• 한국소음진동공학회논문집
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• 제22권1호
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• pp.29-37
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• 2012

This paper is concerned with the natural vibration characteristics of a rectangular plate with a rectangular hole in contact with the water. The addressed problem was solved by using the Rayleigh-Ritz method combined with the Green function method. This study presents the numerical approach, numerical results and experimental results. In addition, the validity of the approximate formula which mainly depends on the so-called non-dimensionalized added virtual mass incremental factor and the natural mode shape change due to the presence of the water were investigated. Experiments were also carried out to validate theoretical results. The theoretical results are in good agreement with the experimental results. It was found that the effect of a square hole on the natural frequencies of the square plate in contact with water is different from the effect of a square hole on the natural frequencies of the square plate in air and the approximate formula can predict lower natural frequencies in water with a good accuracy.

• 한국소음진동공학회논문집
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• 제12권10호
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• pp.785-791
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• 2002

A modeling method for the dynamic characteristic analysis of a translationally accelerated trapezoidal cantilever plate is presented in this paper. The equations of motion for the plate are derived and transformed into a dimensionless form. The effects of the inclination angles and the acceleration on the vibration characteristics of the plate are investigated. Incidentally, natural frequency loci veering and associated mode shape variations are observed and discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.908-913
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• 2002

An analytical study is presented on the hydroelastic vibration of two rectangular identical plates coupled with a bounded fluid by using the finite Fourier series expansion method. It is observed that the two contrastive modes, the so called the out-of-phase and in-phase modes appear. The proposed analytical method is verified by observing a good agreement to three dimensional finite element analysis results. All natural frequency of the in-phase modes can be predicted well by the combination of the dry beam modes. The theoretical prediction for the out-of-phase mode can be improved by using the polynomial functions satisfying the plate boundary conditions and fluid volume conservation instead of using dry beam modes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.269-274
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• 2007

With the importance of comfortable environment, research about noise reduction of construction is consisting much. If construction receives the input force, noise will be generated thereby. We must predict vibration and noise characteristic to reduce structured borne noise, and construction which become a basis of such research is plate. In order to predict the radiating noise from the vibrating surface. It is required to know the velocity distribution of vibration surface exactly. It is good to use bead for reducing vibration and noise of plate. In this study, we have analyzed structure-borne noise of plate with bead and compare with plate that there is no bead about equal exciting force.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.629-633
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• 1998

본 연구에서는 연성손실계수가 구조물의 진동에 미치는 영향을 살펴보았다. 세부시스템의 두께가 동일할 경우 평판으로 이루어진 구조물이 접수되면 연성손실계수가 감소하게 된다. 특히, 저주파수 대역에서 연성손실계수가 크게 낮아졌다. 그 주된 원인은 접수로 인해 평판에서 전파되는 굽힘파의 그룹속도가 줄어들기 때문이며, 접수로 인한 파워투과계수의 변화는 크지 않았다. 내부에 격벽을 가진 steel box에 공기중 연성손실계수와 접수시 연성손실계수를 적용하여 세부시스템의 속도를 구한 결과, 공기중 연성손실계수를 이용하여 구한 속도가 접수시 연성손실계수를 이용하여 구한 속도보다 약 2-3 dB정도 높게 나타났다. 선박과 같은 복잡한 구조물인 경우 연성손실계수에 의한 속도 차이는 더욱 커질 것으로 추정된다. 따라서, SEA를 이용한 접수 구조물의 진동해석에서 해석오차를 줄이기 위해서는 연성손실계수에 접수의 영향을 고려해 주어야 함을 확인하였다. 특히, 접수효과가 고려된 연성손실계수를 사용하면 SEA가 큰 오차를 보이는 중, 저주파수 대역에서 해석 결과에 대한 신뢰성을 높일 것으로 판단된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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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.

• 한국소음진동공학회논문집
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• 제13권10호
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• pp.821-827
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• 2003

The so-called boundary node method (or NDIF method) that was developed by the authors has been extended for free vibration analysis of arbitrarily shaped plates with free edges. Since the proposed method requires no interpolation functions. no integration Procedure is needed on boundary edges of the plates and only a small amount of numerical calculation is involved, compared with FEM and BEM. In order to explain tile reason why spurious eigenvalues are generated when the NDIF method is applied to free plates, the NDIF method has been considered for free vibration analysis of both a fixed string and a free beam. Finally, verification examples show that natural frequencies obtained by the present method agree well with those given by an exact method or a numerical method (ANSYS).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.65-72
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• 2001

직사각형 평판이 수직방향으로 조화가진력을 받을 때 그 변위가 큰 경우 두 개의 모드 간의 비선형적 상호작용에 대한 연구이다. 폰 칼만 운동방정식에서 유도된 두 개의 상미분 방정식으로부터 수차에 걸친 좌표변환을 거쳐 자유진동의 경우 정지해와 주기해를 구한다. 말굽형태의 분기 현상이 일어날 수 있는 조건을 호모클리닉 또는 헤테로클리닉 궤적의 유무로부터 결정한다. 혼돈 현상의 발생조건을 구하기 위해 멜니코프 방법이 적용되어질 수 있는 형태로 변환하여 광역섭동법의 수학적 결과를 직접적으로 적용할 수 있는 형태로 변환한다.

• 한국소음진동공학회논문집
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• 제11권4호
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• pp.22-30
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• 2001

In this paper, active control of vibrational intensity at a reference point in an infinite, elastic plate was discussed. The plate is excised harmonically by a vibrating source, which has a vertical point force. The optimal condition of controller was investigated to minimize the vibrational intensity being transmitted from the vibrating source to a reference point. Hence the method of feedforward control was employed for the control strategy and then the cost function was evaluated to find the optimal control force. Three types of control force (Vertical force, Moment, and Coupling force (a set of vertical force and moment) ) and controller's positions were examined to define the optimal condition of the controller. The vibrational intensity at a reference point was found to be reduced down to a zero level, compared with the uncontrolled case. Especially maximum reduction of vibrational intensity was achieved when the controller was collinearly positioned between a vibrating source and a reference point.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.602-608
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• 2016

The paper proposes a practical meshless method for the free vibration analysis of clamped plates having arbitrary shapes by extending the non-dimensional dynamic influence function (NDIF) method, which was developed by the author in 1999. In the proposed method, the domain and boundary of the plate of interest are discretized using only nodes without elements unlike FEM and the system matrices are obtained by making domain nodes and boundary nodes satisfy the governing differential equation and boundary conditions, respectively. However, since the above system matrices are not square ones, the problem of free vibrations of clamped plates is not reduced to an algebraic eigenvalue problem. An additional theoretical treatment is considered to produce an algebraic eigenvalue problem. It is revealed from case studies that the proposed method is valid and accurate.