• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.489-492
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• 2000

Film Bulk Acoustic Wave Resonator(FBAR) used in microwave region was analyzed with Finite Difference Time-Domain Methods(FDTD) in this paper. FBAR have been analyzed with one dimensional Mason model analysis or Finite Element methods(FEM), but the first couldn't analyze effect of area variation and spurious characteristics, the second had difficulty in element separation because of thin electrode. So in this paper FBAR was analyzed by Finite Difference Time-Domain Methods and it's results were transformed to frequency domain using Discrete Fourier Transform.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 추계학술대회 논문집
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• pp.59-64
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• 1997

This paper investigates the relationship between cutting conditions and Acoustic Emission(AE) signals; AEavg, AErms, AEmode, as the base working to monitor the tool wear with in-process. For this purpose, cutting tests were conducted on a CNC lathe with comprehensive cutting conditions.. It is known that AEavg and AErms are proportionaly increased as the increasing of cutting velocity and depth of cut respectively. It is also known that AEmode among three kinds of AE signals may be applied for in-process monitoring to make the self diagnosis system because of its stability to the variation of cutting condition.

• 한국생산제조학회지
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• 제7권6호
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• pp.64-71
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• 1998

This paper investigates the relationship between cutting conditions and Acoustic Emission(AE) signals; $AE_{avg}$, $AE_{rms}$, $AE_{mode}$$AE_{avg}$ and $AE_{rms}$ are increased as the increasing of cutting velocity and depth of cut respectively. The new parameters, derived from $AE_{avg}$ and $AE_{rms}$, which may be used for the in-process detection of tool wear is discussed. It is also known that $AE_{mode}$

• 대한기계학회논문집
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• 제14권1호
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• pp.130-137
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• 1990

본 연구에서는 Bueckner의 가중함수법을 열충격 문제에 도입하여 열충격 응력 세기계수를 구하고, 평면변형을 파괴인성치와 비교하여 재료가 열충격을 받은 후 파괴 되는 시간을 이론적으로 계산한다. 또한 음향 방출법을 이용하여 파괴시간을 측정하 고 이론치와 비교한다.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.148-156
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• 2001

Computational Fluid Dynamics (CFD) analysis was carried out to investigate exhaust gas flow and acoustic characteristics in the exhaust system of a passenger car. Transient 3-dimensional flow field in the front and rear mufflers was simulated by CFD and far-field sound pressure was modeled by a simple monopole source method. Engine performance simulation was also performed to obtain the boundary condition of instantaneous fluid flow variation at the inlet of the exhaust system. Detailed exhaust gas flow characteristics such as velocity and pressure distribution inside the mufflers were presented and the pulsating pressure amplitude was compared at several positions in the exhaust system to deduce sound pressure level. The present method of the acoustic analysis coupled with CFD techniques would be very effective for the prediction of sound noise from vehicle exhaust systems although the effects of the inlet boundary condition and heat transfer on the accuracy of the prediction have to be validated through further studies.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.861-864
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• 2006

In general, 4-pole parameter and three-point method are used for predicting transmission loss which is one of characteristics of Muffler using CAE tools. However, these mehtods show different results from experiment when the flow effects are presented in practical model. In this parer, to overcome these problems, both Fluent and.Sysnoise are used to analyze the performance of extended inlet/outlet muffler including flow effects with varying flow velocity at inlet of duct. Flow fields and quadrupole source is calculated by Fluent. And Sysnoise is used to analyze acoustic performances of muffler with quadrupole source data extracted from Fluent. Finally, the variation of transmission loss is estimated according to various inlet flow velocity.

• 소음진동
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• 제7권3호
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• pp.449-455
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• 1997

A theoretical study is presented for the prediction of the scattering of obliquely incident plane acoustic wave by transversely isotropic cylindrical shells immersed in water. In dorder to illustrate the vailidity of the theory backscattering form functions are compared with the existing results for degenerated problems: the catterings by isotropic shell and transversely isotropic solid cylinder. The unidirectional fiber reinforced boron-aluminum composites are selected as a model of transversely isotropic materials having potential applications in practice. From the resonant scattering analysis of the partial backscattering form functions, the dispersion curves for fluid-borne Stoneley wave, guided wave along the shell, and the lowest three Lamb type waves can be found. The Lamb type dispersions are compared with those of the flat plate. The variation of anisotropy significantly affects the properties of circumferential waves. From these results, it can be possible to identify parametrically the material properties of anisotropic cylindrical targets.

• The Journal of the Acoustical Society of Korea
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• 제20권2E호
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• pp.46-50
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• 2001

The characteristics of radiation impedance are analyzed by algorithms which consists of Finite Element Method (FEM) and Hybrid type Infinite Element Method. The changes of radiation impedance for piston source according to the size and the material properties of baffles are studied. The results of the radiation impedance for rigid finite baffle coincide with other reports. The more the material properties of baffle that comes across the acoustic medium, the more the calculation results of radiation impedance approach the ones without baffle. Therefore, these results can be applied to the design and the radiation characteristics analysis of acoustic transducers.

• 한국공작기계학회논문집
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• 제11권1호
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• pp.52-60
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• 2002

The purpose of this research is to study the vibration and acoustic pressure radiation from a thin isotropic flat plate stiffened by a rectangular array of beams, and excited by a time harmonic point force. These constructions on aircraft and ship structures are often subjected to fiequency dependent pressure fluctuations and forces. Forces from the these excitations induce structural vibrations in a wide range of fiequencies, which may cause such things as acoustic fatigue and internal cabin noise in the aircraft. It is thus important that the response characteristics and vibration modes of such periodic structures be horn. From this theoretical model, the sound pressure levels(SPL) in a semi-infinite fluid(water) bounded by the plate with the variation in the locations of an external time harmonic point farce on the plate can be calculated efficiently using three numerical tools such as the Gauss-jordan method the LU decomposition method md the IMSL numerical package.

• 한국생산제조학회지
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• 제5권3호
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• pp.15-21
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• 1996

This study is focused on the prediction of appropriate tool life by clarifying the correlation between progressive tool wear and AE(Acoustic Emission) signals, while cutting stainless steel by end mill on the machining center. The results of this study were that RMSAE tends to increase linearly along with the increase of the cutting speed, and it was more sensitive to depth of cut than to the variation of feed rate at the same cutting conditions, and RMSAE increases around 0.21mm flank wear hereby AE-HIT also increases. AE signals depend upon tool wear and fracture from the above results. Therefore, the AE signals can be utilized in order to monitor the tool condition.