• Title, Summary, Keyword: mode superposition method

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Finite Element Analysis of Unbalance Response of a High Speed Flexible Polygon Mirror Scanner Motor Considering the Flexibility of Supporting Structure (지지구조의 유연성을 고려한 고속 유연 폴리곤 미러 스캐너 모터의 유한 요소 불평형 응답 해석)

  • Jung, Kyung-Moon;Seo, Chan-Hee;Kim, Myung-Gyu;Jang, Gun-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.859-865
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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 bearing and flexible supporting structures by using the finite element method and the mode superposition method. The appropriate finite element equations for polygon mirror are described by rotating annular sector element using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. The rotating components except for the polygon mirror are modeled by Timoshenko beam element including the gyroscopic effect. The flexible supporting structures are modeled by using a 4-node tetrahedron element and 4-node shell element with rotational degrees of freedom. Finite element equations of each component of the polygon mirror scanner motor and the flexible supporting structures are consistently derived by satisfying the geometric compatibility in the internal boundary between each component. The rigid link constraints are also imposed at the interface area between sleeve and sintered bearing to describe the physical motion at this interface. A global matrix equation obtained by assembling the finite element equations of each substructure is transformed to a state-space matrix-vector equation, and both damped natural frequencies and modal damping ratios are calculated by solving the associated eigenvalue problem by using the restarted Arnoldi iteration method. Unbalance responses in time and frequency domain are performed by superposing the eigenvalues and eigenvectors from the free vibration analysis. The validity of the proposed method is verified by comparing the simulated unbalance response with the experimental results. This research also shows that the flexibility of supporting structures plays an important role in determining the unbalance response of the polygon mirror scanner motor.

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Parametric Study on Earthquake Responses of Soil-structure Interaction System by Substructure Method. (부분구조법에 의한 지반-구조물 상호작용 시스템의 지진응답 매재변수 해석)

  • 조양희
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.117-125
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    • 1997
  • ABSTRACT This paper presents results of parametric studies of the seismic responses of a reactor containment structure on layered base soil. Among the numerous parameters, this study concentrates on the effects of embedment of structure to the base soil, thickness of the soil layers, stiffness of the base soil, and the definition point of the input motion. For the analysis, a substructure method using frequency independent impedances is adopted. The method is based on the mode superposition method in time domain using the composite modal damping values of the SSI system computed from the ratio of dissipated energy to the strain energy for each mode. From the study results, the sensitives of each parameter on the earthquake responses have been suggested for the practical application of the substructure method of SSI analysis.

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Dynamic interaction analysis of submerged floating tunnel and vehicle (튜브형 수중교량의 교량-차량 동적상호작용 해석방법)

  • Kim, Moon-Young;Kwark, Jong-Won;Min, Dong-Ju
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.83-88
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    • 2013
  • The purpose of this study is to develop the algorithm for dynamic interaction analysis of submerged floating tunnel and vehicles. The dynamic behavior characteristic of submerged floating tunnel is certainly different with general structures, because the submerged floating tunnel is floating in the middle of water, and subjected to constant buoyance. Therefore the analyses in various aspects should be carried out to secure structural stability and practicality of structures. To conduct the dynamic interaction analysis, the structure is modeled by commercial FEM program ABAQUS to investigate modal characteristic. Also the added mass concept is applied to represent the inertial force by a fluid, and then dynamic interaction analyses are conducted with superposition method when the KTX is moving along the submerged floating tunnel. And the time histories are presented for vertical and lateral displacement at the center of the tunnel.

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Structural Intensity Analysis of Stiffened Plate Using Assumed Mode Method (Assumed Mode Method를 이용한 보강판의 진동인텐시티 해석)

  • Dae-Seung Cho;Sa-Soo Kim;Sang-Min Jung
    • Journal of the Society of Naval Architects of Korea
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    • v.35 no.4
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    • pp.76-86
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    • 1998
  • Structural intensity of plates experiencing bending vibration is analytically evaluated using the modal analysis based on assumed mode method. To evaluate the convergence of structural intensity according to the number of superposition modes, the power obtained by structural intensity integration over the closed curve containing the excitation source is compared with the power injected into plates. The erect of power reduction due to the material internal loss is evaluated using the intensity around a localized damping point, In addition, the dominant component among internal forces in the power transfer by the bending vibration of plates and the change of power flow due to stiffener are also investigated.

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Efficient Mode Superposition Method or Non-classically Damped Systems (비비례 감쇠시스템의 해석을 위한 효율적인 모드 중첩법)

  • 조상원;조지성;이인원
    • Journal of the Earthquake Engineering Society of Korea
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    • v.4 no.1
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    • pp.89-98
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    • 2000
  • 본 연구에서는 비비례 감쇠시스템을 효율적으로 해석할 수 있도록 모드 가속도법(mode acceleration method)과 모드 절삭 보강법(modal truncation augmentation method)을 확장하고 그 사용성을 검증하였다,. 비례 감쇠시스템의 동응답해서에 널리 사용되는 모드 가속도법과 모드 절삭보강법은 누락된 고차모드의 영향을 보정하여 모드 중첩법의 결과를 개선하는 방법이다. 기존의 방법들로 비비례 감쇠시스템을 해석하는 경우 비비례 감쇠특성을 무시하지 않으며 정확하고 효율적으로 해석할 수 있도록 모드 가속도법과 모드 절삭보강법을 확장하였다. 비례 감쇠시스템에서는 모드 가속도법보다 모드 절삭보강법이 더 효율적인 반면에 비비례 감쇠시스템에서는 대부분의 경우에 있어서 확장된 두 방법의 효율성이 동일하다. 그러나 수치적 안정성은 확장된 모드 가속도법이 모드절삭 보강법보다 우수하다. 이와 같은 확장된 모드 가속도법과 모드 절삭보강법의 사용성 검?을 위해서 이론적 방법과 수치예제를 수행하였다.

