• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.850-851
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• 2008

This paper compares and investigates the vibration and noise characteristics through simulations of 12/8 and 6/4 switched reluctance motors (SRMs). The radial force which is the main source of vibration is computed from two-dimensional(2D) transient magnetic finite element analysis (FEA) and compared in both time and frequency domain. At the same output power, the radial force of 6/4 SRM is found to be more than two times as that one of 12/8 SRM. Three-dimensional structural finite-element analysis (3D FEA) is used to study the mechanical characteristics. It can be concluded from static structural analysis that the maximum total deformation could be reduced to 1/26 if the motor is designed with 12/8 structure instead of 6/4. The dominant vibration modes are verified by modal analysis.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.9-16
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• 1997

In this paper, a newly radial electronic shearography system was developed in order to study vibration characteristics of symmetrical objects. We utilized the electro-optic holography theory for quantificational analysis and a porror prism for shearing two inages radially in this study. These image data obtained by this shearography give us various distributions of the gradient of vibration amplitude, and they are useful informations to study vibrational characteristics of symmetrical objects. Finally this developed system with phase stepping and modulation was applied to fans and disks to inspect characteristics of the vibration and the blance of symmetrical objects and obtained good results.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.3
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• pp.563-572
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• 2001

With the results of calculation for natural frequencies the reponses of forced coupled vibration of propulsion shafting system were investigated by the modal analysis method. For the forced vibration response analysis, the axial exciting forces, the axial damper/detuner, propeller exciting forces and damping coefficients were extensively considered. As the conclusion of this study, some items are cleared as follows.-The torsional vibration amplitudes are not influenced by the radial excitation forces of the crank shaft. -The axial vibration amplitudes are influenced by the tangential exciting forces as well as the radial exciting forces of the crank shaft. The increase of the amplitudes is observed in the speed range at the neighbourhood of any torsional critical speed. 1The closer the torsional and axial critical speed. the larger coupling effect becomes. -The axial exciting force of propeller is relatively strong comparing with axial exciting forces of cylinder gas pressure and oscillating inertia of reciprocating mechanism. Therefore, the following conclusions are obtained. -Torsional vibration calculation with the classical one dimensional model is still valid. -The influence of torsional excitation at each crank upon the axial vibration is improtant. especially in the neighbourhood of a torsional critical speed. That means that the calculation of axial vibration with the classical one dimensional model is inaccurate in most of cases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.414-421
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• 1996

The study of the vibration characteristics of annular sector plates which are clamped along their inner circumferential edge is important for structural engineers. The present analysis consists of experimental method and numerical method. The experimental method using time-average holographic interferometry is obtained vibration modes and frequencies. The experimental results are verified by a numerical method using F.E.M. The important aspects of the present paper is the dependence of the natural frequencies and the mode shape on the annular area changing sector angle. The radial nodal lines converge to the center of the plate. As increasing sector angle, the radial modes are predominant.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1379-1388
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• 2008

In this paper, we present the equations of motion by which the natural vibration of a rotating annular disk can be accurately analyzed. These equations are derived from the theory of finite deformation and the principle of virtual work. The radial displacements of annular disk which is rotating at constant angular velocity are determined by non-linear equations formulated using 1-dimensional finite elements in radial direction. The equations of the in-plane vibrations at disturbed state are also formulated using 1-dimensional finite elements in radial direction along the number of nodal diameters. They are expressed as in functions of the radial displacements at the steady state and the disturbed displacements about the steady state. In-plane static deformation modes of the annular disk are used as the interpolation functions of 1-dimensional finite elements in radial direction. The natural vibrations of an annular disk with different boundary conditions are analyzed by using the presented model and the 3-dimensional finite element model to verify accuracy of the presented equations of motion. Its results are compared and discussed.

• Coupled systems mechanics
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• v.12 no.2
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• pp.127-149
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• 2023

A theoretical method is developed to analyze the free vibration of an elastic annular plate in contact with an ideal liquid. The displacement potential functions of the contained liquid are expressed as a combination of the Bessel functions that satisfy the Laplace equation and the liquid boundary conditions. The compatibility condition along the interface between the annular plate and the contained liquid is taken into account to consider the fluid-structure coupling. The dynamic displacement of the wet annular plate is assumed to be a combination of dry eigenfunctions, allowing for prediction of the natural frequencies using the Rayleigh-Ritz method. The study investigates the effect of radial liquid boundary conditions on the natural frequencies of the wet annular plate, considering four types of liquid bounding: outer container bounded, outer and inner bounded, inner bounded, and radially unbounded. The proposed theoretical method is validated by comparing the predicted wet natural frequencies with those obtained from finite element analysis, showing excellent accuracy. The results indicate that the radial liquid bounding effect on the natural frequencies is negligible for the axisymmetric vibrational mode, but relatively significant for the mode with one nodal diameter (n =1) and no nodal circle (m' = 0). Furthermore, the study reveals that the wet natural frequencies are the largest for the plate with an inner bounded cylinder among the radial liquid boundary cases, regardless of the vibration mode.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.895_896
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• 2009

this paper presents a rotor shape optimization of interior type permanent magnet (IPM) motor for vibration minimization. the vibration of permanent magnet motor is generated by cogging torque, radial force and commutation torque ripple which are electromagnetic source of vibration. In order to minimize the vibration, the optimal notches are put on the rotor pole face and the arc type pole face is applied. The variations of cogging torque and radial force of each model vibration frequency are computation by finite element method (FEM) and the validity of the analysis and rotor shape design is confirmed by vibration experiments.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.107-109
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• 2007

This paper presents a dynamic force analysis of switched reluctance motor using 2D-transient finite element method. The main exciting of the vibration is the electiromagnetic force in the stator that is calculated Maxwell stress method. The advantage for elimation of vibration of 12/8 SRM was explained by comparing the radial force of 12/8 and 6/4 SRM in both time and frequency domain. In order to effective mitigate the vibration during turning off process, effects of different commutation method were investigated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.739-745
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• 2011

This paper proposes a method for reducing the negative spatial harmonics of the radial flux density of an interior-type permanent magnet (IPM) motor. The reliability of the motor is increased by minimizing its vibrations under dynamic eccentricity (DE) state and normal state due to reduction of a negative spatial harmonics component through the influx of a zero spatial harmonics component in the radial flux density. To minimize the vibrations, optimal notches corresponding to the distribution shape of the magnetic field are designed on the rotor pole face. The variations of vibration computation by finite element method (FEM) and the validity of the analysis and rotor shape design are confirmed by vibration and performance experiments.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.147-154
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• 2003

Radial Dual Mass Flywheel(RDMF) is designed to reduce torsional vibration and noise occurring in automotive powertrain. In this paper, finite element method is used to evaluate stress level and critical area of the torsional spring box, a major part of RDNF system. In finite element analysis, both static and dynamic loadings are considered and it is found that the most critical spot is the welded zone of spring box. Also, fatigue test is performed and fractured surfaces are examined to find fatigue stress level by experiment.