• Title, Summary, Keyword: mode superposition method

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Dynamic Simulation for High-speed Pantograph and Overhead-line using a Vibration Mode Superposition Method (모드중첩법을 이용한 고속용 팬터그래프와 전차선의 동적 상호작용 시뮬레이션)

  • Cho, Yong-Hyeon;Lee, Ki-Won;Park, Hyun-Jun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.494-497
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    • 2004
  • A dynamic simulation for a high-speed pantograph-overheadline has been performed using mode superposition method to predict contact forces between pantograph and overheadline. We can deal with non-linear dampers of the pantograph and pre-sag of overhead-line for the simulation. But, we can not consider slackness of dropper in the overhead-line. According to the simulation results, the contact forces and displacements are reasonably predicted, compared with other foreign simulation results.

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Estimation of Structural Displacements for Cantilever Beam Using Mode Shapes and Accelerometers Under Free Vibration (모드 형상과 가속도계를 이용한 자유 진동하는 외팔보의 변위 추정)

  • Kim, Kyung Jong;Lee, Yong Hwan;Lee, Kyu Beom;Lee, Cheol Soon;Cho, Jin Yeon;Kim, Jeong Ho
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.45 no.5
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    • pp.376-385
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    • 2017
  • In this paper, a method for the estimation of structural displacements using structure's mode shapes and accelerations is suggested to reduce the disadvantages of acceleration time integration method. Acceleration time integration method requires accurate information on initial conditions, and errors caused by noise can be accumulated during time integration. To avoid these problems, the method for the estimation of structural displacements based on mode superposition method is developed and two vibration experiments for cantilever beam are conducted to verify this method. Static displacements and dynamic displacements of beam structure are estimated using measured accelerations from experiments and mode shapes of cantilever beam, and they are compared with measured displacements using laser displacement sensor. From these results, the validity and usefulness of this method are verified.

A Time Domain Analysis for Hydroelastic Behavior of a Mat-type Large Floating Structure in Calm Water under Dynamic Loadings by Mode Superposition Method (모드중첩법을 이용한 정수중의 매트형 거대부유구조물의 동하중에 대한 시간영역 유탄성 해석)

  • D.H. Lee;K.N. Jo;Y.R. Choi;S.Y. Hong;H.S. Choi
    • Journal of the Society of Naval Architects of Korea
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    • v.38 no.4
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    • pp.39-47
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    • 2001
  • In this paper, the hydroelastic behavior of a mat-type large floating structure is analyzed in time domain by using mode superposition method. The time-memory function is estimated by Fourier transforming the wave damping coefficients, which are computed by a higher-order boundary element method based on potential theory. Meanwhile, the structural response is obtained by time integrating the eigenmodes of the structure. Numerical examples are made for three test cases on the scaled model of a mat-type large floating structure ; weight pull-up case, weight drop case and weight moving case. In all three cases, the numerical results coincide well with experimental data.

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Finite Element Analysis of Unbalance Response of a High Speed Flexible Polygon Mirror Scanner Motor with Asymmetric Finite Element Equations (비대칭 유한 요소 방정식으로 표현되는 고속 유연 폴리곤 미러 스캐너 모터의 유한 요소 불평형 응답 해석)

  • Seo, Chan-Hee;Jung, Kyung-Moon;Jang, Gun-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1022-1027
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    • 2007
  • This paper presents a method to analyze the unbalance response of a high speed polygon mirror scanner motor supported by sintered metal bearing and flexible structures by using the finite element method and the mode superposition method considering the asymmetry of the gyroscopic effect and sintered metal bearing. The eigenvalues and eigenvectors are calculated by solving the eigenvalue problem and the adjoint eigenvalue problem by using the restarted Arnoldi iteration method. The decoupled equations of motion can be obtained from global finite element motion equations by using the orthogonal relation between the right eigenvectors and left eigenvectors. The decoupled equations of motion are used to analyze the unbalance response of a high speed polygon mirror scanner motor. The validity of the proposed method is verified by comparing the simulated unbalance response with the experimental results.

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Dynamic stiffness based computation of response for framed machine foundations

  • Lakshmanan, N.;Gopalakrishnan, N.;Rama Rao, G.V.;Sathish kumar, K.
    • Geomechanics and Engineering
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    • v.1 no.2
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    • pp.121-142
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    • 2009
  • The paper deals with the applications of spectral finite element method to the dynamic analysis of framed foundations supporting high speed machines. Comparative performance of approximate dynamic stiffness methods formulated using static stiffness and lumped or consistent or average mass matrices with the exact spectral finite element for a three dimensional Euler-Bernoulli beam element is presented. The convergence of response computed using mode superposition method with the appropriate dynamic stiffness method as the number of modes increase is illustrated. Frequency proportional discretisation level required for mode superposition and approximate dynamic stiffness methods is outlined. It is reiterated that the results of exact dynamic stiffness method are invariant with reference to the discretisation level. The Eigen-frequencies of the system are evaluated using William-Wittrick algorithm and Sturm number generation in the $LDL^T$ decomposition of the real part of the dynamic stiffness matrix, as they cannot be explicitly evaluated. Major's method for dynamic analysis of machine supporting structures is modified and the plane frames are replaced with springs of exact dynamic stiffness and dynamically flexible longitudinal frames. Results of the analysis are compared with exact values. The possible simplifications that could be introduced for a typical machine induced excitation on a framed structure are illustrated and the developed program is modified to account for dynamic constraint equations with a master slave degree of freedom (DOF) option.

