• Title/Summary/Keyword: modes of vibration

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Natural Vibration Analysis of Thick Rings (두꺼운 링의 고유진동 해석)

  • Park, Jung-Woo;Kim, Sehee;Kim, Chang-Boo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.10 s.103
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    • pp.1186-1194
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    • 2005
  • In this paper, we have systematically formulated the equations concerned to the in-plane and out-of-plane motions and deformations of a thick circular beam by using the kinetic and strain energies in order to analyse natural frequencies of a thick ring. The effects of variation of radius of curvature across the cross-section and also the effects of bending shear, extension and twist are considered. The equations of motion for natural vibration analysis of a ring are obtained utilizing the cyclic symmetry of vibration modes of the ring. The frequencies calculated using thick ring model and thin ring model are compared and discussed with the ones obtained from finite element analysis using the method of cyclic symmetry with 20-node hexahedral solid elements for rings with the different ratio of radial thickness to mean radius.

Nonlinear dynamic stability and vibration analysis of sandwich FG-CNTRC shallow spherical shell

  • Kamran Foroutan;Akin Atas;Habib Ahmadi
    • Advances in nano research
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    • v.17 no.2
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    • pp.95-107
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    • 2024
  • In this article, the semi-analytical method was used to analyze the nonlinear dynamic stability and vibration analysis of sandwich shallow spherical shells (SSSS). The SSSS was considered as functionally graded carbon nanotube-reinforced composites (FG-CNTRC) with three new patterns of FG-CNTRC. The governing equation was obtained and discretized utilizing the Galerkin method by implementing the von Kármán-Donnell nonlinear strain-displacement relations. The nonlinear dynamic stability was analyzed by means of the fourth-order Runge-Kutta method. Then the Budiansky-Roth criterion was employed to obtain the critical load for the dynamic post-buckling. The approximate solution for the deflection was represented by suitable mode functions, which consisted of the three modes of transverse nonlinear oscillations, including one symmetrically and two asymmetrical mode shapes. The influences of various geometrical characteristics and material parameters were studied on the nonlinear dynamic stability and vibration response. The results showed that the order of layers had a significant influence on the amplitude of vibration and critical dynamic buckling load.

Analytical and experimental modal analyses of a highway bridge model

  • Altunisik, Ahmet Can;Bayraktar, Alemdar;Sevim, Baris
    • Computers and Concrete
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    • v.12 no.6
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    • pp.803-818
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    • 2013
  • In this study, analytical and experimental modal analyses of a scaled bridge model are carried out to extract the dynamic characteristics such as natural frequency, mode shapes and damping ratios. For this purpose, a scaled bridge model is constructed in laboratory conditions. Three dimensional finite element model of the bridge is constituted and dynamic characteristics are determined, analytically. To identify the dynamic characteristics experimentally; Experimental Modal Analyses (ambient and forced vibration tests) are conducted to the bridge model. In the ambient vibration tests, natural excitations are provided and the response of the bridge model is measured. Sensitivity accelerometers are placed to collect signals from the measurements. The signals collected from the tests are processed by Operational Modal Analysis; and the dynamic characteristics of the bridge model are estimated using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods. In the forced vibration tests, excitation of the bridge model is induced by an impact hammer and the frequency response functions are obtained. From the finite element analyses, a total of 8 natural frequencies are attained between 28.33 and 313.5 Hz. Considering the first eight mode shapes, these modes can be classified into longitudinal, transverse and vertical modes. It is seen that the dynamic characteristics obtained from the ambient and forced vibration tests are close to each other. It can be stated that the both of Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are very useful to identify the dynamic characteristics of the bridge model. The first eight natural frequencies are obtained from experimental measurements between 25.00-299.5 Hz. In addition, the dynamic characteristics obtained from the finite element analyses have a good correlation with experimental frequencies and mode shapes. The MAC values obtained between 90-100% and 80-100% using experimental results and experimental-analytical results, respectively.

Computation for Deformation Modes of a Flexible Body in Multibody System using Experimental Modal Analysis (실험적 모드해석을 이용한 다물체계내 유연체의 변형보드 계산)

  • Kim, Hyo-Sig;Kim, Sang-Sup
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1718-1723
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    • 2003
  • This paper presents a computational method for deformation modes of a flexible body in multibody system from the experimental modal analysis and an efficient method for flexible multibody dynamic analysis by use of the modes. It is difficult to directly use experimental modal parameters in flexible multibody dynamic analysis. The major reasons are that there are many inconsistencies between experimental and analytical modal data and experimental noises are inherent in the experimental data. So two methods, such as, a method for ortho-normalization of experimental modes and the other one for mode expansion, are suggested to gain deformation modes of a flexible body from the experimental modal parameters. Using the virtual work principle, the equation of motion of a flexible body is derived. The effectiveness of the proposed method will be verified in the numerical example of cab vibration of a truck by comparing analysis and test results.

