• International Journal of Naval Architecture and Ocean Engineering
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• 제8권5호
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• pp.487-495
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• 2016

In the offshore project such as semi-submersible FPU and FPSO, the free fall type life boat called TEMPSC (Totally Enclosed Motor Propelled Survival Craft) has been installed for the use of an emergency evacuation of POB (People on Board) from the topside platform. For the design of life boat arrangement for semi-submersible FPU in the initial design stage, the drop height and launch angle are required fulfill with the limitation of classification society rule and Company requirement, including type of approval as applicable when intact and damage condition of the platform. In this paper, we have been performed the numerical studies to find proper arrangement for the life boats consider drop height in various environmental conditions such as wave, wind and current. In the calculations, the contributions from static and low frequency (LF) motions are considered from the hydrodynamic and mooring analysis as well as damage angle from the intact and damage stability analysis. Also, Air-gap calculation at the life boat positions has been carried out to check the effect on the life boat arrangement. The air-gap assessment is based on the extreme air-gap method includes the effect of 1st order wave frequency (WF) motions, 2nd order low frequency roll/pitch motion, static trim/heel and set down.

• Steel and Composite Structures
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• 제33권3호
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• pp.433-444
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• 2019

Fatigue failure of a grid structure using bolt-sphere joints is liable to occur in a high-strength bolt due to the alternating and reciprocal actions of a suspension crane. In this study, variable amplitude fatigue tests were carried out on 20 40 Cr steel alloy M30 high-strength bolts using an MTS fatigue testing machine, and four cyclic stress amplitude loading patterns, Low-High, High-Low, Low-High-Low, and High-Low-High, were tested. The scanning electron microscope images of bolt fatigue failure due to variable amplitude stress were obtained, and the fractographic analysis of fatigue fractures was performed to investigate the fatigue failure mechanisms. Based on the available data from the constant amplitude fatigue tests, the variable amplitude fatigue life of an M30 high-strength bolt in a bolt-sphere joint was estimated using both Miner's rule and the Corten-Dolan model. Since both cumulative damage models gave similar predictions, Miner's rule is suggested for estimating the variable-amplitude fatigue life of M30 high-strength bolts in a grid structure with bolt-sphere joints; the S-N fatigue curve of the M30 high-strength bolts under variable amplitude loading was derived using equivalent stress amplitude as a design parameter.

• 동력기계공학회지
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• 제21권1호
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• pp.43-49
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• 2017

This work aims to investigate on the low cycle fatigue life assessment, which is adopted on the strain-life relationship, or better known as the Coffin-Manson relationship, and also the strain energy density-based model. The low cycle fatigue test results of Alloy 617 weldments under $900^{\circ}C$ have been statistically estimated through the Coffin-Manson relationship according to the provided strain profile. In addition, the strain energy density-based model is proposed to represent the energy dissipated per cycle as fatigue damage parameter. Based on the results, Alloy 617 weldments followed the Coffin-Manson relationship and strain energy density-based model well, and they were compatible with the experimental data. The predicted lives based on these two proposed models were examined with the experimental data to select a proper life prediction parameter.

• 전기학회논문지
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• 제63권2호
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• pp.325-330
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• 2014

In order to operate trains both mainline railroad platform and metropolitan subway line platform, it is necessary to develop the door step equipment of the rolling stock regardless of low(500mm, mainline) and high level platforms(1,135mm, metropolitan subway line) because of the requisite door safety system. In this study, TMS-DCU interface is studied for low and high level railway platforms. As a result, Design circuit of TMS(Train Management System)-DCU(Door Control Unit) interface is suitable for telescopic sliding type doorstep unit to minimize damage to the carbody underframe of railway vehicles.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.28-31
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• 2023

This study presents a comprehensive procedure for the low cycle fatigue test of ultrasonically welded (UW) coated conductor (CC) lap-joints. The entire process is examined in detail, from the robust fabrication of the UW REBCO CC joints to the reliability testing under a low number of repeated cycle fatigue conditions. A continuous I_c measurement system enables real-time monitoring of I_c variations throughout the fatigue tests. The study aims to provide a step-by-step procedure that involves joint fabrication, electromechanical property (EMP) tests under uniaxial tension for stress level determination, and subsequent low-cycle fatigue tests. The joints are fabricated using a hybrid method that combines UW with adding In-Sn soldering, achieving a flux-free hybrid welding approach (UW-HW flux-free). The selected conditions for the low cycle fatigue tests include a stress ratio of R=0.1 and a frequency of 0.02 Hz. The results reveal some insights into the fatigue behavior, irreversible changes, and cumulative damage in the CC joints.

