• 소성∙가공
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• 제17권4호
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• pp.292-301
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• 2008

Type 2 compressed natural gas(CNG) storage vessels for automobiles are becoming widely used. They are not only supplied to automakers in Korea, such as Hyundai Motors, but increasingly, they are being exported overseas. Autofrettage is a process that produces beneficial residual stresses in a vessel by subjecting it to excessive internal pressure. This strengthens the vessel and improves its fatigue resistance. This paper presents research investigating the autoftettage process and residual stresses it produces in type 2 CNG storage vessels. A finite element analysis technique and a closed form equation are used. Then, fatigue resistance is analyzed through a fatigue evaluation performed according to ASME section VIII.

• 한국지반공학회지:지반
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• 제2권3호
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• pp.15-26
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• 1986

말뚝박기에서 항타지지력을 추정하기 위하여 수많은 항타공식이 널리 사용되고 있으나 말뚝의 지지력은 해머-말뚝-지반토의 복잡한 상호작용에 의하여 변화하기 때문에 어느 공식이 현장조건에 가장 적합한 공식이라 판단하기는 매우 어렵다. 본 연구에서는 파동이론과 말뚝의 잔류응력에 의하여 항타지지력을 해석하므로서 현장에서 간편하게 추정할 수 있는 신뢰도가 높은 산출식을 유도하여 이를 고찰하였다.

• 한국공간구조학회논문집
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• 제19권3호
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• pp.77-83
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• 2019

AU(A plus U-shaped) composite beam was developed for reducing the story height in the residential buildings, and saving the cosrtuction cost of floor structures. Structural performance and economic feasibility of the composite beam have been sufficiently approved through the structural experiments and the analytical studies. Fire safety for the practical application of the composite beam has also been verified through the fire resistance tests and the heat transfer analyses. In this study 2-points bending tests were performed on the four specimens already tested for fire resistance to evaluate the residual bending strength of AU composite beam after fire accident. The same bending test was performed on the one fresh specimen having the same section and span of the specimens for practically comparative study.

• 대한건축학회논문집:구조계
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• 제35권3호
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• pp.35-41
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• 2019

In this study, the fire resistance performance of polymer cement mortars which are used as a representative repair material for section restoration, is evaluated and residual bond strength is measured by considering unity with concrete. According to the evaluation of fire resistance performance of re-emulsification type polymer cement mortars, residual compressive strength was drastically decreased according to heating temperatures with an increase of polymer addition rate, and this seems to be attributable to the application of polymer film. In addition, an explosion phenomenon occurred frequently with an increase of addition rate, so this should be considered when selecting repair materials and processing.

• 센서학회지
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• 제4권4호
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• pp.29-40
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• 1995

본논문(本論文)에서는 정전유도(靜電誘導) 트랜지스터의 잡음원인분석(雜音原因分析)을 위하여 직류(直流) 및 잡음특성(雜音特性), 잔존성분(殘存成分), 입력용량등(入力容量等)의 정무화(定武化)에 필요(必要)한 잡음(雜音) 등가회로(等價回路)를 제안(提案)하였다. 가장 단순(單純)한 잡음(雜音) 등가회로(等價回路)는 정전유도(靜電誘導) 트랜지스터의 동작원리(動作原理)에 의한 모델이며, 이 모델에 의한 실측치(實測値)가 산탄(shot) 잡음(雜音)보다 작게 나타났다. 소스 저항(抵抗)이 삽입(揷入)된 등가회로(等價回路)에서는 소스 저항(抵抗)의 부귀환효과(負歸還效果)에 의하여 산탄 잡음(雜音)이 저감(低減)됨을 확인(確認)하였다. 정확(正確)한 잡음저감원인(雜音低減原因)을 분석(分析)하기 위하여 소스 저항(抵抗)과 드레인 저항(低抗)의 계산식(計算式)을 유도(誘導)하기 위한 등가회로(等價回路)를 제안(提案)하였다. 등가회로(等價回路) 확인(確認) 실험(實驗)에서는 잔존성분(殘存成分)에 대한 신호원저항(信號源抵抗)과 출력부하저항(出力負荷抵抗)의 영향(影響)은 작으며, 잔존성분(殘存成分)은 입력환산등가잡음저항(入力換算等價雜音抵抗)으로 나타낼 수 있다. 또한, 입력용량(入力容量)은 부하저항(負荷抵抗)이 $0{\Omega}$일 때 13.6pF이며, 게이트 배선등(配線等) 정전유도(靜電誘導) 트랜지스터 동작(動作)에 직접(直接) 관여(關與)하지 않는 용량(容量)은 10pF정도(程度)이다.

