicated that normal force had almost no affection on the friction, however there was difference about friction or coefficient of friction according to real contact conditions of wood grain and contact area.

The Elastic Contact Analysis of 3D Rough Surface including the Kurtosis (Kurtosis를 고려한 3차원 거친 표면의 탄성 접촉 해석)

  • 김태완;강민호;구영필;조용주
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2000.06a
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    • pp.34-41
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    • 2000
  • Surface roughness plays a significant role in friction, wear, and lubrication in machine components. Most engineering surfaces have the nongaussian distrubution. So, in this study, contact simulation are conducted for not only gaussian surfaces but also nongaussian surfaces. Nongaussian rough surface censidering the kurtosis is generated numerically, And the effects of kurtosis on real contact area fraction, average gap, and mean asperity contact pressure are studied. It will be shown that the real contact area fraction and the mean asperity contact pressure are sensitive to the characteristics of surface geometry according to kurtosis.

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The Elastic-Plastic Contact Analysis of 3D Rough Surface of Nongaussian Height Distribution (비정규 높이분포를 가진 3차원 거친 표면의 탄.소성접촉해석)

  • 김태완;구영필;조용주
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2001.06a
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    • pp.374-381
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    • 2001
  • Surface roughness plays a significant role in friction, wear, and lubrication in machine components. Most engineering surfaces have tile nogaussian height distrubution. So, in this study, elastic-plastic contact simulations are conducted for not only gaussian surfaces but also nongaussian surfaces. Nongaussian rough surface considering the kurtosis is generated numerically. The contact simulation model takes into account the plastic deformation behaviors of asperities by setting a celing on their contact pressure at material hardness value. It will be shown that the performace variables such as real contact area fraction, plastic area fraction and average gap are sensitive to the characteristics of surface geometry according to kurtosis.

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The Elastic Contact Analysis of 3D Rough Surface of Nongaussian Height Distribution (Kurtosis를 고려한 3차원 거친 표면의 탄성접촉해석)

  • Kim, Tae-Wan;Koo, Young-Pil;Cho, Yong-Joo
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.10
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    • pp.53-60
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    • 2001
  • Surface roughness plays a significant role in friction, wear, and lubrication in machine components. Most engineering surfaces have the nongaussian height distribution. So, in this study, contact simulations are conducted for not only gaussian surfaces but also nongaussian surfaces. Nongaussian rough surface considering the kurtosis is generated numerically And the effects of kurtosis on real contact area fraction, average gap, and mean asperity contact pressure are studied. It will be shown that the real contact area fraction and the mean asperity contact pressure are sensitive to the characteristics of surface geometry according to kurtosis.

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Effect of Contact Area on Friction and Wear Behavior in Atomic Force Microscope (원자 현미경을 이용한 접촉 면적에 따른 마찰 및 마멸 특성 분석)

  • Choi Dukhyun;Hwang Woonbong
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.12
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    • pp.167-173
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    • 2004
  • Recently, it has been reported that frictional behavior at nanometer scale can be different from that at macro scale. In this article, friction and wear tests were conducted using an AFM to investigate the effect of real contact area on the coefficient of friction and wear property. SiO$_2$, Hica, and SiGe were used in friction test and the AFM tip was Si$_3$N$_4$. The real contact area between an AFM tip and flat surface was calculated by the Johnson-Kendall-Roberts (JKR) theory. Wear specimen was Mica, and the diamond tip was used. We found that the coefficient of friction is constant below a critical area, but it is degraded over the area. Moreover, it is found that wear depth increased rapidly from a certain load and was degraded as a function of the number of the scanning cycles. Also, the range of scanning velocity used in this study had little effect on the wear depth.

Effects of Combination of the Load and the Apparent Area of Contact on Sliding Wear behavior of Mild Steel in a Pin-on-disc Type Apparatus (Pin-on-Disc식 미끄럼마모시험 시 마모 거동에 미치는 접촉면적 및 하중 조합의 영향)

  • Lee, Han-Young
    • Tribology and Lubricants
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    • v.29 no.2
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    • pp.85-90
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    • 2013
  • The effects of contact pressure on the sliding wear behavior of mild steel in a pin-on-disc type apparatus were investigated. Sliding wear tests were conducted with various combinations of the load and apparent area of contact. The wear behavior of mild steel as a function of sliding speed was independent of contact pressure. However, the wear rate at different sliding speeds was influenced by the load regardless of the apparent area of contact. This was attributed to the fact that there may be no difference in the real area of contact for any combination of the load and apparent area of contact.

3D Elastic Contact Analysis of Sharkskin Surface Pattern (상어 표피 형상의 3차원 탄성접촉해석)

  • Kim, Tae Wan
    • Tribology and Lubricants
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    • v.28 no.6
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    • pp.297-302
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    • 2012
  • We conducted 3D elastic contact analysis of a sharkskin surface pattern for the characteristic assessment of biomimetic shark skin structure pattern for engineering applications. Rough sharkskin surfaces of similar size with real shark skin scales are generated numerically. Under the assumption of the contact of a plate on the generated sharkskin surface, contact performances such as contact pressure, real contact area, and surface separation are evaluated.

Mixed Lubrication Analysis of Parallel Thrust Bearing Considering Surface Roughness (표면거칠기를 고려한 평행 스러스트 베어링의 혼합윤활 해석)

  • 이동길;임윤철
    • Tribology and Lubricants
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    • v.16 no.6
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    • pp.455-460
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    • 2000
  • The real area of contacts, average film thickness, mean real pressure, and mean hydrodynamic pressure are investigated numerically in this study, especially for the parallel thrust bearing. Model surface is generated numerically with given autocorrelation function and some surface profile parameters. Then the average Reynolds equation contained flow factors and contact factor is applied to predict the effects of surface roughness in mixed lubrication regimes. In this equation, flow factors are defined as correction terms to smooth out high frequency surface roughness and contact factor is introduced to relieve from obtaining the average film thickness. Therefore the computation time to obtain barh h can be reduced.

Computer Modeling of Hot Spot Phenomena in Ventilated Disk Brake Rubbing Surface

  • Kim, Chung-Kyun;Cho, Seung-Hyun;Ko, Young-Bae
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.229-230
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    • 2002
  • This paper presents the hot spot behaviors on the rubbing surface of ventilated disk brake by using finite element method. The depth of asperities on the rubbing surface is usually $2-3\;{\mu}m$ so the real contact area is microscopically. Non-uniform contacts between the disk and the pads lead to high local temperatures, which may cause the material degradation, and develops hot spots, thermal cracking, and brake system failures at the end. High contact asperity flash temperatures in rubbing systems, which is strongly related to the hot spot. It was generally known that high temperature over about $700^{\circ}C$ may form martensite on the cast iron which is material for automotive disk brakes. In this paper, the contact stress, temperature distribution and strain have been presented for the specific asperities of real contact area microscopically by using coupled thermal-mechanical analysis technique.

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