• 제목/요약/키워드: Micro-tribology

검색결과 194건 처리시간 0.017초

고속전철용 디스크 브레이크의 열탄성 마멸에 관한 수치적 연구

  • 황준태;김청균
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 1999년도 제30회 추계학술대회
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    • pp.269-275
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    • 1999
  • This paper presents the results of thermoelastic wear phenomena in ventilated disk brakes for a high-speed train using finite element method. The computed results show that the sinusoidal distortions due to non-uniform distributions of temperature profiles may lead to thermoelastic wears at the rubbing surface. This may decrease the life of a disk brake and produce micro-cracks, noise and squeals between two rubbing surfaces.

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식물잎의 표면형상 및 마이크로-스케일에서의 마찰 특성 (Surface Characteristics and Micro-Scale Friction Property of Natural Surface)

  • 윤의성;김홍준;아르빈드싱;김진석
    • Tribology and Lubricants
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    • 제22권5호
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    • pp.237-242
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    • 2006
  • Surfaces found in nature, including biological surfaces have been providing inspiration to modify/fabricate artificial surfaces as solutions for tribological applications. As an example, the concept of 'lotus-effect' has motivated tribologists world wide to modify/fabricate surfaces for enhanced tribological performance. These was done by creating nano/micro-scale asperities on various surfaces using ion beam milling and ion-beam assisted roughening. In order to understand the attributes of natural surfaces, which are inspirational to tribologists, we characterized the surface of two natural surfaces-Nelumbo nucifera (lotus) and Colocasia esculenta leaves. Further, we evaluated their micro-scale friction property, both in their fresh and dried conditions. The characterization of surfaces was conducted using a confocal microscope and SEM, which involved the evaluation of size and distribution of protuberances. The micro-scale friction property was evaluated using a ball-on-flat type micro-tribo tester, under reciprocating motion. A soda lime glass ball (2 mm diameter) was used in these tests. Tests were conducted at the applied normal load of $3000{\mu}N$, at a sliding speed of 1 mm/sec for a scan length of 3 mm. All experiments were conducted at ambient temperature ($24{\pm}1^{\circ}C}$) and relative humidity ($45{\pm}5%$). It was observed that the friction behaviour of the natural surfaces was influenced by their surface characteristics (morphology and distribution of protuberances) and also by the condition (fresh or dried) in which they were tested.

마이크로 압입 크리프 시험기 개발 및 성능평가 (Development and its Performance Evaluation of a Micro-Impression Creep Machine)

  • 양경탁;김현준;김호경
    • Tribology and Lubricants
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    • 제24권1호
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    • pp.27-33
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    • 2008
  • A micro-impression creep machine was designed and developed, adopting a small punch in diameter of 150 um, displacement gage with an accuracy of sub-${\mu}m$ scale, and load-cell with an accuracy of mN scale in order to investigate creep behavior of small solder ball in diameter of less than 1 mm. Creep behavior of lead-free solder ball(Sn-3.0Ag-0.5Cu) in diameter of $760\;{\mu}m$ was investigated in the stress range of $8{\sim}60\;MPa$ and at $303\;K{\sim}393\;K$. The applied load became decreased slightly and continuously in the creep rate of $10^{-4}/s$ range during the current experiments. Also, the machine frame was so sensitive to the environmental temperature that nm scaled displacement recording was unstable according to the change in environmental temperature.

깊이 측정이 가능한 마이크로 압입 시험기 개발 및 성능평가 (Development and its Performance Evaluation of a Depth-Sensing Micro-Indentation Testing Device)

  • 정진성;김호경
    • Tribology and Lubricants
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    • 제25권3호
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    • pp.163-170
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    • 2009
  • We developed a compact micro indentation testing device (designated SNUT) which is capable to measure Young's modulus of a sample using depth and applied load data during indentation. Performance of this device was evaluated using pure Ti, pure Ni, and die steel (SKD11). As a result of analysing the indentation test data, the frame compliance $C_f$ was found to influence mainly the modulus by 80% among several factors affecting accuracy of Young's modulus. Project area, which was determined by indirect indentation method, was modified using direct SEM observation. Finally, Young's modulus error was reduced to 5% after taking into consideration the frame compliance and modified projected area from 80% error without any these two correction factors. The performance of SNUT and MTS instruments was compared using same specimen (pure Ti).

