• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.119-124
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• 2004

A water hammer mostly comes out when a valve fixed at the downstream end of the pipe-line system is rapidly closed or opened. A simple phenomenon of water hammer is often caused around us, and this phenomenon imperils the pipe systems occasionally. In this paper, we confirmed the phenomenon of water hammer by an experiment and forecasted a change of pressure in the pipe-line system by a numerical method. Also a vibration response, which is caused by water hammer, of the pipe-line system confirmed by an experiment and analyzed by a numerical method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1945-1950
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• 2000

When one build a building that posses Precison production process to be sensitive to vibration and SMD to procuce a large dynamic force, how do one predict & answer vibration control problem at building structure design at first stage, That is a question. It has tried to predict dynamic response and establish answering about global or local dynamic problem in building using experimental and analysis method. One of such a try, it be proposed Semi-Empirial Method that reduce error element of input information about dynamic analysis using dynamic experimental study and measurement data in the basis of real-structure. In this paper, the dynamic response problem about RC-structure building that will be set-up SMD produce large transient dynamic force using Semi-Empirical Method.

• Smart Structures and Systems
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• 제17권5호
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• pp.753-771
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• 2016

This paper addresses the free and transient responses of a SDOF linear complex stiffness system by making use of the Hilbert transform and the convolution integral. Because the second-order differential equation of motion having the complex stiffness give rise to the conjugate complex eigen values, its time-domain analysis using the standard time integration scheme suffers from the numerical instability and divergence. In order to overcome this problem, the transient response of the linear complex stiffness system is obtained by the convolution integral of a green function which corresponds to the unit-impulse free vibration response of the complex system. The damped free vibration of the complex system is theoretically derived by making use of the state-space formulation and the Hilbert transform. The convolution integral is implemented by piecewise-linearly interpolating the external force and by superimposing the transient responses of discretized piecewise impulse forces. The numerical experiments are carried out to verify the proposed time-domain analysis method, and the correlation between the real and imaginary parts in the free and transient responses is also investigated.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.203-208
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• 2016

In this paper, vibration characteristics in terms of the airfoil cross-sectional shape was examined by using the EDISON co-rotational plane beam-transient analysis. Assuming aircraft wing as a cantilevered beam with a constant cross-sectional shape, natural frequencies of each airfoil shape was compared while varying airfoil maximum thickness and maximum camber length, using Fast Fourier Transformation(FFT). When the airfoil maximum thickness was varied, natural frequency showed peak value at 18% chord, and decreased afterwards. When the airfoil maximum camber length was varied, natural frequency either increased or decreased at 6% chord, while at 8% the natural frequency showed its maximum. Applying such trends to B-737 wing airfoil, an improved B-737_mod airfoil shape was obtained with regard to the vibration characteristics.

• 소음진동
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• 제8권5호
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• pp.957-963
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• 1998

A new signal processing technique, the directional harmonic wavelet map(dHWM), is presented to characterize the instantaneous planar motion of a measurement point in a structure from its transient complex-valued vibration signal. It is proven that the directional auto-HWM essentially tracks the shape and directively of the instantaneous planar motion, whereas the phase of the directional cross-HWM indicates its inclination angle. Finally, the technique is suessfully applied to an automobile engine for characterization of its transient motion during crank-on/idling/engine-off.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.385-393
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• 2013

In this paper, the mechanism identification and the avoidance measures on the phenomena of transient acoustic vibration amplified at the water-supply piping system to regulate the steam temperature of the boiler reheater in 500MW class supercritical power plant are presented. The pressure pulsation waves induced by the impeller passing of two feed-water pumps with five blades are coincident with the local acoustic modes of boiler reheater water-supply piping system. There are the phenomena amplified at the peaks of 5X, 10X, 15X and 20X in spectrums of piping vibration, sound pressure, and the feed-water's pressure pulsation waves. The shut-off device is installed in the piping system for the interception of pressure pulsation waves transmitted from two feed-water pumps and the modified design change of the piping layout is applied for the acoustic resonance avoidance. The acoustic natural frequencies are separated from the harmonics of pressure pulsation waves induced by the pump impellers passing through the design change of the span length. The acoustic vibration is gone by resonance avoidance measures. As a result, more than 20 dBA reduction is achieved from 100 dBA to 80 dBA.

• 소음진동
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• 제6권4호
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• pp.499-502
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• 1996

Interior noise, engine speed and vehicle speed are measured under transient road-load condition and interior noise signal is transformed by using the transient signal analysis methods, such as the spectrogram and wavelet transform. Using the analyzed results, subjective noise metrics such as the loudness, sharpness and articulation index at each vehicle speed can be estimated and characteristics of interior noise for various running modes can be discussed in the viewpoint of noise quality.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1334-1339
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• 2006

Dynamic response of buried pipelines both in the axial and the transverse directions on concrete pipe and steel pipe, FRP pipe were investigated through a forced vibration analysis. The dynamic behavior of the buried pipelines for the forced vibration is found to exhibit two different forms, a transient response and a steady state response, depending on the time before and after the transfer of a seismic wave on the end of the buried pipeline. The former is identified by a slight change in its behavior before the sinusoidal-shaped seismic wave travels along the whole length of the pipeline whereas the latter by the complete form of a sinusoidal wave when the wave travels throughout the pipeline. The transient response becomes insignificant as the wave speed increases. From the results of the dynamic responses at the many points of the pipeline, we have found that the responses appeared to be dependent critically on the boundary end conditions. Such effects are found to be most prominent especially for the maximum values of the displacement and the strain and its position.

• 소음진동
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• 제10권6호
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• pp.977-984
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• 2000

Vibration of disk drive spindle is one of the major limiting factors in achieving higher track densities in hard disk drives. Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the motor air-gap. In this paper, radial magnetic forces for symmetric and asymmetric BLDC motor are calculated with respect to the various rotor eccentricity using analytic method. Based on the results of the radial magnetic forces, transient whirl responses of the spindle motor are analyzed using finite element and transfer matrices. Results show that an asymmetric motor has a worse effects on unbalanced magnetic forces and vibration when mechanical and magnetic coupling exists.

• 대한기계학회논문집A
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• 제30권12호
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• pp.1596-1602
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• 2006

In this paper, a hybrid sensor is proposed that has two capabilities: the first is to sense longitudinal or flexural transient vibration signals selectively which are transmitted along the target shaft, and the second to measure the rotating speed of the shaft. All measurements are made in a non-contact manner since this sensor uses magnetostriction as its measuring principle. The signal selection between two vibration modes requires only electrical switching operations and the switching between these two sensing capabilities-vibrations and rotational speed-are accomplished by a very simple mechanical operation. To verify the capabilities of the proposed sensor, a prototype sensor is fabricated and the experiments are made. The results show this sensor can embody two sensing capabilities in one sensor configuration.