• 소성∙가공
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• 제20권4호
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• pp.273-278
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• 2011

Employing the TRIZ problem solving technique, a hybrid-type center plate for the molten carbonate fuel cell(MCFC) was developed for the purpose of improving gas sealing and maintenance. The manufacturing method of the hybrid-type center plate was divided into a trimming operation and a two-step bending process. In the latter, a modified punch shape was used to reduce springback. Using finite element(FE) simulations, bending stresses in the thickness and the in-plane directions were computed and the bending conditions were optimized. The optimized results of the two-step bending process were used as a basis for the design of the trimming process of the hybrid-type center plate. Finally, the external manifold-type center plate and the hybrid-type center plate were fabricated using a die set that accounts for the optimized conditions. It was found that the numerical simulation results were in good agreement with the experiments.

• Advances in aircraft and spacecraft science
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• 제5권3호
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• pp.319-334
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• 2018

In this study, the failure mode and energy absorption capabilities of a composite shock absorber device, during an emergency landing are evaluated. The prototype has been installed and tested in laboratory simulating an emergency landing test condition. The crash absorber presents an innovative configuration able to reduce the loads transmitted to a helicopter fuselage during an emergency landing. It consists of a composite tailored tube installed on the landing gear strut. During an emergency landing this crash absorber system should be able to absorb energy through a pre-designed deformation. This solution, compared to an oleo-pneumatic shock absorber, avoids sealing checks, very high values of the shock absorber pressure, and results to be lighter, easy in maintenance, inspect and use. The activities reported in this paper have become an attractive research field both from the scientific viewpoint and the prospect of industrial applications, because they offer benefits in terms of energy absorbing, weight savings, increasing the safety levels, and finally reducing the costs in a global sense.

• Advances in Computational Design
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• 제4권3호
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• pp.295-305
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• 2019

The sealing cement of total hip arthroplasty is the most widely used binder in orthopedic surgery for anchoring implants to their recipient bones. Nevertheless, this latter remains a fragile material with weak mechanical properties. Inside this material cracks initiate from cavities. These cracks propagate under the effect of fatigue and lead to the failure of this binder and consequently the loosening of the prosthesis. In this context, this work consists to predict the position of cracks initiation and their propagations path using the Extended Finite Element Method (XFEM). The results show that cracks can only be initiated from a sharp edges of an ellipsoidal cavity which the ratio of the minor axis over the major axis is equal to 0.1. A maximum crack length of 19 ?m found for a cavity situated in the proximal zone position under a static loading. All cracks propagate in same(almost) way regardless of the cavity(site of initiation) position and its inclination in the proximal zone.

• 한국기계가공학회지
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• 제21권1호
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• pp.66-72
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• 2022

The Mooney-Rivlin second order optimal strain energy function derived through uniaxial tensile test and analysis was applied to a gasket to confirm the internal stress and surface pressure generated during compression. The Taguchi method, a statistical technique, was used to design the optimum shape of the gasket, and through characteristic evaluation, the optimum shape of the gasket was obtained when the reference plane (T: 0.15 mm), contact surface (W: 1.00 mm), and curvature (R: 0.30 mm) were used. It was determined that the optimum shape yields a von Mises stress of 4.83 MPa, and the contact pressure stress is 20.14 MPa, which satisfies breakage and sealing requirements. In the future, we plan to manufacture a jig that can measure surface pressure to conduct comparative verification studies between the test results and analysis results.

• 공업화학
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• 제19권1호
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• pp.86-91
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• 2008

다양한 고무 충전제가 연료전지 스택용 가스켓의 재료로서의 적합성 및 스택체결에 있어 미치는 영향을 살펴보기 위하여, 카본블랙 및 실리카계 충전제를 사용하여 고무를 배합하였다. 이렇게 배합된 고무재료를 PEMFC (polymer electrolyte membrane fuel cell)의 구동환경을 고려하여 열과 상대유에 대한 장기평가를 실시하였다. 가스켓에 가장 요구되는 압축 영구 줄음율은, 1000 h까지의 장기평가에서도 15% 이하의 우수한 특성을 보였다. 다양한 충전제를 사용한 배합한 고무재료로 가스켓을 제작하고, 체결시 가스켓과 가스켓 사이의 밀봉력을 FEM (finite element method)을 실시하여 최소 0.2 MPa에서 최대 2.5 MPa일 것으로 예측되었다.

• 한국재료학회지
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• 제14권7호
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• pp.470-476
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• 2004

The fail safety filter is an assistant filter element to be mounted in order to intercept the particles leaked when the main filter elements are broken. So it should have two contrary functions of being plugged easily to meet the purpose of dust sealing and a high permeability to save the space. The permeability of the metal filter elements were effectively controlled by the following factor: powder size(53-840 ${\mu}m$) and applied pressure(1000-2000 $kgf/cm^2$), and then the compact were sintered for 1 hour at $1200^{\circ}C$ in vacuum sintering furnace. The sintered metal filters was evaluated for the function of the fail safety filter in an experimental unit. The maximum allowable particle size was 420-840 ${\mu}m$, when a CIP pressure of 1500 $kgf/cm^2$ was applied reveals a permeability of about $1.2{\times}10^{10}m^2$ and pore size of about 60 ${\mu}m$. The metal filter produced with stainless steel powder of 480-840 ${\mu}m$ size, which presented excellent permeability than commercial ceramic filter element and plugged with in 3 minutes with the leak of the maximum particle size less than 3 ${\mu}m$.

