• Title, Summary, Keyword: Substructure Response Function Sensitivity Method

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Structural Dynamic Modification Using substructure Response Function Sensitivity Method(SRFSM) (부분구조응답함수감소법을 이용한 동적구조변경)

  • Ji, Tae-Han;Park, Yeong-Pil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.12
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    • pp.3782-3791
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    • 1996
  • A great deal of effert has been invested in upgrading the performance and the efficiency of mechanical structures. Using experimental modal analysis(EMA) or finite element analysis(FEA) data of mechanical structures, this performance and efficiency can be effectively evaluated. In order to analyze complex structures such as automobiles and aircraft, for the sake of computing efficiency, the dynamic substructuring techniques that allow to predict the dynamic behavior of a structure based on that of the composing structures, are widely used. By llinking a modal model obtained from EMA and an analytical model obtained from FEA, the best conditioned structures can be desinged. In this paper, a new algorithm for structural dynamic modification-SRFSM (substructure response function sensitivity method) is proposed by linking frequency responce function synthesis and response function sensitivity. A mehtod to obtain response function sensitivity using direct derivative of mechanical impedance, is also used.

A Study on the Vibration Analysis of a Power Transmission Converter by Substructure Synthesis Method (부분구조합성법에 의한 동력전달 변화기의 진동해석에 관한 연구)

  • 박석주;왕지석;박성현;오창근;박영철
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.3
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    • pp.52-57
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    • 2000
  • This study intends to reduce the weight of structure without changing the dynamic characteristics. At first, the Vibration analysis by the Substructure Synthesis Method and FFM using the ANSYS are performed for the engine speed converter to confirm the reliability of the analyzing tools. Weight minimization is performed by the Sensitivity Analysis and the Optimum Structural Modification. To decrease the converter weight ideally, the parts with low sensitivity are to be cut mainly, and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with high sensitivity. As the unique mathematical solution for the homogeneous problem(i.e. 0 object function problem) does not exist, the converter is redesigned with much thinner initial thickness. The goal of this study is to recover the dynamic characteristics of redesigned structure to those of the original one. To say in the other words, the modified structure has the same dynamic characteristics and the more lighter weight to compare with the original one.

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A Study on the Vibration Analysis of a Power Transmission by Substructure Synthesis Method (부분구조합성에 의한 동력전달기의 진동해석에 관한 연구)

  • 박석주;박성현;박영철
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.161-166
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    • 2001
  • This study intends to reduce the weight of structure without changing the dynamic characteristics. At first, the Vibration analyses by the Substructure Synthesis Method and FEM using the ANSYS are performed for the engine speed converter to confirm the reliability of the analyzing tools. Weight minimization is performed by the Sensitivity Analysis and the Optimum Structural Modification. To decrease the converter weight ideally, the parts with low sensitivity are to be cut mainly, and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with high sensitivity. As the unique mathematical solution for the homogeneous problem( i.e. 0 object function problem) does not exist, the converter is redesigned with much thinner initial thickness. The goal of this study is to recover the dynamic characteristics of redesigned structure to those of the original one. To say in the other words, the modified structure has the same dynamic characteristics and the more lighter weight to compare with the original one. In this analysis, the modification was performed with the redesigned initial thickness of 60 mm and 70 mm. And the numbers of the interesting natural frequencies are 1, 2, 4 respectively. Consequently 27% of weight reduction effects were earned.

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A Study on the Weight Minimization of an Automobile Engine Block by Optimum Structural Modification (최적구조변경법에 의한 자동차 엔진 블록의 중량최소화에 관한 연구)

  • 길병래
    • Journal of Advanced Marine Engineering and Technology
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    • v.22 no.4
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    • pp.560-568
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    • 1998
  • Recently to develop an automobile with better properities many researches and investments have been executed. In this paper we intend to improve the automobile properties by reducing the weight of the engine without changing the dynamic characteristics. At first the vibration analysis by the Substructure Synthesis Mehtod and the exciting test of the engine model performed to confirm the reliability of the analyzing tools. And the weight minimiza-tion is performed by the Sensitivity Analysis and the Optimum Structural Modificationl. To decrease the engine weight ideally the weight of the parts with the low sensitivity is to cut mainly and the changing quantity of the natural frequency by the cut is to be recovered by the weight modification of the parts with the high sensitivity. As actually the mathematical unique solution for the homogeneous problem(i. e. 0 object func-tion problem)does not exist we redesign the engine block with much thinner initial thickness and recover the natural frequencies and natural modes of original structure by the sensitivity analy-sis and then observe the Frequency Response Function(FRF) for the interesting points. In this analysis the original thickness of the engine model is 8mm and the redesigned initial thicknesses are 5mm and 6mm, And the number of the interesting natural frequencies are 1, 2, 3, 4 and 5 respectively.

