• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.901-906
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• 2001

Finite element method is used for the structural analysis of low speed large diesel engine structures, and the kinematic and mechanism analysis is performed to compute loads applied to the engine structures. A typical diesel engine is used as an example and static and dynamic structural analyses are demonstrated. Dynamic stress of engine is measured during the sea-trial operation of the ship.

• 동력기계공학회지
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• 제1권1호
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• pp.91-97
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• 1997

Recently, it is increased by degrees to construct complex and large structures. In general, in order to solve the dynamic problem of these structures they have used finite element method(FEM). In this method, however, it is necessary to prove whether its results are correct or not. Therefore it requires much effort, time and many expenses for dynamic analysis of complex and large structures. Authors have developed the transfer dynamic stiffness coefficient method(TDSCM) which is the new vibration analysis method for complex and large structures on personal computer, and confirmed that the results of this method are good for these structures on personal computer. In this paper, TDSCM is applied to the torsional vibration analysis for the shaft system which consist of concentrated disks and shafts of continuous body. First, we formulate algorithms for torsional free and forced vibration analysis, and compare the results of TDSCM and FEM.

• 대한토목학회논문집
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• 제26권3A호
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• pp.465-471
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• 2006

지진과 같은 동적 반복하중을 받는 강구조물의 이력거동을 구현하기 위해서는 사용된 강재의 정 동적 상태에서의 응력-변형률 관계 및 특성을 고려한 동적반복소성모델이 필요하다. 본 연구에서는 SM490강재의 정 동적 단조 및 반복하중 실험을 수행하여 역학적 특성 및 응력-변형률 관계를 명확히 하였다. 그리고 실험결과에 기초하여 SM490강재의 동적반복소성모델을 제안하였으며 이를 유한변위이론에 기초한 3차원 탄소성 유한요소해석에 적용하였다. 실험시편을 모델링하여 정 동적 단조, 반복 및 변형률속도변화에 따른 3차원 탄소성 유한요소해석을 수행하였으며 이를 실험결과와 비교하였다. 비교를 통하여 본 연구에서 개발한 해석기법이 강부재의 정 동적 변형상태를 정도있게 예측할 수 있음을 검증하였다.

• Structural Engineering and Mechanics
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• 제29권4호
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• pp.355-380
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• 2008

In this study, the new three-dimensional finite element analysis model of guideway structures considering ultra high-speed magnetic levitation train-bridge interaction, in which the various improved finite elements are used to model structural members, is proposed. The box-type bridge deck of guideway structures is modeled by Nonconforming Flat Shell finite elements with six DOF (degrees of freedom). The sidewalls on a bridge deck are idealized by using beam finite elements and spring connecting elements. The vehicle model devised for an ultra high-speed Maglev train is employed, which is composed of rigid bodies with concentrated mass. The characteristics of levitation and guidance force, which exist between the super-conducting magnet and guideway, are modeled with the equivalent spring model. By Lagrange's equations of motion, the equations of motion of Maglev train are formulated. Finally, by deriving the equations of the force acting on the guideway considering Maglev train-bridge interaction, the complete system matrices of Maglev train-guideway structure system are composed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.443-444
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• 2011

This paper discusses a model order reduction for large order rotor dynamics systems results from the finite element discretization. Typical rotor systems consist of a rotor, built-on parts, and a support system, and require prudent consideration in their dynamic analysis models because they include unsymmetric stiffness, localized nonproportional damping and frequency dependent gyroscopic effects. When the finite element model has a very large number of degrees of freedom because of complex geometry, repeated dynamic analyses to investigate the critical speeds, stability, and unbalanced response are computationally very expensive to finish within a practical design cycle. In this paper, the Krylov-based model order reduction via moment matching significantly speeds up the dynamic analyses necessary to check eigenvalues and critical speeds of a Nelson-Vaugh rotor system. With this approach the dynamic simulation is efficiently repeated via a reduced system by changing a running rotational speed because it can be preserved as a parameter in the process of model reduction. The Campbell diagram by the reduced system shows very good agreement with that of the original system. A 3-D finite element model of the Nelson-Vaugh rotor system is taken as a numerical example to demonstrate the advantages of this model reduction for rotor dynamic simulation.

