• 제목/요약/키워드: Maximum roughness

검색결과 398건 처리시간 0.03초

반응표면분석법에 의한 화인세라믹스$(Al_{2}O_{3})$ 원통래핑의 최적화에 관한 연구 (A Study on the Optimization of Cylindrical Lapping Process for Engineering Fine-Ceramics $(Al_{2}O_{3})$ by Response Surface Methodology)

  • 김정두;최민석
    • 대한기계학회논문집
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    • 제18권4호
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    • pp.856-865
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    • 1994
  • Cylindrical fine-ceramics, $Al_{2}O_{3}$, was lapped on its outer surface by vibrational lapping unit manufactured in the laboratory. Cylindrical lapping of fine-ceramics is necessarily be characterized and optimized because its process as other finishing methods is time-spending and, so, inefficient one, and because it is very complicated and random process affected by numerous factors in itself and in its environment. In this study, an efficient experimental approach, experimental design method, was used to analyze characteristics of the cylindrical lapping of fine-ceramics, $Al_{2}O_{3}$, and response surface methodology(RSM) to find out the optimal variables combination for the maximum improvement of surface roughness($R_a$). From the final surface roughness point of view in the given lapping conditions, a stationary point or optimal lapping conditions as well as the possible maximum improvement of surface roughness($R_a$) was predicted.

표면 거칠기를 고려한 볼 조인트 접촉의 미세 탄성유체윤활 해석 (Micro-EHL Analysis of a Ball Joint Contact with Surface Roughness)

  • 김태종
    • Tribology and Lubricants
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    • 제19권3호
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    • pp.123-132
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    • 2003
  • The effect of surface texture on elastohydrodynamic lubrication (EHL) point contact of a ball Joint mechanism in small reciprocating compressors is studied numerically by using multigrid method. Pressure and film thickness profiles have been calculated for surface roughness with waviness of different orientations and transverse ridge and dent at minimum and maximum Hoes M parameter conditions. The influence of the amplitude and the wavelength of the surface roughness was also studied. Results show that the oblique waviness with orientation angle of 30$^{\circ}$generates the smallest minimum film thickness as compared with those of longitudinal, transverse, and other oblique roughness. The influence of transverse waviness on the minimum film thickness is smaller than for the longitudinal waviness case.

양측벽면에 반복돌출형 거칠기가 있는 이중관통로내의 난류유동과 열전달 (Turbulent Flow and heat Transfer in the Annular Passage with Repeated-Ribbed Roughness on Both Walls)

  • 안수환;김덕현
    • Journal of Advanced Marine Engineering and Technology
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    • 제20권1호
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    • pp.1-12
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    • 1996
  • The fully developed tubulent momentum and heat transfer induced by the square- ribbed roughness elements on both the inner and outer wall surfaces in the concentric annuli are studied analytically based on a modified turbulence model. Heat transfer coefficients for two conditions, i.e, a) inner wall heated as constant heat flux and outer wall insulated b) inner wall insulated and outer wall heated as constant heat flux, are investigated. The analytical results of the fluid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity profiles and friction factors, and etc. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Nusselt number and Prandtl number.

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4각 리브로된 표면조도에 의한 유체유동 및 열전달 증진에 관한 연구 (A Study on the Enhanced Heat Transfer and Fluid Flow Induced by Square-Ribbed Surface Roughness)

  • 이충구
    • 설비공학논문집
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    • 제4권3호
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    • pp.155-162
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    • 1992
  • Theoritical Study is performed on heat transfer and fluid flow induced by square-ribbed roughness elements in a concentric annulus. The fluid properties were assumed to be constant, and the radius($r_m$) of the maximum speed point was found by using the principle of equation of Leung and Labib. The Nusselt number and friction factor as a function of the Reynolds number($R_e=10^4$, $5{\times}10^4$, $7{\times}10^4$, $10^5$) in artifical roughness $S/{\epsilon}=5,10,20,30$, $P/{\epsilon}=2,5,8$ and prandtl number = 0.72 have been discussed. In this study, it has been found that the Nusselt number and friction factor of rough wall are larger than those of smooth ones.

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FRACTAL SURFACE ROUGHNESS OF CONCRETE

  • 노영숙;;정란
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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    • pp.595-602
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    • 2004
  • In this study, the roughness of fracture surfaces in cementitious material has been characterized by roughness number (RN). A systematic experimental investigation was carried out to examine the dependency of fracture parameters on the aggregate sizes as well as the loading rates. Three aggregate sizes (0.1875 in, 0.5 in, and 0.75 in) and two loading rates (slow and fast loading rate) were used. A total of 52 compression tests and 53 tension tests were performed. All fracture parameters exhibited an increase, to varying degrees, when aggregates were added to the mortar matrix. The fracture surfaces of the specimens were digitized and analyzed. Fracture roughness was monotonically increased as maximum aggregate sizes increase.

