• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.125-129
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• 2009

본 연구에서는 동강성법을 이용하여 2자유도 진동시스템을 모델링하였다. 등가 모델을 구성한 후 Inertance의 크기에 따라 변화되는 시스템의 특성을 규명하였다. 2자유도 진동 시스템을 단일 모우드 소거에 적용할 경우 해석적인 설계 방법론을 1) 감쇠가 없는 경우 2) 1개의 감쇠기를 갖는 경우로 나누어 제시하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.339-348
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• 1990

Techniques which are able to predict and control dynamic characteristics, not affecting the vibrational characteristics on the modification of structural design, are being studied. As one of these techniques, experimental modal analysis is widely applied by many researchers. In this study, modal analysis is performed using transfer matrix method by a macro computer. The developed program would estimate the structural modal parameters precisely, and the validity of this program is certified by comparing with the experimental results of .GAMMA A. structure. Estimated modal parameters(natural frequency, vibrational mode, equivalent mass, etc.) are in accord with the experimental results. Also, the optimal location of the additive mass is determined by the evaluation of the vibrational mode and the equivalent mass. The relation between the additive mass and the equivalent mass is specified, and we come to know that the ratio of equivalent mass to additive mass alter linearly within the range of 20%.

• Computational Structural Engineering
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• v.5 no.4
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• pp.93-102
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• 1992

The design of reactor internals requires the accurate vibration characteristics of each component for subsequent dynamic structural response analyses. For Korean standard nuclear power plant some modifications on the Control Element Assembly shroud from the reference design have been made, Since the shroud is complex in geometry having an array of vertical round tubes and webs in a square grid pattern, and being tied down by preloaded tie rods into position, it is planned to perform a vibration measurement program consisting of both experimental and analytical modal studies upon that component. The shroud modal testing was performed on the low frequency global survey to measure the first several modes. The analysis using the finite element model was also performed for the as-tested conditions. The natural frequencies and mode shapes from both test and analysis have been acquired and compared to be in good agreement. It is concluded that finite element model generated is good enough to be used in the design for the dynamic response analysis under various loading conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.225-230
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• 1994

본 연구에서는 진동특성을 개선하기 위한 방법으로서 구조물이 가지는 공간적인 좌표를 설계변수로 하여 감도를 구하고, 이를 이용하여 구조물의 길이와 높이에 대한 형상을 변경하는 최적구조변경법에 대해 예시하고자 한다. 먼저 모우드합성법을 이용하여 임의 치수의 L형 구조물의 진동특성을 해석하고, 진동 특성을 변경하기 위해 감도해석법으로 변경할 부분의 감도를 구하여 변경할 부분의 변경량을 계산한다. 그리고 변경한 후 재해석을 통해 결과를 비교함으로써 제시한 방법의 타당성을 고찰하고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.52-57
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• 1994

본 논문에서는 실험적 모우드해석법을 이용하여 현재, 국내에서 가동 또는 건설 중인 반도체공장의 세가지 유형에 대한 격자보의 동적특성을 분석, 결정하고 이를 격자보의 동적설계에 활용하고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.116-120
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• 1997

The modal testing results of a generator stator frame for a 500MW fossil power plant are presented, which will be used to tune and to validate the finite element model of the stator frame.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.191-203
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• 2006

The vibration characteristics of composite stiffened laminated plates with stiffener is presented using the assumed natural strain 9-node shell element. To compare with previous research, the stiffened plates are composed of carbon-epoxy composite laminate with a symmetric stacking sequence. Also, the result of the present shell model for the stiffener made of composite material is compared with that of the beam model. In the case of torsionally weak stiffener, a local buckling occurs in the stiffener. In this case, the stiffener should be idealized by using the shell elements. The current investigation concentrates upon the vibration analysis of rectangular stiffened and unstiffened composite plates when subjected to the in-plane compression and shear loads. The in-plane compression affect the natural frequencies and mode shapes of the stiffened laminated composite plates and the increase in magnitude of the in-plane compressive load reduces the natural frequencies, which will become zero when the in-plane load is equal to the critical buckling load of the plate. The natural frequencies of composite stiffened plates with shear loads exhibit the higher values than the case of without shear loads. Also, the intersection, between the curves of frequencies against in-plane loads, interchanges the sequence of some of the mode shapes as a result of the increase in the inplane compressive load. The results are compared with those available in the literature and this result shows that the present shell model for the stiffened plate gives more accurate results. Therefore, the magnitude, direction type of the in-plane shear and compressive loads in laminated composite stiffened plates should be selected properly to control the specific frequency and mode shape. The Lanczos method is employed to solve the eigenvalue problems.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.134-144
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• 1993

Sandwich plate is consisted of equal two isotropic, thin, stiff and strong sheets of dense material separated symmetrically by an isotropic thick layer which may be much less stiff and strong. This study analyzed the dependency of the natural frequencies and mode shapes of sandwich plates on material properties, thicknesses of faces and cores, and various boundary conditions using Rayleigh-Ritz method. E-glass Woven Roving and another two kinds of materials were selected as a face, P.V.C. and another kinds of materials were selected as a core. Natural frequencies and mode shapes obtained by Rayleigh-Ritz method were compared with F.E.M. solutions using ADINA program.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.675-681
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• 1988

A simplified FRF(frequency response function) model of an indeterminate cantilever system with viscoelastic material layers is derived. A way to calculate modal damping of the system from the dynamic properties of the viscoelastic material is proposed. The model is experimentally verified.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.4
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• pp.118-123
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• 1997

The study suggests a method to analyze the vibration of the multi-stepped beam having the different circular cross-sections. The rotatory inertia, the shear deformation and the torque applied at both ends of the beam are considered in the governing equation. The complex displacement and the variable separation are introduced to derive the solution of the equation of each uniform beam element having constant cross-section. Then boundary conditions are applied to solve the total system. This method uses the mathematically exact solutions unlike numerical method such as the finite element method in solving the problem having the simultaneous differential equations of Timoshenko beam theory. the natural frequencies and the corresponding mode shapes are precise, especially the mode shapes are continuous.