• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.642-650
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• 2008

In this paper, structural behavior of Gasket and GDL of a PEMFC stack is studied to improve the performance and to secure the safety. In the Gasket analysis Mooney-Rivlin strain energy function is used to consider hyperelasticity of load and displacement. The material properties is determined by testing specimens of the gasket at uni-axial and equi-biaxial mode and compared with finite element analysis results. By measuring a thickness change, the material property of GDL is determined. The pressure drop of a unit cell is measured along the channel for the clamping force. A cross sectional change of channel base on the experimental data is obtained experimentally and compare with FEM analysis results.

• Journal of Conservation Science
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• v.37 no.6
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• pp.689-700
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• 2021

This study aims to optimize the measurement conditions of handmade Hanji paper to reduce the time required for measurement while meeting folding endurance standards, for various basis weights. Thirteen types were selected, including 12 types of Hanji with grammages of 17 g/m², 30 g/m², and 45 g/m², and one type of 75 g/m² copy paper, and 24 sheets were prepared in the laid and chain directions. Subsequently, folding endurance experiments at different load (14.72 N, 9.81 N, 4.91 N) and specimen width conditions (15 mm, 10 mm, 5 mm) were performed, using a 4-MIT folding endurance tester. The results showed that, for specimen widths of 15 mm and 10 mm under a load of 4.91 N, the folding endurance falls within the reference range (10~10000 times). In particular, reduced folding endurance range and measurement time were observed at a width of 10 mm under a load of 4.91 N. Moreover, the endurance trend lines based on the average values of load and specimen width ranges enabled the prediction of the folding endurance within those ranges, according to the decreasing slope. Furthermore, for a specimen width of 15 mm under a load of 4.91 N, the folding endurance in the comparison group (35 to 17723 times) significantly exceeds the upper limit of the reference range (10~10000 times). Therefore, the measurement conditions of 4.91 N with a specimen width of 10 mm are proposed.

• International Journal of Highway Engineering
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• v.8 no.3 s.29
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• pp.143-153
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• 2006

The differences in the stress distribution and the critical stresses in concrete pavement systems were analyzed when the dual-wheel single-, tandem-, and tridem-axle loads were applied at the interior and the edge of the pavement. The effects of the concrete elastic modulus, slab thickness, foundation stiffness, and tire contact pressure were investigated. The stresses under the interior loads were calculated using the transformed field domain analysis and stresses under the edge loads were obtained using the finite element method. The critical stresses under the interior and the edge loads were compared with respect to various parameters and the equations to predict the ratio between the stresses under the edge and the interior loads were developed and verified. From this study, it was found that the trends of the changes in the critical concrete stresses under the interior and the edge loads were very similar and the critical stress locations under those loads were identical. The critical stress ratio, which was obtained by dividing the critical stress under the edge loads into that under the interior loads, decreased with increasing the number of axles. That ratio became larger as the concrete elastic modulus increased, the slab thickness increased, the foundation stiffness decreased, and the tire contact pressure increased.

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.271-279
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• 2003

Many researches have been conducted to describe the elastic and inelastic behavior of H-shaped beams with web openings, and were generally concentrated on the uniaxial loading conditions. With previous research results, the formulae for the design of beams with web openings, considering local buckling, have been proposed by Darwin. Although the formulae are so simple and useful to apply to real situations, it needs more research on cyclic loading conditions. In this experimental study, a total of seven H-shaped beams with circular web openings under cyclic loading conditions were investigated. The dimension criteria were based on the formulae proposed by Darwin. The suitability of the existing design formulae, the effects of plastic hinges on beams with web openings, and the local bucking around the web openings to the beam strength under cyclic loading were also investigated through by the observations of the behavior of these beams with various dimensional openings.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.137-146
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• 2010

This study was conducted to develop the design methodology of gap slabs for the post-tensioned concrete pavement (PTCP). The gap slabs were considered as unbonded, half bonded, and bonded types. According to the types of the gap slabs, the curling stresses were investigated first under the environmental loads. The stresses due to the vehicle loads were analyzed considering both the single and tandem axles. The method to calculate the prestressing amount was suggested by comparing the combined stresses due to both loads and the allowable tensile stress of concrete. The prestressing amount for the unbonded type gap slab could be designed by considering only the gap slab; however, for the half bonded and bonded gap slabs, the whole PTCP slab should be analyzed to properly design the prestressing amount.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.37-44
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• 2023