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미세입자 분사가공시 직교배열표의 통계적 분석에 의한 표면형상의 최적 분사 조건 (Optimal Blasting Conditions for Surface Profile when Micro Particle Blasting by Statistical Analysis of Orthogonal Arrays)

  • 권대규;왕덕현
    • 한국기계가공학회지
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    • 제15권4호
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    • pp.148-154
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    • 2016
  • A study on the micro particle blasting was conducted to find the optimum conditions of the blasted surface of aluminum 6061. The particle type such as $Al_2O_3$ and SiC, nozzle diameter, pressure, standoff distance and injection time were used as blasting conditions. Statistical method of orthogonal arrays(ANOVA) was used to find optimum conditions of maximum depth and maximum diameter of blasted surface. Particle type, nozzle diameter, and pressure were found to be the main factors of maximum blasted depth and diameter. Maximum blasted diameter was affected by increasing pressure and nozzle diameter but saturated maximum diameter. Maximum blasted depth was affected by pressure and nozzle diameter when aluminum 6061 was blasted with $Al_2O_3$ particle. The value of surface roughness was increased as pressure and nozzle diameter increased when aluminum 6061 was blasted with SiC.

적층구조에 적용하기 위한 WO3/Ag/WO3 투명전극막의 표면 특성 제어 (Surface Properties of WO3/Ag/WO3 Transparent Electrode Film with Multilayer Structures)

  • 강동수;이붕주;권홍규;신백균
    • 전기학회논문지
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    • 제64권9호
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    • pp.1323-1329
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    • 2015
  • The WO3/Ag/WO3 transparent thin films are fabricated by the RF magnetron sputtering. This has a transmittance of front and rear about 90% in the visible light range and surface resistance of 6.41Ω/□. In this paper, we analyzed the surface characteristics caused by the working pressure and O2 plasma surface treatment to apply a transparent electrode that was prepared to the laminated structure with other materials. The working pressure was changed in the WO3 film to 10mTorr, 7mTorr, and 5mTorr, it showed a lower than roughness of conventional ITO. In addition, by 55.5774 J/m2 at 5mTorr, it shows the hydrophobic property with lower process pressure. O2 plasma surface treatment was changed at the condisions of the RF power to 150W, 100W, and 50W and the process time to 240s, 180s, 120s, and 60s. The surface roughness are the maximum roughness(Rmax) 6.437nm and the average roughness(Rq) 0.827nm at RF power 150W, and the maximum roughness (Rmax) 6.880nm and the average roughness (Rq) 0.839nm at process time 240sec. It showed a lower value than the surface treatment. also about working pressure and process time is increased, it showed the hydrophobic.

표면 거칠기가 가스 포일 스러스트 베어링의 성능에 미치는 영향 (Effects of Surface Roughness on the Performance of a Gas Foil Thrust Bearing)

  • 황성호;김대연;김태호
    • Tribology and Lubricants
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    • 제39권2호
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    • pp.81-85
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    • 2023
  • This study presents an experimental investigation of the effects of surface roughness on gas foil thrust bearing (GFTB) performance. A high-speed motor with the maximum speed of 80 krpm rotates a thrust runner and a pneumatic cylinder applies static loads to the test GFTB. When the motor speed increases and reaches a specific speed at which a hydrodynamic film pressure generated within the gap between the thrust runner and test GFTB is enough to support the applied static load, the thrust runner lifts off from the test GFTB and the friction mechanism changes from the boundary lubrication to the hydrodynamic lubrication. The experiment shows a series of lift-off test and load-carrying capacity test for two thrust runners with different surface roughnesses. For a constant static load of 15 N, thrust runner A with its lower surface roughness exhibits a higher start-up torque but lower lift-off torque than thrust runner B with a higher surface roughness. The load capacity test at a rotor speed of 60 krpm reveals that runner A results in a higher maximum load capacity than runner B. Runner A also shows a lower drag torque, friction coefficient, and bearing temperature than runner B at constant static loads. The results imply that maintaining a consistent surface roughness for a thrust runner may improve its static GFTB performance.

방향족 디아조늄염의 광분해에 관한 연구 (A Study on Photolysis of Aromatic Diazonium Salt)

  • 이형관
    • 한국인쇄학회지
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    • 제12권1호
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    • pp.93-105
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    • 1994
  • A new ink transfer model based on the physical mechanism for the maximum ink transfer rate is proposed, and examined by the experimental data of P.J Mangin et, al. for the relations of the maximum ink transfer rates to the printing pressure, the speed and the roughness of paper substrates. The free ink split coefficient and immobilized ink under the maximum ink transfer rate are calculated by the new model and the experimental data. It is concluded that the new model is very useful, and the free ink split coefficient and the immobilized ink are inversely propotional and propotional to the paper roughness respectively and both are saturated eventually under the critical values.

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내·외벽에 거칠기가 있는 이중동심관 유동에 대한 실험적 연구 (Experimental Investigation on the Flow in Concentric Annuli with Both Rough Walls)

  • 안수환;정양범;김경천
    • 설비공학논문집
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    • 제7권1호
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    • pp.81-88
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    • 1995
  • Fully developed turbulent flow through three concentric annuli with both the rough inner and outer walls was experimentally investigated for a Reynolds number range Re=15,000-85,000. Measurements were made of the pressure drop, the positions of zero shear stress and maximum velocity, and the velocity distributions in annuli of radius ratios, ${\alpha}=0.26$, 0.4 and 0.56, respectively. The experimental results showed that the positions of zero shear streess and maximum velocity were only weakly dependent on the Reynolds number. It was also found that the position of zero shear stress was not coincident with that of maximum velocity. Furthmore, the former was influenced more sensitively than the latter on the square-ribbed roughness along the axial direction.

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