• Journal of Korean Association for Spatial Structures
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• v.6 no.3 s.21
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• pp.35-41
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• 2006

Various monitoring sensors have been used for the monitoring, damage and vibration prediction of structures. They have been used for sensing damage in a variety of materials and structures such as piezoelectric materials (PZT) and electric strain gauges. But, many experiments of vibration were not performed. The PZT changes physical force if load cell to electrical signal due to deformation of structure. The voltage change of piezoelectric sensors for plates are used for vibration prediction. In this study, a fundamental study for vibration prediction using piezoelectric sensors are discussed in plates.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.7
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• pp.692-700
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• 2012

Vibration intensity has been used to localize vibration source of a vibrating system. Not only that, vibration intensity has also been used for structural diagnostic in identifying crack and mounted stiffeners. To clearly identify the location of vibration source and understand the changes of energy transmission path, clear flow visualization is required. Most of previous works used vectors to indicate the magnitude and direction of emerging vibration energy and transmission paths. However, due to the large surface area of a plate like-structure, clear transmission paths cannot be achieved using vector visualization. This becomes an issue when detail vector flow at all locations of the whole plate surface is required. In this study, streamlines visualization is used to clearly indicate the power flow transmission path at all plate surface. By using streamlines representation, not only clear transmission paths are obtained, but also improves the vector visualization which helps us to understand the changes of the energy flow especially for stiffened plates. In this study, vibration intensity computation is firstly compared to previous work to validate the vibration intensity computation. To clearly show the power flow transmission paths, streamlines representation is shown. This representation overcomes the unclear vector direction especially for stiffened plates. Different pattern of energy transmission path can be observed using streamlines representation for stiffened and unstiffened plate. The complex streamlines pattern can also be observed at high resonance frequencies which is unclear by using vector representation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.289-290
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• 2012

본 연구에서는 고정식 해양구조물의 지지각으로 사용되는 원형실린더에 나선형 판을 부착하여 와류유기진동에 미치는 영향을 고찰하였다. 연구의 목적을 달성하기 위해 $Re=6.5{\times}10^3$의 균일유입유동에서 2-프레임 그레이레벨 상호상관 PIV기법을 이용한 실험적인 방법을 적용하였다. 모델의 직경은 40mm이며 후류 유동구조, 난류강도, 응력분포에 대한 통계적 유동정보를 계측하였다. 실험결과로는 원형실린더와 뱃전판을 부착한 실린더와의 비교를 통해 뱃전판의 유동특정을 평가하였으며, 뱃전판의 영향은 후류에서 와의 생성과 소멸 메커니즘의 변화에 큰 영향을 미치고 후류 칼만 와열의 안정적인 제어를 통해 와류유기진동을 억제하였다.

• Journal of Korean Association for Spatial Structures
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• v.6 no.4 s.22
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• pp.45-52
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• 2006

FRP laminated plates have strong material-nonlinearity. Through vibration Analysis of FRP laminated plates, the result of nonlinearity analysis is compared with the result of linearity analysis according to stacking angle and squency. This study is a fundamental study about displacement in nonlinearity dynamic behavior of FRP laminated plates.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.5
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• pp.432-438
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• 2004

Acoustic levitation induced by ultrasonic flexural vibration at 28.4 KHz with a vibration amplitude of 10 micrometers is presented. Levitation of multiple objects along the length of the beam in a gap of 8.3 mm which is the half of acoustic wavelength is experimentally demonstrated. Analytical analysis predicts that levitated objects for the gap of half-the wavelength converges to the center of the gap, which is experimentally verified. It is observed that levitated objects with well-balanced mass distribution are set into rotation due to acoustic streaming. For cylinder-shaped Styrofoam with a diameter of 1.8 mm and a length of 3 mm, measured rotational velocity is 2400 revolution per minute. Applications of standing wave field levitation (SWFL) include manipulation of biological cells and blood constituents in biotechnology, and fine powder in material engineering.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.623-628
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• 2004

In this study, the assumed-mode method using characteristic polynomials of Timoshenko beam is applied for the free vibration analysis of rectangular stiffened plates. The polynomial is derived considering the rotational constraint along the boundary edges of plate and the orthogonal relation of Timoshenko beam functions, which enables to simplify the free vibration analysis of plate structure having various boundary conditions. To verify the validity and effectiveness of the adopted method, numerical analysis for cross-stiffened plates were carried out and its results were compared with those obtained by the general purpose FEA software.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.563-571
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• 1999

변단 면과 다양한 경계조건을 갖는 보와 타워구조물의 제1모드에서의 고유진동수를 구하는 정확한 해는 1974년에 Kim에 의해 발표되었다. 최근 이 방법은 복합재료 적층 판을 포함하는 2차원 문제의 제 1모드 진동해석에 확장되었으며, 다양한 경계조건과 불규칙 단면을 갖는 판에 매우 효과적이다. 이 논문에서는 변단 면과 경계조건에 따른 특별직교 이방성 판에 대한, Kim에 의해 개발된 간편한 진동해석 방법의 응용결과가 주어진다. 또한 집중하중들에 대한 영향이 연구되었다.

• Journal of Power System Engineering
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• v.1 no.1
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• pp.124-143
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• 1997

본 논문은 능동 구속층 감쇠(active constrained layer damping) 처리된 관의 동적 모델링과 정식화를 제시한다. 판의 운동방정식은 Hamilton정리를 이용하여 전개된 판, piezoelectric film 및 점탄성층의 운동방정식을 조합하므로서 유도된다. 이 운동방정식은 외부인가전압의 영향하에서 적층판의 해석적 모델을 제공할 뿐만이 아니라, 판 구조내에서 진동에너지를 감소시킬 수 있는 전단층의 효과에 대한 변위관계식을 나타낸다. 그리고 운동방정식에 대응하는 경계조건도 유도되었다. 또한 판과 능동구속층감쇠계의 동특성을 설명하기 위한 유한요소모델이 유도되었다. 이 모델의 타당성을 실온조건에서 실험적으로 입증하였다. 개발된 이론 및 실험적인 결과들은 판과 능동구속층 감쇠계가 구조진동의 감쇠를 위한 매우 유효한 수단으로 사용될 수 있음을 나타내었다.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.76-86
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• 1998

Structural intensity of plates experiencing bending vibration is analytically evaluated using the modal analysis based on assumed mode method. To evaluate the convergence of structural intensity according to the number of superposition modes, the power obtained by structural intensity integration over the closed curve containing the excitation source is compared with the power injected into plates. The erect of power reduction due to the material internal loss is evaluated using the intensity around a localized damping point, In addition, the dominant component among internal forces in the power transfer by the bending vibration of plates and the change of power flow due to stiffener are also investigated.

• Composites Research
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• v.12 no.4
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• pp.25-32
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• 1999

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the special orthotropic plates on elastic foundation with free boundaries is presented. Such plates represent the concrete highway slab and hybrid composite pavement on bridges. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation and the aspect ratio of the plate on the natural frequency is thoroughly studied. The effect of neglecting the mass of the plates on the natural frequency, as the ratio of the point mass/masses to the plate mass increases, is also studied, in deep.