• 신재생에너지
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• 제8권1호
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• pp.44-51
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• 2012

Due to a high tidal range of up to 10 m on the west coast of Korea, numerous tidal current projects are being planned and constructed. The turbine, which initially converts the tidal energy, is an important component because it affects the efficiency of the entire system. Its performance is determined by design variables such as the number of blades, the shape of foils, and the size of a hub. To design a turbine that can extract the maximum power on the site, the depth and duration of current velocity with respect to direction should be considered. Verifying the performance of a designed turbine is important, and requires a circulating water channel (CWC) facility. A physical model for the performance test of the turbine should be carefully designed and compared to results from computational fluid dynamics (CFD) analysis. In this study, a horizontal axis tidal current turbine is designed based on the blade element theory. The proposed turbine's performance is evaluated using both CFD and a CWC experiment. The sealing system, power train, measuring devices, and generator are arranged in a nacelle, and the complete TCP system is demonstrated in a laboratory scale.

• 구강회복응용과학지
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• 제33권3호
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• pp.189-198
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• 2017

목적: 외측 육각형과 내측 원추형 연결부로 설계된 임플란트 지지 하악 구치 수복물에 교합력을 가할때 발생하는 생역학 현상을 분석하고자 한다. 연구 재료 및 방법: 외측 연결형 임플란트(EXHEX)와 내측 연결형 임플란트(INCON) 그리고 이와 결합할 해당 나사와 지대주 및 크라운을 제작하였고, 하악 무치악 치조골을 설계하였다. 각 부분을 조립하여 2종의 유한요소 모형을 제작하였다. 총 120 N 크기의 수직력(L1)과 45도 측방력(L2)을 가하였고, 유한요소 응력 분석을 시행하였다. 결과: L2 측방력 하중에 의해 발생한 최대 응력은 L1 수직력 하중에 의한 것 보다 6 - 15배 더 컸다. INCON 모델은 EXHEX 모델보다 크라운 교두부에서 2.2배 더 큰 변위량을 보여 주었다. 측방력에 의해 EXHEX 모델은 나사에서, INCON 모델은 임플란트 고정체의 상단 변연부에서 폰미세스 응력의 최대값이 관찰 되었다. INCON 모델에서는 임플란트 내부 계면에서 긴밀한 접촉이 유지 되었다. 결론: 측방력이 큰 변형과 응력을 발생하였으나, 임플란트에서의 최대 응력 발생부위는 INCON과 EXHEX 모델이 서로 상이하였다.

• 한국가스학회지
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• 제10권3호
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• pp.34-40
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• 2006

본 논문은 LPG 충전노즐의 밀봉성능에 밀접한 관련을 맺고 있는 구형 그루브와 도브테일 그루브에 장착된 O-링의 최적화 설계를 위해 수행된 연구이다. O-링 그루브에 대한 최적설계 해석결과를 얻기 위해 비선형 유한요소해석 프로그램 MARC와 다구찌 설계법을 이용하였다. O-링을 최적의 조건으로 설치할 수 있도록 설계하기 위해 4개의 그루브 모델과 3개의 소재를 고려하였다. 그루브의 설계 파라미터로 폴리머 소재, 그루브의 깊이와 폭, O-링의 직경을 선정하였다. FEM 해석결과에 의하면, 최적설계에 가장 큰 영향을 미치는 기여도는 O-링의 직경과 소재특성으로 그루브의 폭, 깊이, 압축률에 비하여 높다는 사실을 알 수 있다. 가스 공급압력 1.764MPa에 적합한 O-링을 안전하게 설치되어야 할구형 그루브는 모델 3이, 그리고 도브테일 그루브는 모델 4가 가장 우수한 것으로 해석되었다.

• 한국자동차공학회논문집
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• 제18권4호
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• pp.121-126
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• 2010

The automotive weather strip has functions of isolating of water, dust, noise and vibration from outside. To achieve good sealing performance, weather strip should be designed to have the high contact force and wide contact area. However, these design causes excessive permanent deformation of weather strip. The causes of permanent deformation is generally explained to be the chemical material detrioration and physical variation and cyclic loading, etc. This paper introduces a numerical method to predict the permanent deformation using the time dependent viscoelastic model which is represented by Prony series in ABAQUS. Uniaxial tension and creep tests were conducted to obtain the material data. And the lab. test for the permanent deformation was accelerated during shorter time, 300 hours. The permanent deformation of weather strip was successfully predicted under the different loading conditions and different section shapes using the suggested numerical process.