In this study, the performance of the support modular system, as substructure of the proposed sustainable-perpetual modular road system to reduce road construction time and maintenance costs was evaluated. A modular road system consisting of 4 support modular cross-beams with a lower curved surface was constructed on the test-bed. Six load cells and eight LVDTs were installed in the center part of two cross-beam support modular systems. Two loads, 50kN and 100kN, were applied to 15 points on the pavement slab to measure the load and displacement occurring in the modular road system. The measured displacements were less than 1 mm, so it is considered that there was no problem in the stability of the actual road. When comparing the two applied loads and the measured loads in the field test, it was considered that the load transmitted to the ground under the support modular system is very small. It is considered that the modular road system with the support modular system is applicable to the actual road site.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.566-567
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• 2011

본 논문에서는 500kV급 composite bushing에 사용되는 FRP tube 및 금구류에 대하여 풍하중에 대한 강도안전성을 평가하였다. 제품의 평가는 유한요소법을 이용한 구조해석을 진행하였으며, 해석 결과 풍하중에 대하여 충분한 강도 안전성 및 안전율을 가지고 제품이 설계된 것으로 나타났다. 따라서 본 연구에서 제시한 결과를 바탕으로 composite bushing은 강도안전성 측면에서 신뢰성 있는 제품으로 개발이 이루어지고 있음을 확인할 수 있으며, 향후 유한요소법을 이용한 해석을 통해 제품 개발 기간의 단축과 소비자에게 보다 향상된 품질을 보증하는데 기여할 수 있을 것으로 사료된다.

• Journal of the Korean Ceramic Society
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• v.38 no.6
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• pp.575-581
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• 2001

세라믹/금속기지 복합재료에서 횡방향의 단축인장하중을 받는 경우, 복합재료의 특성에 관한 시뮬레이션 결과이다. 세라믹과 금속기지간 계면에 강한 결합이 존재하는 복합재와, 계면에서의 결합이 약한 복합재의 두 경우에 대하여 횡방향 평균응력과 평균변형율에 대한 관계를 계산하였다. 복합재료의 미시역학적개념과 유한요소해석법을 적용하여 세라믹체적분율의 변화에 따라 각기 해석되었다. 본 연구에서 계산된 횡방향 탄성계수는 문헌에 알려져 있는 미시역학개념으로 유도된 식에 의한 횡방향탄성계수값과 잘 일치되었다. 계면에서 강한 결합이 있는 복합재와는 달리, 약한 결합의 복합재는 인장하중에 의하여 세라믹/금속계면에서 금속재료와 세라믹간의 분리가 발생된다. 이 분리는 전체복합재의 강성을 감소시키며, 금속의 부피분율이 감소될수록 (즉, 세라믹의 부피분율이 증가할수록) 횡방향 평균응력의 평균변형율에 대한 감소로 나타났다. 미시역학의 개념을 적용한 유한요소해석기법을 통하여, 이미 알고 있는 복합재 각 성분의 특성으로부터 복합재료의 계면특성과 횡방향특성을 예측할 수 있다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.411-418
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• 1992

본 연구에서는 인장하중을 받는 균열이 없는 박판 시험편과 45˚경사균열시험 편의 고유진동수 측정을 위하여 레이저 홀로그래피법을 이용하여 진동모드 측정을 하 여 그 결과를 비교분석하는 실험방법을 택하였으며, 균열이 없는 박판에 대해서만 무 차원하중의 증가에 따른 고유 진동수의 변화관계를 실험치와 Ritz Method에 의한 유한 요소 해석치와 비교하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.43-43
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• 2002

인공위성은 일반적으로 추력기(thruster)에서 플룸(plume)을 거의 진공에 가까운 외부환경으로 사출하여 자세를 제어한다. 이 때, 사출되는 플룸에 의해 위성체의 고도에 영향을 줄 수 있는 교란추력/교란토크, 열하중(thermol loading), 정밀계측장비에 영향을 주는 오염(contamination) 등, 여러 부정적인 효과들이 야기될 수 있으며, 이들 효과들은 결론적으로 위성체의 수명을 단축하기 때문에 이들에 대한 정확한 예측은 위성체 설계단계에서 매우 중요하다.