• Title/Summary/Keyword: 초음파감쇠계수

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Measurement of Crack Length by Ultrasonic Attenuation Coefficients on Interfaces of Al/Epoxy Bonded Dissimilar Materials (Al/Epoxy 이종재 접합 계면의 초음파 감쇠계수에 의한 균열길이의 측정)

  • Park, Sung-Il;Chung, Nam-Yong
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1109-1114
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    • 2003
  • The initial crack often occurs on the bonded interface and it is the general cause of the interface fracture. It is very significant to establish the measurement method of interfacial crack by applying the ultrasonic technology into the interface of bonded dissimilar materials. In this paper, the interfacial crack length was measured by ultrasonic attenuation coefficient in the Al/Epoxy bonded dissimilar materials of double-cantilever beam(DCB). The energy release rate, G, was obtained by the experimental and Ripling's equation measurement of compliance. The experimental results represent that the relation between interfacial crack length for the ultrasonic attenuation coefficient and energy release rate is increased proportionally. From the experimental results, a measurement method of the interfacial crack length by the ultrasonic attenuation coefficient was proposed and discussed.

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Measurement of Interfacial Crack Length by Ultrasonic Attenuation Coefficients on Adhesively Bonded Components (접착부재의 초음파 감쇠계수에 의한 계면균열 길이의 측정)

  • 정남용;박성일
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.1
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    • pp.130-137
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    • 2004
  • The ultrasonic attenuation coefficients were measured by interfacial crack length in the adhesive components of double-cantilever beam(DCB). The energy release rate, G, was obtained by the experimental measurement of compliance. The numerical analysis by the boundary element method(BEM) and Ripling's equation was investigated. The experimental results represent that the relation between interfacial crack length for the ultrasonic attenuation coefficient and energy release rate is increased proportionally. A measurement method of the interfacial crack length by the ultrasonic attenuation coefficient was proposed and discussed.

Measurement of Crack Length by Ultrasonic Attenuation Coefficient (초음파 감쇠계수에 의한 균열길이의 측정)

  • Chung, Nam-Yong;Park, Sung-Il
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.4
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    • pp.386-393
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    • 2004
  • In this paper, the ultrasonic attenuation coefficient was measured by variation of crack length for double-cantilever beam(DCB) specimen. The energy release rate, G, was obtained by the experimental measurement of compliance. The experimental results represents that the crack length for the ultrasonic attenuation coefficient and energy release rate is increases proportionally From the experimental results, we proposed a detecting method of the crack length by the ultrasonic attenuation coefficient and discussed it.

Measurements of Ultrasonic Velocity and Attenuation by Signal Processing Techniques in Time and Frequency Domains (시간 및 주파수 영역에서의 신호 처리 기술에 의한 초음파 속도와 감쇠의 측정)

  • Jang, Young-Su;Kim, Jin-Ho;Jeong, Hyun-Jo;Nam, Young-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.2
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    • pp.118-128
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    • 1999
  • There are many ultrasonic measurement methods that are used in nondestructive testing applications. Some typical applications include material property determination, microstructural characterization. and flaw detection. Ultrasonic parameters such as velocity and attenuation are most commonly required in these applications. The accuracy and repeatability of testing results are dependent on both the hardware used to generate and receive the ultrasonic waves and on the analysis software for calculating these parameters. In this study, five analysis algorithms were implemented on a computer for measuring wave speed in a pulse echo. immersion testing configuration. In velocity measurements comparisons were made between the overlap. cross-correlation. Fourier transform. Hilbert transform, wavelet transform algorithms. Velocity measurement was applied to an isotropic steel sample using the five analysis algorithms. Frequency-dependent phase/group velocity and attenuation were also measured using the Fourier transform and wavelet transform algorithms on a composite laminate containing voids.

