• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2634-2645
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• 1993

Dome structures of pressure vessels subjected to internal pressure are usually analyzed by linear elastic theory assuming small deformation. Geometric and material nonlinear behaviors appear in actual dome structures because of large deformation and loads exceeding yield strength. In this paper, linear and nonlinear analyses were performed for various hemispherical and torispherical domes to check the effects of geometric and material nonliearity on the stress and displacement by the finite element method. The effect of the geometric nonlinearity decreased the stress levels a lot for very thin general torispherical domes, which enables more realistic and effective design. The material nonlinear effects are negligible for hemispherical and optimum torispherical domes, and those are large for most of the general torispherical domes.

• Journal of the Korean Society of Combustion
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• v.17 no.2
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• pp.1-8
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• 2012

Laminar flame speeds of Methane at elevated temperatures and pressures were investigated using constant volume spherical chamber. Pressure trace during combustion was measured in each test and this was used in calculating laminar flame speed of Methane. To have large amount of data, experimental apparatus was fabricated with fully automatically controlled feature. A calculating code which calculates laminar flame speeds at various temperatures and pressures with one experimental result was used to calculate laminar flame speeds. The experimental and calculating methods were verified using the calculated laminar flame speed result with PREMIX code.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.119-119
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• 2003

탄화규소나 열분해 탄소는 고온 특성 및 화학적인 안정성 이 우수하여 단미 혹은 코팅재로로 소재의 성능을 향상시키기 위하여 에너지 관련 분야, 반도체 치구 분야, 방위산업 및 항공우주 분야와 원자력 분야에서 다양하게 사용된다. 특히 원자력 분야에서는 고온형 원자로의 노심 요소 부품으로 적용 및 개발을 고려하고 있으며, 대표적인 예로 수소생산용 초고온 가스냉각로의 코팅 핵연료 입자를 들 수 있다. 일반적으로 TRISO라 불리는 가스냉각로 핵연료는 구형 $UO_2$ kemel의 주변을 PyC-SiC -PyC의 삼중 코팅층으로 둘러싸는 구조를 하고 있으며, 이 코팅층들은 kernel물질이 분열하는 동안 발생되는 내부 기체 압력을 견디는 압력용기 역할과 기체나 금속 핵분열 생성물들을 가두는 확산 장벽 역할을 하게 된다. 본 연구에서는 구형의 $UO_2$대신 선행연구를 위하여 구형 ZrO$_2$를 이용하여 증착온도나 시간 및 입력기체비 등의 화학증착 변수로 조절하여 SiC 및 PyC을 코팅하고, 각 변수들에 의한 증착층의 거동을 고찰하고자 하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1171-1175
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• 2017

Cryogenic helium gas is used as the pressurant for the oxidizer pressurization of DR(Damper Receiver) sphere in the PSD(Pogo Suppression Device) system and liquid oxygen is used as the oxidizer for the propellant in Korea Space Launch Vehicle-II. The helium gas is stored in pressurant cylinders inside the cryogenic liquid oxygen tank and liquid oxygen is stored in the oxidizer tank. In this study, the performance test of PSD liquid oxygen drain valve for KSLV-II was considered.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.11-16
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• 1997

원자로 압력용기강의 제조열처리인 ？칭과 템퍼링 중간에 페라이트와 오스테나이트가 공존하는 영역에서 2상영역열처리를 추가한 후 템퍼링조건을 조정함으로써 파괴인성을 향상시키는 열처리 공정을 개발하였다. 새 열처리공정을 적용하면 기존공정에 비하여 강도는 크게 감소하지 않으면서 충격인성과 연성이 크게 증가하고, 천이온도가 약 2$0^{\circ}C$ 감소하였다. 2상영역열처리를 하면 연한 템퍼드 베이나이트 기지에 비교적 강한 템퍼드 마르텐사이트가 균일하게 분산된 복합조직을 얻을 수 있고, 유효 결정립의 크기가 감소하여 균열진전이 억제되었다. 또한 기존공정의 판상 탄화물 대신 구형 탄화물이 형성되기 때문에 응력집중이 완화되어 파괴저항성이 향상되었다. 그리고 2상 영역열처리후 템퍼링 정도를 낮추면 탄화물 크기가 작아지기 때문에 균열발생이 억제되어 저온 충격인성이 향상되었다.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.5
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• pp.564-570
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• 1997

