• 한국지진공학회논문집
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• 제19권6호
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• pp.293-302
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• 2015

ASCE 4 requires that a hard stop be built around the seismic isolation system in nuclear power plants. In order to maintain the function of the isolation system, this hard stop is required to have clearance-to-stop, which should be no less than the 90th-percentile displacements for 150% Design Basis Earthquake (DBE) shaking. Huang et al. calculated clearance-to-stop by using a Latin Hypercube Sampling technique, without considering the rocking behavior of the isolated structure. This paper investigates the effects on estimation of clearance-to-stop due to 1) rocking behavior of the isolated structure and 2) sampling technique for considering the uncertainties of isolation system. This paper explains the simplified analysis model to consider the rocking behavior of the isolated structure, and the input earthquakes recorded at Diablo Canyon in the western United States. In order to more accurately approximate the distribution tail of the horizontal displacement in the isolated structure, a modified Latin Hypercube Sampling technique is proposed, and then this technique was applied to consider the uncertainty of the isolation system. Through the use of this technique, it was found that rocking behavior has no significant effect on horizontal displacement (and thus clearance-to-stop) of the isolated structure, and the modified Latin Hypercube Sampling technique more accurately approximates the distribution tail of the horizontal displacement than the existing Latin Hypercube Sampling technique.

• 한국항공우주학회지
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• 제46권12호
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• pp.994-1003
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• 2018

유한요소 해석을 이용하여 분할 너트를 이용하는 파이로테크닉 분리 너트의 체결부 특성을 파악하였다. 분할 너트를 이용하는 경우, 체결 과정에서 분할 너트가 반경 방향으로 벌어지는 것을 막기 위해 구속해주는 구속원통이 필수적이다. 이때, 제작 과정에서 공차로 인해 분할 너트의 외경과 구속원통 내경 사이에 발생하는 틈새의 영향을 파악하기 위하여 적절한 유한요소 볼트 체결 모델링 기법을 연구하였으며, 틈새가 0.00, 0.03, 0.06, 0.10 mm인 모델을 만들어 해석 결과를 검토하였다. 해석 결과를 통해 너트의 분할 여부 및 틈새 크기에 따라 달라지는 체결부의 특성을 확인하였으며 이로부터 신뢰성 있는 파이로테크닉 분리 너트 설계를 위해 고려해야 할 사항을 파악하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.231-232
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• 2013

• Journal of the Korean Wood Science and Technology
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• 제44권5호
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• pp.736-742
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• 2016

나무못은 다양한 구조물의 목재부재들을 연결하는데 일반적으로 사용된다. 하지만 국산재의 나무못 유지력에 대한 자료는 매우 부족하다. 본 연구는 나무못의 직경과 천공여척이 유지력 특성에 미치는 영향에 대해 알아보기 위해 실시했다. 실험 블록은 두께 15 mm인 소나무와 잣나무 목재로 제작했다. 6, 8 및 10 mm 직경인 나무못은 밤나무, 잣나무 및 백합나무 목재로 각각 제작했다. 연구결과 나무못 직경이 증가하면 유지력은 선형으로 증가했지만 유지력 강도는 감소했다. 본 연구는 또한 천공여척이 작아질수록 유지력과 유지력 강도도 선형으로 증가하는 것을 보였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.137-146
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• 2002

This paper presents a quasi-3-dimensional calculation method considering secondary flows in the impellers of diagonal flow blowers. A Quantitative estimation of the secondary flow effects is made by using secondary flow theories. In order to verify the validity of the adopted models, that is, span-wise mixing model and the tip clearance model, numerical simulations are performed for two different types of impellers of diagonal flow blowers which are designed differently. Numerical experiments are conducted for each of a constant tangential velocity type impeller, and a free vortex type impeller, both at two different flow coefficients. According to the simulation results, it was found that the present model considering span-wise mixing and tip clearance effect shows better agreements with the experimental data than those without these models in terms of the flow velocity and the angle distribution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.358-363
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• 2003

