• 한국기계가공학회지
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• 제21권7호
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• pp.98-104
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• 2022

Circular sawing and milling are general machining processes used for routing fiber-reinforced plastics (FRP). In this study, the productivity and cutting quality of a circular saw and flat endmill were compared. As a result, the productivity of the circular saw was approximately ten times higher than that of the endmill for the same tool life, and the burr size of the circular saw was 14 times smaller than that of the flat-end mill. The spectrogram analysis of the cutting sound also showed that the acoustic emission of the circular saw was more uniform than that of the flat end mill. Circular sawing is thus a more suitable process for the straight cutting of pultrusion FRP than a flat endmill.

• 한국초전도ㆍ저온공학회논문지
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• 제9권1호
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• pp.61-66
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• 2007

A transmission class high-temperature superconducting(HTS) power cable system is being developed in Korea. For insulation design of this cable the grading method of insulating paper is proposed. Two kinds of laminated polypropylene paper that has different thickness has been used as the electrical insulation material. The use of graded insulation gives improved mechanical bending properties of the cable. In a HTS cable technology the terminations are important components. A HTS cable termination is energized with the line-to-ground voltage between the coaxial center and outer surrounding conductors. in the axial direction. There is also a temperature difference from ambient to about 77 K. For insulation design of this termination, glass fiber reinforced plastic(GFRP) was used as the insulation material of the termination body, and the capacitance-graded method is proposed. This paper will report on the experimental investigations on impulse breakdown and surface flashover characteristics of the insulation materials for insulation design of a transmission class HTS power cable and termination. Based on these experimental data, the electrical insulation design of a transmission class HTS power cable and termination was carried out.

• 한국초전도ㆍ저온공학회논문지
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• 제8권1호
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• pp.65-70
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• 2006

Transient heat transfer caused by an impulsive heating in subcooled liquid nitrogen is investigated experimentally. This study is part of out ongoing efforts directed to a stable cryogenic cooling system lot superconducting fault current limiters (SFCL). A thin heater attached by epoxy on one surface of a GFRP plate is immersed in liquid-nitrogen bath at temperatures between 77 K and 55 K. A strong heat flux up to $150W/cm^2$ is generated lot 100 ms, and the temperature of the heater sulfate is measured as a function of time. The behavior of bubbles on the heating surface can be explained by comparing the measured temperature history for vertical and two horizontal (up and down) orientations. It is concluded that the subcooling of liquid nitrogen below 70 K is very effective in suppressing bubbles, resulting in better thermal protection and faster recovery from an impulsive heat.

• Composites Research
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• 제22권2호
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• pp.14-17
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• 2009

접착제에 의한 접합기술은 다양한 목적과 환경에서 널리 사용되는 방법이다. 그 중 우레탄 접착제는 액화천연가스 운반선과 같이 극저온에서 사용되는 환경에서의 접착에 사용되고 있다. 현장 적용에 있어, 본 접착제를 사용시 경화된 접착제 층의 기공들이 발생하게 된다. 본 연구에서는 우레탄 접착제와 Triplex 복합재료 접착에 있어 인공적으로 기공을 제작 삽입 후 전단응력 (Single Lap Shear) 시험을 실시하여 그 영향을 검토하였다. 실험 결과 접착력은 본 시험에서 적용한 기공의 크기 및 위치에 영향을 받지 않는다는 것을 확인하였다.

• Journal of the Korean Wood Science and Technology
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• 제51권6호
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• pp.458-469
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• 2023

Text mining techniques provide valuable insights into research information across various fields. In this study, text mining was used to identify research trends in wood science from 2012 to 2022, with a focus on representative journals published in Korea and Japan. Abstracts from Journal of the Korean Wood Science and Technology (JKWST, 785 articles) and Journal of Wood Science (JWS, 812 articles) obtained from the SCOPUS database were analyzed in terms of the word frequency (specifically, term frequency-inverse document frequency) and co-occurrence network analysis. Both journals showed a significant occurrence of words related to the physical and mechanical properties of wood. Furthermore, words related to wood species native to each country and their respective timber industries frequently appeared in both journals. CLT was a common keyword in engineering wood materials in Korea and Japan. In addition, the keywords "MDF," "MUF," and "GFRP" were ranked in the top 50 in Korea. Research on wood anatomy was inferred to be more active in Japan than in Korea. Co-occurrence network analysis showed that words related to the physical and structural characteristics of wood were organically related to wood materials.

• 대한기계학회논문집A
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• 제37권2호
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• pp.199-204
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• 2013

최근 차량 경량화를 통한 에너지 절감을 위해서 무거운 철강재료를 경금속이나 복합재료로 대체하는 연구가 많이 진행되고 있다. 이중, 폴리머 기반의 복합재료는 사출성형을 통해서 복잡한 형상의 제작이 가능하고, 유리섬유나 탄소섬유를 함께 사용하여 철강재료 수준으로 기계적 물성을 높일 수 있는 장점이 있다. 하지만 엔진의 고온과 우기에서의 높은 습도 환경은 폴리머의 기계적 물성을 낮추기 때문에 재료선택 과정에서 반드시 고려해야 한다. 본 연구에서는 사출성형을 통해 만들어진 유리섬유강화플라스틱을 엔진룸 내부 온도와 유사한 $85^{\circ}C$ 환경과 우기시의 최대 수분흡수 환경하에서의 기계적 물성변화를 인장시험을 통해 알아보았다. 그 결과, 고온환경에서 최대인장강도가 약 23% 감소를 보였고, 수분에 의해서는 약 30% 감소하였으며, 고온과 수분 모두에 대해서는 약 70% 감소를 확인하였으며 이는 재료 선정시 반드시 고려해야 할 영향으로 판단되었다.

