• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.49-52
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• 2009

The response times of monopropellant thrusters at a pulse mode were investigated experimentally as design parameters and feed pressure conditions. Five different model thrusters as injection direction/uniformity, aspect ratio of reactor, volumes of manifold and chamber were designed. As a results, two parameters, aspect ratio and manifold volume, were directly related to response characteristics. Additionally, chugging instability at reaction chamber was observed when pressure drop across the catalyst bed was increased due to high aspect ratio or when low pressure was built at reaction chamber.

• Journal of Biomedical Engineering Research
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• v.20 no.5
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• pp.601-608
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• 1999

동맥의 일부분의 팽창하는 동맥류는 높은 사망률을 야기하는 혈관계 질환이다. 동맥류의 발생 및 파열에는 동맥류 내부의 혈류의 유동에 의한 혈관벽 전단 응력 및 압력이 주용한 원인 중 하나로 의심되고 있다. 복부대동맥류 내부의 혈류 유동 특성을 밝히기 위해서 동맥류의 최대 확장부가 복부동맥의 1.5배, 2배인 유리 모델을 제작하였다. 정상류 상태에서 다양한 레이놀즈수에 대해서 속도 및 난동도를 입자영상속도계를 이용하여 측정하였다. 경계층 박리로 인한 재순환 부분이 끝나는 재부착점은 동맥류 최대 확장부 후부에서 발생하였으며, 이 위치는 레이놀즈수의 변화에 따라 바뀌었다. 축방향 속도의 난동은 최대 확장부 후부에서 크게 나타났으며, 이 위치에서 난동에 의한 부가적 응력이 크며 혈관벽 구조변화가 발생하리라 예측된다. 동맥류 내부의 압력분포는 수치해석에 의해 계산되었다. 동맥류 내부 압력은 크기가 증가함에 따라 커졌으며 압력은 동맥류 최대 확장부 후부에서 발생하는 재부착점에서 최대값을 나타내었다. 동맥류 최대확장부 후부는 압력이 최대값을 가지며, 전단력의 변화 및 난동이 큰 지역이므로 동맥류의 파열이 발생하기 쉬운 지역으로 예측된다.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1061-1069
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• 2005

다짐화강풍화토의 강도와 변형특성을 조사하기 위하여 불포화배수 삼축압축실험을 실시하였다. 본 실험을 위하여 야마구치현의 시모네세키에서 화강풍화토를 구하였으며 주응력방향과 다짐방향을 0, 45, 90도의 세가지 방향성을 갖도록 하였다. 등방압축시 발생하는 압축변형률은 다짐각도에 따라 크게 영향을 받는다. 이차압축시의 변형거동에 관한 시간의존성은 다짐각도와 관계가 없다. 다짐각도가 압축강도와 변형에 미치는 영향은 특히 낮은 구속압력시에 크다. 다짐각도가 다르다 하더라도 다일러탄시 비율은 다일러턴시로 인한 강도증가와 상관하여 변화한다. 따라서 다짐풍화토는 초기 비등방성 조직을 갖고 있는 모래와 같이 비등방성 역학적 성질을 갖는다고 할 수 있다.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.2
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• pp.36-43
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• 2003

The analytic solution of radial displacements of thin cylindrical pressure vessel with carbon fiber T700/Epoxy orthotropic composites was obtained using equilibrium equations of the orthogonal curvilinear coordinate system. The governing equations with the simplified strain versus displacement relation of 3-dimensional curvilinear coordinate system were derived from the variational principle and the virtual work principle. Some theoretical analyses were presented and compared with the results of hydraulic tests for the pressure vessels with some various thicknesses. The results of the theoretical analysis and the hydraulic test were reasonably matched.