경사 돌기 표면의 젖음 특성 평가 (Hydrophobicity Evaluation of Oblique Micro-asperities Structures)

  • 백승익;김태완
    • Tribology and Lubricants
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    • 제39권2호
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    • pp.56-60
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    • 2023
  • In this study, we evaluate the anisotropic flow of droplets according to the directionality of asperities. We manufacture a mold with an inclined hole by adjusting the jig angle using a high-power diode laser. Using the manufactured mold, we prepare specimens for wettability studies by the micro molding technique. We fabricate twelve kinds of surfaces with micro-asperities inclined at 0°, 15°, 30°, and 45° for asperity pitches of 100 ㎛, 200 ㎛, and 300 ㎛. We evaluate the static and dynamic behaviors of the droplets as a function of the asperities pitch and inclination angles. The anisotropic effect increases as the pitch increases between asperities, and the anisotropic flow characteristics increase as the inclination angle of the asperities increases. On the surface with hole pitches of 100 ㎛ and 200 ㎛, the contact angle of the droplet shows high hydrophobicity at approximately 160°, but on the surface with the 300-㎛ hole pitch, the contact angle is approximately 110°, indicating that the hydrophobic effect rapidly reduces. Additionally, when the inclination angle of the asperities is approximately 30°, the left and right contact angle deviations of the droplet are the lowest, showing that the roll-off angle is relatively low.

$CO_2$ 환경하에서 접촉 표면에 적용한 마이크로 딤플 패턴이 마찰 및 마멸에 미치는 영향 연구 (Friction and Wear Characteristics of the Micro-dimple Surfaces in Rotary Compressor with Carbon Dioxide as Refrigerants)

  • 이영제;전홍규;한규철;최진호;김규만;조성욱
    • Tribology and Lubricants
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    • 제24권6호
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    • pp.374-377
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    • 2008
  • Due to the environmental concerns, especially the greenhouse effect and GWP (Global Warming Potential), the carbon dioxide was investigated as an alternative natural refrigerant to replace HFCs (HydroFluoroCarbons) in refrigerator or air conditioning systems. Because new compressor with carbon dioxide is going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To improve of wear resistance in compressor parts, especially rotary type, the friction and wear characteristics of improved sliding surfaces between vane and flange were evaluated in this paper. The method of reformed sliding surface, such as micro-dimple processes, was applied on surfaces in order to improve the tribological characteristics, and their performances were evaluated experimentally. The vane-on-flange type lubricated sliding tests were performed with a high pressure wear tester using carbon dioxide. Test results showed that the reformed surfaces were very effective to reduce the friction and the wear amounts of vane surfaces. The method of improved surfaces showed good tribological properties at vane and flange.

Cyclone separator의 형상에 따른 미세플라스틱 입자 거동 수치해석 연구 (Numerical Analysis Study on Micro-plastic Particle behavior According to the Shape of Cyclone Separator)

