• 대한기계학회논문집A
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• 제20권3호
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• pp.753-764
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• 1996

The metal matrix composites(MMC) are currently receiving a great deal of attention. These composites possess exellent mechanical and physical properties such as modulus, strength, wear resistance and thermal stability, which make them very attractive for use in automotive piston. In this study, $Al/{Al_2}{O_3}$(15%) composites are fabricated by the squeeze casting method. Mechanical properties such as tensile strength and ductility are performed at room and elevated temperature($250^{\circ}C$ and $350^{\circ}C$), respectively. Through thermomechanical analyser, thermal expansion coefficient of $Al/{Al_2}{O_3}$ composites are conducted for ranging from room temperature to ($400^{\circ}C$.And bending fatigue tests are also performed by the rotary bending machine at room temperature.The tensile strength and elastic modulus have been improved up to 38% and 35% by the addition of the reinforcements, respectively. Thermal expansion coefficients of MMCs which is located normal and parralel to the applied pressure are showed slightly different less than 10%. Fatigue strengh of the composite was improved by about 20% compared with that of unreinforced Al alloy. The results of this study will be used to understand the basic fracture behavior of MMCs and eventually to expand the applocation of MMCs as a machine parts undertaken various loadings.

• Composites Research
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• 제27권2호
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• pp.52-58
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• 2014

사출 성형을 통해 제조된 단섬유 강화 복합재는 사출 성형 중 발생하는 수지 유동으로 인해 동일 시편 내에서도 다양한 섬유 배향을 갖는다. 이러한 섬유의 배향은 최종 복합재의 기계적, 열적 특성에 많은 영향을 주므로, 본 연구에서는 사출 성형된 탄소단섬유 강화 PA6/PPO 복합재의 섬유 배향을 광학 현미경 분석을 통하여 측정하고 섬유의 배향이 복합재의 충격강도 및 열팽창 계수에 미치는 영향을 분석하였다. 충격강도의 경우에 섬유의 배향이 크랙이 전파되는 방향에 수직으로 배향되어 있을수록 더 높은 충격강도를 보였으며, 이는 섬유의 배향에 따른 충격내성 강화 메커니즘과 밀접한 연관성을 보여주었다. 열팽창 계수의 경우에는 섬유가 열팽창률을 측정하는 방향과 동일한 방향으로 배향되어 있을수록 더 낮은 열팽창계수를 보였으며, 이 결과 역시 섬유의 배향이 열팽창 특성에 미치는 메커니즘과 밀접한 연관성을 보였다.

• 한국분말재료학회지
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• 제19권4호
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• pp.253-258
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• 2012

The characteristics of $Al_2TiO_5$ ceramics were influenced by the additives and the heat treatment that controls the microcrack behavior at grain boundaries. The effect of additives on $Al_2TiO_5$ ceramics were investigated in terms of mechanical properties and thermal expansion at high temperature. The $Al_2TiO_5$ were synthesized at $1500^{\circ}C$, $1550^{\circ}C$ and $1600^{\circ}C$ for 2h by reaction sintering. The formation of $Al_2TiO_5$ phase was increased by additives that enhanced the volume of the microcrack that can lead to low thermal expansion. The mechanical properties of the stabilized $Al_2TiO_5$ ceramics were increased remarkably at $1100^{\circ}C$, $1200^{\circ}C$ and $1300^{\circ}C$ due to the oneset of mechanical healing of grain-bondary microcracks at a high temperature. The amount of microcrack was decreased at lower sintering temperature that causes the increase of mechanical properties at high temperature.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.182-182
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• 2010

The behavior of properties of ion exchanged substrate glasses was investigated in this study. In order to study the effects of ion exchange, ion exchange behavior with ion penetration depth, amount of ion exchange, density and thermal expansion was measured according to the time and temperature. The mechanical properties were evaluated by the three point bending test and curvature change, and then fracture patterns were investigated by optical microscope.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1989년도 가을 학술발표회 논문집
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• pp.15-18
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• 1989

The planar effects on the concrete pavements Is mainly due to the concrete shrinkage, subgrade friction, and thermal expansion or contraction. A complete understanding of analytical behavior of concrete pavement requires the development of computer model, stiffness matrix and equivalent nodal load matrices due to the effects mentioned above. A computer program, INPLANE II, has been written to evaluate the planar effects on concrete pavements. The planar effects determine to what degree the joint open and also help In determining factors which affect the joint stiffnesses and structural behavior of concrete Pavements.

