• Journal of Electrical Engineering and Technology
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• 제2권1호
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• pp.55-60
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• 2007

This paper proposes a hydraulic pump system that uses a variable speed SR drive and constant capacity pump. For the design of the SRM (Switched Reluctance Motor) and digital controller, base speed and rating torque are determined from the mechanical specifications of the hydraulic pump. In order to minimize the power consumption during the maintaining of preset oil-pressure, the pressure control system changes the maximum oil-pressure band and flow rate according to the motor speed. The DSP control system adjusts the oil-pressure and the speed of the SRM from the pressure sensor signal, due to conservation of power consumption by the hydraulic pump. A 2.2Kw, 12/8 pole SR motor and DSP based digital controller are designed and tested with experimental set-up. The test results indicate that the system has some good features such as high efficiency and rapid response characteristics.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1807-1812
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• 2007

A bulge testing system was developed to measure mechanical properties of thin film materials. A bulge pressure test system for pressurizing the bulge window of the film and a micro out-of-plane ESPI(Electronic Speckle Pattern Interferometric) system for measuring deflection of the film were included in the testing system developed. For the out-of-plane ESPI system, whole field speckle fringe pattern, corresponding to the out-of-plane deflection of the bulged film, was 3-dimensionally visualized using 4-bucket phase shifting algorithm and least square phase unwrapping algorithm. The bulge pressure for loading and unloading was controlled at a constant rate. From the pressure-deflection curve measured by this testing system, ain-plane stress-strain curve could be determined. In this study, elastic modulus of an electrolytic copper film 18 ${\mu}m$ was determined. The modulus was calculated from determining the plain-strain biaxial elastic modulus at the respective unloading slopes of the stress-strain curve and for the Poisson's ratio of 0.34.

• 지질공학
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• 제12권4호
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• pp.459-469
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• 2002

재성형된 해성점토 시료를 연직·수평방향으로 채취하여 표준압밀시험(SCT)과 일정변형률속도 압밀시험(CRSC)을 실시하여 연약 해성점토지반에 대한 압밀정수들의 구성관계를 확인하였다. 또한, 불교란 교란 화강암질 풍화토의 표준·일정변형률속도 압밀시험을 통하여 화강암질 풍화토에 대한 압밀 정수들의 특성과 적용성을 고찰하였다. 그 결과 해성점토 시료의 연직·수평방향과 표준·일정변형률속도압밀시험 방법에 따라 선행압밀응력, 압축지수, 과잉간극수압, 간극수압비 등이 달리 산정됨을 알 수 있었다. 또한, 불교란·교란 화강암질 풍화토 시료에서도 해성점토와 유사하게 과압밑·정규압밀 구간에서 압밀정수들의 변화를 확인하였다.

• 한국지반공학회논문집
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• 제29권8호
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• pp.15-25
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• 2013

본 연구에서는 다짐된 편마풍화토의 불포화토 전단강도특성을 규명하기 위하여, Constant Water Content Compression (CWCC) 시험을 실시하였다. 두 가지 상대밀도로 구분하여 정적 다짐으로 공시체가 제작되었고, 초기 포화도를 변화시킴으로써 초기 흡수력 및 최대전단강도가 구현될 때의 흡수력에 따른 전단거동을 살펴보았다. 흡수력은 세라믹디스크와 간극수압계의 설치에 의해 직접 측정되었고, 이 흡수력을 적용하여 흡수응력(ps)이 추정되었다. CWCC 시험에서 얻어진 최대압축강도에 대한 결과는 삼축압축시험에서의 포화상태 파괴선(Mp Line)과의 관계, 즉 흡수력에 의해 발현된 전단강도의 변화를 흡수응력을 이용하여 살펴보았다. 또한, Kim 등(2010)이 제안한 Suction stress-SWCC Method (SSM)을 활용하여 흡수응력의 적용성에 대해 논하였다.

• 한국지반신소재학회논문집
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• 제13권4호
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• pp.33-43
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• 2014

최근 들어 연약지반상에 구조물을 건설하는 경우가 증가하고 있으며, 사회기반 시설의 유지관리 및 건설 비용의 절감을 위해 사전압밀공법 및 연직배수공법과 같은 기존의 방법을 이용하여 지반 개량이 행해지고 있다. 이와 같이 연약점성토 지반상에 다양한 개량공법이 적용 될 때, 점성토의 낮은 투수계수로 인한 장기간에 걸친 압밀침하가 중요하게 된다. 압밀침하와 관련된 기존 연구결과에 따르면, 기존의 표준압밀시험의 재하기간은 압밀정수 산정에 최소한 10일 이상의 시간을 요하게 된다. 따라서 이 연구에서는 서남해안의 대표적인 연약지반으로 구성된 광양만 재성형 해성점토를 이용하여 표준압밀시험과, 일정변형률 압밀시험의 변형률 속도를 변화시킨 실험을 수행하였다. 실내시험결과를 통해 등변형률 속도에 따른 압축특성, 변형률-유효응력관계, 재하속도에 따른 간극수압 변화특성, 압밀정수와 등변형률 속도의 관계를 비교/분석하였다.

