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항공기 박판부품의 멤브레인 제거장치의 구조해석과 성능평가
성승학(Seung Hak Seong),이득우(Deug Woo Lee),백효정(Hyo Jeong Baek),최운집(Un Jip Choi),정원재(Won Jae Jeong) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
This paper is on the development of a new machine for removing membranes and deburring which is exclusively designed for aircraft frame components of slender shape. The machine has been developed from innovative ideas at the early stage of concept design and modifications through a series of design changes. Some structural analysis results for the development and test results for the performance evaluation are reported. Some technical difficulties such as on fixtures caused by the particular configuration that is thin layer shape of long slender body are also discussed.
다공성 방풍펜스가 대기경계층내에 놓인 삼각프리즘 표면압력에 미치는 영향에 관한 연구
박철우,성승학,Park, Cheol-U,Seong, Seung-Hak 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.8
Effeccs of porous wind fence on surface-pressure around 2-dimensional prism model of triangular cross-section were investigated experimentally. The pressure data were obtained at a Reynolds number based on the model height of Re=2.1*10$^{5}$ . Flow visualization also carried out to investigate the flow structure qualitatively. The mean velocity and turbulent intensity profiles measured at fence location were well fitted to the neutral atmospheric surface boundary layer over the open terrain. Various fences with different porosity and height were tested to investigate their effects on the surface pressure acting on a prism model at different locations. As the results, porous fence with porosity 40 ~ 50% is most effective for abating wind erosion. With decreasing porosity of the fence, pressure fluctuations on the model surface are increased. The mean pressure coefficients are decreased only when the fence height is greater than the model height. The effect of distance between wind fence and triangular prism was not significant, compared to that of the fence porosity and height.
두꺼운 난류경계층 내부에 놓인 직사각형 프리즘 주위의 유동구조
김경천,지호성,추재민,이석호,성승학,Kim, Gyeong-Cheon,Ji, Ho-Seong,Chu, Jae-Min,Lee, Seok-Ho,Seong, Seung-Hak 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.4
Flow structures around a rectangular prism have been investigated by using a PIV(Particle Image Velocimetry) technique. A thick turbulent boundary layer was generated by using spires arid roughness elements. The boundary layer thickness, displacement thickness and momentum thickness were 650mm, 117.4mm and 78mm, respectively. The ratio between the model height(40mm) and the boundary layer thickness H/$\delta$, was 0.06. The Reynolds number based on the free stream velocity and the height of the model was 7.9$\times$10$^3$. The PIV measurements were performed at three different wall normal planes. Three recirculation regions at forward facing step, top of the roof and backward facing step are clearly seen and show three dimensional features. Dramatic changes of flow patterns are observed in the wake regions in the different spanwise wall normal planes. Instead of reattachment and recirculation zone, rising streamlines are depicted at the normal planes near the side wall due to the interaction with a rising horse shoe vortex. The peak of turbulent kinetic energy occurs at the separation bubble on top of the roof and the magnitude is 2.5 times higher compared with that of the wake region.
상용 CFD code를 이용한 GeRotor 펌프 유동해석 및 포트 최적화
김병조(Byung-Jo Kim),성승학(Seung-Hak Seong),윤순현(Soon-Hyun Yoon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
GeRotor pump is widely used in the automotive industry for fuel lift, injection, engine oil lubrication, and also in transmission systems. The CFD study of the pump, which is characterized by transient flow with moving rotor boundaries, has been performed to obtain the most optimum shape of the inlet/outlet port of the pump. Various shapes of the port have been tested to investigate how they affect flow rates and fluctuations. Based on the parametric study, an optimum shape has been determined for the maximum flow rate and minimum fluctuations. The result has been confirmed by experiments. For the optimization, Taguchi method has been adapted. The groove shape has been found to be the most important factor among the selected several parameters related to flow rate and fluctuations.
PIV를 이용한 직렬배열에서의 두 정사각기둥 주위의 유동특성에 관한 연구
이종민(Jong-Min Lee),김동건(Dong-Keon Kim),성승학(Seung-Hak Seong),윤순현(Soon-Hyun Yoon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The flow fields including velocities, turbulence intensities, and Reynolds shear stress were investigated using particle image velocimetry(PIV) to study the flow characteristics around two square cylinders in a tandem arrangement. The experiments were carried out in the range of the spacing from 1.0 to 4.0 widths of cylinder, Reynolds number of 5.3×10³ and 1.6×10⁴ respectively. Discontinuous jumping at the drag coefficient variation was found for two cylinders simultaneously when the spacing between two cylinders is varied. This phenomenon is attributed to a sudden change of the flow pattern which depends on the reattachment of the shear layer separated from the upstream cylinder. Near such a critical spacing, the changes of the flow fields as well as the effect of Reynolds number were studied in detail.
5-Head Router Machine용 2면 구속 공구시스템 설계를 위한 선행 연구
백효정(Hyo Jeong Baek),옥주선(Ju-Seon Oak),최운집(Un-Jip Choi),성승학(Seung Hak Seong) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
As part of development of the 5-head router machine, design of a tooling system has been studied. As a preliminary study, various types of tool holding systems are investigated and analysed. The machine under development is designed to pursue high productivity and high precision. As a result, it requires multiple heads and high speed spindle. For the high speed design, it is important to prevent an elastic deformation by the high speed, which may be significant at the end of spindle. The deformation causes inaccurate fitting and vibrations which directly affect the precision of machining and overall performance of the machine. For the high speed design the two-face-contact tooling system such as HSK type is considered. A BT type which has one-face contact and been traditionally used is compared with the HSK type by numerical calculations of the deformation. It is found the two-face-contact system has better performance with respect to the reduction of deformation. Also important design factors to improve performance of tool holder are identified which include clamping force, contact area, taper angle etc.
임의의 표본상호상관함수와 비정규확률분포를 갖는 다중 난류시계열의 디지털 합성방법을 이용한 풍속데이터 시뮬레이션
성승학,김욱,김경천,부정숙 한국대기환경학회 2003 한국대기환경학회지 Vol.19 No.5
A method of synthetic time series generation was developed and applied to the simulation of homogeneous turbulence in a periodic 3-D box and the hourly wind data simulation. The method can simulate almost exact sample auto and cross correlations of multiple time series and control non-Gaussian distribution, and one-direction anisotropy on homogeneous structure were studied by investigating the spatial distribution of turbulence kinetic energy and enstrophy. An hourly wind data of Typhoon Robin was used to illustrate a capability of the method to simulate sample cross correlations of multiple time series. The simulated typhoon data shows a similar shape of fluctuations and almost exactly the same sample auto and cross correlations of the Robin.