• 한국소음진동공학회논문집
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• 제16권5호
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• pp.495-502
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• 2006

A fault diagnosis method is developed in this study using automaton through quantization of vibration signals for normal and faulty conditions, respectively. Automaton is a kind of qualitative model which describes the system behaviour at the level of abstraction. The system behavior was extracted from the probability of the output sequence of vibration signals. The sequence was made as vibration levels by reconstructing the originally measured vibration signals. As an example, a fault diagnosis for the bearing of ATM machine was done, which detected the bearing fault with confident level compared to any other existing methods of kurtosis or spectrum analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.985-990
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• 2003

With the rotational speed of the hard disk drive (HDD) increased, the low frequency structural vibration induced by the unbalance force gives rise to the structure home noise of the personal computer, and finally degrades the noise quality. As the unbalance of the hard disk drive is decided by the mechanical assembly allowance between clamping and platter disk, there is limit to control this unbalance by the improved assembly method. To improve the noise and vibration performance of PC, basically the unbalance of HDD needs to be measured absolutely and reduced during the stage of the disk assembly. This study introduces the HDD unbalance measurement methods of the absolute magnitude based on the mobility concept, and the unbalance location information with the acceleration orbit.

• 한국소음진동공학회논문집
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• 제18권11호
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• pp.1199-1205
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• 2008

The vehicle design engineers have studied the method of applying damping materials to the vehicle bodies by computer simulations and experimental methods in order to improve the vibration and noise characteristics of the vehicles. The unconstrained layer damping, being concerned with this study, has two layers(base layer and damping layer) and proyides vibration control of the base layer through extensional damping. Generally this kind of surface damping method is effectively used in reducing structural vibration at frequencies beyond 150Hz. The most important thing is how to apply damping treatment with respect to location and size of the damping material. To solve these problems, the current experimental methods have technical limits which are cumbersome, time consuming, and expensive. This Paper proposes a method based on finite element method and it employes averaged ESE(element strain energy) percent of total of dash panel assembly for 1/1 octave band frequency range by MSC/NASTRAN. The regions of high ESE percent of total are selected as proposed location of damping treatment. The effect of damping treatment is analyzed by comparing the frequency response function of the SPCC bare Panel and the damping treated panels.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.630-635
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• 2012

Nearfield acoustic holography method predicts an unmeasured sound field, therefore it depends on its prediction methods. In particular, if one has radiators or scatters, which cannot be expressed by simple geometry, then inverse boundary element method (BEM) is normally employed to reconstruct the sound field induced by sound sources with irregular profiles. The characteristics of boundary element, including the element shape, characteristic length, order of shape function and others, affect the reconstruction error. Investigating the errors by means of changing these factors will provide a guide line for selecting appropriate factors, associated with the elements of BEM. These factors are investigated by numerical simulations, and the accuracies with respect to the variant factors are compared. Novel suggestions for selecting appropriate boundary element factors are described based on the simulation results.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.449-453
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• 2007

After over a century of effort by researchers and engineers, the problem of bluff body flow, in particular vortex shedding frequency, remains almost entirely in the empirical, descriptive realm of knowledge. Computational methods have been systematically applied for vortex-induced vibrations of the cable-stayed bridge with steel composite deck by unsteady wind loadings due to vortex-shedding. The focus of this paper is to predict the vortex-induced vibration of the cable-stayed bridge with steel composite deck based computational fluid dynamics(CFD).

• 한국소음진동공학회논문집
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• 제22권1호
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• pp.9-14
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• 2012

This paper investigates the prediction of the dynamic strain response using acceleration response only. Two methods are proposed for the strain prediction; one is based on beam theory and the other is calculated by the frequency response function between acceleration and strain. First, it is estimated the dynamics of the simple notched beam, including the non-linearity, through the uni-axial vibration testing. Then, the dynamic strain response is predicted under two different methods using acceleration response. The validation of proposed methods is conducted by the comparison between measured strain and predicted values. The comparison reveals that the proposed method based on the FRF between acceleration and strain is more reliable one than that stemmed from beam theory and the maximum relative error is less than 8 %.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1348-1353
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• 2006

This paper is concerned with the comparison of component mode synthesis md substructure synthesis methods. Those two methods were developed for the dynamic analysis of complex structure. However, the difference between two methods in solving the dynamic problem has never been explained. In this paper, a structure consisting of two beams is considered for the application of two methods. The dynamic formulation shows the characteristics and differences of two methods. The procedure for choosing proper substructure modes in each method is explained in detail. In addition, the advantage of the substructure synthesis method is discussed based on the numerical example. Numerical examples show how two methods are applied to the addressed problem.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.782-788
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• 2008

In this paper, a comparison about two representative Transfer Path Analysis(TPA) methods for air-borne noise based on, matrix inversion method and pressure transmissibility, are presented on the view point of crosstalk effect between sources. In order to assess accuracy of two methods according to path models between virtual airborne noise sources, experiments are made for two cases, weak and strong crosstalk effect condition, by using acrylic vehicle model. Based on this assessment, the paper presents a reasonable application criteria for TPA method according to the circumstances of air-borne noise sources.

• Journal of Advanced Marine Engineering and Technology
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• 제27권5호
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• pp.590-599
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• 2003

In this study. object transport method based on ultrasonic flexural vibration is presented. Ultrasonic vibration generates ultrasonic traveling waves on the surface of elastic medium. Objects are transported through the interaction with traveling waves propagating in medium. Two types of transport methods are studied： frictional drive and acoustic levitation. With frictional drive, objects are transported in contact with the beam in the opposite direction of wave propagation whereas with acoustic levitation, objects are acoustically levitated above the beam surface and transported in the wave propagation direction. Transport characteristics are experimentally investigated using objects of different shapes and sizes. The transition from acoustic levitation mode to frictional drive mode is also examined. and it is found to occur when the ratio of mass to area of an object exceeds the threshold ratio of mass to area. It is envisaged that this feasibility study will serve as a stepping-stone for ultrasonic vibration to become an effective industrial material handling device in the future.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.358-362
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• 2002

The HDD unbalance, with higher rotational speed, is directly influenced by the mechanical assembly allowance between clamping disk and platter disk. The low frequency structural vibration induced by the unbalance force finally gives rise to the structure borne noise of the personal computer. To meet the noise and vibration requirements, the absolute unbalance mass of HDD needs to be measured and adjusted in the disk assembling stage. This study introduces the measurement methods of the absolute magnitude and position of the unbalance mass of HDD based on the mobility and acceleration orbit. The absolute unbalance mass can be obtained by the acceleration responses and the mobility of the mechanical part, while the position of the unbalance mass ran be obtained by the rotation acceleration orbit.