• The Journal of the Acoustical Society of Korea
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• v.12 no.1
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• pp.12-19
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• 1993

진동시험 동안 구조물은 진동시험기로부터 높은 진동에너지를 받게 되는데 공급되는 에너지를 시험물에 전달하기 위해서는 시험물에 따라 다양한 종류의 진동시험치구가 필요하게 된다. 이중에서 T-형상 진동시험치구는 진동시험축에 대해 3방향으로 시험물을 설치할 수 있고, 형상이 간단하며, 또한 값이 저렴하므로 많은 설계자들은 T-형상 치구를 설계하여 사용한다. 그러나 이 치구는 수직판이 어떤 주파수에서 평판처럼 공진현상을 일으키기 때문에 동역학적으로 설계하기가 어렵다. 본 논문에서는 진동시험치구의 기능을 향상시키기 위해 모우드 시험(Model Testing)기법을 사용하는 방법과 시험결과를 근거로 설계변경을 위해 수직보강판, 수평보강판, 그리고 천연 고무패드를 사용하여 이것들이 치구의 동특성에 미치는 영향을 기술하며 그 결과를 치구설계 때 응용 가능하도록 한다.

• The Journal of the Acoustical Society of Korea
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• v.14 no.5
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• pp.29-35
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• 1995

Nonlinear distortion arising from the nonlinear movement of the loudspeaker diaphragm degradates the tone quality. The distortion is, in low frequency range, mainly caused by nonlinear characteristics of the suspension stiffness and the force factor. In this paper, the nonlinear suspension stiffness and the nonlinear force factor are modeled to the quadratic functions and a method is proposed to determine their coefficients. An additional mass to the diaphragm moved the quiescent point of the diaphragm and uncoupled the stiffness and the force factor. This made it possible to deter mine the coefficients of the nonlinear suspension stiffness by measuring the resonance frequencies at several quiescent points. The coefficients of the nonlinear force factor are then determined by fitting the curve which is calculated from the waveforms of input voltage and input current, and the displacement of the diaphragm at resonance frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1992.10a
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• pp.147-152
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• 1992

본 연구에서는 같은 직경의 2개 원형구멍이 동축상에 있는 4변고정, 등반성 정사각형판의 자유진동특성을 충격진동실험과 유한요소 해서방법으로 원형 구멍직경의 변화에 다른 고유진동수와 무차원 진동수 매개변수를 구하고자 한다.

• Journal of Korean Association for Spatial Structures
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• v.5 no.4 s.18
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• pp.91-100
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• 2005

Composite slab structures consisted with steel deck plate and concrete material show generally anisotropic structural behavior because of different stiffness between the major direction and sub-direction of deck plate, and also the structures can be regarded as the laminated slab structures. It is necessary for the composite deck slab structures to carry out the exact vibration analysis to evaluate the serviceability. Also, it is needed to evaluate the exact structural behavior of composite deck slab with a layered orthotropic materials. In this paper, the thickness of topping concrete and deck plate are used to calculate the material coefficient stiffness of a sub-direction, and an equivalent depth calculated from sectional stiffness of concrete and deck plate is applied to get the stiffness of a major direction. The stiffness of two layered composite plates with different depth is determined by laminated theory. It is concluded that the presented method can efficiently analyze the structural behavior of composite deck slab consisted with steel deck plate and concrete material in the practical engineering field.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.2
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• pp.123-132
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• 1996

환형판은 항공기, 선박, 자동차, 섬유기계 등에서 널리 사용되고 있다. 최근에는 각종기계 또는 구조물을 경량화하고 크기를 줄이기 위하여, 두께가 변화하는 환형판을 기계요소설계에 많이 응용하고 있다. 본 논문에서는 회전관성과 전단변형을 고려하여 두께가 변화($H=h_0(1-{\alpha}x^n)$, n=1, 2, 3, 4)하는 환형판의 동적 모델링을 하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2306-2314
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• 1992

Using the Lagrangian equation, nonlinear vibration analysis of laminated hybrid composite plates is carried out. The effects of stacking sequences, aspect ratios, number of modes, number of layers and various elastic properties on nonlinear vibration are investigated. The presence of bending-extension coupling in antisymmetric plates yields a second power term in addition to a cubic nonlinear term in governing differential equation of motion. In the other symmetric case, this second term vanishes. The fundamental frequency of analytic results are compared with that of ABAQUS FEM analysis. For nonlinear vibration of antisymmetric unimaterial plate, the result of reference is presented for comparison with this result.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.37-44
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• 1991

A powerful analytical procedure and strain energy analysis to investigate the free vibration of antisymmetric cross-ply laminated plates, having one pair of opposite edges simply supported, are develped on the basis of the Yang, Norris abd Stavsky (YSN) theory. The equation of motion of the plate are solved by the use of collation method. A range of results are presented for plates to show the effects of modulus ratio and number of layers on natural frequency. In addition, an analysis of the strain energy distributions is used as an aid for the better understanding of the vibration characteristics of the plates.

• Composites Research
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• v.29 no.6
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• pp.347-352
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• 2016

This work presents the free vibration characteristics of laminated composite corrugated rectangular plates using the analytical method. Because it is very difficult to determine its mechanical behavior of 3-dimensional corrugated structures analytically, the equivalent homogenization model is adapted to investigate the overall mechanical behavior of corrugated structures. The corrugated element can be homogenized as an orthotropic material. Both the effective extensional and flexural stiffness of this homogenized equivalent orthotropic material are considered in the analysis. The present analytical results are validated by those obtained from 3D finite element analysis based on shell elements. The natural frequencies and global vibration mode shapes obtained from present analytical and finite element analysis are presented. Some numerical results are presented to check the effect of the geometric properties.

• Composites Research
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• v.33 no.6
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• pp.377-382
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• 2020

The free vibration characteristics of corrugated laminated composite plates with axial stiffeners is investigated using the Rayleigh-Ritz method. The plate is stiffened by beams with open cross-section area. The equivalent homogenization model is used for the corrugated laminated composite plates. This homogenization model is treated a corrugated plate as an orthotropic plate that has different material properties in two perpendicular directions. The motion of equivalent plate is represented on the basis of the first order shear deformation theory (FSDT) to account for the effect of rotary inertia and transverse shear deformation. Stiffeners are considered as discrete elements to predict the local vibration mode to be generated by the presence of stiffeners. To validate the proposed analytical approach, natural frequencies and vibration mode shapes from the analytical method are compared with those from the FEA by ANSYS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.294-297
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• 2000

본 연구에서는 압전형 음향변환기를 제작하기 위한 금속과 세라믹스로 적층된 원형의 압전음향소자와 음향변환기 케이스를 설계하였다. 먼저 음향소자인 복합원형평판의 진동운동 방정식을 세우고 그 진동모드를 알아보았다. 음향소자의 세라믹스는 두께 1 mm, 지름 10 mm의 PZT(IV)를 사용하였고, 금속판의 지름과 두께를 다양하게 변화시키면서 음향소자의 공진주파수를 계산하고, 각각의 금속판에 따른 감도지수의 변화를 계산하였다. 설계하고자 하는 음향소자의 공진주파수를 200 KHz로 청하고, 위의 계산을 통하여 음향변환소자에 가장 적합한 금속진동판을 찾아보았다. 음향변환기의 복합원형평판으로 이루어진 음향소자의 물리적 변화에 따른 공진주파수와 감도지수를 구하고 음향변환기 케이스의 공진주파수를 계산하여 압전형 음향변환기에 알맞은 금속진동판과 음향변환기 케이스를 알아보았다.