• 한국농공학회지
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• 제28권1호
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• pp.68-74
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• 1986

The governing differential equations and the boundary conditions for the free vibra- tion of the unsymmetric parabolic arch with fixed ends are derived on the basis of the equilibrium equations and the D'Alembert principle. The effect of the rotary inertia as well as the extensional and the flexural deformations is considered in the governing differential equations. A trial eigenvalue method is used for determining the natural frequencies. The Ru- uge-Kutta method is used in this method to perform the integration of the differential equations. The detailed studies are made of the lowest three vibration frequencies for the par- abolic chord length equal to 10m. The effect of the rotary inertia is analyzed and it's numerical data are presented in table. And as the numerical results the frequency versus the rise of arch and the radius of gyration are presented in figures.

• 한국소음진동공학회논문집
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• 제12권3호
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• pp.187-194
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• 2002

A seven-port impedance and admittance matrices of multilayered piezoelectric beam are derived for the analysis of piezoelectric AFM ( atomic force microscope) cantilever that is partially covered by the piezoelectric layer. The variational principle is used for deriving the extensional and flexural motional equations and the conjugate parameters. Overall impedance matrix of AFM cantilever can be obtained by combining two impedance matrices of the covered and the non-covered. she resonance and antiresonance frequencies and the effective electromechanical coupling factors are calculated using the derived matrices. The results and the three dimensional finite element solutions are compared with the experimental results in other publication.

• 한국소음진동공학회논문집
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• 제24권10호
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• pp.788-794
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• 2014

In this paper, the transient response analysis of the trapezoidal corrugated plate subjected to the pulse load is investigated by the theoretical method. Three types of pulse loads are considered: stepped, isosceles triangular and right triangular pulse loads. The corrugated plates can be represented as an orthotropic plate. Both the effective extensional and flexural stiffness of this equivalent orthotropic plate are considered in the analysis. The plate is stiffened by concentric stiffeners perpendicular to the corrugation direction. The stiffening effect is represented by the discrete stiffener theory. This theoretical results are validated by those obtained from 3D finite element analysis based on shell elements. Some numerical results are presented to check the effect of the geometric properties.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.160-165
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• 1997

Structural boundary condition is very important as a part of a structural system because it determines the dynamic characteristics of the structure. It is often to experience that experimental measurements of structural dynamic characteristics are somewhat different from the analytical predictions in which idealized boundary conditions are usually assumed. However, real structural boundary conditions are not so ideal; not perfectly clamped, for instance. Thus this paper introduces a new method to determine the non-ideal structural boundary conditions in the frequency domain. In this method, structural boundary conditions are modeled by both extensional (vertical) and torsional elastic springs. The effective springs are then determined from experimental FRFs (frequency response functions) by using the spectral element method (SEM). For a cantilevered beam experiments are conducted to determine the real boundary conditions in terms of effective springs. Dynamic characteristics (analytically predicted) based on identified boundary conditions are found to be much closer to experimental measurements when compared with those based on ideal boundary conditions.

• Steel and Composite Structures
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• 제23권3호
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• pp.251-261
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• 2017

In this paper, thermal effect on the vibration and stability of initially stressed sandwich plates with functionally graded material (FGM) face sheets is analyzed. Material properties of FGM face sheet are graded continuously in the thickness direction. The variation of FGM properties assumes a simple power law distribution in terms of the volume fractions of the constituents. The governing equations of arbitrarily initially-stressed sandwich plates including the effects of transverse shear deformation and rotary inertia are derived. The initial stress is taken to be a combination of a uniaxial extensional stress and a pure bending stress in the examples. The eigenvalue problems are formed to study the vibration and buckling characteristics of simple supported initially stressed FGM/metal/FGM plates. The effects of volume fraction index, temperature rise, initial stress and layer thickness of metal on the natural frequencies and buckling loads are investigated. The results reveal that the volume fraction index, initial stresses and layer thickness of metal have significant influence on the vibration and stability of sandwich plates with FGM face sheets.

