• Title/Summary/Keyword: 일반화 모드법

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Structural Dynamic Modification Using Improved Modal Synthesis Method (개선된 모드합성법을 이용한 구조물의 동특성 변경)

  • 송영래;장경진;박영필
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.176-183
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    • 1997
  • 본 논문에서는 모드합성법의 단점이라고 할 수 있는 고차모드의 생략오차를 보완하면서 합성 후의 전체구조물의 자유도를 줄일 수 있는 자유경계합성법을 대형복합구조물에 적용하기 위하여 일반화된 다중모드합성법을 제시하고 판구조물과 모형차에 적용하여 그 효율성을 검증하였다. 또한 모드합성법의 개념을 구조물의 동적구조변경에 적용하기 위한 부분구조 모드물성치 감도법을 제안하였으며, 이의 타당성을 확인하기 위하여 판구조물에 적용하였다. 이 방법은 물성치가 변하는 분계에서만 모드물성치의 감도를 다시 계산하여 합성하면 되므로 대형구조물의 구조변경시 효과적인 방법이다.

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Model Updating of a Car Body Structure Using a Generalized Free-Interface Mode Sensitivity Method (일반화 자유경계 모드 감도법을 이용한 차체구조물의 모델개선)

  • Jang, Gyeong-Jin;Park, Yeong-Pil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.5 s.176
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    • pp.1133-1145
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    • 2000
  • It is necessary to develop an efficient analysis method to identify the dynamic characteristics of a large mechanical structure and update its finite element model. That is because these processes need the huge computation of a large structure and iterative estimation due to the use of the first- order sensitivity. To efficiently carry out these processes, a new method, called the generalized free-interface mode sensitivity method, has been proposed in the authors' preceeding paper. This method is based on substructuring approach such as a free-interface method and a generalized synthesis algorithm. In this paper, the proposed method is applied to the model updating of a car body structure to verify its accuracy and reliability for a large mechanical structure.

Investigation on the Generalized Hydrodynamic Force and Response of a Flexible Body at Different Reference Coordinate System (기준 좌표계에 따른 탄성체의 일반화 파랑 하중 및 응답에 대한 연구)

  • Heo, Kyeonguk;Choi, Yoon-Rak
    • Journal of the Society of Naval Architects of Korea
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    • v.58 no.6
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    • pp.348-357
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    • 2021
  • In this paper, the generalized hydrodynamic force and response of a flexible body are calculated at different reference coordinate systems. We generalize the equation of motion for a flexible body by using the conservation of momentum (Mei et al., 2005). To obtain the equations in the generalized mode, two different reference coordinates are adopted. The first is the body-fixed coordinate system by a rigid body motion. The other is the inertial coordinate system which has been adopted for the analysis. Using the perturbation scheme in the weakly-nonlinear assumption, the equations of motion are expanded up to second-order quantities and several second-order forces are obtained. Numerical tests are conducted for the flexible barge model in head waves and the vertical bending is only considered in the hydroelastic responses. The results show that the linear response does not have the difference between the two formulations. On the other hand, second-order quantities have different values for which the rigid body motion is relatively large. However, the total summation of second-order quantities has not shown a large difference at each reference coordinate system.

A Hydroelastic Analysis of a Floating Fish Cage in Waves (부유식 가두리 양식장의 파랑중 유탄성 응답 해석)

  • Choi, Yoon-Rak;Yeo, Hwan-Tae
    • Journal of Ocean Engineering and Technology
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    • v.23 no.6
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    • pp.7-11
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    • 2009
  • The dynamic responses and drift forces in waves of a floating circular fish cage are analyzed considering hydroelastic effects. The method of generalized mode is used to calculate the hydroelastic responses of the floater of cage. The elastic mode shapes, generalized mass, and stiffness in dry mode are evaluated by using a structural analysis code. The higher-order boundary element method is adopted to analyze the interaction between fluid and deformable structure. Some results of vertical motions and drift forces are shown and compared with those for a rigid body.

Hydroelastic Responses for a VLFS close to a Breakwater by the Velocity Potential Continuation and Singularity Distribution Method (속도포텐셜접속법과 특이점분포법에 의한 방파제에 근접한 부유식 해상공항에 대한 유탄성 응답 해석)

  • Ho-Young Lee;Young-Ki Kwak;Jong-Hwan Park
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.2
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    • pp.11-18
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    • 2002
  • In this paper, the method calculating hydroelastic responses of very large floating structure close to a breakwater in waves is presented. The source-dipole distribution method is used to calculate the generalized radiation problem considering breakwater effects and the diffraction problem is analyzed by using the source-dipole distribution andvelocity potential continuation method. The response of a VLFS is approximated by anexpansion in terms of a free-free beam. Calculated model is a VLFS with 1000m in length in a sea with a straight breakwater. The vertical displacements and bonding moments around a VLFS are calculated by variations for distance between a VLFS and a breakwater and incident wave angle to know the effect of a breakwater.

