• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.502-507
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• 2000

Fundamental studies on the drag reduction of the circular cylinder having dimple were conducted by the measurement of the fluid force acting on the cylinder and by the flow visualization around the cylinder. The drag coefficients were changed by the shape and the space for the arrangement of the dimple. The drag of the cylinder was reduced about 50% by the proper arrangement of the dimple. The flowfield around the cylinder having dimple, which was the minimum drag, was visualized by the hydrogen bubble technique. In this case, the separation points were moved rearward and the wake region was small in comparison with the cylinder having no dimple.

• 한국정밀공학회지
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• 제17권7호
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• pp.147-155
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• 2000

To reduce the noise from wood cutting saw at the saw mill(lumber mill) or a construction area, some multi-layer sandwich saw blades which a aluminum or copper plate was inserted between the two steel plates were developed and were tested of the wood cutting noise level at various test places. From the research, it was found that the multi-layer saw blade with copper or aluminum plate between steel plates and spot welded 60 points could reduce the wood cutting sound level about 8.3 dB(97.031 dB - 88.743 dB) at indoor test and 3.8 dB(84.805 - 81.638 dB) at field test.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.314-319
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• 1995

The effect of liquid level on the natural frequencies and mode shapes of a partially liquid-filled circular cylindrical shell with various boundary conditions is investigated by means of a theoretical analysis based upon Fourier series expansion method and a finite element analysis using ANSYS computer program. Two dimensional mode shapes of the liquid-coupled shell structure are obtained by the ANSYS finite element analysis and show that the liquid level affect the nodal point movement. It is found that the variation of normalized naturalfrequencies (natural frequencies of liquid-filled shell/antural frequencies ofempty shell) to the liquid level is depend on the axial mode numbers and circumferential wave numbers. Additionally, it is found that the number of variational steps of normalized natural frequencies is identicial to that of axial nodal points of the mode shape.

• Steel and Composite Structures
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• 제17권6호
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• pp.951-965
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• 2014

Point bending is commonly used for cambering and curving steel girders to large radii. In this system, a hydraulic ram or press is used to apply concentrated loads at selected points to obtain the required vertical (cambering) or horizontal (curving) curved profile from induced permanent deformations. This paper derives closed form solutions that relate loads to permanent deformations for horizontally curving wide flange steel beams based on their post-yield response. These solutions are presented in a parametric form to identify the relationship between key variables and their impact on the accuracy of the curving operation. It is shown that point bending could yield parabolic curved profiles that are within 1% of a desired circular curve if the span length to radius of curvature ratio (L / R) is less than 1.5 and the point loads are spaced at one third the beam length. Safe limits are then established on loads, strains and curvatures to avoid damaging the steel section. This leads to optimization of the point bending operation for inducing a circular profile in wide flange steel beams of any size.

• Tribology and Lubricants
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• 제24권5호
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• pp.221-227
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• 2008

This paper presents a step-by-step design of noncircular gears. From the diagram of angular velocity ratio of a noncircular gear pair, the pitch curves of the two mating gears are determined, and the perimeter of the pitch curve has been divided into equal-length segments by the number of teeth. A master tooth profile, which is a composite curve of circular arcs that represents involute, has been introduced. A noncircular gear pair has been designed by imposing the master tooth on the divided points of the pitch curve, and a full fillet has been achieved between neighbour teeth. Thus, the whole profile of the noncircular gear is a composite curve of arcs only, and consequently NC codes for wire EDM can be easily generated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.568-574
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• 2000

This paper presents the vibration characteristics of a continuous circular cylindrical shell multi-simply supported at arbitrary axial positions for searching design parameters. In this modal test the impulse test method is applied to the excitation of experimental model. Natural frequencies are obtained from the peak points of frequency response function(FRF) through frequency analyzer and vibration behaviors are investigated. FE analysis is performed with ANSYS 5.5 to improve the reliability of experimental results. Their results are compared with experimental results. The effect of dynamic characteristics is analyzed for the number of support point on the shell.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.334-334
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• 2015