• 조명전기설비학회논문지
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• 제22권7호
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• pp.43-48
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• 2008

The characteristics of heat transfer of the bimetal disc for over-current protection device is specified. Bimetal consists of two metals which have a different thermal expansion coefficient. To analyze the thermal characteristics, temperature distribution when bimetal acts as a switch is calculated. As usual, heat source is applied to the bimetal and electric current is heat source in the over-current protection switch. In this paper, thermal distribution are obtained by solving a coupled electro-thermal field with 3D finite element method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.696-698
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• 2001

This paper considers the research of the hybrid interrupter which adopts both rotating arc and thermal expansion technology. The operating principle of this device depends on rapid arc rotation due to the magnetic field created by the fault current through a coil which is mounted on contacts and also relies on the principle of thermal expansion created by arc energy in extinguishing chamber and finally causes pressure rise in expansion volume. To develope this type of interrupter, we introduced analytical analysis including electromagnetic and arc fluid simulation and experimental analysis including construction of current source generation facility and arc behavior measurements. In this research, the principle of the interrupting techniques are given and analytical and experimental results of hybrid interrupter which is developed by new technology is introduced.

• 콘크리트학회논문집
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• 제23권5호
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• pp.667-674
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• 2011

이 연구는 교량의 생애 동안의 온도 변화와 콘크리트의 시간 의존 영향을 고려하여 PSC 거더 일체식 교량의 해석 방법과 교대의 변위를 예측하는 모델 개발에 관한 것이다. 비선형 수치 해석 모델은 지반-구조물의 상호작용을 고려하며, 재료의 비선형 또한 고려되었다. 개발된 수치 해석 모델을 이용하여 총 243가지의 경우에 대하여 변수 연구를 하였다. 고려된 변수는 (1) 열팽창 계수, (2) 교량 길이, (3) 뒤채움재의 높이, (4) 뒤채움재의 강성, 그리고 (5) 말뚝-지반 강성이다. 변수 연구의 결과는 열팽창 계수, 교량 길이, 말뚝-지반의 강성이 지배적인 영향을 나타내는 것으로 드러났다. 또한, 교량의 길이는 교대의 윗부분의 변위에 지배적인 영향을 미치며 자유팽창 수축과 유사하였다. 하부의 변위에는 다른 변수들의 영향으로 추정이 쉽지 않았다. 개발된 교대의 변위 추정 모델은 기본 설계시에 사용될 수 있을 것이다.

• 한국전기전자재료학회논문지
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• 제19권3호
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• pp.280-286
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• 2006

As a way to expand electric capacity in conductor with electric power demand, STACIR/AW (Super Thermal-resistant Aluminum-alloy Conductors Aluminum-clad Invar-Reinforced) conductor which has high electric current and heat resistance characteristics have been developed. STACIR/AW power line is mechanical composite wire composed of steel cores for dip control and aluminum conductors for sending electric current. Recently, to ensure stable operation and prediction of wire life span of STACIR/AW conductor, a heat property of STACIR/AW conductor have been investigated. In the present work, a change of essential property with long term-heat exposure of STACIR/AW conductor and its structure material, INVAR wire and Al conductor, have been investigated. INVAR/AW is approximately $3.2\;{\mu}m/m^{\circ}C$. thermal expansion coefficient of INVAR/AW wire increases with time of heat exposure. the thermal expansion coefficient of INVAR/AW is markedly influenced by heat and mechanical treatment. creep rate(0.242) of STACIR/AW $410\;mm^2$ conductor at room temperature is much higher than that(0.022) at $210\;^{\circ}C$ STACIR/AW $410\;mm^2$ conductor has minimum creep rate at operating temperature. To lower creep rate with increase temperature is more unique characteristics in STACIR/AW. It is expected that STACIR/AW turned its tension to INVAR/AW at the transition temperature. at room temperature, the tension apportionment of INVAR/AW in STACIR/AW is about $50\;\%$. but whole tension of STACIR/AW is placed on the INVAR/AW alone of core metal above transition temperature.

• 대한조선학회논문집
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• 제58권2호
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• pp.66-72
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• 2021

As the demand for natural gas that satisfies environmental regulations increases, the quantities of natural gas cargo that carrier can load is also increasing. Natural gas is transported in a liquefied state at -163 ℃ to increase loading efficiency. Among several LNG CCS types, MARK-III types are generally adopted in terms of loading efficiency. The secondary barrier adhesives of the MARK-III, nevertheless, is subjected to tensile stress due to thermal contraction and tension in the environment. In terms of these reasons, local analysis of the adhesive to evaluate the stress state must be carried out. According to previous studies, local analysis is unavailable since material properties for secondary barrier adhesives have not been reported. Thus, in this study, the cryogenic tensile test and coefficient of thermal expansion of epoxy and polyurethane (PU15, PU45), which are most widely used at cryogenic temperatures, were experimentally analyzed. At cryogenic temperature, the mechanical behavior of the polyurethane adhesive was better than epoxy of the adhesive. the joint of FSB and epoxy adhesive of the secondary barrier has the maximum coefficient of thermal expansion difference at 25 ℃ and minimum at -150 ℃, respectively.