• Composites Research
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• 제12권5호
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• pp.65-79
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• 1999

본 논문은 단순지지된 복합재료 사각판과 원통쉘이 결합된 구조물의 자유진동해석을 위한 해석적 방법에 대하여 기술하였다. 결합전 단순지시된 사각판과 원통쉘의 응답을 얻기 위하여 고전적 판이론과 Love의 얇은 쉘이론에 기초한 에너지법을 적용하였다. 결합구조물의 해석에는 동적응답법을 적용하였고, 길이방향 판과 쉘의 결합부에서의 동적 주기 하중과 모멘트는 Dirac 델타 함수와 정현 함수를 사용하였을 때 연속조건을 만족함을 보였다. 또한 원통쉘의 기하하적 매개변수인 쉘의 길이 대 반경비와 반경 대 두께비에 따른 진동특성의 변화를 고찰하였고, 복합재료의 섬유 방향각과 직교이방성 매개변수가 결합 원통쉘의 기본 진동수에 미치는 영향에 미치는 영향에 대하여 연구하였다.

• 한국정밀공학회지
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• 제27권6호
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• pp.55-63
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• 2010

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feedwater heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare degree of shell wall thinning mitigation rate to squared type with mitigation rate of other type baffle plate, three different types of impingement baffle plate-squared, curved and mitigating type-applied inside the shell. With these comparison data, this paper describes operation of experiments and numerical analysis which is composed similar condition with real feed water heater. And flow visualization is operated for verification of experiments and numerical analysis. In conclusion, this study shows that mitigating type baffle plate is more effective than other baffle plate about prevention of pressure concentration and pressure value decrease.

• Structural Engineering and Mechanics
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• 제20권4호
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• pp.451-463
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• 2005

Structural members commonly employed in marine and off-shore structures are usually fabricated from plates and shells. Collision of this class of structures is usually modeled as plate and shell structures subjected to dynamic impact loading. The understanding of the dynamic response and energy transmission of the structures subjected to low velocity impact is useful for the efficient design of this type of structures. The transmissions of transient energy flow and dynamic transient response of these structures under low velocity impact are presented in the paper. The structural intensity approach is adopted to study the elastic transient dynamic characteristics of the plate structures under low velocity impact. The nine-node degenerated shell elements are adopted to model both the target and impactor in the dynamic impact response analysis. The structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of the structures. Numerical results, including contact force and transient energy flow vectors as well as structural intensity stream lines, demonstrate the efficiency of the present approach and attenuating impact effects on this type of structures.

• 한국강구조학회 논문집
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• 제23권4호
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• pp.455-464
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• 2011

본 논문에서는 곡선 보강 복부판의 좌굴해석을 대체전단변형률 장을 갖는 8, 9절점 평면 쉘요소를 이용한 유한요소해석을 통하여 수행하였다. 수평보강재 및 수직보강재를 갖는 경우의 수직면내 곡선 복부판의 좌굴거동을 조사하기 위해 면내 모멘트 하중을 받는 경우에 대해서 복부판의 폭(b)의 변화, 보강재와 복부판의 휨-강성비(${\gamma}=EI/bD$)의 변화에 대한 변수연구를 수행하였다. 보강재를 갖지 않는 경우의 수직면내 곡선 복부판의 정적거동에 대해서도 조사되었다. 또한 모멘트 하중을 받는 경우에서 수평 보강재 및 수직 보강재의 좌굴능력이 비교 되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.335.1-335
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• 2002

Among many structural dynamics modification methods for plate and shell vibration problems, embedding an emboss to the surface is very efficient. But deciding an optimal position and shape using optimization algorithm needs defining geometry and remeshing the model for every iteration step to implement the method, which takes much numerical cost. (omitted)

• 동력기계공학회지
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• 제19권5호
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• pp.52-59
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• 2015

This paper is presented for the free vibration of a conical shell with annular plates or circular plate using the transfer of influence coefficient. The governing equations of vibration of a conical shell, including annular plate, are written as a coupled set of first order differential equations by using the transfer matrix of the shell. Once the transfer matrix of a single component has been determined, the entire structure matrix is obtained by the product of each component matrix and the joining matrix. The natural frequencies and the modes of vibration were calculated numerically for joined conical-annular plates. The validity of the present method is demonstrated through simple numerical examples, and through comparison with the results of finite element method, transfer matrix method and ANSYS. The conclusion show that the present method can accurately obtain natural vibration characteristics of the conical shell with annular or circle end plates.