  • 강인선;서원준;유동호;김영식;김형철;임석연
    • Tribology and Lubricants
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    • 제40권2호
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    • pp.61-66
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    • 2024
  • Micro-plastics are synthetic high-differentiation chemicals of less than 5mm in size, and are deposited not only on the sea surface but also on the coast. If these micro-plastics are not properly separated from the sand, they can threaten marine ecosystems. Thus, in the present study, we aimed to apply cyclone separator to the micro-plastic retrieval in order to predict the movement of particles according to the formation of the cyclone separator by applying the centrifugal force of the particle in accordance with the rotational movement of the air. The cyclone separator has three shapes, the first one is a typical interconnected cyclone separator. The second is the horn form, except for the cylinder in a regular cyclone separator, and the third is a form that increases the horn's height twice in the second. The numerical analysis simulation of the Cyclone separator used the Fluent software package. The output speed of the Cyclone separator was 5 to 13m/s at 1m/s intervals. The simulated particles include sand, Styrofoam, PET, PP, and PU. Sand particles are assigned a fixed diameter of 2mm, while other particles have a diameter of 3mm. As a result of the analysis, the first form was not separated from plastic. The Styrofoam separation efficiency in the second showed its highest efficiency at 72.7% at 7m/s, and the efficiency decreased after 12m/s as the sand particles were mixed into the plastic attachment location. In the third form, the separation efficiency of Styrofoam at 12m/s was highest at 67.9%.

Contact Start-Stop 방식에서의 극저부상 높이에서 Head-Disk Interface Interactions 연구 (A Study on Head-Disk Interactions at Ultra-low Flying Height in Contact Start-Stop)

  • 조언정
    • Tribology and Lubricants
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    • 제19권2호
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    • pp.102-108
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    • 2003
  • The height of laser bumps has been considered as the limit of the minimum flying height in the contact start-stop (CSS) of hard disk drives. In this paper, tribological interactions at flying height under laser bumps are investigated in a spin stand for development of ultra-low flying head-disk interface. With the reduction of the spinning speed in a spin stand, the flying height is decreased under the height of laser bumps and, then, head-disk interactions are investigated using AE and stiction/friction signals. During seek tests and 20000 cycle-sweep tests, AE and stiction/friction signals are not significantly changed and there are no catastrophic failures of head-disk interface. Bearing analysis and AFM analysis show that there are signs of wear and plastic deformation on the disks. It is suggested that flying height could be as low as and, sometimes, lower than laser bump height.

표면 거칠기가 나노 응착력에 미치는 영향에 관한 실험적 연구 (An Experimental Study on the Effect of Surface Roughness on Nanoscale Adhesion)

  • 양승호
    • Tribology and Lubricants
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    • 제21권1호
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    • pp.1-7
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    • 2005
  • Effect of Surface roughness on nanoscale adhesion was studied experimentally by using colloidal probe technique. Glass micro balls having the radius of $3.3\~17.4{\mu}m$ were glued at the end of AFM cantilevers to prepare colloidal probes. Adhesion force between the colloidal probe and Si-wafer was measured using pull-off force measuring method. Results showed that the measured adhesion forces are not the function of the radius of the glued balls because the ball surfaces are rough. It is also found that roughness parameters such as $R_a,\;R_q\;and\;R_{max}$ do not have important role on nanoscale adhesion. In order to find the effect of surface roughness on nanoscale adhesion, the bearing areas were extracted from the measured topography of glued balls. After normalizing the measured adhesion force with the bearing area, it was found that the normalized adhesion force kept constant as function of the radius of glued ball.

디스크 브레이크의 마찰열 접촉거동에 관한 트라이볼로지적 연구 - 벤트홀의 방열효과를 중심으로 - (Tribological Analysis on the Contact Behaviors of Disk Brakes Due to Frictional Heatings -Cooling Effects By Vent Holes-)

  • 김청균;황준태
    • Tribology and Lubricants
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    • 제15권2호
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    • pp.199-205
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    • 1999
  • Using a coupled thermal-mechanical analysis, the thermal distortion of the ventilated disk brakes has been investigated based on the air cooling effects during 15 braking operations. The FEM results show that the bendings and distortions of the disk toward the left side are decreased, but the sinusoidal distortion of the disk rubbing surface along the arc length of the vent hole is highly increased by increasing the convective air cooling effects, which is heavily related to the squeal, wear and micro-thermal crackings at the rubbing surfaces due to uneven dissipation rates of friction heatings.