• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.53-55
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• 2013

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.601-605
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• 2007

This paper describes the experimental method to monitor the structural integrity. The crack on structures changes the wave propagation characteristics of structures. To monitor this change, frequency dependent variation of dynamic stiffness of beam structures is obtained by using beam transfer function method, and its trends are compared to undamaged one for identifying the location and size of the crack. Piezoelectric actuators were used to generate flexural vibrations. It eliminated various restrictions of continuously measuring wave propagation characteristics and monitoring structural integrity. The structural integrity was identified with minimal number of measurements and smart structures employing PZT actuations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.54-60
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• 2006

This study looks over the relation between propeller and noise in ship stern structure. Near field noise and vibration measurements are compared with the analytical results using wave number method. To avoid singularity in wave number integration method, fast field method is introduced. Analytical results show that main transmission mechanism of high frequency noise is structure-borne type and that of low frequency noise is a air-borne type.

• Structural Engineering and Mechanics
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• v.53 no.3
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• pp.575-587
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• 2015

This paper focuses on vibration analysis of functionally graded cylindrical shell submerged in an incompressible fluid. The equation is established considering axial and lateral hydrostatic pressure based on first order shear deformation theory of shell motion using the wave propagation approach and classic Fl$\ddot{u}$gge shell equations. To study accuracy of the present analysis, a comparison carried out with a known data and the finite element package ABAQUS. With this method the effects of shell parameters, m, n, h/R, L/R, different boundary conditions and different power-law exponent of material of functionally graded cylindrical shells, on the frequencies are investigated. The results obtained from the present approach show good agreement with published results.

• Steel and Composite Structures
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• v.22 no.2
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• pp.277-299
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• 2016

In this paper, free vibration, forced vibration, resonance and stress wave propagation behavior in nanocomposite plates reinforced by wavy carbon nanotube (CNT) are studied by a mesh-free method based on first order shear deformation theory (FSDT). The plates are resting on Winkler-Pasternak elastic foundation and subjected to periodic or impact loading. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness and their mechanical properties are estimated by an extended rule of mixture. In the mesh-free analysis, moving least squares (MLS) shape functions are used for approximation of displacement field in the weak form of motion equation and the transformation method is used for imposition of essential boundary conditions. Effects of CNT distribution, volume fraction, aspect ratio and waviness, and also effects of elastic foundation coefficients, plate thickness and time depended loading are examined on the vibrational and stresses wave propagation responses of the nanocomposite plates reinforced by wavy CNT.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.394-402
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• 2009

To investigate the heavy-weight impact noise of apartment houses, numerical analysis was performed. The analysis acoustic pressure consider acoustic mode by finite element method. The variables considered effecting on the acoustic pressure are the Acoustic mode, acoustic damping, and the impulse load. The heavy-weight impact noise is a changeable value in the room. Since the most part of the frequency component of heavy-weight impact noise has low frequency. The noise in low frequency is related to the vibration of structure, the reflection of acoustic wave caused by wall and the standing wave called by acoustic mode. The prediction by the numerical analysis was verified with test result of the heavy weight-impact noise at apartment houses.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.6 no.1
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• pp.30-37
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• 2003

This paper describes vibration control of a suspended system using wave absorption method. A moving multiple-pendulum system and a moving wire-and-load system are treated. The wire-and-load system is extended to a model crane system that has a motor system to roll up and down the suspended mass like a real crane. The same program with different parameter values controls these three systems. Both numerical simulation and experiment have been conducted, and the present control method has shown to be quite effective.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.102-107
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• 2013

It is important to understand the vibrating behavior of plate structures for many engineering applications. In this study, vibration characteristics of strip plates which have finite width and infinite length are investigated theoretically and numerically. The waveguide finite element approach is used in this study which is known as an effect tool for waveguide structures. WFE method requires only cross-sectional FE model and uses theoretical harmonic solutions for the wave propagation along the longitudinal direction. First of all for a simple strip plate, WFE results are compared with theoretical ones such as the dispersion diagrams, point mobilities, etc. to validate the numerical model. Then in the numerical analysis, the several different types of longitudinal stiffeners are included to the plate model to investigate the effects of the stiffeners in terms of the dispersion curves and mobilities.

• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.299-315
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• 2016

In this work, a strategy for passive vibration control of periodic structures is proposed which involves adding a periodic array of simple resonant devices for creating band gaps. It is shown that such band gaps can be generated at low frequencies as opposed to the well known Bragg scattering effects when the wavelengths have to meet the length of the elementary cell of a periodic structure. For computational purposes, the wave finite element (WFE) method is investigated, which provides a straightforward and fast numerical means for identifying band gaps through the analysis of dispersion curves. Also, the WFE method constitutes an efficient and fast numerical means for analyzing the impact of band gaps in the attenuation of the frequency response functions of periodic structures. In order to highlight the relevance of the proposed approach, numerical experiments are carried out on a 1D academic rod and a 3D aircraft fuselage-like structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1241-1246
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• 2007

In recent years, the semiconductor industry and the optical industry are developed rapidly. The recent demands have expanded for optical components such as the optical lens, the optical semiconductor and the measuring instrument. Object transport systems are driven typically by the magnetic field and the conveyer belt. Recent industry requires more faster and efficient transport system. However, conventional transport systems are not adequate for transportation of optical elements and semiconductors. The conveyor belts can damage precision optical elements by the contact force and magnetic systems can destroy the inner structure of semiconductor by the magnetic field. In this paper, the levitation transport system using ultrasonic wave is developed for transporting precision elements without damages. The steady state flexural vibration of the beam is expressed using Euler-Bernoulli beam theory. The transport direction of an object is examined according to phase difference and frequency. The theoretical results are verified by experiments.