• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.4
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• pp.384-391
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• 2011

This paper deals with free vibrations of the parabolic hollowed beam-columns with constant volume. The cross sections of beam-column taper are the hollowed regular polygons whose depths are varied with the parabolic functional fashion. Volumes of the objective beam-columns are always held constant regardless given geometrical conditions. Ordinary differential equation governing free vibrations of such beam-columns are derived and solved numerically for determining the natural frequencies. In the numerical examples, hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. As the numerical results, the relationships between non-dimensional frequency parameters and various beam-column parameters such as end constraints, side number, section ratio, thickness ratio and axial load are reported in tables and figures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.345-349
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• 2003

The dynamic behavior of CANDU nuclear fuel channel was analyzed by the use of 3-dimensional finite element method, under the various fault conditions such as a fault in the end fitting support and the removal/migration of the garter spring in the fuel channel, in order to predict the dynamic behavior for a degraded symptoms of CANDU nuclear fuel channel. Moreover, the frequency response analysis for possible fault conditions was also peformed considering the effects of the pressure tube vibration and flow-induced vibration by the coolant flow. From the analysis of the frequency responses, defects in the garter spring have influenced the changes of 2nd and 3rd modes and all the important modes are varied for the failure in the journal bearing in the end fitting body.

• Journal of KSNVE
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• v.3 no.4
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• pp.331-339
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• 1993

The main purpose of this paper is to present an analytical method for free vibration of arches with thickness varying in a discontinuous fashion. The ordinary differential equations governing the free vibration of these arches are derived as nondimensional forms including the effect of rotatory inertia. The governing equation are solved numerically for the circular and sinusoidal arches with hinged-hinged-hinged end clamped-clamped end constraints. As the numerical results, the effect of rotatory inertia on the natural frequencies is reported. The lowest four natural frequencies are presented as the functions of four nondimensional system parameters; the rise to span length ratio, the slenderness ratio, the section ratio and the ratio of discontinuous section.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1000-1004
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• 2001

This study explores the free vibrations of tapered column with hinged end restricted by rotational spring. The ordinary differential equation governing the free vibration of such column is derived as nondimensional form in which three kinds of cross-sectional shape are considered. In order to obtain the natural frequencies of column, the governing differential equation is solved by numerical procedures. Numerical results are compared with existing solutions by other methods. It is expected that the results obtained herein can be practically utilized in the structural and the vibration control fields.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.510-511
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• 2012

• Structural Engineering and Mechanics
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• v.5 no.3
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• pp.297-306
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• 1997

The bouncing of a cantilever with the free end pressed against a stop can create high-frequency vibration that the Bernoulli-Euler beam theory is inadequate to solve. An analytic procedure is presented using Timoshenko beam theory to obtain the non-linear response of a cantilever supported by an elastic stop with clearance at the free end. Through a numerical example, the bouncing behavior of the Timoshenko and Bernoulli-Euler beam models are compared and discussed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.11
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• pp.898-906
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• 2014

This paper presents a reduction method for a straight-line path error of a flexible beam deploying from a rotating rigid hub. Previous studies discussed about only vibration phenomena of flexible beams deploying from rotating hubs; however, this study investigates a vibration reduction of a rotating beam with variable length. The equation of motion and associated boundary conditions are derived for a flexible beam deploying from a rotating rigid hub, and then they are transformed to a variational equation. By applying the Galerkin method, the discretized equations are obtained from the variational equation. Based on the discretized equations, the dynamic responses of a rotating/deploying beam are analyzed when the beam end has a straight line motion. A reduction method for the trajectory error is proposed, using the average length of a rotating/deploying beam. It is shown that the proposed method is able to reduce the residual vibration of a rotating/deploying beam.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.911-914
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• 2005

The vibrational characteristics of the piezoelectric disc for a torsional vibration transducer is theoretically studied in this paper. The characteristic equation of the piezoelectric annular disc has been derived from Newton's End law and Gibb's free energy equations. With an anisotropic material property of the disc, the characteristic equation has yielded resonance frequencies. Numerically-calculated results were compared with the values obtained by finite element analysis and experiments

• Wind and Structures
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• v.29 no.1
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• pp.75-84
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• 2019

A steady slot suction near the free-end leading edge of a finite-length square cylinder was used to control its aerodynamic forces and vortex-induced vibration (VIV). The freestream oncoming flow velocity ($U_{\infty}$) was from 3.8 m/s to 12.8 m/s. The width of the tested cylinder d = 40 mm and aspect ratio H/d = 5, where H was the height of the cylinder. The corresponding Reynolds number was from 10,400 to 35,000. The tested suction ratio Q, defined as the ratio of suction velocity ($U_s$) at the slot over the oncoming flow velocity at which the strongest VIV occurs ($U_{\nu}$), ranged from 0 to 3. It was found that the free-end slot suction can effectively attenuate the VIV of a cantilevered square cylinder. In the experiments, the RMS value of the VIV amplitude reduced quickly with Q increasing from 0 to 1, then kept approximately constant for $Q{\geq}1$. The maximum reduction of the VIV occurs at Q = 1, with the vibration amplitude reduced by 92%, relative to the uncontrolled case. Moreover, the overall fluctuation lift of the finite-length square cylinder was also suppressed with the maximum reduction of 87%, which occurred at Q = 1. It was interesting to discover that the free-end shear flow was sensitive to the slot suction near the leading edge. The turbulent kinetic energy (TKE) of the flow over the free end was the highest at Q = 1, which may result in the strongest mixing between the high momentum free-end shear flow and the near wake.

• Journal of the Korean Institute of Navigation
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• v.21 no.3
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• pp.55-66
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• 1997

In this paper, applications of neural networks to vibration control of flexible single link robot manipulator are ocnsidered. The architecture of neural networks is a hidden layer, which is comprised of self-recurrent one. Tow neural networks are utilized in a control system ; one as an identifier is called neuro identifier and the othe ra s a controller is called neuro controller. The neural networks can be used to approximate any continuous function to any desired degree of accuracy and the weights are updated by dynamic error-backpropagation algorithm(DEA). To guarantee concegence and to get faster learning, an approach that uses adaptive learning rates is developed by introducing a Lyapunov function. When a flexible manipulator is ratated by a motor through the fixed end, transverse vibration may occur. The motor torque should be controlle dinsuch as way, that the motor is rotated by a specified angle. while simulataneously stabilizing vibration of the flexible manipulators so that it is arrested as soon as possible at the end of rotation. Accurate vibration control of lightweight manipulator during the large body motions, as well as the flexural vibrations. Therefore, dynamic models for a flexible single link manipulator is derived, and LQR controller and nerual networks controller are composed. The effectiveness of the proposed nerual networks control system is confirmed by experiments.