• 한국지반환경공학회 논문집
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• 제14권3호
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• pp.35-40
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• 2013

일반적으로 동결대상지역에 설치되는 지반구조물은 동결피해에 대한 별도의 대책을 필요로 한다. 그러나 국내의 경우 터널, 옹벽 등과 같은 지반구조물에 대한 동결피해 조사 및 사례보고가 거의 이루어지지 않고 있어, 이를 저감시키기 위한 연구는 매우 미미한 실정이다. 이러한 이유로 국내의 구조물 관련 설계기준도 특별하게 이를 규정화하고 있지 않다. 본 연구에서는 터널, 비탈면, 옹벽의 동결피해에 대한 현장조사 및 1종, 2종 시설물에 대한 약 40여 년간의 지반구조물 유지관리 이력을 분석하여 구조물 설치지역의 기온에 따른 구조물의 유지관리 특성을 파악하였다. 그 결과 우리나라에서 동결깊이가 약 120cm 이상이고, 기온이 비교적 낮은 강원 산간지역 및 강원 북부, 경기 북부지역의 지반구조물은 기온이 비교적 따뜻한 타 지역과 달리 훨씬 더 오랫동안 보수보강을 필요로 하는 것으로 분석되었다. 이로부터 국내 동결피해 대상지역에 설치되는 구조물에 대한 설계기준 개정의 필요성을 제안하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2979-2986
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• 2011

In this study, we review all matters for system application based on the international and the domestic standards. Considering the minimization of bottom frame damage, ease of maintenance, withstanding-environmental performance (condensation or rain), maintenance of airtightness, customer convenience and safety issues in railway vehicle, the conceptual design for doorstep equipment for both the low and the high level platforms is carried out. On the basis of conceptual design, the prototype is manufactured. We perform the vibration test based on the international standard IEC-61373 for securement of the reliability and enhancement of design & production. Finally we would like to describe the test results.

• 한국터널지하공간학회 논문집
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• 제25권2호
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• pp.157-173
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• 2023

본 현장은 265 m 구간이 무진동 굴착공법으로 설계되어 있지만 시공성과 경제성의 저하가 우려된다. 이러한 이유로 미진동 전자발파공법이 제안되었다. 미진동 전자발파의 적용성 평가를 위해서 본 현장 직전 적용하였던 미진동 전자발파(제안 I)와 본 현장과 같이 지하철 근거리에서 시공된 미진동 전자발파(제안 II)의 발파진동 영향범위를 분석하였다. 두 제안의 발파진동 영향범위 비교결과, 제안 II의 영향범위가 더 보수적으로 산출되었다. 본 현장의 근거리라는 특수성을 고려할 때, 보다 안전한 시공을 위해 설계변경에 제안 II를 선정하였다. 결과적으로 무진동 굴착구간 265 m 구간 중 72 m 구간에 대하여 미진동 전자발파공법으로 변경하여도 구조물에 미치는 영향이 없을 것으로 예측된다. 그리고 총 예상 굴진 소요 기간 662.5일에서 144일 단축할 수 있기 때문에 높은 경제적 이익을 얻을 수 있다고 평가된다.

• 한국정밀공학회지
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• 제18권11호
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• pp.93-100
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• 2001

Brittle materials are very weak for impact because of typical characteristics which happen to be easily fractured with low fracture toughness and crack sensitivity. When brittle materials are subjected to impact due to small spheres, high contact pressure is occurred to impact surface and then local damage on specimen is developed, since there are little plastic deformations due to contact pressure compared to metals. This local damage is a dangerous factor which gives rise to final fracture of structures. In this research, the crack propagation process of soda lime glass by impact of small sphere is explained and the effects of the constraint conditions of impact spheres and materials for the material damage were studied by using soda-lime glass. that is the effects for the materials and sizes of impact ball, thickness of specimen and residual strength. Especially, this research has focused on the damage behavior of ring crack, cone crack and several kinds of cracks.

• 반도체디스플레이기술학회지
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• 제10권4호
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• pp.113-118
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• 2011

According to the high accuracy of semiconductor equipments, PCB substrate with much thin thickness is required. However, it is very difficult to sustain the PCB substrate without deformation in case of horizontal installation, due to low bending stiffness. In this research, new PCB process equipment with vertical installation has been developed in order to solve the problem of PCB substrate damage during etching process. As the main parts of etching system on PCB substrate, PCB substrate and JIG are analyzed through finite element method and experimental test. Through the analysis results of stress state, we could find the optimal JIG design to make the damage as low as possible.