• 한국강구조학회 논문집
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• 제21권3호
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• pp.245-255
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• 2009

산업용 건축물은 일반적으로 박공지붕형 저층의 형태로 많이 건설된다. 본 연구는 박공지붕형 저층건물의 풍압분포와 특성을 알아보기 위하여 풍동실험을 수행하였다. 풍동실험은 경사각 변화에 따른 외장재용 피크외압계수 분포양상을 알아보기 위하여 동일한 폭과 높이, 길이를 가지지만 지붕 경사각이 서로 다른 7가지의 모형을 제작하여 실험하였다. 실험결과 지붕과 벽면의 모서리 부분에서 최대 피크외압계수가 나타났으며, 이를 KBC-2005 및 각국의 기준과 비교하여 보았다. 실험에 의한 피크외압계수는 AIJ-2004와 매우 유사하게 나타났지만 KBC -2005보다는 다소 크게 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• 제25권6호
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• pp.1228-1236
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• 2001

In this study, CT specimens were prepared from ASTH A5l6 steel which was used for pressure vessel plates for moderate and lower temperature service. And we got the fellowing characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$ , $-30^{\circ}C$, $-60^{\circ}C$, $-80^{\circ}C$, $-100^{\circ}C$ and $-120^{\circ}C$ and in the range of stress ratio of 0.1, 0.3 by means of opening mode displacement. At the constant stress ratio, the Threshold stress intensity factor range ΔAKth in the early stage of fatigue crack growth (Region I) and stress intensity factor range $\DeltaK$ in the stable of fatigue crack growth (Region II) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da/dN-$\Delta$K in Region II that is, the fatigue clack growth exponent m increased with descending temperature at the constant stress ratio. It assumed that the fatigue crack growth rate da/dN is rapid in proportion to descend temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.

• 터널과지하공간
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• 제2권2호
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• pp.224-236
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• 1992

It is very important to determine the thermo-mechanical characteristics of the rock mass surrounding the repository of radioctive waste and the LPG storage cavern. In this study, Hwasoon-Shist. Dado-Tuff adn Chunan-Tonalite were the selected rock types. Temperature dependence of the mechanical properteis such as uniaxial compressive strength, tensile strength, Young's modulus was investigated by measuring the behaviour of these properties due to the variation of temperature. Also, the characteristics of strength and deformation of these rocks were examined through high-temperature triaxial compression tests with varing temperatures and confining pressures. Important results obtained are as follows: In high temperature tests, the uniaxial compressive strength and Yong's modulus of Tonalite showed a sligth increase at a temperature up to 300$^{\circ}C$ and a sharp decrease beyond 300$^{\circ}C$, and the tensile strength showed a linear decrease with increasing heating-temperature. In high-temperature triaxial compression test, both the failure stress and Young's modulus of Tonalite increased with the increase of confining pressure at constant heating-temperature, and the failure stress decreased at 100$^{\circ}C$ but increased at 200$^{\circ}C$ under a constant confining pressure. In low temperature tests, the uniaxial compressive and tensile strengths and Young's modulus of these rocks increased as the cooling-temperature is reduced. Also, the uniaxial compressive and tensile strengths of wet rock specimens are less than those of dry rock specimens.

• 한국분무공학회지
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• 제13권4호
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• pp.206-211
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• 2008

In this research, combustion and spray characteristics were investigated experimentally in a constant volume chamber by applying bio-diesel fuel to a common-rail system in which precise control is available for utilizing environmentally friendly properties of bio-diesel fuel. The experiment was conducted at fuel temperatures $20^{\circ}C$ and $-20^{\circ}C$ to investigate combustion characteristics of bio-diesel fuel provoking problems in fluidity specially in a low temperature. For the visualization, the experiment was carried out under various conditions of ambient pressure, injection pressure and fuel temperature. The test was made by three different types of diesel fuels, conventional diesel, BD20 and BD100. In summary, this research aims to investigate combustion characteristics in the application of bio-diesel fuels and compare the results with performance of conventional diesel fuel. This experimental data may provide fundamentals of spray and combustion of bio-diesel fuels at a low temperature and contribute to the development of bio-diesel engines in future.

• 한국해양공학회지
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• 제14권3호
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• pp.78-83
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• 2000

In this study, CT specimens were prepared from AST SA516 Gr. 70 which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at 25$^{\circ}C $, -60$^{\circ}C $, -80$^{\circ}C $ and -100$^{\circ}C $ and in the range of stress ratio of 0.05, 0.3 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ${\delta} K_{th}$ in the early stage of fatigue crack growth (Region I) and stress intensity factor range $\delta $K in the stable of fatigue crack growth (Region II) were increased in proportion to descending temperature. It was assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da/dN -$\delta $K in Region II, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It was assumed that the fatigue crack growth rate da/dN is rapid in proportion to descending temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.