• Title/Summary/Keyword: matrix stiffness method

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Comparison of Damping Matrix Estimation Methods for Model Updating (모형개선을 위한 감쇠행렬 추정법의 비교)

  • Lee, Gun-Myung;Ju, Young-Ho;Park, Mun-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.10
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    • pp.923-930
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    • 2010
  • Finite element models of dynamic systems can be updated in two stages. In the first stage, mass and stiffness matrices are updated neglecting damping, and in the second stage, damping matrices are estimated with the mass and stiffness matrices fixed. Three methods to estimate damping matrices for this purpose are proposed in this paper. The methods include one for proportional damping systems and two for non-proportional damping systems. Method 1 utilizes orthogonality of normal modes and estimates damping matrices using the modal parameters extracted from the measured responses. Method 2 estimates damping matrices from impedance matrices which are the inverse of FRF matrices. Method 3 estimates damping using the equation which relates a damping matrix to the difference between the analytical and measured FRFs. The characteristics of the three methods are investigated by applying them to simulated discrete system data and experimental cantilever beam data.

Free Vibration Analysis of Lattice Type Structure by Transfer Stiffness Coefficient Method (전달 강성계수법에 의한 격자형 구조물의 자유 진동 해석)

  • 문덕홍;최명수;강화중
    • Journal of KSNVE
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    • v.8 no.2
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    • pp.361-368
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    • 1998
  • Complex and large lattice type structures are frequently used in design of bridge, tower, crane and aerospace structures. In general, in order to analyze these structures we have used the finite element method(FEM). This method is the most widely used and powerful tool for structural analysis. However, it is necessary to use a large amount of computer memory and computation time because the FEM resuires many degrees of freedom for solving dynamic problems exactly for these complex and large structures. For overcoming this problem, the authors developed the transfer stiffness coefficient method(TSCM). This method is based on the concept of the transfer of the nodal dynamic stiffness coefficient which is related to force and displacement vector at each node. In this paper, the authors formulate vibration analysis algorithm for a complex and large lattice type structure using the transfer of the nodal dynamic stiffness coefficient. And we confirmed the validity of TSCM through numerical computational and experimental results for a lattice type structure.

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Derivation of Added Mass Matrix and Sloshing stiffness matrix of the Ideal Fluid using BEM and Application to the Seismic Analysis of Cylindrical Liquid storage tanks. (경계요소법에 의한 이상유체의 부가질량 및 슬러싱 강성행렬 도출과 원통형 액체 저장 탱크 지진응답 해석)

  • 김재관;이진호;진병무
    • Journal of the Earthquake Engineering Society of Korea
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    • v.4 no.3
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    • pp.83-98
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    • 2000
  • 유연한 액체 저장탱크 내 유체의 부가질량 및 슬러싱 강성행렬을 도출하는 새로운 방법을 제시하였다. 비점성, 비압축성 이상유체를 표면 출렁임을 고려하여 경계요소법에 의하여 모델링하였다. 유체의 표면과 저장탱크 벽체의 접촉면과 같은 불연속 경계를 다루기 위해 특별한 과정을 도입하였다. 원통형 액체저장탱크의 지진응답해석에 적용하여 우수한 결과를 얻을 수 있음을 확인하였다.

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A Study on the Stiffness of Frustum-shaped Coil Spring (원추형 코일스프링의 강성에 대한 연구)

  • 김진훈;이수종;이경호
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2001.11a
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    • pp.21-27
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    • 2001
  • Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression, principle of virtual work is adapted The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacements, that is, the step by step method is used in this paper. The results of the finite element method are fairly well agreed with those of various experiments. Using MATLAB program developed in this paper, spring constants and stresses can be predicted by input of few factors.

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An efficient method for computation of receptances of structural systems with sparse, non-proportional damping matrix (성긴 일반 감쇠행렬을 포함하는 구조물에 대한 효율적인 주파수 응답 계산 방법)

  • Park, Jong-Heuck;Hong, Seong-Wook
    • Journal of the Korean Society for Precision Engineering
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    • v.12 no.7
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    • pp.99-106
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    • 1995
  • Frequency response functions are of great use in dynamic analysis of structural systems. The present paper proposes an efficient method for computation of the frequency rewponse functions of linear structural dynamic models with a sparse, non-proportional damping matrix. An exact condensation procedure is proposed which enables the present method to condense the matrices without resulting in any errors. Also, an iterative scheme is proposed to be able to avoid matrix inversion in computing frequency response matrix. The proposed method is illustrated through a numerical example.

