• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.556-557
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.481-482
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• 2010

• Journal of Industrial Technology
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• v.16
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• pp.239-245
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• 1996

Modal parameters determine the frequency response characteristics of vibration system or acoustic system. When the two systems are fully coupled, however, coupling changes the vibrational and acoustic model parameters into those of the coupled system. In this case, it is very difficult to obtain the modified model parameters and response characteristics. In this paper, coupling effect is analytically investigated on the natural frequency, mode and frequency response characteristics. The result can be applied to understand and to design the frequency response characteristics of the vehicle passenger compartment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.197-200
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• 1995

Corrugation of railway track can be caused by the various dynamic behavior of travelling wheels and track. In this paper, the coupled vibrations of travelling wheel and railway track are analyzed as the cause of corrugations. To analyze the coupled vibrations, the track supported by the sleepers and the traveling wheel are identified to the elastically supported infinite beam and the spring-mass system which runs at constant speed. The Hertzian contact spring is considered betwen the infinite beam and spring-mass system. The dynamic responses of elastically supported infinite beam and spring-mass system are calculated. The cause and development of rail corrugation are discussed in the view point of contact force fluctuation affected by the elastic supports and the corrugated surface profile of the track. By the obtained results, the possibilities of resonance are checked between the excitation by the corrugated surface profile and the natural frequency of contact spring-moving mass system. It may be thought to a development of railway corrugation.

• Smart Structures and Systems
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• v.15 no.3
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• pp.523-541
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• 2015

Structural health monitoring of steel truss bridge based on changes in modal properties was investigated in this study. Vibration measurements with five sensors were conducted at an existing Warren truss bridge with partial fractures in diagonal members before and after an emergency repair work. Modal properties identified by the Eigensystem Realization Algorithm showed evidences of increases in modal damping due to the damage in diagonal member. In order to understand the dynamic behavior of the bridge and possible mechanism of those increases in modal damping, theoretical modal analysis was conducted with three dimensional frame models. It was found that vibrations of the main truss could be coupled internally with local vibrations of diagonal members and the degree of coupling could change with structural changes in diagonal members. Additional vibration measurements with fifteen sensors were then conducted so as to understand the consistency of those theoretical findings with the actual dynamic behavior. Modal properties experimentally identified showed that the damping change caused by the damage in diagonal member described above could have occurred in a diagonal-coupled mode. The results in this study imply that damages in diagonal members could be detected from changes in modal damping of diagonal-coupled modes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.311-318
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• 1998

In this paper, the power flow analysis(PFA) method is applied to the prediction of the vibrational energy density and intensity of coupled co-planar plates. To cover the energy transmission and reflection at the joint of the plates, the wave transmission approach is introduced with the assumption that all the incident waves are normal to the joint. By changing the frequency ranges and internal loss factors, we have obtained the PFA results, and compared them with the analytical exact solutions.

• Interaction and multiscale mechanics
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• v.2 no.2
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• pp.189-207
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• 2009

Dynamics of the electric system for the toroidal drive under mechanical disturbance is presented. Using the method of perturbation, free vibrations of the electric system under mechanical disturbance are studied. The forced responses of the electric system to voltage excitation under mechanical disturbance are also presented. We show that as the time grows, the resonance vibration caused by voltage excitation still exists and the vibrations caused by mechanical disturbance are enlarged. The coupled resonance vibration caused by mechanical disturbance and voltage excitation is discussed. The conditions of the occurrence of coupled resonance are studied.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.831-835
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• 2003

The objective of this paper is to suggest an experimental technique to measure the out-of-plane vibration intensity of a coupled plate. In order to measure the out-of-plane vibration intensity of the plate, the frequency response technique has been implemented. In this technique, the 2-D intensity vector at a measurement point has been estimate from the frequency response functions measured at 4 points in the neighborhood of the measurement point. The experimental result has been compared with a theoretical result. It showed that the experimental technique can be effectively used to measure the out-of-plane vibration intensity of plates.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.11
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• pp.696-701
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• 2014

In this study, in order to develop coupled vibration mode piezoelectric devices for Acoustic Emission (abbreviated as AE) sensor application with outstanding displacement and piezoelectric properties have been simulated by ATILA FEM program. And, From the results of ATILA simulation, the AE sensor specimen, obtained superior electromechanical coupling factor and displacement, when the size of specimen is $3.45mm{\Phi}{\times}3.45mm$ with ratio of diameter/thickness(${\Phi}/T$)= 1.0. Therefore, AE sensor was fabricated by (Na,K,Li)(Nb,Ta) $O_3$(abbreviated as NKL-NT) system piezoelectric ceramics using coupled vibration mode. The piezoelectric properties of NKL-NT ceramics was exhibited that piezoelectric constant($d_{33}$), piezoelectric voltage constant($g_{33}$) and electro mechanical coupling factor($k_p$) have the excellent values of 261[pC/N], 40.10[$10^{-3}Vm/N$], and 0.44, respectively. The manufactured piezoelectric device with ratio of ${\Phi}/T$= 1.0 indicated the optimum values of resonant frequency(fr)= 556.5[kHz], antiresonant frequency(fa)=631.1[kHz], and effective electromechanical coupling factor(keff)= 0.473. The maximum sensitivity of the coupled vibration mode AE sensor was 55[dB] at the resonant frequency of 75[kHz]. The results show that the coupled vibration mode piezoelectric device is a promising candidate for the application AE sensor piezoelectric device.

• Nuclear Engineering and Technology
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• v.41 no.3
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• pp.335-346
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• 2009

This paper deals with a hydroelastic vibration analysis of two rectangular plates partially coupled with a liquid, which is bounded by two plates and two rigid side walls. The wet displacement of each plate is assumed to be a combination of the modal functions of a dry uniform beam with a clamped boundary condition. As the liquid is assumed to be an ideal liquid, the displacement potential satisfying the Laplace equation is determined so that the liquid boundary conditions can meet the requirements at the rigid surfaces and the free liquid surface. The wet dynamic modal functions of each plate are expanded by using the finite Fourier transform to obtain an appropriate form of the compatibility requirement along the contacting surfaces between the plates and the liquid. The liquid-coupled natural frequencies of the plates are derived by using the Rayleigh-Ritz method. Finite element analyses using commercial software are carried out to verify the proposed theory. It is observed that the theoretical method agrees excellently with the three-dimensional finite element analyses results. The effects of the liquid depth and the liquid thickness on the normalized natural frequencies are investigated to identify the dynamic characteristics of the liquid coupled system.