• Journal of the Korean Geotechnical Society
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• v.25 no.7
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• pp.35-46
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• 2009

Pressure grouting is a common technique in geotechnical engineering to increase the stiffness and strength of the ground mass and to fill boreholes or void space in a tunnel lining and so on. Recently, the pressure grouting has been applied to a soil-nailing system which is widely used to improve slope stability. The soil-nailing design has been empirically performed in most geotechnical applications because the interaction between pressurized grouting paste and the adjacent ground mass is complicated and difficult to analyze. The purpose of this study is to analyze the increase of pullout resistance induced by pressurized grouting with the aid of performing laboratory model tests and field tests. In this paper, two main causes of pullout resistance increases induced by pressurized grouting were verified: the increase of mean normal stress and the increase of coefficient of pullout friction. From laboratory tests, it was found that dilatancy angle could be estimated by modified cavity expansion theory using the measured wall displacements. The radial displacement increases with dilatancy angle decrease and the dilatancy angle increases with injection pressure increase. The measured pullout resistance obtained from field tests is in good agreement with the estimated one from the modified cavity expansion theory.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.163-172
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• 2000

The postbuckling behavior and progressive damage of composite laminated cylindrical shell under uniform external pressure were investigated by nonlinear finite element method programming. For the finite element analysis, nine-node 3-D degenerated elements were utilized, and arc-length method including line search was adopted for the iteration and load-increment along postbuckling equilibrium path. As results. buckling load, postbucking behavior, and progressive failure f3r various composite laminated cylindrical shells were discussed.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.74-82
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• 1996

수면상에 떠있는 2차원 물체에 작용하는 시간평균 표류력 및 표류모오멘트를 비점성 선형 포텐셜 이론을 사용하여 계산하는 방법에 대하여 검토하였다. 부유체 접수면상의 압력을 직접적분하여 구한 수평방향 표류력이 특정주파수 부근에서 음의 값을 보이고 있다. 이는 무한원방에서의 에너지 보전방법에 의한 표류력이 항상 양의 값을 취한다는 기존 이론과 상이하다. 본 논문에서, 이러한 차이가 부유체의 횡요 및 상하동요에 기인한 복원력의 성분과 횡요와의 연성효과에 의하여 발생하였음을 규명하였다. 이는 횡요가 있는 경우, 표류력을 산출하는 기존의 무한원방 방법에 결함이 있음을 보이고 있다. 이에 반하여 기존의 접수면압력 직접적방법은 부유체에 작용하는 시간평균 표류력 및 표류모오멘트를 모든 주파수에 대하여 정확하게 산출한다고 결론지울 수 있다.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.1
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• pp.17-26
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• 2011

CANDU reactor core is composed a few hundreds pressure tubes, which support and locate the nuclear fuels in the reactor. Each pressure tube provides pressure boundary and flow path of primary heat transport system in the core region. In order to guarantee the structural integrity of pressure tube flaws which can be found by in-service inspection, crack growth and fracture initiation assessment have to be performed. Stress intensity factors are important and basic information for structural integrity assessment of planar and laminar flaws (e. g. crack). This paper reviews and confirms the stress intensity factor of axial crack, proposed in CSA N285.8-05, which is an fitness-for-service evaluation code for pressure tubes in CANDU nuclear reactors. The stress intensity factors in CSA N285.8-05 were compared with stress intensity factors calculated by three methods (finite element results, API 579-1/ASME FFS-1 2007 Fitness-For-Service and ASME Boiler and Pressure Vessel Code Section XI). The effects of Poisson's ratio and anisotropic elastic modulus on stress intensity factors were also discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.469-473
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• 2010

In this study, combustion tests using liquefying fuels with fast regression rate were performed. The chamber pressure oscillation was analyzed and hazards of combustion instabilities were examined. In case of Liquefying fuel with fast regression rate, the amplitude of chamber pressure oscillation was increased compared to the polymeric fuels. However, the critical combustion instability can hardly occur in liquefying fuel. This is because the rapid change of inner chamber diameter limits the amplification of chamber pressure oscillation. The chamber pressure oscillation due to the large increase of fuel production and the vortex shedding in pre-chamber violently occurs during combustion using single-port axial injector.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.127-132
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• 2023

In this study, designing of a Type 4 pressure vessel using the filament winding method was conducted. In order to prevent leakage in consideration of the design of the hydrogen storage tank, a liner was designed by applying high-density polyethylene (HDPE), and the composite structure was designed by stacking carbon/epoxy in the hoop and helical directions. As a theoretical approach, the angle of the helical fiber and fiber thickness of each hoop and helix were designed. The safety of the design was verified using the commercial software ANSYS.