• 한국소음진동공학회논문집
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• 제24권5호
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• pp.414-420
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• 2014

In this paper, the vibration characteristics of the trapezoidal corrugated plate with axial stiffeners and lumped masses are investigated by the analytical method. The corrugated plate can be treated as an equivalent orthotropic plate as this plate has different flexure properties in two perpendicular directions; flexible in the corrugation direction and stiff in the transverse direction. The effective extensional and flexural stiffness of the equivalent plate are considered to obtain the precise solution in the analysis. The plate is stiffened by concentric stiffeners horizontally to the corrugation direction. The discrete stiffener theory is adopted to consider the position of stiffener. To demonstrate the validity of the proposed approach, the comparison is made with the results of 3D ANSYS finite element solutions. Some numerical results are presented to check the effect of the geometric properties.

• Composites Research
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• 제29권6호
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• pp.347-352
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• 2016

적층 복합재료 주름판에 대한 진동특성을 이론적 방법을 이용하여 분석하였다. 고려된 주름 형상은 사다리꼴을 기본으로 삼각형, 사각형 및 요각 사다리꼴형이다. 3차원 주름 구조물을 해석적으로 기계적 거동을 표현하는 것이 매우 어렵기 때문에 본 해석에서는 주름판의 진동특성을 분석하기 위해 등가균질모델을 적용하였다. 이를 위해 단위 주름을 직교이방성재료로 등가시켰으며, 해석에서 등가 신장 강성 및 굽힘 강성이 모두 고려되었다. 이론해석 결과의 타당성을 검증하기 위해 셸요소를 적용한 3차원 유한요소해석을 수행하였으며, 두 방법을 이용해 얻은 고유진동수 및 진동형상을 비교하였다. 주름판의 기하형상에 따른 영향을 분석하기 위해 다양한 수치예가 제시되었다.

• Advances in concrete construction
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• 제13권4호
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• pp.327-337
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• 2022

This paper is concerned with the vibration analysis of middle layer cylindrical shell made of functionally graded material. The outer layers and inner layer are composed of functionally graded and isotropic material respectively. The Rayleigh Ritz method is applied to solve the presented shell dynamics equations. Two configurations are constructed with layers distributions. Fundamental natural frequencies of the three layered cylindrical shell is plotted against the circumferential wave number with different power law exponents. The frequency decreases with the increase of power law exponent. The fundamental natural frequencies first decreases and fall down to its minimum value, after frequencies increases with circumferential wave number. This is due to change in the magnitude of extensional and bending energies of the cylindrical shells. The computer software MATLAB has been employed for the computation of presented frequencies and tested the results obtained in order to assess the accuracy and validity of the cylindrical shell model for predicting the vibration frequencies of cylindrical shell.

• 대한기계학회논문집A
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• 제20권4호
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• pp.1320-1332
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• 1996

In the present study, we consider modified 5-node equivalent solid element which has smallest degree of freedom among 2-dimensional solid elements accounting bending deformation as well as extensional and shear deformations, We shall investigate static and dynamic characteristics of this element, which is very effective in thin beam, thick beam, large displacement problems, beam of variable thickness, and asymmetrically stepped beam, etc., as well as relatively simple problems of beam. The degree of freedom of this element is 10, which is smaller than 18 of 9-node element, 16 of 8-node elemtns, 12 of modified 6-node element and Q6 element. Therefore, this element is expected to broaden the effective range of application of the solid elements in the bending problems further.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1479-1480
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• 2011

In this paper, a novel design ultrasonic linear motor is proposed. The proposed motor consists of a ring type stator and a mover. They have spirals on their inner and outer surface, respectively. Along the spiral, a mover is travelled by a travelling extensional vibration mode of a ring type stator. Hence, a linear up-and-down motion is generated. Through the experimental data, we can verify the applicability regarding the autofocus lens drive.