• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1201-1207
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• 2007

The Timoshenko beam theories are used to model the rotating shaft. The nondimensional equations of motion for the rotating shaft subjected to moving mass and compressive axial forces are derived by using Hamilton's principle. Influence of system parameters such as the speed ratio. the mass ratio and the Rayleigh coefficient is discussed on the response of the moving system. The effects of compressive axial forces are also included in the analysis. The results are presented and compared with the available solutions of a rotating shaft subject to a moving mass and a moving load.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.150-157
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• 2005

The vibration system in this study is consisted of a rotating cantilever pipe conveying fluid and a tip mass. The equation of motion is derived by using the Lagrange's equation. The influences of the rotating angular velocity and the velocity of fluid flow on the natural frequencies of a cantilever pipe have been studied by the numerical method. The effects of a tip mass on the natural frequencies of a rotating cantilever pipe are also studied. The influences of a tip mass, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the natural frequency of a cantilever pipe are analytically clarified. The natural frequencies of a cantilever pipe conveying fluid are proportional to the angular velocity of the pipe in both axial direction and lateral direction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.1
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• pp.13-19
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• 1995

An experimental investigation has been made for flow in a circular cylinder with a rotating bottom disk. Flow system considered in this paper is a characteristic model of interior flows of an electric washing machine. Flows in a tub of an electric washing machine are driven by a rotating bottom disk called a pulsator. The simple and characteristic model was composed of a circular cylinder with impulsively rotating endwall disk and a viscous fluid in it. Rotational motion of the pulsator is periodic and alternative in rotation direction. The flow field in the interior region is governed by a horizontal boundary layer forms on the impulsively rotating disk. Experimental approach was accomplished by adopting an image processing technique for velocity measurements. Comprehensive details of the flow structure are presented. Also a meridional circulation is obtained by tracking image particles suspended in the fluid. Flow structure and data are successfully procured for this complex rotating flow field.

• Structural Engineering and Mechanics
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• v.22 no.2
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• pp.151-167
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• 2006

A p-version of the finite element method in conjunction with the modeling dynamic method using the arc-length stretch deformation is considered to determine the bending natural frequencies of a cantilever flexible plate mounted on the periphery of a rotating hub. The plate Fourier p-element is used to set up the linear equations of motion. The transverse displacements are formulated in terms of cubic polynomials functions used generally in FEM plus a variable number of trigonometric shapes functions representing the internals DOF for the plate element. Trigonometric enriched stiffness, mass and centrifugal stiffness matrices are derived using symbolic computation. The convergence properties of the rotating plate Fourier p-element proposed and the results are in good agreement with the work of other investigators. From the results of the computation, the influences of rotating speed, aspect ratio, Poisson's ratio and the hub radius on the natural frequencies are investigated.

• Structural Engineering and Mechanics
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• v.30 no.4
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• pp.427-444
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• 2008

A mathematical model for the nonlinear dynamics of a rotating beam with flexible root attached to a rotating hub with elastic foundation is developed. The model is developed based on the large planar and flexural deformation theory and the potential energy method to account for axial shortening due to bending deformation. In addition the exact nonlinear curvature is used in the system potential energy. The Lagrangian dynamics and the assumed mode method is used to derive the nonlinear coupled equations of motion hub rotation, beam tip deflection and hub horizontal and vertical displacements. The derived nonlinear model is simulated numerically and the results are presented and discussed for the effect of root flexibility, hub stiffness, torque type, torque period and excitation frequency and amplitude on the dynamic behavior of the rotating beam-hub and on its stability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.534-539
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• 2000

A flexible rotating beam test bed has been developed for experimental verification of flexible rotating beam dynamics and vibration. It consists of a flexible arm, harmonic driver reducer, ac servo motor and DSP board with PC. To capture the motion induced stiffening effects of the flexible rotating beam, substructuring model has been established in multibody dynamics simulation. Substructuring model provides better results comparing with experimental data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.99-105
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• 2009

Crack detection method of a rotating blade was suggested in this paper. A rotating blade was modeled with a cantilever beam connected to a hub undergoing rotating motion. The existence and the location of crack were able to be recognized from the vertical response of end tip of a rotating cantilever beam by employing Discrete Hidden Markov Model (DHMM) and Empirical Mode Decomposition (EMD). DHMM is a famous stochastic method in the field of speech recognition. However, in recent researches, it has been proved that DHMM can also be used in machine health monitoring. EMD is the method suggested by Huang et al. that decompose a random signal into several mono component signals. EMD was used in this paper as the process of extraction of feature vectors which is the important process to developing DHMM. It was found that developed DHMMs for crack detection of a rotating blade have shown good crack detection ability.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.26-32
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• 2003

The vibrational system of this study is consisted of a rotating cantilever pipe and the flow in the pipe. The equation of motion is derived by using Lagrange equation. The influences of the rotating angular velocity and the velocities of fluid flow in the pipe have been studied on the dynamic characteristics of a rotating cantilever pipe by numerical method. The tip-amplitude of axial vibration and maximum tip-deflection of axial direction of cantilever pipe are directly proportional to the velocity of fluid and rotating angular velocity of pipe In the steady state. respectively The bending tip-amplitude of cantilever pipe is inversely proportional to the velocity of fluid in the steady state. When the rotating angular velocity is 5 rad/s, the velocity of fluid increase with increasing the natural frequency of axial vibration at second mode and third mode, but the natural frequency axial direction of first mode is decreased. The natural frequency of lateral direction is decreased due to increase of the rotating angular velocity. It identifies that the Influence of velocity of fluid give much variation lower mode of vibration in lateral direction. And the Influence of velocity of fluid give much variation higher mode of vibration in axial direction.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.101-109
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• 2008

The stability of a rotating cantilever pipe conveying fluid with a crack and tip mass is investigated by the numerical method. That is, the effects of the rotating angular velocity, mass ratio, crack severity and tip mass on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived by using the Euler-Bernoulli beam theory and the extended Hamilton's principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. Also, the crack is assumed to be in the first mode of fracture and always opened during the vibrations. When the tip mass and crack are constant, the critical flow velocity for flutter is proportional to the rotating angular velocity of pipe. In addition, the stability maps of the rotating pipe system as a rotating angular velocity and mass ratio ${\beta}$ are presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.399.2-399
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• 2002

This paper concerns on a non-rotating single-DOF beam-active magnetic bearing(AMB) system subject to arbitrary shaped base motion. In such a system, it is desirable to retain the beam within the predetermined air-gap under foundation excitation. Motivated form this, an adaptive acceleration feedforward control is proposed to reduce the base motion response without deteriorating other feedback control performances. Experimental results demonstrate the effectiveness of the acceleration feedforward control.