• Title/Summary/Keyword: Modal Characteristic

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Vibration experiment of precision stage that use laser vibrator (비접촉식 진동측정 장치를 이용한 정밀 스테이지의 진동특성 평가시험)

  • Lee, Jae-Woo;Lee, Kang-Wook;Yim, Hong-Jae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.1224-1230
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    • 2007
  • In this study, a new modal test method is presented to evaluate vibration characteristic of the nano imprint stage system. Since it is difficult to measure vibration level without contacting the machine component, non contacting modal test method, laser scanning system is ultrared. Finite element analysis results are compared with the modal test results.

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Time Domain based Structural System Identification using Shaking Table Test (진동대 실험을 통한 시간영역에 기반한 시스템 식별)

  • 이상현;민경원;강경수;이명규
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2004.10a
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    • pp.331-338
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    • 2004
  • In this paper, stiffness and damping matrices are experimentally constructed using structural modal information on frequencies, damping ratios and modal vectors, which are obtained by shaking table tests. The acceleration of the shaking table is used as the input signal, and the resulting acceleration of each floor is measured as output signal. The characteristic and limitation of modal information from shaking table test are obtained by Common Based-normalized System Identification(CBSI) technique which is based on time domain information.

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Response Characteristics Of Steel Frame Structures With Added Elastic Dampers (탄성 댐퍼가 추가된 대형철골 구조물의 응답특성)

  • Bae, Chun-Hee;Cho, Cheul-Whan;Yang, Kyeong-Hyeon;Park, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.361.1-361
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    • 2002
  • Coupling adjacent steel frame using elastic dampers fer control of response to low and moderate dynamic event is investigated in this paper. The complex modal superposition method is first used to determine dynamic characteristic, mainly modal damping ratio and modal frequency, of damper linked linear adjacent steel frame for fractical use. Dynamic response of steel frame linked by hydraulic-excitation method. (omitted)

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Effects of Viscoelastic Dampers on the Improvement of Torsional Response of Asymmetric Buildings (비대칭 건물의 거동 개선을 위한 점탄성 감쇠기의 활용에 관한 연구)

  • 김진구;방성혁;이진수
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2000.10a
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    • pp.249-256
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    • 2000
  • The visco-elastic dampers were used to improve the torsional responses of an asymmetric buildings. The modal characteristic equation of an asymmetric structure with added viscoelastic dampers were derived using the complex modal analysis method. Parametric study has been performed based on the modal characteristics, and the appropriate condition for compensating the stiffness eccentricity was investigated. According to the results the torsional response of the asymmetric buildings could be improved significantly once the dampers were properly placed

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Effect of Scale-down of Structure on Dynamic Characteristic Parameters in Bolted-Joint Beams (구조물의 소형화가 볼트 결합부의 동특성 파라미터에 미치는 영향 분석)

  • Kim, Bong-Suk;Lee, Seong-Min;Song, Jun-Yeob;Lee, Chang-Woo;Lee, Soo-Hun
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.3 s.192
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    • pp.108-116
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    • 2007
  • To overcome many defects such as the high product cost, large energy consumption, and big space capacity in conventional mechanical machining, the miniaturization of machine tool and micro factory systems has been envisioned recently. The object of this paper is to research the effect of dynamic characteristic parameters in bolted-joint beams, which is widely applied to the joining of mechanical structures in order to identify structural system characteristics and to predict dynamic behavior according to scale-down from macro to micro system as the development of micro/meso-scale machine tool and micro factories. Modal parameters such as the natural frequency, damping ratio, and mode shape from modal testing and dynamic characteristics from finite element analysis are extracted with all 12 test beam models by materials, by size, and by joining condition, and then the results obtained by both methods are compared.

Connectivity Analysis of KTX Stations according to KTX Connection Characteristic Variable and KTX Modal Split (고속철도 연계특성변수와 수단분담률에 따른 고속철도역 연계성 분석에 관한 연구)

  • Shin, Hyun-Ju;Kim, Byung-Kwan
    • Journal of the Korean Society for Railway
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    • v.16 no.6
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    • pp.503-509
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    • 2013
  • Since the opening of KTX, the number of people coming to KTX stations to use KTX has steadily increased. Passengers have a variety of access modes between a KTX station and their origin/destination. But there is no way to confirm the level of connection strength. So this study examines various connection characteristic variables that can show the connectivity, and examines influencing relationships, and chooses variables that affect connectivity by using a KTX modal split. We will suggest connectivity estimation models between a KTX station and origin/destination based on the selected connected variables.

