• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4295-4306
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• 2023

The vibration of fuel rods in axial flow is a universally recognized issue within both engineering and academic communities due to its significant importance in ensuring structural safety. This paper aims to thoroughly investigate the stability and nonlinear vibration of a fuel rod subjected to axial flow in a newly designed high temperature gas cooled reactor. Considering the possible presence of thermal expansion and large deformation in practical scenarios, the thermal effect and geometric nonlinearity are modeled using the von Karman equation. By applying Hamilton's principle, we derive the comprehensive governing equation for this fluid-structure interaction system, which incorporates the quadratic nonlinear stiffness. To establish a connection between the fluid and structure aspects, we utilize the Galerkin method to solve the perturbation potential function, while employing mode expansion techniques associated with the structural analysis. Following convergence and validation analyses, we examine the stability of the structure under various conditions in detail, and also investigate the bifurcation behavior concerning the buckling amplitude and flow velocity. The findings from this research enhance the understanding of the underlying physics governing fuel rod behavior in axial flow under severe yet practical conditions, while providing valuable guidance for reactor design.

• Design & Manufacturing
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• 제12권1호
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• pp.41-46
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• 2018

This study proves the causes of cylinder and piston jam by scratches which is the fatal problem of hydraulic breaker through the thermal analysis and thermal-structural coupled field analysis. The trouble from the scratch is a complex problem which can be caused by manufacturing process (this is an internal factor) and the users mistake or contamination in the hydraulic circuit (these are an external factor). Hence, it's not easy to investigate the causes, also hard to prevent the recurrence. In this reason, hydraulic breaker manufacturers are trying to improve the manufacturing process such as machining, heat treatment, grinding, cleaning, also to prevent the contamination in hydraulic circuit and to remove the remains. It's being managed thoroughly by manufacturers. This study shows the effect of the temperature rise by the frictional heat generated when the piston hits the tool on the hydraulic oil while the hydraulic breaker is operating, also the temperature distribution when it starts to affect main components of hydraulic breaker. The stress and the amount of deformation also could be found through thermal-structural coupled field analysis. It proved that the stress and deformation are proportionally increased according to the temperature rise in hit area, and it affects the cylinder and the viscosity of hydraulic oil inside the cylinder when it heats up beyond the certain temperature.

• 한국산업융합학회 논문집
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• 제23권6_1호
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• pp.881-888
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• 2020

A butterfly valve is a valve that adjusts flow rate by rotating a disc for about 90° with respect to the axis that is perpendicular to the flow path from the center of its body. This valve can be manufactured for low-temperature, high-temperature and high-pressure conditions because there are few restrictions on the used materials. However, the development of valves that can be used in a 600℃ environment is subject to many constraints. In this study, the butterfly valve's stability was evaluated by a fluid-structured interaction analysis, thermal-structure interaction analysis, and seismic analysis for the development of valves that can be used in high-temperature environments. When the reverse-pressure was applied to the valve in the structural analysis, the stress was low in the body and seat compared to the normal pressure. Compared with the allowable strength of the material for the parts of the valve system, the minimum safety factor was approximately 1.4, so the valve was stable. As a result of applying the design pressures of 0.5 MPa and 600℃ under the load conditions in the thermal-structural analysis, the safety factor in the valve body was about 3.4 when the normal pressure was applied and about 2.7 when the reverse pressure was applied. The stability of the fluid-structure interaction analysis was determined to be stable compared to the 600℃ yield strength of the material, and about 2.2 for the 40° open-angle disc for the valve body. In seismic analysis, the maximum value of the valve's stress value was about 9% to 11% when the seismic load was applied compared to the general structural analysis. Based on the results of this study, the structural stability and design feasibility of high-temperature valves that can be used in cogeneration plants and other power plants are presented.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.897-898
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• 2012

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.99-104
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• 2001

Thermally induced vibration response of solar array is investigated. The solar array model consists of composite thin walled beam and solar blanket, spreader bar. The composite thin walled beam incorporates a number of nonclassical effects of transverse shear, primary and secondary warping, rotary inertia and anisotropy of constituent materials. The solar blanket is a membrane subjected to uniform tension in the z direction. The spreader bar is a rigid member. A coupled thermal structure analysis that includes the effects of structural deformations on heating and temperature gradient is investigated. A stability criterion given in parameters for establishes the conditions for thermal flutter.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.569-570
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• 2008

• 한국정밀공학회지
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• 제25권5호
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• pp.7-14
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• 2008

• 한국화재소방학회논문지
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• 제27권3호
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• pp.72-79
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• 2013

최근 건축물은 재료의 고강도화 및 단면형상 최적화를 바탕으로 초고층화, 장대화 및 복합화 추세로 발달하고 있으나, 화재 위험성에 의한 구조적 거동에 관한 연구는 매우 미진한 실정이다. 특히 고강도 구조용 강재로 구성된 강구조 건축물의 구조부재에 대한 화재 노출 시 거동평가를 위한 기초적인 자료조차 거의 없는 실정이다. 따라서 본 연구에서는 고층 강구조 건축물에 활용되고 있는 고강도 구조용 강재의 고온 시 구조적 내력 평가를 위한 기계적 특성과 열적 특성 자료 도출을 목적으로 항복강도, 탄성계수 그리고 열전도율 등을 측정하고, 이를 일반 구조용 강재의 특성과 비교분석을 통하여 상대적 안전성을 평가한다.

• Structural Engineering and Mechanics
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• 제6권6호
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• pp.643-658
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• 1998

A thermal postbuckling analysis is presented for a moderately thick rectangular plate subjected to uniform or nonuniform tent-like temperature loading and resting on an elastic foundation. The plate is assumed to be simply supported on its two opposite edges and the two side edges remain free. The initial geometrical imperfection of the plate is taken into account. The formulation are based on the Reissner-Mindlin plate theory considering the first order shear deformation effect, and including plate-foundation interaction and thermal effects. The analysis uses a mixed Galerkin-perturbation technique to determine the thermal buckling loads and postbuckling equilibrium paths. Numerical examples are presented that relate to the performances of perfect and imperfect, moderately thick plates resting on Pasternak-type or softening nonlinear elastic foundations from which results for Winker elastic foundations follow as a limiting case. Typical results are presented in dimensionless graphical form.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.399-406
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• 2001

Thermally induced vibration response of composite thin walled beams is investigated. The thin-walled beam model incorporates a number of nonclassical effects of transverse shear, primary and secondary warping, rotary inertia and anisotropy of constituent materials. Thermally induced vibration response characteristics of a composite thin walled beam exhibiting the circumferentially uniform system(CUS) configuration are exploited in connection with the structural bending-torsion coupling resulting from directional properties of fiber reinforced composite materials and from ply stacking sequence. A coupled thermal structure analysis that includes the effects of structural deformations on heating and temperature gradient is investigated.