• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.647-648
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.799-800
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.715-716
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• 2013

• The KSFM Journal of Fluid Machinery
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• v.2 no.2 s.3
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• pp.27-31
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• 1999

This paper describes the shaft vibration phenomena measured on a pump-turbine of a pumped storage power plant. The pump-turbine runs at a rotational speed of 450 rpm (7.5 Hz). The power output (load) of the pump-turbine is varied from 100 to 300 MW in the generating mode. The magnitude of the shaft vibration highly depends on the power load. The vibration magnitude of the shaft is very high in the middle load zone from 170 to 210 MW, elsewhere the vibration is low. From nitration spectra, it is shown that the frequency of major nitration in that load zone is 2.5 Hz which is approximately $34\%$ of the shaft rotating speed in Hz. This frequency component does not occur below and above that load zone. This subsynchronous vibration is caused by the flow induced disturbance due to spiral vortex flow downstream of the pump-turbine runner. Furthermore, the shaft vibration is highly decreased due to an increased bearing preload.

• Journal of KSNVE
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• v.6 no.5
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• pp.625-633
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• 1996

This paper addresses a systematic way of understanding the transfer characteristics of whole-body vibration due to the external excitation. Amirouche's and Tamaoki's models are considered, whose analysis shows a new result that resonant frequencies related to the head vibration are well coincided with those of the body. This point reveals that the improvement of the ride quality of passenger cars can be achieved by isolating only external vibration components transfered to the body. Finally, this paper points out the limitation of previous whole-body vibration models, which gives the motivations of setting up more 'practical and generalized' whole-body vibration models of interest in this study.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.111-116
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• 2001

In this paper, a simple 2 D.O.F. planar motion model is proposed in order to analyze the snake motion of a machining center cross head assembly, that is travelling on linear guide rails. In the proposed mathematical model, the friction between head and guide ways is neglected, and also the support structures including guide rails, rear- and side-panels of the machining center are assumed to be rigid. The equations of motion of the proposed model are derived and successfully solved to determine vibration responses of the head assembly due to some applied traction forces.

• Journal of KSNVE
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• v.10 no.5
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• pp.865-872
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• 2000

This paper presents the modeling, theoretical formulation, and stability analysis for a combined system of a spinning disc and a head that contacts the disc. In the analytic model, head interference is considered by a rotating mass-spring-damper system together with a frictional follower force on the damped annular discs. The multiple scale method is utilized to perform the stability system that shows the existence of instability associated with parametric resonances. Using the formulated system , instability regions of optical recording disc are investigated with variation of mass, stiffness and friction force of a head, respectively. The simulation results show that the stiffness of a head is the most sensitive parameter on the instability of the disc.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.875-880
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• 2002

It is necessary to determine the vibration source and its transmission paths in order to develop a low-noise compressor. Through the use of multiple-input/single-output(MISO) mode1, the transmission paths of vibration within a reciprocating compressor have been investigated. In order to identify the transmission path, we measure the accelerations of the block and transverse vibrations of the line discharge tube. As outputs, vibrations of compressor shell were measured at three positions; cylinder head, one near the suction line, and the top of upper shell. The partial coherence function and transfer function are obtained ken the measured data, and the results are observed in order to determine vibration source and its influence on the shell vibration.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.1
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• pp.87-98
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• 1997

In this study, subway train vibration has been measured to characterize the whole body vibration of Seoul subway lines for various human postures. Results show that the floor vibration level of the subway trains in the vertical direction is higher than that in other directions. At the standing human posture, vibration level of the head in the right-left direction are increased while that in the vertical direction is decreased. It is assumed that the different flexibility of the human body and the rolling motion of the subway trains are the main cause. At the sitting posture with back seat on, vibration level in the right and left direction at the human ischial tuberosities is lower than that in other directions. Results also show that there were little difference between back-seat on model and back-seat off model. Transmissibility analysis shows how the subway vibration affects the response of a human body.

• Journal of the Semiconductor & Display Technology
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• v.2 no.1
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• pp.15-19
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• 2003

Spin etcher can process frontside and backside on the wafer, which is used for etching, stripping, cleaning and wafer reclamation. A new generation of spin etchers has been designed to meet 300mm wafer processing. The larger header and higher spin speed make vibration problem a severe problem in developing equipments. This study shows schematic process of solving practical vibration problems, where it is required to analyze the principal ca uses of vibration problem and find out the method of vibration reduction in spin etcher. The vibration under normal operation is measured in time domain and is analyzed in frequency domain. And modal parameters are obtained through modal test. Using the modal parameters from experiments, the model of finite element method is formulated. From diagnosis using many measurements and analyses, it can be shown that main cause of vibration is unbalance of head.