Investigation of water length effects on the modal behavior of a prototype arch dam using operational and analytical modal analyses

  • Sevim, Baris;Bayraktar, Alemdar;Altunisik, Ahmet Can
    • Structural Engineering and Mechanics
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    • v.37 no.6
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    • pp.593-615
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    • 2011
  • This study determines the water length effects on the modal behavior of a prototype arch dam using Operational and Analytical Modal Analyses. Achievement of this purpose involves construction of a prototype arch dam-reservoir-foundation model under laboratory conditions. In the model, reservoir length was taken to be as much as three times the dam height. To determine the experimental dynamic characteristics of the arch dam using Operational Modal Analysis, ambient vibration tests were implemented for empty reservoir and three different reservoir water lengths. In the ambient vibration tests, the dam was vibrated by natural excitations provided from small impact effects and the response signals were measured using sensitive accelerometers. Operational Modal Analysis software process signals collected from the ambient vibration tests, and Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques estimated modal parameters of the dams. To validate the experimental results, 3D finite element model of the prototype arch dam was modeled by ANSYS software for empty reservoir and three different reservoir water lengths, and dynamic characteristics of each model were determined analytically. At the end of the study, experimentally and analytically identified dynamic characteristics compared to each other. Also, changes on the natural frequencies along to water length are plotted as graphs. Results suggest that reservoir water complicates the modal behavior of the arch dam significantly.

Modal Characteristic Optimization of Rotating Cantilever Beams via Shape Variation of Cross-section by Multi-stage Spline Function (다단 Spline 곡선에 의한 단면형상 변화를 통한 회전 외팔보의 진동특성 최적화)

  • 조정은;유홍희
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.1
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    • pp.73-79
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    • 2004
  • When structures undergo rotating motion, their modal characteristics often vary significantly. The variations of modal characteristics are determined from their geometric shapes and their rotating angular speed. Since the modal characteristics vary during the operation of the structures, they should be carefully scrutinized. In this paper, rotating cantilever beams are chosen as design targets which need to meet some specific design requirements. The thickness and the width of the rotating beams are assumed as multi-stage spline functions and the stage values for the thickness and the width are used as design variables for the optimization problems.

Modal Characteristic Optimization of Rotating Cantilever Beams via Shape Variation of Cross-section by Multi-stage Spline Function (다단 Spline 곡선에 의한 단면형상 변화를 통한 회전 외팔보의 진동특성 최적화)

  • 조정은;유홍희
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.684-689
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    • 2003
  • When structures undergo rotating motion, their modal characteristics often vary significantly. The variations of modal characteristics are determined from their geometric shapes and their rotating angular speed. Since the modal characteristics vary during the operation of the structures, they should be carefully scrutinized. In this paper, rotating cantilever beams are chosen as design targets which need to meet some specific design requirements. The thickness and the width of the rotating beams are assumed as multi-stage spline functions and the stage values for the thickness and the width are used as design variables for the optimization problems.

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Shear and Normal Damping Effects of Square Sandwich Plates with Four Edges Clamped (네변이 고정된 사각 샌드위치 평판에서의 수직 및 전단 감쇠 효과)

  • 이병찬;김광준
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.10a
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    • pp.217-223
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    • 1996
  • A structure's vibration characteristic is determined by modal property of the system. Through proper vibration analysis or experiments, the structure can be modified to reduce of vibration and noise. This paper is concerned with the natural frequency and modal loss factor of sandwich plates with viscoelastic core. The effects of shear and normal strain in the viscoelastic layer are investigated on modal properties, natural frequency and modal loss factor, by changing geometry parameter and viscoelastic material property of sandwich plates. The errors of modal parameters resulting from neglecting the extension or compression in the core material for simply supported(S-S-S-S) case are compared with those for clamped(C-C-C-C) boundary condition. Finite difference method(FDM) is utilized as numerical analysis technique of square sandwich plates for fixed boundary conditions. In order to reduce computation time and increase accuracy, improved finite difference expression with fourth order truncation error was used.

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