Spot welded structure is operated in diverse situation because of temperature, humidity and precipitation. In addition factors of environmental pollution such as acid rain, that courses corrosion, have the tendency to increase, But spot welded structure strength is affected by dampness and environment temperatures. Therefore, it is important to evaluate effect of temperature of spot welded part, In this study, the strength distribution of spot welded plates is evaluated about the environmental temperature of zine coated steel plates and test is conducted with welded part immersed in distilled and synthetic sea water. Specimens are immersed into water for 10, 100, 500 and 1000hours to evaluate the effects of water immersion time on tensile-shear strength under the conditions of -40, 0, 20 and $50^{\circ}C$. Strength is evaluated by tensile-shear test. The conditions of spot welding are 240kgf electrode force, 10KA welding current with 0 and 5mm clearance. From this study, spot welded specimens with clearance have lower tensile-shear strength in the distilled water or synthetic sea water comparing with spot welded specimens without clearance. And they have lower tensile-shear strength under $-40^{\circ}C$ and over $50^{\circ}C$.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1073-1078
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• 2009

Finned-tube heat exchangers are often made with aluminum fins and copper tubes. Usually the contact between fin collar and tube surface for finned tube heat exchanger is secured by mechanical expansion of the tubes. The objective of the present study is to apprehend how much effect clearance has on the performance of heat exchanger. This effect is studied using an experimental approach. The thermal fluid measurements are made using a psychometric calorimeter. Frontal air velocity varies in the range from 1.0m/s to 3.0 m/s. The heat transfer rate of sample which has bigger clearance is only 27% compare with the other's in dry condition. In wet condition, its heat transfer rate is 78% compare with the other's.

• 대한기계학회논문집
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• 제18권2호
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• pp.351-358
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• 1994

A probabilistic model and analysis methods to determine the means and variances of the velocity and acceleration in stochastically-defined planar pin jointed kinematic chains are presented. The presented model considers the effect of tolerances on link length and radial clearance and uncertainty of pin location as a net effect on the link's effective length. The determination of the mean values and variances of the output variables requires the calculation of sensitivities of secondary variables with respect to the random variables. It is shown that this computation is straightforward and can be accomplished by a conventional kinematic analysis package with minor modification. Thus, the concepts of tolerance and clearance have been captured by the model and analysis. The only input data are the nominal linkage model and statistical information. The "effective link length" model is shown to be applicable to both analytical solution and Monte Carlo simulation. The results from both methods are compared. This paper Ksolves the higher-order kinematic problems for the probabilistic design analysis of stochastically-defined mechanisms.echanisms.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.147-155
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• 2009

Dynamic characteristics of the clearance flow between an axially oscillating rotational disk and a stationary disk were examined by experiments and computations based on a bulk flow model. In the case without pressure fluctuations at the inlet and outlet of the clearance, parallel and contracting flow paths had an effect to stabilize the axial oscillation of the rotating disk. The enlarged flow path had an effect to destabilize the axial oscillation due to the negative damping and stiffness for outward and inward flows, respectively. It was shown that the fluid force can be decomposed into the component caused by the inlet or outlet pressure fluctuation without the axial oscillation and that due to the axial oscillation without the inlet or outlet pressure fluctuation. A method to predict the stiffness and damping coefficients is proposed for general cases when the device is combined with an arbitrary flow system.

• 한국자동차공학회논문집
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• 제3권5호
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• pp.64-73
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• 1995

A numerical simulation of heat and fluid flow for predicting the effect of passage arrangement in automotive heat battery has been performed. The system is assumed to be a two-dimensional laminar flow and isothermal boundary is applied to the surface of the latent heat storage vessel. In the case of ideal heat battery the flow rate into each flow passage is evenly distributed. The various models are considered in the view of pressure drop and bulk temperature. The effects on the efficiency of the heat battery are examined by varying geometrical factors such as flow passage clearance, length of a inlet and outlet tank and the length of a latent heat storage vessel. The flow clearance is a very important -factor on the efficiency of a heat battery. As the flow passage clearance becomes narrow, the flow distribution becomes uniform and the bulk temperature increases, however the pressure drop is large. Therefore, optimal flow passage clearance has to be chosen. The present work can be used in optimizing heat battery efficiency.