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Aerodynamic loads and aeroelastic responses of large wind turbine tower-blade coupled structure in yaw condition

  • Ke, S.T.;Wang, T.G.;Ge, Y.J.;Tamura, Y.
    • Structural Engineering and Mechanics
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    • v.56 no.6
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    • pp.1021-1040
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    • 2015
  • An effective method to calculate aerodynamic loads and aeroelastic responses of large wind turbine tower-blade coupled structures in yaw condition is proposed. By a case study on a 5 MW large wind turbine, the finite element model of the wind turbine tower-blade coupled structure is established to obtain the modal information. The harmonic superposition method and modified blade-element momentum theory are used to calculate aerodynamic loads in yaw condition, in which the wind shear, tower shadow, tower-blade modal and aerodynamic interactions, and rotational effects are fully taken into account. The mode superposition method is used to calculate kinetic equation of wind turbine tower-blade coupled structure in time domain. The induced velocity and dynamic loads are updated through iterative loop, and the aeroelastic responses of large wind turbine tower-blade coupled system are then obtained. For completeness, the yaw effect and aeroelastic effect on aerodynamic loads and wind-induced responses are discussed in detail based on the calculating results.

Guided Wave Mode Identification Using Wavelet Transform (웨이블릿 변환을 이용한 유도초음파의 모드 확인)

  • Ik-Keun Park
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.12 no.5
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    • pp.94-100
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    • 2003
  • One of unique characteristics of guided waves is a dispersive behavior that guided wave velocity changes with an excitation frequency and mode. In practical applications of guided wave techniques, it is very important to identify propagating modes in a time-domain waveform for determination of detect location and size. Mode identification can be done by measurement of group velocity in a time-domain waveform. Thus, it is preferred to generate a single or less dispersive mode But, in many cases, it is difficult to distinguish a mode clearly in a time-domain waveform because of superposition of multi modes and mode conversion phenomena. Time-frequency analysis is used as efficient methods to identify modes by presenting wave energy distribution in a time-frequency. In this study, experimental guided wave mode identification is carried out in a steel plate using time-frequency analysis methods such as wavelet transform. The results are compared with theoretically calculated group velocity dispersion own. The results are in good agreement with analytical predictions and show the effectiveness of using the wavelet transform method to identify and measure the amplitudes of individual guided wave modes.

GUIDED WAVE MODE IDENTIFICATION USING WAVELET TRANSFORM

  • Park, Ik-Keun;Kim, Hyun-Mook;Kim, Young-Kwon;J. L. Rose
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.79-85
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    • 2003
  • One of unique characteristics of guided waves is a dispersive behavior that guided wave velocity changes with an excitation frequency and mode. In practical applications of guided wave techniques, it is very important to identify propagating modes in a time-domain waveform for determination of defect location and size. Mode identification can be done by measurement of group velocity in a time-domain waveform. Thus, it is preferred to generate a single or less dispersive mode But in many cases, it is difficult to distinguish a mode clearly in a time-domain waveform because of superposition of multi modes and mode conversion phenomena. Time-frequency analysis is used as efficient methods to identify modes by presenting wave energy distribution in a time-frequency. In this study, experimental guided wave mode identification is carried out in a steel plate using time-frequency analysis methods such as wavelet transform. The results are compared with theoretically calculated group velocity dispersion curves. The results are in good agreement with analytical predictions and show the effectiveness of using the wavelet transform method to identify and measure the amplitudes of individual guided wave modes.

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Structural Intensity Analysis of Plate Structures Using Modal Analysis (모달해석기법을 이용한 판 구조물의 진동인텐시티 해석)

  • 정상민;조대승;김사수
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.319-326
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    • 1998
  • Structural intensity of plates experiencing bending vibration is analytically evaluated using the modal analysis based on the assumed mode method. In the analysis, material internal loss and localized damping are considered. The power obtained by structural intensity integration over the circle containing the excitation source is compared with the power injected into plates to verify the accuracy of the presented method and; to evaluate the convergence of mode superposition. The intensity integration is carried out varying the circle radius and the integral step to investigate their effects in case of the power estimation using structural intensities. In addition, the dominant component among internal forces in the energy transfer by the bending vibration of a stiffened plate is investigated.

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VIBRATION ANALYSIS OF FBGA SOLDER JOINTS OF THE MEMORY MODULE SUBJECTED TO HARMONIC EXCITATION

  • Cinar, Yusuf;Jang, Jin-Woo;Jang, Gun-Hee;Kim, Seon-Sik;Jang, Jae-Seok;Chang, Jin-Kyu
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.572-573
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    • 2010
  • Vibration analysis of Fine-pitch Ball Grid Array (FBGA) packages mounted on a Printed Circuit Board (PCB) subjected to harmonic excitation is performed by using finite element method (FEM). A finite element model of a memory module is composed of three main parts, packages, simplified solder balls and bare PCB. At first, natural frequencies and mode shapes of the developed model were confirmed experimentally. Secondly, the harmonic excitation experiment for the module was carried out at the first natural frequency of the memory module, and it was verified with the simulation by using mode superposition method at a constant acceleration.

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