• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1458-1462
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• 2003

High temperature and high pressure heavy water flows through the pipes in atomic power plants. The curved parts of pipes are critical parts in that they change the direction of steam flow, and these parts are especially affected by severe wear. Therefore, most pipes in atomic power plants are tested by non-destructive examination by workers who use ultrasonic sensors to measure the wall thickness of pipes. But not only are these pipes located in a very dangerous environment, but the space is also very limited. For the safety of workers, it is necessary to design a device that uses a mobile robot that can inspect curved pipes. This paper presents the design and construction of a small device that can generate the necessary contact forces between ultrasonic sensors and pipe walls in a limited space. And a mobile robot is used in place ortho worker for successful non-destructive examination.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.754-755
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• 2006

In order to develop the SUS304L housing by powder metallurgy for an optical device useful for the FTTH communication system, the optimum compacting pressure and sintering temperature were investigated using granulated powder as the material to satisfy high air-tightness and high laser-weldability. Then the laser-welding test of specimen made under the optimum condition was carried out to observe welding sputters.

• 대한기계학회논문집B
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• 제36권10호
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• pp.989-999
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• 2012

이젝터는 고압의 유체를 구동관로에서 분출시켜, 그 주변의 저압기체와 운동량 교환을 통하여 저압의 유체를 보다 높은 압력까지 상승시켜 흡인되는 유체를 이송하는 장치이다. 증기-증기 이젝터는 흡입, 혼합 및 탈수에 널리 사용되고 있다. 그리고 이젝터는 기계적인 작동이 없으므로, 고장이 거의 없다. 또한 이젝터는 유체 관련 시스템의 크기에 관계없이 유체와 관련된 다양한 장소에 용이하게 설치할 수 있어, 정비의 필요성이 거의 없고 비용도 합리적이다. 따라서 본 연구는 단순 압축 또는 진공 설비를 위한 펌프 혹은 기계장치 대안으로 사용되는 이젝터 전체에 적용할 수 있는 기초 자료 제공을 목표로 하였다. 이 목표를 위해 실험만으로 획득할 수 없는 자료를 전산유체역학을 적용하여 분석함으로써 이젝터의 유체역학적 특성에 있어 최적의 설계조건을 제시하였다.

• 대한기계학회논문집
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• 제19권8호
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• pp.2022-2029
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• 1995

The experiment was performed by using the condenser discharge ignition device in a constant volume combustion chamber for high pressure, equivalent to the TDC of spark ignition engine, which makes the forced turbulent field possible. The conclusions obtained under various initial pressures, initial temperatures, and turbulent conditions of the methanol-air mixture are as follows : As initial pressure, initial temperature of the mixture, and the ignition energy increase, the inflammability limit expands, but the lean inflammability limit decreases as turbulence intensity increases. Combustion duration is shorter in the case of the lower initial pressure, the higher initial temperature, an equivalence ratio of 1.1-1.2, and even though turbulence intensity increases up to optimum value. Maximum combustion pressure increases in turbulent ambience under the same mixture condition, only in the case each optimum turbulence intensity exists under every condition. As the turbulence intensity increases .tau.$_{10}$ proportion increases while the .tau.$_{pr}$ proportion decreases....

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.774-778
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• 2004

The atomization process of a circular $SF_{6}$ liquid jet issued into an otherwise quiescent, high-pressure $N_2$ gas was observed to explore the breakup mechanism of liquid ligaments involved in turbulent atomization. Both liquid and gas temperatures were fixed at a room temperature but the gas pressure was elevated to more than twice the critical pressure of $SF_{6}$. Therefore, the liquid surface was in a thermodynamic state close to a critical mixing condition with suppressed vaporization. Since the surface tension and the surface gas density approach zero and the surface liquid density, respectively, phenomena equivalent to those which would appear when a very high speed laminar flow of water were injected into the atmospheric-pressure air can be observed by issuing $SF_{6}$ liquid at low speeds in micro-gravity environment which avoid disturbances due to gravity forces. The instability ob near-critical mixing surface jet was quantitatively characterized using a newly developed device, which could issue a very small amount of $SF_{6}$ liquid at small constant velocity into a very high-pressure $N_2$ gas.

• 센서학회지
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• 제33권3호
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• pp.173-178
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• 2024

Development of pressure sensors for harsh environments with high pressure, humidity, and temperature is essential for many applications in the aerospace, marine, and automobile industries. However, existing materials such as polymers, adhesives, and semiconductors are not suitable for these conditions and require materials that are less sensitive to the external environment. This study proposed a pressure sensor that could withstand harsh environments and had high durability and precision. The sensor comprised a piezoresistor pattern and an insulating film directly formed on a stainless-steel membrane. To achieve the highest sensitivity, a pattern design method was proposed that considered the stress distribution in a circular membrane using finite element analysis. The manufacturing process involved depositing and etching a dielectric insulating film and metal piezoresistive material, resulting in a device with high linearity and slight hysteresis in the range of a maximum of 40 atm. The simplicity and effectiveness of this sensor render it a promising candidate for various applications in extreme environments.

