• Title, Summary, Keyword: Structural Dynamic Modification

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The Optimum Modification of Dynamic Characteristics of Stiffened Plate Structure Including the Number of Stiffener (보강재의 수를 포함한 보강판 구조물의 동특성의 최적변경)

  • 박성현;고재용
    • Journal of the Korean Institute of Navigation
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    • v.25 no.4
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    • pp.461-469
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    • 2001
  • The purpose of this paper is the optimum modification of dynamic characteristics of stiffened plate structure including the number of stiffener. This paper shows the optimum structural modification method by dynamic sensitivity analysis and quasi-least squares method and considers it's validity. In the method of the optimization, finite element method, sensitivity analysis and optimum structural modification method are used. The change of natural frequency and total weight are made to be an objective function. Thickness of plate, the number of stiffener and cross section moment of stiffener become a design variable. The dynamic characteristics of stiffened plate structure is analyzed using finite element method. Next, rate of change of dynamic characteristics by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using optimum structural modification method. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure including the number of stiffener.

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Experimental Structural Dynamic Modification of Fixture for Environmental Vibration Test Control (환경진동시험제어를 위한 치구의 실험적 구조변경 설계)

  • 김준엽;정의봉
    • Journal of KSNVE
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    • v.6 no.3
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    • pp.317-323
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    • 1996
  • This paper proposes the method of experimental structural dynamic modification of fixture for environmental vibration test control. This method can predict the responses at any points on the fixture utilizing the experimental data, and structural dynamic modification of fixture is made using the predicted responses for the spectra at the specimen attachment points to meet the specified reference spectrum. From the results of controlling the fixture before and after modification by conventional control method and optimal reference spectrum, which has been previously reported by the authors, the proposed method is shown to be an effective one.

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A Study on the Structural Dynamic Modification of Sub-structure of Clean Room Considering Vibration Criteria (반도체 초정밀장비의 진동허용규제치를 고려한 지지구조의 동특성 개선에 관한 연구)

  • 손성완;이홍기;백재호
    • Journal of the Semiconductor & Display Technology
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    • v.2 no.2
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    • pp.25-30
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    • 2003
  • In the case of a vibration sensitive equipment, it require a vibration free environment to provide its proper function. Especially, lithography and inspection device, which have sub-nanometer class high accuracy and resolution, have come to necessity for producing more improved Giga Class semi conductor wafers. This high technology equipments require very strict environmental vibration criteria in proportion to the accuracy of the manufacturing. In this paper, the dynamic analysis and modal test were performed to evaluate the dynamic properties of the constructing clean room structure. Based on these results, a structural dynamic modification(SDM) were required to satisfiy the vibration allowable limit for pression machine. Therefore, in order to improve the dynamic stiffness of clean room structure, the VSD system which can control the force applied on structure, were adopted and its utility were proved from dynamic test results of the improved structure after a modification work.

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Interior Noise Reduction Using Sensitivity Analysis and Structural Dynamic Modification (민감도 해석 및 구조 변경법을 이용한 차실 소음 저감)

  • 황우석
    • Journal of KSNVE
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    • v.9 no.6
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    • pp.1145-1151
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    • 1999
  • Sensitivity analysis and structural modification technique are used to reduce the interior noise of a passenger car. The sensitivity analysis for the noise level at the rear seat shows that the stiffness change at the front lower member and the rear roof rail are sensitive. Using the structural modification method, we verified that the reinforcements at those members decrease the noise transfer function from the body to the rear seat. The combined application of the sensitivity analysis and structural modification method can decrease the noise level effectively.

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Study on the Optimum Modification and Modal Analysis of Stiffened Plate of Ship Hull Structure (신체의 Stiffened Plate 구조물의 모우드해석과 최적변경법에 관한 연구)

  • 박성현;박석주;고재용
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • pp.51-58
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    • 2000
  • The purpose of this study is the optimum modification of dynamic characteristics of stiffened plate structure. In the method of the optimization ,finite element method (FEM), sensitivity analysis and optimum structural modification method are used. To begin with, using FEM, the dynamic characteristics of stiffened plate structure is analyzed. Next, rate of change of dynamic characteristic by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of plate and cross section moment become a design variable. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure.