The results of flow feature around two circular cylinders in various arrangements are carried out using two-dimensional simulation at Reynolds number of 200. In this work, time-averaged fluid force acting on the upstream and downstream cylinders were calculated for staggered angle ${\alpha}=0{\sim}90^{\circ}$ in the range of L/D = 1.1~5, where ${\alpha}$ is the angle between the free-stream flow and the line connecting the centers of the cylinders, L is centre-to-centre distance and D is cylinder diameter. The dependence of magnitudes and trends of fluid force coefficient on the spacing ratio L/D and ${\alpha}$ are discussed. In all arrangements of two cylinders, tandem arrangement (${\alpha}=0^{\circ}$) is the case produced a minimum drag coefficient for downstream cylinder. Moreover, the locations of separation and stagnation points or pressure coefficient on surface of the cylinder were examined. Acknowledgement: "This research was a part of the project titled 'Development of integrated estuarine management system', funded by the Ministry of Oceans and Fisheries, Korea."

• 한국축산시설환경학회지
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• 제20권4호
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• pp.155-160
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• 2014

This study was researched for use by data for the improvement of ventilation system of optimum environmental control systems. The ventilation system for windowless swine housing was installed negative pressure system that circular pipe duct for inlet was installed on the ceiling and axial flow fan for exhaust was installed on the sidewall. The temperatures in the pen was measured using infrared thermography camera and thermocouple with data-logger. The temperature measurement points was selected by infrared thermography camera is alley (G), inlet (A), front-upper (B), front-lower (C), rear-upper (D), rear-lower (E), forward fan (F). The temperature measured at those selected points for temperature distribution was $28^{\circ}C$ that was maintained setting temperature in suitably. The temperature deviations of F point and A~E points in windowless swine housing was less then average $0.5^{\circ}C$. The result of air velocity of measured points was suitable to the breeding of pigs.

• 한국강구조학회 논문집
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• 제21권6호
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• pp.563-574
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• 2009

본 논문은 기하학적 비선형성을 가진 보존적 단일 하중 매개변수의 탄성 상태 공간구조의 탄성 분기 좌굴이론에 관한 수치 해석적 기본 방법 및 경로 추적, pin-pointing, 경로 전환을 기술하고 있다. 비선형 탄성 불안정 상태는 극한점과 분기점으로 분류될 수 있으며, 평형경로상의 평형점의 계산 및 평형경로상의 특이점을 찾기 위한 pin-pointing 반복계산을 수행하는 일반적인 비선형 수치해석법으로 극한점을 계산할 수 있다. 그러나 분기좌굴 해석을 위해서는 좌굴 후 분기경로의 추적을 위한 분기경로 전환 알고리즘이 추가적으로 필요하다. 본문에서는 에너지이론에 기초한 일반 탄성안정이론을 소개하고, 평형경로 추적, 다분기 좌굴점을 찾기 위한 간접법과 다분기의 경로 전환에 관한 이론을 전개한다. 분기좌굴 해석예제로 트러스로 이루어진 스타돔, 핀지지의 평면아치의 분기좌굴 해석을 수행하여 본문에서 제시한 수치해석법의 정확성 및 적용성을 검증한다.

• 대한기계학회논문집A
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• 제35권3호
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• pp.241-250
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• 2011

본 논문에서는 하이포 및 에피 사이클로이드 곡선 사이에 원호 곡선을 삽입하여 내부로터를 설계하고 로터 회전시뮬레이션 및 간섭회피를 위한 수정법을 통해 외부로터를 설계하는 방식의 제로터를 개발하였다. 또한 접촉점을 이용한 기존의 유량계산법을 사용할 수 없는 경우에 유량 및 유량맥동을 도출할 수 있는 챔버면적 계산법을 개발하였다. 이와 같은 방식의 제로터는 로터 설계시 첨점 및 루프가 발생하지 않으며, 내부로터의 하이포 사이클로이드 및 원호 곡선 연결점에서 새로운 설계변수인 경사각 $\gamma$가 추가되어 편심량 설정시 첨점 및 루프 발생 방지조건 또는 이끝폭의 설계 한계조건으로부터 제한을 받지 않는다. 따라서 설계자는 편심량 및 각도 $\gamma$를 조절함으로써 실제 산업현장에서 보다 효과적으로 로터 최적설계를 수행할 수 있다.