• 센서학회지
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• 제33권1호
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• pp.7-11
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• 2024

Soft-pressure sensors have numerous applications in soft robotics, biomedical devices, and wearable smart devices. Herein, we present a highly sensitive electronic skin device with an isotropic wrinkled pressure sensor. A conductive ink for soft pressure sensors is produced by a solution process using polydimethylsiloxane (PDMS), poly 3-hexylthiophene (P3HT), carbon black, and chloroform as the solvents. P3HT provides high reproducibility and conductivity by improving the ink dispersibility. The conductivity of the ink is optimized by adjusting the composition of the carbon black and PDMS. Soft lithography is used to fabricate a conductive elastic structure with an isotropic wrinkled structure. Two conductive elastic structures with an isotropic wrinkle structure is stacked to develop a pressure sensor, and it is confirmed that the isotropic wrinkle structure is more sensitive to pressure than when two elastic structures with an anisotropic wrinkle structure are overlapped. Specifically, the pressure sensor fabricated with an isotropic wrinkled structure can detect extremely low pressures (1.25 Pa). Additionally, the sensor has a high sensitivity of 15.547 kpa^-1 from 1.25 to 2500 Pa and a linear sensitivity of 5.15 kPa^-1 from 2500 Pa to 25 kPa.

• 한국추진공학회지
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• 제25권4호
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• pp.19-27
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• 2021

한국형발사체용 연소기 성능 고도화를 위한 핵심기술을 검증하기 위해 고압 축소형 연소기를 개발하였다. 성능 고도화를 위한 핵심기술은 고압 연소기용 분사기 설계, 적층제조기법을 적용한 연소안정화 장치 개발, 고압 축소형 연소기 헤드 및 재생냉각 연소실 설계/제작 등이다. 고압 축소형 연소기 개발을 통해 핵심기술을 검증하였고, 이 기술들은 향후 대형 액체로켓엔진 연소기 개발에 활용될 예정이다.

• 센서학회지
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• 제27권3호
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• pp.186-191
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• 2018

Smart textile industries have been precipitously developed and extended to electronic textiles and wearable devices in recent years. In particular, owing to an increasingly aging society, the elderly healthcare field has been highlighted in the smart device industries, and pressure sensors can be utilized in various elderly healthcare products such as flooring, mattress, and vital-sign measuring devices. Furthermore, elderly healthcare products need to be more lightweight and flexible. To fulfill those needs, textile-based pressure sensors is considered to be an attractive solution. In this research, to apply a textile to the second layer using a pressure sensing device, a novel type of conductive textile was fabricated using vapor phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). Vapor phase polymerization is suitable for preparing the conductive textile because the reaction can be controlled simply under various conditions and does not need high-temperature processing. The morphology of the obtained PEDOT-conductive textile was observed through the Field Emission Scanning Electron Microscope (FESEM). Moreover, the resistance was measured using an ohmmeter and was confirmed to be adjustable to various resistance ranges depending on the concentration of the oxidant solution and polymerization conditions. A 3-layer 81-point multi-pressure sensor was fabricated using the PEDOT-conductive textile prepared herein. A 3D-viewer program was developed to evaluate the sensitivity and multi-pressure recognition of the textile-based multi-pressure sensor. Finally, we confirmed the possibility that PEDOT-conductive textiles could be utilized by pressure sensors.

• Composites Research
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• 제34권4호
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• pp.257-263
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• 2021

복합재료는 높은 비 강성 및 비 강도 특성으로 인해 기체 혹은 액체 연료를 저장하기 위한 압력 용기의 설계 및 제작에 널리 활용되고 있다. 이에 따라, 압력용기의 파열압력 또는 파단 변형률의 기계적 특성의 보다 정확한 측정은 상용화 전에 필수적 요소이다. 그러나, 기존의 시험방법을 활용한 복합재료 압력 용기의 안전성 검증은 하중 전달 매체의 변형으로 인한 추가적인 에너지 손실의 발생과, 불필요한 하중 및 모멘트의 발생 등의 한계가 있다. 따라서 본 연구에서는 수직기둥의 이론적인 하중전달 정도와 적용 가능한 수직방향 변위를 고려하여 세그먼트형 링 버스트 시험장치를 설계하였다. 또한, 세그먼트 형 링 버스트 시험장치의 균일한 압력분포를 검증하기 위해 수치해석을 활용하였고, 수압 시험방법과 링 시편의 원주방향 응력 및 변형률 분포를 비교하였다. 복합재료 압력용기의 파괴 거동을 모사하기 위해 Hashin 파손 기준을 적용하였고, 실험적으로 파단 변형률을 측정하여 이를 수치해석 결과와 비교하였다.