• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.3
• /
• pp.411-418
• /
• 1992

본 연구에서는 인장하중을 받는 균열이 없는 박판 시험편과 45˚경사균열시험 편의 고유진동수 측정을 위하여 레이저 홀로그래피법을 이용하여 진동모드 측정을 하 여 그 결과를 비교분석하는 실험방법을 택하였으며, 균열이 없는 박판에 대해서만 무 차원하중의 증가에 따른 고유 진동수의 변화관계를 실험치와 Ritz Method에 의한 유한 요소 해석치와 비교하였다.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.2 s.54
• /
• pp.69-79
• /
• 2007

In this paper, a technique to detect structural damage and estimate its severity using peaks and zeros of frequency response functions (FRFs) is developed. The peaks in FRFs represent the natural frequencies of the structure and the zeros provide additional information. The characteristics of peaks and zeros are defined and the calculation procedure to obtain the peaks and zeros from the relationship between frequency response function and stiffness and mass matrices are clearly explained. A structural system identification theory which is utilizing the sensitivity of stiffness of a structural member to eigenvalues, i.e., peaks and zeros, is established. The proposed method can identify damage location and its severity, with natural and zero frequencies, by estimating structural stiffness of the structure in the process of making a analytical model The accuracy and feasibility is demonstrated by numerical models of a spring-mass system and a beam structure.

• Composites Research
• /
• v.12 no.1
• /
• pp.1-10
• /
• 1999

In order to predict the dynamic behavior of composite laminated plate accurately, the parametric identification is performed using its mechanical properties- $E_1,\;E_2,\;V_{12},\;G_{12}$ as design parameters. After natural frequencies are measured through simple vibration test, the objective function consists of the sum of errors between experimental and numerical frequencies of a structure. As optimization algorithm, conjugate gradient method is used to minimize the objective function. Sensitivity Analysis is performed to update design parameters during this process and can explain the result of parametric identification. In order to check the propriety of result, mode shapes are compared before and after identification. The improved prediction of natural frequencies of composite laminated plate is obtained with updated properties. For the application of result, updated properties is applied to the composite laminated plate that has different stacking sequence.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.95-100
• /
• 2006

Tolerance analysis method for natural frequencies of multi-body systems having a equilibrium position is suggested in this paper. To perform the tolerance analysis, the Monte-Carlo Method is conventionally employed. However, the Monte-Carlo Method has some weakness; spending too much time for analysis and having a low accuracy and hard to converge in the numerical unstable area. To resolve these problems, a tolerance analysis method is suggested in this paper. Sensitivity equations of natural frequencies are derived at the equilibrium position. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivity of natural frequencies can be calculated.

• Journal of KSNVE
• /
• v.11 no.1
• /
• pp.89-95
• /
• 2001

This paper describes the natural frequencies obtained through FEA (Finite Element Analysis) and Numerical Analysis which uses the boundary conditions to each equation of motion and the consecutive conditions at each supporting point. And then. we studied on the optimal position determination of middle supporting points to maximize the natural frequency of a beam at 24 Models. We present the data of optimal condition for designing a beam.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.1 s.118
• /
• pp.65-71
• /
• 2007

Tolerance analysis method for natural frequencies of multi-body systems having a equilibrium position is suggested in this paper. To perform the tolerance analysis, the Monte-Carlo Method is conventionally employed. However, the Monte-Carlo Method has some weakness; spending too much time for analysis and having a low accuracy and hard to converge in the dynamical unstable area. To resolve these problems, a tolerance analysis method is suggested in this paper. Sensitivity equations of natural frequencies are derived at the equilibrium position. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivity of natural frequencies can be calculated.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.91-92
• /
• 2007

본 연구에서는 전력계통에서 발생되는 surge나 고장전류에 의해서 변압기의 고압측 코일에 유도되는 전자력의 크기를 유한요소 전자계해석 프로그램(FLUX2D)의 축대칭FEM을 이용하여 해석하였다. 1MVA, 22900/220(V) 단상 외철형 Cable형 변압기의 권선의 각방향의 전자력을 분석하고, 변압기 권선의 고유진동mode를 Transfer Matrix Method를 이용하여 Cable형권선의 고유진동주파수를 파악하고 ANSYS와 비교하였다. 변압기 권선의 전자력과 진동mode 분석결과는 변압기의 절연설계 및 단락기계력에 대한 프레임 구조 설계를 위한 자료로 활용될 수 있다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.13 no.1 s.53
• /
• pp.125-134
• /
• 2009

This paper deals with the free vibrations of circular strip foundations which have uniform solid rectangular cross-section. The ground which supports circular strips was modeled as the two parameter elastic foundation. Differential equations governing the flexural-torsional free vibrations of circular strips supported by such foundation were derived, and solved numerically for obtaining the natural frequencies and mode shapes. Boundary condition of free-free ends was considered for numerical examples. Four lowest natural frequencies according to the variations of five system parameters i.e. subtended angle, depth ratio, contact ratio, elasticity ratio and soil parameter are reported in the non-dimensional forms. Also, typical mode shapes of both deformations and stress resultants are presented in the figures. Experiment was conducted for validating the theory developed in this study.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.1
• /
• pp.117-124
• /
• 2012

In this paper, an analysis of the joint that transmits power from the blades to the generator is performed using the FEM (finite element method). The mode shapes and natural frequencies were extracted using experimental modal analysis in order to establish the FEM model. Then, the model was verified by comparing the mode shapes and natural frequencies to those obtained from the ANSYS modal analysis. Dynamic stress analysis was performed at the rated and limited wind speeds considering the wind load and gravity.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.4
• /
• pp.661-669
• /
• 1999

이 논문은 탄성지반위에 놓인 원호형 곡선보의 자유진동에 관한 연구이다. 회전관성 및 전단변형을 고려하여 두 개의 매개변수로 표현되는 탄성지반위에 놓인 원호형 곡선보의 자유진동을 지배하는 미분방정식을 유도하고, 이를 수치적분기법과 시행착오적 행렬값탐사법이 결합된 수치해석기법으로 해석하였다. 회전-회전, 회전-고정 및 고정-고정의 단부조건을 갖는 곡선보의 최저차모드 3개의 고유진동수를 산출하였다. 곡선보의 수평높이 지간길이비, Winkler 지반계수, 전단지반계수에 따른 고유진동수 변화를 분석하였으며, 회전관성 및 전단변형의 영향을 고찰하였다.