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Selection of Optimal Supporting Position to Maximize Natural Frequency of the Structure Using Frequency Response Function (주파수 응답함수를 이용한 구조물 고유진동수 극대화를 위한 최적 지지점 선정)

  • 박용화;정완섭;박윤식
    • Journal of KSNVE
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    • v.10 no.4
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    • pp.648-654
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    • 2000
  • A procedure to determine the realizable optimal positions of rigid supports is suggested to get a maximum fundamental natural frequency. a measured frequency response function based substructure-coupling technique is used to model the supported structure. The optimization procedure carries out the eigenvalue sensitivity analysis with respect to the stiffness of supports. As a result of such stiffness optimization, the optimal rigid-support positions are shown to be determined by choosing the position of the largest stiffness. The optimally determined support conditions are verified to satisfy the eigenvalue limit theorem. To demonstrate the effectiveness of the proposed method, the optimal support positions of a plate model are investigated. Experimental results indicate that the proposed method can effectively find out the optimal support conditions of the structure just based on the measured frequency response functions without any use of numerical model of the structure.

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Dynamic Analysis and Design of Uncertain Systems Against Random Excitation Using probabilistic Method

  • Moon, Byung-Young;Kang, Beom-Soo;Park, Jung-Hyen
    • Journal of Mechanical Science and Technology
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    • v.16 no.10
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    • pp.1229-1238
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    • 2002
  • In this paper, a method to obtain the sensitivity of eigenvalues and the random responses of the structure with uncertain parameters is proposed. The concept of the proposed method is that the perturbed equation of each uncertain substructure is obtained using the finite element method, and the perturbed equation of the overall structure is obtained using the mode synthesis method. By this way, the reduced order perturbed equation of the uncertain system can be obtained. And the response of the uncertain system is obtained using probability method. As a numerical example, a simple piping system is considered as an example structure. The damping and spring constants of the support are considered as the uncertain parameters. Then the variations of the eigenvalues, the correlation function and the power spectral density function of the responses are calculated. As a result, the proposed method is considered to be useful technique to analyze the sensitivities of eigenvalues and random response against random excitation in terms of the accuracy and the calculation time.

Reliability analysis of steel cable-stayed bridges including soil-pile interaction

  • Cheng, Jin;Liu, Xiao-luan
    • Steel and Composite Structures
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    • v.13 no.2
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    • pp.109-122
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    • 2012
  • An efficient and accurate algorithm is proposed to evaluate the reliability of cable-stayed bridges accounting for soil-pile interaction. The proposed algorithm integrates the finite-element method and the response surface method. The finite-element method is used to model the cable-stayed bridge including soil-pile interaction. The reliability index is evaluated based on the response surface method. Uncertainties in the superstructure, the substructure and load parameters are incorporated in the proposed algorithm. A long span steel cable-stayed bridge with a main span length of 1088 m built in China is considered as an illustrative example. The reliability of the bridge is evaluated for the strength and serviceability performance functions. Results of the study show that when strength limit states for both girder and tower are considered, soil-pile interaction has significant effects on the reliability of steel cable-stayed bridges. Further, a detailed sensitivity study shows that the modulus of subgrade reaction is the most important soil-pile interaction-related parameter influencing the reliability of steel cable-stayed bridges.

A Study on the Weight Minimization of an Automobile Engine Block by the Optimum Structural Modification (최적구조변경법에 의한 자동차 엔진 블록의 중량최소화에 관한 연구)

  • 김영군;박석주;김성우
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.326-332
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    • 1997
  • Recently to develop an automobile with better prosperities, many researches and investments have been executed. In this paper we intend to improve the automobile properties by reducing the weights of the engine without changing the dynamic characteristics. At first we perform the vibration analysis by the Substructure Synthesis Method and execute the exciting test for the engine model, and observe the coincidences of two results to confirm the reliability of the analyzing tools used. The weight minimization is performed by the Sensitivities of the Natural frequencies of the engine block. To decrease the engine weight ideally, the parts of the sensitivity zero are to be cut mainly, and the changing quantity of natural frequency by the cut is to be recovered by the structural modification for the parts with the good sensitivity. But, as actually the mathematical solution for the homogeneous problem(i.e. 0 object function) do not exist, we hereby redesign the block with much thinner thickness and recover the natural frequencies and natural modes to original structure's by the sensitivity analysis. And the Frequency Response Functions(FRF) are to be observed for the interesting points. In this analysis, the original thickness of the engine model has 8 mm of thickness, and the thickness redesigned is 5 mm and 6 mm. And we are to try to recover the 1, 2, 4, and 5 lower natural frequencies interested.

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Structural Dynamics Modification Using Position of Beam Stiffener on Plate (평판에서 빔 보강재의 결합 위치를 이용한 구조물 변경법)

  • Jung, Eui-Il;Park, Youn-Sik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.599-604
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    • 2002
  • 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 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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