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Structural Dynamics Modification via Reorientation of Modification Elements (구조물의 결합 위치 변경을 통한 구조물 변경법)

  • Jung, Eui-Il;Park, Youn-Sik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.666-669
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    • 2004
  • Substructures position is considered as design parameter to obtain optimal structural changes to raise its dynamic characteristics. In conventional SDM (structural dynamics modification) method, the layout of modifying substructures position is first fixed and at that condition the structural optimization is performed by using the substructures size and/or material property as design parameters. But in this paper as a design variable substructures global translational and rotational position is treated. For effective structural modification the eigenvalue sensitivity with respect to that design parameter is derived based on measured frequency response function. The optimal structural modification is calculated by combining eigenvalue sensitivities and eigenvalue reanalysis technique iteratively. Numerical examples are presented to the case of beam stiffener optimization to raise the natural frequency of plate.

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Structural Dynamic Optimization Using a Genetic Algorithm(GA) (유전자 알고리즘(GA)을 이용한 구조물의 동적해석 및 최적화)

  • 이영우;성활경
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.5
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    • pp.93-99
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    • 2000
  • In many dynamic structural optimization problems, the goal is to reduce the total weight of the structure without causing the resonance. Up to now, gradient informations(i.e., design sensitivity) have been used to achieve the goal. For some class of dynamic problems, especially coalescent eigenvalue Problems with multiobjective optimization, the design sensitivity analysis is too much complicated mathematically and numerically. Therefore, this article proposes a new technique fur structural dynamic modification using a mode modification method with Genetic Algorithm(GA). In GA formulation, fitness is defined based on penalty function approach. Design variables are iteratively improved by using genetic algorithm. Two numerical examples are shown, (ⅰ) a cantilevered plate, and (ⅱ) H-shaped structure. The results demonstrate that the proposed method is highly efficient.

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A Study on the Optimum Modification of Dynamic Characteristics of Stiffened Plate Structure of Ship (선박의 보강판 구조물의 동특성의 최적 변경법에 관한 연구)

  • 박성현;박석주;고재용
    • Journal of the Korean Institute of Navigation
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    • v.25 no.1
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    • pp.45-52
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    • 2001
  • The purpose of this study is the optimum modification of dynamic characteristics of stiffened plate structure. In the method of the optimization, finite element method(FEM), sensitivity analysis and optimum structural modification method are used. To begin with, using FEM, the dynamic characteristics of stiffened plate structure is analyzed. Next, rate of change of dynamic characteristics by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of plate and cross section moment become a design variable. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure.

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Structural Dynamic Modification of Fixture by Antiresonance Frequency Analysis in Environmental Vibration Test Control (환경진동시험 제어에서 반공진 진동수해석에 의한 치구의 구조변경설계)

  • 김준엽;정의봉
    • Journal of KSNVE
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    • v.5 no.4
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    • pp.555-563
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    • 1995
  • This paper proposes the method of antiresonance frequency analysis of multi-input multi-output system. The structural dynamic modification techniques by antiresonance frequency analysis are also applied to reduce the undertest at specimen attachment points on the fixture in environmental vibration test, which is resulted from the inconsistency of antiresonance frequencies at any specified points. Several computer simulations show that the proposed method can remove the undertest problem which is not removed in conventional vibration test control. And the effectiveness of the method is verified with the impact hammer excitation of aluminium fixture model.

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Experimental Approach Method for Strcutural Dynamic Modification of Vibration Test Fixture (진동시험치구의 구조변경을 위한 실험적 접근법)

  • 김준엽;정의봉
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.100-105
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    • 1996
  • This paper proposes the method of experimental structural dynamic modification of fixture for environmental vibration test control. This method can predict the responses at any points on fixture utilizing the experimental data, and structural dynamic modification of fixture is made using the predicted responses for the spectra at the speciment attachment points to meet the specified reference spectrum. From the results of controlling the fixture before and after modification by conventional control method and optimal reference spectrum, which has been previously reported by the authors, the proposed method is shown to be an effective one.

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