The most important factor for the desalination system is the fresh water production cost dependent upon the possible energy source which should be obtained easily and with low price. Recently in Korea the demand of LNG, as a cheap and clean energy which does not cause an environmental problem, has sharply been increased. In general, LNG is storaged in a tank as a liquid state below -162 'C. When it is serviced, however, the LNG absorbs energy from a heating source and transforms to the gaseous state with high pressure. During this process a huge amount of cold energy accumulated in LNG is wasted. This waste cold energy can be utilized for producing fresh water from sea water using a sea water freezing desalination system. In order to develop a sea water freezing desalination system and to establish its design technique, a qualitative and quantitative data regarding the freezing behavior of sea water is needed in advance. The goal of this study, therefore, are to reveal the freezing mechanism of sea water, to measure the freezing rate, and to investigate the freezing heat-transfer characteristics. The experimental results help to provide a general understanding of the sea water freezing behavior in a Rectangular vessel cooled from below.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.529-537
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• 1998

Currently as due to the rapid development of industry and increase in population we meet serious problems concerning the shortage and pollution of water. In the country many experts predict a shortage of water approaching 450 million tons by the year 2006. To cope with this serious problem it is necessary to construct desalination plants. In the adoption of a desalination system the most important factor is the cost of fresh water production,. In general LNG is stored in a tank as a liquid state below $-162^{\circ}C$. When it is serviced, however the LNG absorbs energy from a heat source and transforms to a high pressure gaseous state. During this process a huge amount of cold energy accumulated in cooling LNG is wasted. This wasted cold energy can be utilized to produce fresh water by using a sea water freezing desalination system. In order to develop a sea water freezing desalination system and to establish its design technique qualitative and quantitative data regarding the freezing behavior of sea water is required in advance, The goals of this study are to reveal the freezing behavior of sea water is required in advance. The goals of this study are to reveal the freezing mechanisms of sea water to measure the freezing rate and to investigate the freezing heat-transfer characteristics,. The experimental results will provide a general understanding of sea water freezing behavior in a rectangular vessel cooled from above.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1187-1194
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• 2009

During the last decade, possibility of flaw occurrences has been rapidly increased world-widely as the increase of operating times of petro-chemical facilities. For instance, from a recent in-service inspection, three different sized surface cracks were detected in welding parts of a spherical oxygen holder in Korea. While API579 code provides corresponding engineering assessment procedures to determine crack driving forces, in the present work, numerical analyses are carried out for the cracked oxygen holder to investigate effects of complex geometry, analysis model and residual stress. With regard to the detailed finite element analysis, stress intensity factors are determined from both the full three-dimensional model and equivalent plate model. Also, as an alternative, stress intensity factors are calculated for equivalent plate model by employing the noted influence stress function technique. Finally, parametric structural integrity evaluation of the cracked oxygen holder is conducted in use of failure assessment diagram method, J/T method and DPFAD method. Effects of the geometry and so forth are examined and key findings from the simulations are fully discussed, which enables to determine practical safety margins of spherical components containing a defect.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.3
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• pp.42-50
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• 1992

다공성 물질이 충전된 밀폐용기 내에서 수용성 이원혼합용액($H_2O{+}NaCl$)이 수평한 상부전열면으로 부터 동결될 때 혼합용액의 초기농도, 액체의 과열 및 다공성물질의 입자직경 크기가 온도와 농도분포에 미치는 영향을 실험하였으며, 동결이 진행됨에 따라 이동하는 고액상 혼합영역의 계명위치를 측정하였다. 다공성물질은 평균직경이 2.85mm, 6mm인 구형의 유리구슬을 이용하였다. 수용성 혼합용액의 초기농도는 공융농도도 이하로 하였으며 상부 전열면은 공융온도 이하로, 하부전열면은 액상선온도 이상으로 유지하여 동결 실험한 결과 상부 전열면으로 부터 고체 영역, 고액상혼합영역, 액체영역으로 구분되었다. 액체의 초기농도가 5%인 경우 과냉현상이 관찰되었으나 10%, 15%인 경우 액체온도는 액상선 온도보다 더 높았다. 용액의 초기농도를 감소시킬수록 고체와 고액상혼합영역의 범위는 증대되었으며 고액상혼합영역과 고체영역의 계면은 더욱 강해진 자연대류에 의하여 2차원성이 증가된 형상을 보였다. 용액의 자연대류는 다공성물질의 직경이 클수록 증가되었으며 계면에서의 제융해현상은 관찰되지 않았다.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.752-757
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• 2001

To reduce stress concentration around the intersection between a spherical pressure vessel and a cylindrical nozzle under various load conditions using less material, the optimization for the distribution of reinforcement has researched. The ranked bidirectional evolutionary structural optimization(R-BESO) method is developed recently, which adds elements based on a rank, and the performance indicator which can estimate a fully stressed model. The R-BESO method can obtain the optimum design using less iteration number than iteration number of the BESO. In this paper, the optimized intersection shape is sought using R-BESO method for a flush and a protruding nozzle. The considered load cases are a radial compression, torque and shear force.