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Dynamic Stability Analysis of Nonconservative Systems for Variable Parameters using FE Method (유한요소기법을 이용한 비보존력이 작용하는 보-기둥 구조의 다양한 제변수 변화에 따른 동적 안정성 해석)

  • Lee Jun-Seok;Min Byoung-Cheol;Kim Moon-Young
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.17 no.4
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    • pp.351-363
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    • 2004
  • Equation of motion of non conservative system considering mass matrix, elastic stiffness matrix, load correction stiffness matrix by circulatory force's direction change and Winkler and Pasternak foundation stiffness matrix is derived. Also stability analysis due to the divergence and flutter loads is performed. And the influence of internal and external damping coefficient on flutter load is investigated applying the quadratic eigen problem solution. Additionally the influence of non-conservative force's direction parameter, internal and external damping and Winkler and Pasternak foundation on the critical load of Beck's and Leipholz's and Hauger's columns are investigated.

Investigating the effect of edge crack on the modal properties of composite wing using dynamic stiffness matrix

  • Torabi, Ali Reza;Shams, Shahrokh;Fatehi-Narab, Mahdi
    • Steel and Composite Structures
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    • v.39 no.5
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    • pp.543-564
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    • 2021
  • In this study free vibration analysis of a cracked Goland composite wing is investigated. The wing is modelled as a cantilevered beam based on Euler- Bernoulli equations. Also, composite material is modelled based on lamina fiber-reinforced. Edge crack is modelled by additional boundary conditions and local flexibility matrix in crack location, Castigliano's theorem and energy release rate formulation. Governing differential equations are extracted by Hamilton's principle. Using the separation of variables method, general solution in the normalized form for bending and torsion deflection is achieved then expressions for the cross-sectional rotation, the bending moment, the shear force and the torsional moment for the cantilevered beam are obtained. The cracked beam is modelled by separation of beam into two interconnected intact beams. Free vibration analysis of the beam is performed by applying boundary conditions at the fixed end, the free end, continuity conditions in the crack location of the beam and dynamic stiffness matrix determinant. Also, the effects of various parameters such as length and location of crack and fiber angle on natural frequencies and mode shapes are studied. Modal analysis results illustrate that natural frequencies and mode shapes are affected by depth and location of edge crack and coupling parameter.

DEVELOPMENT OF PARALLEL COMPUTATION METHOD FOR THE p VERSION IN THE FINITE ELEMENT METHOD

  • Kim, Chang-Geun;Cha, Ho-Jung
    • Journal of applied mathematics & informatics
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    • v.6 no.2
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    • pp.649-659
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    • 1999
  • This paper presents a parallel implementation of stiff-ness matrix calculation based on the processor farm model on a net-work of workstations running PVM programming environment. As the computational characteristics of stiffnes matrix exhibits good po-tentials for effective prallel computation the performance improve-ment is show to be almost linear with the number of sorkstations involved in the computation.

Development of a Wall Analysis Model Grafting FE-BEM (FE-BEM을 결합한 벽체의 해석모델 개발)

  • Jung , Nam-Su;Choi, Won;Lee, Ho-Jae;Kim , Han-Joong;Lee , Jeong-Jae;Kim, Jong-Ok
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.5
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    • pp.61-68
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    • 2004
  • Methodologies of the finite element and boundary element are combined to achieve an efficient and accurate analysis model of frame structure containing shear wall. This model analyzes the frame by employing the finite element method and the shear wall by boundary element method. This study is applicable to a specific situation, where the boundary element is surrounded by finite elements. By employing FE dominant method in which boundary stiffness matrix is transformed into finite element stiffness matrix, boundary element and finite element method are combined to analyze frame structure with walls.

Forced Vibration Analysis of a Hollow Crankshaft by using Transfer Matrix Method and Finite Element Method (전달 행렬법과 유한요소법을 이용한 중공 크랭크축의 강제 진동 해석)

  • 김관주;최진욱
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.6
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    • pp.44-52
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    • 1997
  • As part of the effort to reduce the weight of powertrain, a hollow crankshaft has been designed. The mass reduction of the crankshaft changes the dynamic properties of the crankshaft such as moment of inertia, and torsional, bending stiffness. The purpose of this paper is to compare the dynamic behavior of the hollow crankshaft with that of the original, solid crankshaft. Global dynamic behavior of the crankshaft is analyzed bgy the transfer matrix method(TMM). The crankshaft has been modeled by 38 lumped mass and stiffness elements. The dynamic patameters of each lumped element are provided by Finite Element Method(FEM). The responses of the crankshaft from TMM are fed back as loading conditions to the Finite Element model to obtain dynamic stresses for critical areas of the crankshaft.

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