공구파손의 파괴역학적 해석에 관한 기초적 연구

  • 이태세
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1992.04a
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    • pp.33-37
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    • 1992
  • 구조물과 기계부품에 부하를 주는 하중은 여러가지 종류가 있고, 이에 따르는 파괴의 형식도 여러가지가 있다. 그중에서도 연강압연용 로울러, 베어링 레일등은 집중 압축하중을 받는데 이들 부재의 파괴사고가 빈번히 일어나고 잇다. 압축에 의한 파괴 중 frectting, 피팅등과 같은 마모 현상은 두 재료의 표면이 서로 미끌어질때 일어나며, 이것이 공구나 기계부품의 성능과 수명을 저하시키는 주원인이 되며, 이러한 궁구나 기계 부품을 수리 또는 교환을 하기위한 인적, 경제적 손실은 막대하다. 본 연구에서는 금형등 공구의 마모편이 발생되는 마지막 과정인 크렉의 성장을 고찰하기 위하여 Sub-surface크랙 모델을 설정하여 2차원 유한요소 법으로 경계층 근방에 크랙이 존재하는 반무한 평면에 집중하중이 작용할때의 응력확대계수를 해설하였는데, 일반화된 해석법으로 혼합모드에서의 응력확대계수를 결정하였다.

Generalized Scattering Matrix of Multi-port($2{\times}2$port, 1port) Rectangular Waveguide Using $TE^z_{mn}$ Mode Matching Method ($TE^z_{mn}$ 모드정합법을 이용한 다중포트($2{\times}2$포트, 1포트) 직사각형 도파관의 일반화 산란행렬 추출)

  • Lee, J.K.;Mun, S.Y.;Park, K.U.;Heo, Y.K.;Cho, Y.K.
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.79-83
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    • 2003
  • Multi-port($2{\times}2$port, 1port) rectangular waveguide discontinuity problem has been analyzed by use of $TE^x_{mn}$ (mono)mode matching method. Matrix size can be reduced significantly in comparison with $TE_{mn}&TM_{mn}$(full-wave)mode matching method. the present results is compared with those by CST MicroWave Studio to validate the presint method.

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Evaluation of Free-Edge Delamination in Composite Laminates (복합재 적층판의 자유단 층간분리의 평가)

  • 김인권;공창덕;방조혁
    • Composites Research
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    • v.14 no.1
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    • pp.8-14
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    • 2001
  • A simplified method for determining the three mode(I, II, III) components of the strain energy release rate of free-edge delaminations in composite laminates is proposed. The interlaminar stresses are evaluated using the interface moment and the interface shear forces which are obtained from the equilibrium equations at the interface between the adjacent layers. Deformation of an edge-delaminated laminate is analysed by using a generalized quasi-three dimensional classical laminated plate theory. The analysis provides closed-form expression for the three components of the strain energy release rate. The analyses are performed for composite laminates subjected to uniaxial tension, with free-edge delaminations located symmetrically and asymmetrically with respect to the laminate midplane. The analysis results agreed with a finite element solution using the virtual crack closure technique.

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A Simplified Method for Determining Modal Strain Energy Release Rate of Free-Edge Delaminations in Laminated Composite (적층복합재의 자유단 박리에 대한 모드별 스트레인 에너지해방률의 간이계산법)

  • Kim, Taek-Hyun;Oh, Taek-Yul;Kim, In-Kweon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.3
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    • pp.423-429
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    • 1997
  • A simplified method for determining the mode components of the strain energy release rate of free-edge delaminations in laminated composite is proposed. The interlaminar stresses are evaluated as an interface moment and interface shear forces that are obtained from the equilibrium equations at the interface between the adjacent layers. Deformation of an edge-delaminated laminate is calculated by using a generalized quasi-three dimensional classical laminated plate theory developed by the authors. The analysis provides closed-form expression for the three components of the strain energy release rate. Comparison of results with a finite element solution using the virtual crack closure technique shows good agreement. In the present study, laminated composite with stacking sequences of [30/-30/90]$_{s}$ were examined. The simple nature of the method makes it suitable for primary design analysis for the delaminations of laminated composite.e.