• Geomechanics and Engineering
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• 제8권1호
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• pp.53-66
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• 2015

Plastic wastes, particularly polyethylene terephthalate (PET) generated from used bottled water constitute a worldwide environmental issue. Reusing the PET waste for geotechnical applications not only reduces environmental burdens of handling the waste, but also improves inherent engineering properties of soil. This paper investigated factors affecting shear strength improvement of PET-mixed residual soil. Four variables were considered: (i) plastic content; (ii) plastic slenderness ratio; (iii) plastic size; and (iv) soil particle size. A series of unconfined compression tests were performed to determine the optimum configurations for promoting the shear strength improvement. The results showed that the optimum slenderness ratio and PET content for shear strength improvement were 1:3 and 1.5%, respectively. Large PET pieces (i.e., $1.0cm^2$) were favorable for fine-grained residual soil, while small PET pieces (i.e., $0.5cm^2$) were favorable for coarse-grained residual soil. Higher shear strength improvement was obtained for PET-mixed coarse-grained residual soil (148%) than fine-grained residual soils (117%). The orientation of plastic pieces in soil and frictional resistance developed between soil particles and PET surface are two important factors affecting the shear strength performance of PET-mixed soil.

• 한국정밀공학회지
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• 제27권2호
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• pp.94-101
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• 2010

Composite materials have a higher specific strength and modulus than traditional metallic materials. Additionally, these materials offer new design flexibilities, corrosion and wear resistance, low thermal conductivity and increased fatigue life. These, however, are susceptible to impact damage due to their lack of through-thickness reinforcement and it causes large drops in the load-carrying capacity of a structure. Therefore, the impact damage behavior and subsequently load-carrying capacity of impacted composite materials deserve careful investigation. In this study, the residual strength and impact characteristics of plain-woven CFRP composites with impact damage are investigated under axial tensile test. Impact test was performed using drop weight impact tester. And residual strength behavior by impact was evaluated using the caprino model. Also we evaluated behavior of residual strength by change of mass and size of impactor. Examined change of residual strength by impact energy change through this research and consider impactor diameter in caprino model.

• Corrosion Science and Technology
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• 제17권4호
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• pp.176-182
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• 2018

Corrosion of the Cu alloy with 10wt% Ni in stagnant seawater with residual free chlorine was investigated. Despite that fact that Cu alloys are widely used for seawater applications due to their stubborn resistance to chloride attack, not much is known as to how the residual free chlorine in seawater affects corrosion of Cu and its alloys. In this work, immersion tests were conducted in the presence of different levels of chlorine for 90-10 Cu-Ni samples, one of the most frequently used Cu alloys for seawater application, mostly in shipbuilding. The results revealed no evidence for accelerated corrosion of the Cu-Ni alloy even in the presence of 5 ppm residual chlorine in seawater, signifying that the Cu-Ni alloy can be more tolerant to residual chlorine that has been commonly cited by the shipbuilding industry. However, comparison of polarization behavior of the alloy samples in the presence of different electrolytes with different concentrations of residual chlorine suggests that higher concentration of chlorine could increase the corrosion rate of the Cu-Ni alloy. Furthermore, it is suggested that microorganisms in the seawater could increase the corrosion rate of the Cu-Ni alloy by encouraging exfoliation of the corrosion product off the metal surface.

• 한국해양공학회지
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• 제10권2호
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• pp.106-119
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• 1996

The ceramic has various high mechanical properties such as heat, abrasion, corrosion resistance and high temperature strength compared with metal. It also has low speciffic weight, low thermal expansibillity, low thermal conductivity. However, it could not be used as structural material since it is brittle and difficult for the machining. Therefore, there have been many researches to attempt to join ceramic with metal which is full of ductillity in order to compensate the weakness of ceramic.The problem is that residual stress develops around the joint area while the ceramic/metal joint material is cooled from high joining temperature to room temperature due to remarkable difference of thermal expansion coefficients between ceramic and metal. Especially, the residual stress at both edges of the specimen reduces the strngth of joint to a large amount by forming a singular stress field. In this study, two dimensional finite element method is attempted for the thermal elastic analysis. The joint residual stress of ceramic/metal developed in the cooling process is investigated and the change of joint residual stress resulted from the repetitive heat cycle is also examined. In addition, it is attempted to clarify the joint stress distribution of the case of tensile load and of the case of superposition of residual stress and actual loading stress.

• 한국지반공학회논문집
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• 제20권1호
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• pp.75-82
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• 2004

본 연구에서는 지지대상층이 아닌 투수 대상층으로서의 풍화토 지반에 초점을 맞추어 불교란 풍화토 시료를 이용해 다양한 구속압 조건에서 동수경사를 변화 시켜가면서 연성벽체 투수시험을 수행하였다. 동수경사 및 구속압이 풍화토의 투수특성에 미치는 영향을 투수계수를 이용하여 분석하였으며, 사질토에 대해서도 유사한 시험을 수행하여 사질토와는 구별되는 풍화토만의 침투 특성을 평가하였다. 또한 풍화토 지반의 파이핑 특성을 분석하기 위하여 모형 파이핑 시험을 수행하였다. 실험결과로부터 동수경사의 범위에 따라 풍화토는 서로 다른 투수특성을 보임을 알 수 있으며, 파이핑에 대하여 사질토에 비해 매우 높은 저항 능력을 가짐을 알 수 있었다.