• 한국전산유체공학회지
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• 제15권3호
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• pp.73-80
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• 2010

In this paper, we present the exact Riemann solver for the compressible liquid-gas two-phase shock tube problems. We hereby consider both isentropic and non-isentropic two-phase flows. The shock tube has a diaphragm in the mid-section which separates the liquid medium on the left and the gas medium on the right. By rupturing the diaphragm, various waves are observed on the phasic field variables such as pressure, density, temperature and void fraction in the form of rarefaction wave, shock wave and material interface (contact discontinuity). Both phases are treated as compressible fluids using the linearized equation of state or the stiffened-gas equation of state. We solve several shock tube problems made of a high/low pressure in the liquid and a low/high pressure in the gas. The wave propagations are well resolved by the exact Riemann solutions.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.47-50
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• 2004

It is very important that the analysis of postbuckling characteristics for stiffened composite structure. Damage tolerance design concept has been imported in many aerospace structures design to increase the structural efficiency and material failure is an inevitable process in postbuckling behavior. These design concepts are very efficient but consume very much calculation time in analytical process. The proper analysis method for reducing calculation time was researched and the total analysis time was reduced. A selection of proper element, the large load increments in linear response region, and the termination of analysis for unnecessary region were imported in the analysis and about $70\%$ time reduction was achieved with keeping a high accuracy of results.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.268-271
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• 2005

Researches based on genetic algorithms have been performed in composite laminated structures optimization since 1990. However, conventional genetic algorithms have a disadvantage that its augmentation of calculation costs. A lot of variations have been proposed to improve the performance and efficiency, and micro genetic algorithm is one of them. In this paper, micro Genetic Algorithm was employed in the optimization of laminated stiffened composite structures to maximize the linear critical buckling load and the results from both conventional genetic algorithm and micro genetic algorithm were compared.

• 소음진동
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• 제6권6호
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• pp.735-747
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• 1996

In this paper, buckling reliability analyses of stiffened cylinder with random initial geometric imperfection under axial impact load are performed by the combined response surface method. The effect of random geometric imperfection on the failure probability and reliability is recognized quantitatively. Buckling reliability decreases with the increase of mean value, cov of initial geometric imperfection under the same external load. Buckling probability under impact load is greater than those under static load with the same condition. From the probabilistic characteristics of imapct buckling load, relation between reliability index and safety parameter can be obtained in addition to the relation between load and reliability index. And those results can be used to determine the range of required safety parameter and acceptable imperfaction.

• Ocean Systems Engineering
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• 제1권3호
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• pp.223-239
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• 2011

In combat operations, naval ships may be subjected to considerable air blast and underwater shock loads capable of causing severe structural damage. As the experimental study imposes great monetary and time cost, the numerical solution may provide a valuable alternative. This study emphasises on numerical analysis for optimization of stiffened and unstiffened plate's structural response subjected to air blast load. Linear and non linear finite element (FE) modeling and analysis was carried out and compared with existing experimental results. The obtained results reveal a good agreement between numerical and experimental observations. The presented FE models can eliminate confusion regarding parameters selection and FE operations processing, using commercial software available currently.

• 한국지진공학회논문집
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• 제5권3호
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• pp.57-64
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• 2001

보강된 판 및 쉘구조의 동적 비선형해석을 수행하기 위하여, 유한회전을 고려한 변형된 쉘유한요소를 이용하여 total Lagrangian formulation이 제시된다. 전단구속 (shear locking) 현상과 가상의 제로에너지 모우드를 동시에 제거하기 위하여 가정변형도 개념을 채용한다. 탄소성해석에서는 return mapping 미해rithm이 쉘구조의 붕괴 해석에 적용된다. Newmark 직접적분법을 사용하여 동하중 및 지진하중을 받는 쉘구조의 동적 비선형해석 결과를 제시한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.952-956
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• 2004

The soil-structure interactions are caused by the point sources of explosions, deriving piles, compaction of foundations and excavations those are frequently arose in the construction sites. Thus the analysis of soil-structure interactions is one of the most important subjects in the fields of dynamic analysis and vibration control. From this viewpoint, the aim of this study is to collect the basic data for designing foundation structures throughout understanding the dynamic structural behavior, which is embodied by the dynamic analysis of soil-structure systems. In this study, the dynamic analyses of stiffened thick plates subjected to in-plane stress on elastic foundations are carried out. The foundation is modeled as Pasternak foundation that includes the continuity effect of foundations. Also both the Mindlin plate theory and Timoshenko beam-column theory are used for analyzing the thick plates and beams, respectively.

• 소음진동
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• 제9권3호
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• pp.485-492
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• 1999

The effects of boundary conditions on vibration characteristics for the ring stiffered composite cylindrical shells are investigated by theoretical and experimental method. In the theoretical procedure, the Love's thin shell theory combined with the discrete stiffener theory to consider the ring stiffening effect are adopted to derive the frequency equation. In experiment, the impact exciting method is used to obtain the vibraton results. Five different boundary conditions: clamped-clamped, simply supported-simply supported, free-free, clamped-free, clamped-simply supported are considered in this study.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.794-798
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• 2004

This paper is analysis of stiffened opening thick plate on foundation. This paper has the object of investigating natural frequencies of opening thick plates on Pasternak foundation by means of finite element method and providing Kinematic design data for mat of building structures. In this paper, vibration analysis of rectangular opening thick plate is done by use of Serendipity finite element with 8 nodes by considering shearing strain of plate. And vibration analysis of stiffener is done by used of Timoshenko beam-column element wit 3 nodes. It is shown that natural frequencies depend on not only Winkler foundation parameter but also shear foundation parameter, opening position, opening size, stiffener size.

• Structural Engineering and Mechanics
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• 제60권4호
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• pp.615-631
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• 2016

In this paper, an analytical method for the Post-buckling response of cylindrical shells with spiral stiffeners surrounded by an elastic medium subjected to external pressure is presented. The proposed model is based on two parameters elastic foundation Winkler and Pasternak. The material properties of the shell and stiffeners are assumed to be continuously graded in the thickness direction. According to the Von Karman nonlinear equations and the classical plate theory of shells, strain-displacement relations are obtained. The smeared stiffeners technique and Galerkin method is used to solve the nonlinear problem. To valid the formulations, comparisons are made with the available solutions for nonlinear static buckling of stiffened homogeneous and un-stiffened FGM cylindrical shells. The obtained results show the elastic foundation Winkler on the response of buckling is more effective than the elastic foundation Pasternak. Also the ceramic shells buckling strength higher than the metal shells and minimum critical buckling load is occurred, when both of the stiffeners have angle of thirty degrees.