• International Journal of Aerospace System Engineering
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• 제3권1호
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• pp.10-16
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• 2016

A trigonometric Layerwise higher order shear deformation theory (TLHSDT) is developed and implemented for free vibration and buckling analysis of laminated composite and sandwich plates by analytical and finite element formulation. The present model assumes parabolic variation of out-plane stresses through the depth of the plate and also accomplish the zero transverse shear stresses over the surface of the plate. Thus a need of shear correction factor is obviated. The present zigzag model able to meet the transverse shear stress continuity and zigzag form of in-plane displacement continuity at the plate interfaces. Hence, botheration of shear correction coefficient is neglected. In the case of analytical method, the governing differential equation and boundary conditions are obtained from the principle of virtual work. For the finite element formulation, an efficient eight noded $C^0$ continuous isoparametric serendipity element is established and employed to examine the dynamic analysis. Like FSDT, the considered mathematical model possesses similar number of variables and which decides the present models computationally more effective. Several numerical predictions are carried out and results are compared with those of other existing numerical approaches.

• 한국터널지하공간학회 논문집
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• 제21권2호
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• pp.211-225
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• 2019

최근 우리나라 전 지역에서 지진이 발생하고 이에 각 분야에서의 내진해석 연구가 활발히 진행되고 있고 지반을 고려하는 SSI 해석 연구 또한 지속적으로 수행되고 있다. 하지만 지반을 고려한 대부분의 기존 동적해석의 경우, 수치해석 방법에 따른 건물의 동적거동에 대한 비교 분석이 부족한 실정이다. 따라서 본 연구에서는 초고층 건물을 대상으로 유한요소 프로그램인 MIDAS GTS NX와 유한차분 프로그램인 FLAC 2D를 사용하여 동적해석을 수행하고, 결과를 비교 분석하고자하였다. 연구 결과, 건물 지상 및 지하부의 휨응력의 경우 최대 압축 및 인장 모두 MIDAS GTS NX가 FLAC 2D보다 다소 크게 발생하였지만, 최대 수평변위값 및 분포양상, 취약부의 위치는 유사하게 나타났다. 따라서 동적해석을 위해 사용자의 편의에 따라 유한요소법이나 유한차분법에 근거한 프로그램 중 어느 것을 사용해도 차이가 없음을 확인하였다.

• Steel and Composite Structures
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• 제18권1호
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• pp.51-69
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• 2015

In recent years, the use of fiber reinforced polymer composites has increased because of their unique features. They have been used widely in the aircraft and space industries, medical and sporting goods and automotive industries. Thanks to their beneficial and various advantages over traditional materials such as high strength, high rigidity, low weight, corrosion resistance, low maintenance cost, aesthetic appearance and easy demountable or moveable construction. In this paper, it is aimed to determine and compare the geometrically nonlinear static and dynamic analysis results of footbridges using steel and glass fiber reinforced polymer composite (GFRP) materials. For this purpose, Halgavor suspension footbridge is selected as numerical examples. The analyses are performed using three identical footbridges, first constructed from steel, second built only with GFRP material and third made of steel- GFRP material, under static and dynamic loadings using finite element method. In the finite element modeling and analyses, SAP2000 program is used. Geometric nonlinearities are taken into consideration in the analysis using P-Delta criterion. The numerical results have indicated that the responses of the three bridges are different and that the response values obtained for the GFRP composite bridge are quite less compared to the steel bridge. It is understood that GFRP material is more useful than the steel for the footbridges.

• Structural Engineering and Mechanics
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• 제11권4호
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• pp.407-422
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• 2001

The linear constitutive relations and the failure criteria of composite materials made of thermoviscoelastic solids are presented. The post-failure material behavior is proposed and the dynamic finite element equations are formulated. However, a nonlinear term is kept in the energy equation because it represents the effect of the second law of thermodynamics. A general purpose nonlinear three-dimensional dynamic finite element program COMPASS is upgraded and employed in this work to investigate the interdependence among stress wave propagation, stress concentration, failure progression and temperature elevation in composite materials. The consequence of truthfully incorporating the second law of thermodynamics is clearly observed: it will always cause temperature rise if there exists a dynamic mechanical process.

• Structural Engineering and Mechanics
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• 제55권3호
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• pp.583-603
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• 2015

There are so many applications of perforated pates with various penetration patterns. If they are penetrated regularly, it can be represented by solid plate with equivalent material properties, which has a benefit of finite element modelling and reducing computation time for the analysis. Because the equivalent material properties suggested already are not proper to be applicable for the dynamic analysis, it is necessary to extract the equivalent material properties for the dynamic analysis. Therefore, in this study, the equivalent modulus of elasticity are obtained for the perforated plate with a triangular penetration pattern by comparing the natural frequencies of the perforated plate with those of solid plate, which are represented with respect to the ligament efficacy. Using the equivalent material properties suggested, the modal analyses of the partially perforated rectangular plate with a triangular penetration pattern are performed and its applicability is shown by comparing natural frequencies of perforated and homogeneous solid plates from finite element method and analytical method.