• Structural Engineering and Mechanics
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• 제18권1호
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• pp.41-58
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• 2004

The postbuckling behaviour of thin shells has fascinated researchers because the theoretical prediction and their experimental verification are often different. In reality, shell panels possess small imperfections and these can cause large reduction in static buckling strength. This is more relevant in thin laminated composite shells. To study the postbuckling behaviour of thin, imperfect laminated composite shells using finite elements, explicit incremental or secant matrices have been presented in this paper. These incremental matrices which are derived using Marguerre's shallow shell theory can be used in combination with any thin plate/shell finite element (Classical Laminated Plate Theory - CLPT) and can be easily extended to the First Order Shear deformation Theory (FOST). The advantage of the present formulation is that it involves no numerical approximation in forming total potential energy of the shell during large deformations as opposed to earlier approximate formulations published in the literature. The initial imperfection in shells could be modeled by simply adjusting the ordinate of the shell forms. The present formulation is very easy to implement in any existing finite element codes. The secant matrices presented in this paper are shown to be very accurate in tracing the postbuckling behaviour of thin isotropic and laminated composite shells with general initial imperfections.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권3호
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• pp.454-467
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• 2013

A practical Ship Inner Shell Optimization Method (SISOM), the purpose of which is to improve the safety of the seagoing transport ship by decreasing the maximum Still Water Bending Moment (SWBM) of the hull girder under all typical loading conditions, is presented in this paper. The objective of SISOM is to make the maximum SWBM minimum, and the section areas of the inner shell are taken as optimization variables. The main requirements of the ship performances, such as cargo hold capacity, propeller and rudder immersion, bridge visibility, damage stability and prevention of pollution etc., are taken as constraints. The penalty function method is used in SISOM to change the above nonlinear constraint problem into an unconstrained one, which is then solved by applying the steepest descent method. After optimization, the optimal section area distribution of the inner shell is obtained, and the shape of inner shell is adjusted according to the optimal section area. SISOM is applied to a product oil tanker and a bulk carrier, and the maximum SWBM of the two ships is significantly decreased by changing the shape of inner shell plate slightly. The two examples prove that SISOM is highly efficient and valuable to engineering practice.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.505-510
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• 2001

Advanced Pressurized Reactor 1400(APR1400), which is a standard evolutionary advanced light water reactor(ALWR), has been developed from 1992 as one of long-term Government Project(G-7). The APR-1400 is designed to operate at the rated output of 4000MWt to produce an electric power output of around 1450MWe. Due to the increased electric power, In Nuclear Power plant huge quantities of heat are generated in the thermo-dynamic process used for producing electrical energy. So, There is considerationly additional cooling, Heat transfer area and increased cooling water of Heat Exchanger which take care of the different smaller cooling duties within the nuclear power plant. We review applying to PRE instead of Shell-and-Tube Heat exchanger. In this paper, we describe the major design features of PRE, Comparison between a PHE and a Shell-and-Tube Heat Exchanger, and then Applicability of Plate Heat Exchanger in Nuclear Power Plant Component Cooling water systems.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.402-407
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• 1997

For cylindrical shells, the closed-form solutions are limited only to the cases with special boundary and/or loading conditions. Though the finite element method is certainly a powerful solution approach for the general structural dynamics problems, it is known to provide reliable solutions only in the low frequency region due to the inherent high sensitivities of structural and numerical modeling errors. Instead, the spectral element method has been proved to provide extremely accurate dynamic responses even in the high frequency region. Since the wave characteristics of a cylindrical shell becomes identical to that of a flat plate as the frequency increases, an equivalent plate model (EPM) representing the high-frequency dynamic characteristics of a cylindrical shell is introduced herein. The EPM-based spectral element analysis solutions are compared with the known analytical solutions for the corresponding cylindrical shell to confirm the validity of the present modeling approach.