Dynamics of a HDD spindle system due to the change of FDBs (유체베어링의 설계변화에 따른 HDD 스핀들 시스템의 동특성 해석)

  • Park, Ki-Yong;Jang, Gun-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.407-413
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    • 2008
  • This paper investigates the dynamics of a HDD spindle system due to the change of FDBs. Flying height of the HDD spindle system is determined through the static analysis of the FDBs, and the stiffness and damping coefficients are calculated through the dynamic analysis of the FDBs. Free vibration characteristics and shock response of the HDD spindle system are analyzed by using the finite element method and the mode superposition method. Experimental modal test is also performed to verify the accuracy of the proposed method. This research shows that the stiffness coefficients of journal heating mostly affect the rocking frequencies because their magnitude are within the range of the stiffness of supporting structure. It also shows that the damping coefficients of thrust bearing mostly affect the axial frequency because the stiffness of thrust bearing is much smaller that that of supporting structure.

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Hydroelastic Analysis of Pontoon Type VLFS Considering the Location and Shape of OWC Chamber (공기챔버 위치에 따른 폰툰형 초대형 구조물 유탄성응답 해석)

  • Hong, Sa-Young;Kyoung, Jo-Hyun;Kim, Byoung-Wan
    • Journal of Ocean Engineering and Technology
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    • v.22 no.1
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    • pp.22-29
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    • 2008
  • A numerical investigation is made on the effects of the location and shape of the front wall of an OWC(Oscillating Water Column) chamber on the hydroelastic response of a VLFS. Most of the studies on the effects of an OWC chamber on the response of a VLFS have assumed the location of the OWC chamber to be at the front of the VLFS. In the present study, an OWC-chamber is introduced at an arbitrary position in relation to a VLFS to determine the influence of the location and shape of the OWC chamber on the hydroelastic response of the VLFS. A finite element method is adopted as a numerical scheme for the fluid domain. or the finite element method, combined with a mode superposition method, is applied in order to consider the change of mass and stiffness The OWC chamber in a piecewise constant manner. or the facilitated anefficient analysis of The hydroelastic response of the VLFS, as well as the easy modeling of different shape and material properties for the structure. Reduction of hydroelastic response of the VLFS is investigated for various locations and front wall shapes of the owe chamber.

Dynamic Analysis for Mechanical Systems with Multi-Degree of Freedom under Base Excitation Using Relative Acceleration (상대 가속도를 이용한 기초 가진을 받는 다자유도 기계 시스템의 동적 해석)

  • Lee, Tae Won
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.3
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    • pp.36-41
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    • 2020
  • Mechanical systems installed in transport devices, such as vehicles, airplanes, and ships, are mostly subject to translational accelerations at the joints during operations. This base acceleration excitation has a large influence on the performance of the system, therefore, its response must be well analyzed. However, the existing methods for dynamic analysis of structures have some limitations in use. This study presents a new numerical method using relative acceleration to solve these limitations. If the governing equation of motion is linear and the mass matrix, the damping matrix, and the stiffness matrix are constant over time in the finite element analysis, the proposed method can be applied to the transient behavior analysis and the harmonic response analysis of the structure. Because it is not necessary to introduce a virtual mass and the rigid body motions are removed from the analysis, it is possible to use not only the direct integration method in the time domain but also the mode superposition method to obtain the dynamic responses. This paper demonstrates with three examples how the present method is suitable for the dynamic analysis of a structure with multi-degree of freedom.

Modal Analysis of Curved Beam. (곡선보의 모우드 해석)

  • 김영문;유기표
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.349-354
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    • 2000
  • The modal analysis based on deformations is the method to drived dynamic responsed from superposition of natural frequency and mode shape. In order to free vibration analysis of the structures, Aluminum-made model is used in experiment. The dynamic characteristic of the structures are determined from acceleration measurements using impulse hammer. Experimenrt input and output signal are derive from impact hammer and the one accerometer. This paper present three methods for calculating the natural frequencies and mode shapes of the structure with theory value and finite element analysis, experiment. The results were good approximated about natural frequency and mode shape.

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Dynamic analysis for complex structures using the improved component mode method (개선된 콤포넌트 모드법을 이용한 거대구조물의 동적해석)

  • 심재수;박명균
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.37-44
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    • 1993
  • There are a lot of linear dynamic analysis methods for complex structures. Each method has advantages and shortcomings. Method of dynamic analysis for complex structure is selected considering characteristics of dynamic loading, computer facility available number of degree of freedem and accuracy of results. It is a main point of view to get economical results rather then accurate ones for analysis of general complex structures, Mode superposition method and direct integration method are generally used. However, the characteristics of load is not considered in mode superpositon method, the personal computer cannot be used in direct integration methods. To over-come these shortcomings, the component mode method incorporating Ritz algorithm updated is proposed to solve economically dynamic behavior of the structures. The purpose of study is a formulation of algorithm, and computer programing suitable for dynamic analysis of the complex structure in personal computer environment.

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