• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.3
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• pp.162-168
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• 2006

Speckle interferometry with phase-shifting method has been applied to measurement of micro-scale displacement through optical signal processing. Four-step phase-shifting method by PZT is used to measure out-of-plane displacement in spot-welded cantilever and results of optical experiments are comparable to those of FEM. Phase-shifting method using Fourier transform by PZT is applied to measurement of in-plane displacement on rectangular steel plate with a circular hole. The results of optical experiment agree well with theoretical calculation. New phase-shifting method in speckle interferometry has been implemented with a quarter wave plate. In-plane displacement of specimen is measured by the new phase-shifting method. Results of optical experiment show that the quarter wave plate can be used for phase-shifting method that is cheap and easy to use in speckle interferometry.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.2
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• pp.150-158
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• 1988

On a refrigeration compressor, damage of a discharge valve is one of the annoying troubles for an engineer. Small size compressors, having ring plate type discharge valve are recently used. Therefore, it is very important for engineers to measure and analyze strains of discharge valve. The purpose of this study is to obtain the basic data of the strain of the flexible ring valve. Measurements were performed by the strain gauge bonded on the surface of the flexible ring valve. Stress and strain of the valve were calculated by the method of uniformly loaded circular plates with a central hole. The results obtained are as follows; (1) the strain of flexible ring discharge valve in refrigeration compressor was influenced by tension and compression strain simultaneously. (2) for a given discharge pressure, the tangential and radial strains was increased with increasing discharge pressure. (3) the valve of radial strain was larger than that of tangential strain.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.785-790
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• 2000

The resonant frequency of a gas-filled cylindrical Helmholtz resonator in a liquid is obtained analytically. The equation of motion of the resonator is derived by using the condition of equilibrium of forces acting on the mass in the neck of the resonator. The reaction force on the upper side of the cylinder due to the acceleration of external fluid and sound radiation is obtained by using the analytical results for the baffled circular-piston problem. From the frequency response function of the resonator, a formula to predict the resonant frequency of the resonator is derived. It is shown that the resonant frequency of the Helmholtz resonator significantly decreases due to the cushioning effect of gas inside the cavity. Therefore, when a pressure transducer is to be installed in a pin-hole type mounting method, much care should be paid to remove the gas from the cavity.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.102-108
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• 1995

Internal contact scheme between two free surfaces on one deforming body has been proposed by using the penalty method. It has been imposed to be internal boundary condition on two-dimensional thermo-viscoplastic finite element method so as to analyze one deforming body, which has two free surfaces penetrating each others. Analysis of side pressing with a circular void and a inclined elliptic hole have been carried out in order to verity the proposed contact scheme. A finite element code imposed internal boundary condition has been applied to two-dimensional analysis of free forging of large ingot with a void. Through the analysis, effects of working parameters in order to consolidate voids have been investigated.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.172-175
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• 2008

In the last five years, 45 people died and 104 were wounded because of carbon monoxide poisoning accident. CO poisoning accident is higher than any other gas accident in the rate of deaths/incidents. Most of these CO poisoning accidents were caused by defective exhaust tube in the old gas boiler and multi-use facility. In this study, the spread of CO gas released from leakage hole of exhaust tube was analyzed by computational flow modeling and concentration measuring test. CO gas leaked form exhaust tube in a building was highest concentrated near the ceiling and formed the circular currents along the walls. Through these experiments and simulation, the reasonable installation location of CO alarm was made certain and suggested.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.4 s.23
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• pp.136-145
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• 2005

특이응력해석을 위한 일반화된 가역상반일 경계적분식이 섬유강화복합재를 모형화한 직교 이방성 크랙평판의 수치해를 위하여 발전시켰다. 이 적분방정식은 평판경계에서의 탄성변위와 트랙션의 변수로 구성된 경계적분식의 형태로 하중이 없다는 두 크랙면의 경계조건과 유한의 탄성변형에너지의 개념에서 경계적분식에 필요한 특성해를 규정하고 대응되는 보조해를 계산하였다. 대칭모우드 I형의 중앙원공크랙평판 및 복합모우드형의 반원편측크랙 일단고정평판의 응력확대계수가 임의의 섬유방향각에 따라서 계산되었다.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.125-131
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• 2000

The local heat/mass transfer coefficients for arrays of impinging circular air jets on a plane surface are determined by means of the naphthalene sublimation method. Spent fluid makes a crossflow in the confined space. The crossflow reduces heat/mass transfer at the small gap distance between the jet plate and impingement surface because of reentrainment of the spent fluid. The present study suggests a new exhaust system having effusion holes in the impinging jet plate. The spent air flow out after impingement just through effusion holes located in the upper plate. This system increases heat/mass transfer coefficients and uniformity for small gap distances$(H/d{\leq}2)$

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.49-50
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• 2006

Photoelasticity is widely and conveniently used methods for whole field stress analysis. In this paper, 8-step photoelastic phase shifting method was performed by using a multi-purpose polariscope to measure the fringe orders along a specified line on the specimen containing a square hole. The material of the specimen is made of Polycarbonate. The measurement results by 8-step phase shifting method were compared with the those calculated by ABAQUS.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.770-778
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• 1986

This paper is studied on the Junctiion of the large tank and the cylinderical outlet such as a pressure vessel attached a pipe or nozzle theoretically. It is assumed that the diameter of tank is much larger than that of the nozzle, so it can be approximated that nozzle is attached to plate. The analysis procedure can be viewed as the solution of interdependent subproblems: (a) the stress analysis of the cylinderical shell(nozzle), (b) the plane-stress analysis of the plate membrane problem, and (c) the analysis of the transverse bending deformation in the plate. On the procedure of (a), the Flugge formula are used, and the variables are the length and the ratio of the thickness to the radius of cylinderical shell. The solutions of thess problems are interrelated in the total solution through continuity and equilibrium conditions at the interface of middle planes of the plate and cylinderical shell.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.116-116
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• 2004

편마비 환자의 보행운동 개선을 위한 보조기구로 족부보장구(Ankle Foot Orthosis, A.F.O.)가 활용되고 있다 족부보장구는 Fig. 1에 제시한 바와 같이 보행특성상 무수히 반복되는 충격과 굽힘하중을 받는다. 따라서 족부보장구용 재료는 피로특성이 우수한 탄소섬유 강화재(Carbon Fiber Reinforced Plastic, 이하 CFRP)를 주로 사용한다. 그러나 CFRP의 상용재인 프리프레그(prepreg)는 강한 이방성의 단방향 섬유이므로 섬유방향과 하중작용방향의 관계에 매우 민감하다.(중략)