• 한국인터넷방송통신학회논문지
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• 제11권2호
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• pp.35-40
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• 2011

본 논문에서는 복합재 샌드위치 구조를 가지는 이중대역(1.575, 2.645 GHz) 안테나의 충격 및 굽힘 특성에 관하여 연구하였다. 평면형 안테나에 복합재료인 Carbon Fiber Reinforced Plastic, Glass Fiber Reinforce Plastic을 접착하여 기계적 성능을 향상시킬 수 있다. 시험 규격 ASTM D7137에 따라 충격 시험과 시험규격 ASTM C393, MIL-STD401B에 따라 굽힘 시험을 실시한 후, S11 및 이득 측정을 통하여 안테나의 전기적 성능과 기계적 성능을 확인하였다. 제안된 안테나는 복합재료 보강 전보다 약 4배인 충격 하중 4 kN, 약 2배인 400 N의 굽힘 하중을 견디며, GPS, DMB 대역에서 6 dBi, 4.6 dBi의 이득을 가진다. 복합재 샌드위치 구조는 구조체 또는 운송체 표면에 적용 가능함을 확인하였다.

• Steel and Composite Structures
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• 제35권5호
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• pp.641-657
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• 2020

A unique lightweight string truss deployable bridge assembled by thin-walled fiber reinforced polymer (FRP) and metal profiles was designed for emergency applications. As a new structure, investigations into the static structural performance under the serviceability limit state are desired for examining the structural integrity of the developed bridge when subjected to unsymmetrical loadings characterized by combined torsion and bending. In this study, a full-scale experimental inspection was conducted on a fabricated bridge, and the combined flexural-torsional behavior was examined in terms of displacement and strains. The experimental structure showed favorable strength and rigidity performances to function as deployable bridge under unsymmetrical loading conditions and should be designed in accordance with the stiffness criterion, the same as that under symmetrical loads. In addition, a finite element model (FEM) with a simple modeling process, which considered the multi segments of the FRP members and realistic nodal stiffness of the complex unique hybrid nodal joints, was constructed and compared against experiments, demonstrating good agreement. A FEM-based numerical analysis was thereafter performed to explore the effect of the change in elastic modulus of different FRP elements on the static deformation of the bridge. The results confirmed that the change in elastic modulus of different types of FRP element members caused remarkable differences on the bending and torsional stiffness of the hybrid bridge. The global stiffness of such a unique bridge can be significantly enhanced by redesigning the critical lower string pull bars using designable FRP profiles with high elastic modulus.

• 콘크리트학회논문집
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• 제15권1호
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• pp.78-86
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• 2003

섬유보강재를 사용한 철근콘크리트 부재의 보강공법은 재료의 내부식성 및 시공의 편리성 등 여러 가지 장점으로 인하여 최근 그 사용이 현저하게 증가하고 있는 실정이다. 본 연구에서는 여러 가지 종류의 섬유보강재를 사용하여 휨보강된 철근콘크리트 보의 휨성능을 비교하고, 그 특성을 고려한 보강설계식을 제안하였다. 섬유보강재의 종류(아라미드, 유리, 탄소섬유) 및 보강비에 따른 철근콘크리트 보의 휨성능을 검토하기 위하여 3.2m 스팬의 단순보에 대한 실험을 실시하였으며, 실험의 결과를 최대내력, 강성 및 연성도의 관점에서 분석하였다. 본 연구의 실험결과, 부재의 휨보강내력은 보강재의 종류에 따른 인장강도보다는 강성에 주로 관계하는 것으로 나타났으며, 연성도는 강성이 증가할수록 감소하는 경향을 나타내었다. 본 연구에서는 이와 같은 실험결과를 기반으로 휨보강설계식을 제안하였으며, 이를 신뢰성있는 선행 연구자들의 연구결과와 비교하여 그 타당성을 검증하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제5권3호
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• pp.34-37
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• 2003

A 1 MVA single-phase high temperature superconducting (HTS) transformer with BSCCO-2223 wire was designed in this paper. The rated voltages of each sides of the transformer are 22.9 kV and 6.6 kV respectively. Double pancake HTS windings arranged reciprocally will be used for the transformer windings, because of the advantages of insulation and distribution of surge voltage in case of a large power and high voltage transformer. Single HTS wire was used for the primary windings and four parallel wires were used for the secondary windings of the transformer with transposition. A core of the transformer was designed as a shell type core separated with the windings by a cryostat made of GFRP with a room temperature bore. The operating temperature of the HTS windings will be about 65K with sub-cooled liquid nitrogen. A cryogenic cooling system using a GM-cryocooler for this HTS transformer by natural convection of liquid nitrogen was designed. This type of cooling system can be a good option for compactness, efficiency, and reliability of the HTS transformer.