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The control characteristic evaluation of Desktop machine tool (Desktop 가공기의 제어특성 평가)

  • 박종영;이득우;김정석;정우섭
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.137-140
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    • 2003
  • Recently, as the demand of small-sized precision parts is rising in precision industry such as mobile, automobile, optic. etc. the requirement of small-sized machine tool is increasing. Desktop machine tool define small-sized machine tool that is able to install in table. According to diminishing in size, Desktop machine tool is able to economize production cost by reducing work area and consuming electric power. But Desktop machine tool generates vibration in acceleration and deceleration modes by inertia force of moving part. Also vibration is generated when it move simultaneously two axis or three axis. Such generating vibration situation is reason of declining stiffness of machine tool structure because of smallizing in size. And this vibration has a large effect on precision of machining products. Therefore, evaluating of the control characteristic is necessary for minimizing vibration of machine tool as much as possible to accomplish precision machining of small-sized parts

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독립모달공간 제어기법에서 작동기 수의 절감에 대한 연구

  • 황재혁;김준수;박명호
    • Journal of KSNVE
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    • v.7 no.2
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    • pp.273-279
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    • 1997
  • Reduction of number of actuators for independent modal space control In this paper, a new modified independent modal space control (IMSC), which relaxes the fundamental hardware limitation of IMSC, is suggested to handle the vibration and attitude control problem for flexible large structures. This method has adapted a new switching algorithm between controlled modes and a novel design technique for modal control force. The main advantage of this method is to minimize the discontinuity of the modal control forces and to assure the asymptotic stability of the closed-loop systems. This process is shown to be simple and efficient in a realistic example of vibration control of a cantiloever beam. It has been found that the modified IMSC suggested in this paper, which can reduce the number of actuators, is highly excellent compared to other previous methods in terms of the performance and stability of the vibration control systems.

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Reduction of Number of Actuators for Independent Modal Space Control (독립모달공간 제어기법에서 작동기 수의 절감에 대한 연구)

  • 황재혁;김준수;박명호
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1996.10a
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    • pp.166-174
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    • 1996
  • In this paper, a new modified independent modal space control(IMSC), which relaxes the fundamental hardware limitation of IMSC, is suggested to handle the vibration and attitude control problem for flexible large structures. This method has adapted a new switching algorithm between controlled modes and a novel design technique for modal control force. The main advantage of this method is to minimize the discontinuity of the modal control forces and to assure the asymptotic stability of the closed-loop systems. This process is shown to be simple and efficient in a realistic example of vibration control of a cantilever beam. It has been found that the modified IMSC suggested in this paper, which can reduce the number of actuators, is highly excellent compared to other previous methods in terms of the performance and stability of the vibration control systems.

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RESEARCH ON THE RELATIONSHIP BETWEEN RIDING COMFORT AND CAR SEAT MATERIALS

  • Kubo, Mitsunori;Terauchi, Fumio;Aoki, Hiroyuki;Suzuki, Tsutomu;Isobe, Masahiro;Okubo, Kazuhiko
    • Proceedings of the Korean Society for Emotion and Sensibility Conference
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    • 2000.04a
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    • pp.312-317
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    • 2000
  • The relationship between riding comfort and the properties of flexible polyurethane foam used in car seats was quantitatively illustrated through vibration experiments with humans sitting in car seats, which were vertically shaken by vibrator. Riding comfort was estimated according to SD (Semantic Differential)-method using questionnaire, and was analyzed with a factor analysis which demonstrated the principal factors of riding comfort. At the same time, riding comfort was related to the properties of the flexible polyurethane foam with coefficients of correlation. It was also related to the behaviour of its vibration of humans sitting in the seats. As a result, it was demonstrated that the relationship between riding comfort and the flexible polyurethane foam properties varies according to the frequency of the vibration shaking the human sitting in the seat. and it was demonstrated that the frequency dependence of the relationship is strongly affected by the physical changes of the vibration modes of the human-seat vibration system.

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Study on the Shape Review of Rail Web-damper for Simulation of Rail Vibration Mode (레일 진동모드 해석을 통한 레일 웹댐퍼 형상 검토에 관한 연구)

  • Kim, Jin-Ho;Kim, Kyoung-Min;Lee, Kwang-Do
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.2866-2869
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    • 2011
  • Concrete track to increase R&D compared to the existing gravel track 3dB(A) over the growing problem of noise has been raised. Accordingly, the noise reduction solutions for reducing the vibration of the rail that you want to reduce the noise of the concept is to develop the rail web-damper. For this purpose, first, that occurs while driving the train to simulate the vibration modes of rail vibration part of the main draw for this part of the effective vibration reduction to be made, a review of various shapes to try.

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A Study on Comparison of Input-Shaping Filter for Optimum Design between Artificial Immune Algorithm and Genetic Algorithm (입력성형필터 최적 설계를 위한 인공 명역망과 유전 알고리즘 비교에 관한 연구)

  • Lee, Dong-Je;Choi, Young-Kiu
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.8
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    • pp.1482-1488
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    • 2010
  • Recently to increase the productivity and improve the quality in the industrial process, suppressing the residual vibration in motion control systems becomes the essential problem to solve. One of the methods to suppress the residual vibration is the input shaping technique. It is based on parameters of the system model; however, the parameters are usually difficult to obtain. This paper shows the effects of the residual vibration caused by the variation of the general velocity profile for the system with two vibration modes, and also shows the effects of the input shaping filter based on the parameters of system model. Finally, the simulation results show that the proposed input shaping filter using an artificial immune algorithm is more effective for suppressing residual vibrations than genetic algorithm.