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Measurements of Acoustic Properties of Materials by Spectral Analysis of Ultrasonic Pulses (초음파 펄스의 주파수해석에 의한 재료의 음향특성 측정)

  • Ha, Kang-Lyeol;Kim, Moo-Joon;Lee, Jong-Kyu;Kim, Sung-Boo;Noriyoshi, Chubachi
    • The Journal of the Acoustical Society of Korea
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    • v.14 no.6
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    • pp.40-47
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    • 1995
  • A system for measurement of ultrasonic velocity, attenuation and complex modulus of materials by using the spectral analysis method of pulses has been constructed and its performances are estimated. The system has a mechanical scanning part of an acoustic microscope with a ZnO plane wave transducer of the resonant frequency of 85MHz. Ultrasonic velocity has been obtained by the intervals of maxima (or minima) on the power spectrum of a pulse train reflected from the surface and bottom of a specimen, and attenuation has been obtained by the power spectra of three pulses reflected from the surface and the bottom of a specimen and the surface of a standard specimen. The measured results for materials such as fused quartz, polyester show that the system has very high accuracy.

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Use of Guided Waves for Monitoring Material Conditions in Fossil-Fuel Power Plants (판파를 이용한 화력 발전 설비의 물성 평가)

  • Cho, Youn-Ho;Jung, Kyung-Sik;Lee, Jae-Sun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.6
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    • pp.695-700
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    • 2010
  • Material properties of the lock plate, which covers the gas-turbine blade, are studied using ultrasonic guided waves. The lock plate is a crucial part of a gas-turbine power plant. The wave velocity and attenuation coefficient are measured to investigate the changes in the material properties under three heat-treatment conditions. Compared to the destructive mechanical tests, the material characterization of Inconel X-750 can be performed more efficiently and nondestructively by using ultrasonic guided waves; this characterization helps identify the changes occurring in its elastic moduli and Poisson's ratio under different heat-treatment conditions. The wave velocity and hardness of Inconel X-750 are proportional to each other. This nondestructive technique for the measurement of material properties can be widely used in various industries to avoid catastrophic failure. It is also expected that the guided-wave technique can be applied as a new cost- and time-saving inspection tool for longer and wider inspection ranges.

A Study on Fatigue Damage Accumulation of MMC using Ultrasonic Wave and Acoustic Emission (초음파와 AE기법을 이용한 금속복합재료의 피로손상진전 평가)

  • 이진경;이준현
    • Composites Research
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    • v.13 no.4
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    • pp.1-10
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    • 2000
  • SiC particulate reinforced metal matrix composites(MMCs) are emerging as candidate materials for the automobile and aerospace industries due to their significant increase in elastic modulus and strength compared to conventional metallic materials. However, in order to make successful application of MMCs, it is very important to understand micro-failure mechanism under cyclic loading because failure mechanism of MMC is dominated by accumulation of micro-failure due to applied loading. In this study, ultrasonic Lamb wave and acoustic emission(AE) have been used to monitor microscopic damage accumulation under cyclic loading for SiC particulate reinforced metal matrix composite(SiCp/A356). It was found that the change in velocity and attenuation of ultrasonic Lamb wave due to the increase of loading cycles could be characterized by three different stages corresponding to the microscopic fracture processes. The characteristic of AE signal at each stage was analyzed and discussed by comparing with the change of ultrasonic characteristic in MMCs.

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Dependences of Ultrasonic Parameters for Osteoporosis Diagnosis on Bone Mineral Density (골다공증 진단을 위한 초음파 변수의 골밀도에 대한 의존성)

  • Hwang, Kyo Seung;Kim, Yoon Mi;Park, Jong Chan;Choi, Min Joo;Lee, Kang Il
    • Journal of the Korean Society for Nondestructive Testing
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    • v.32 no.5
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    • pp.502-508
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    • 2012
  • Quantitative ultrasound technologies for osteoporosis diagnosis measure ultrasonic parameters such as speed of sound(SOS) and normalized broadband ultrasound attenuation(nBUA) in the calcaneus (heel bone). In the present study, the dependences of SOS and nBUA on bone mineral density in the proximal femur with high risk of fracture were investigated by using 20 trabecular bone samples extracted from bovine femurs. SOS and nBUA in the femoral trabecular bone samples were measured by using a transverse transmission method with one matched pair of ultrasonic transducers with a center frequency of 1.0 MHz. SOS and nBUA measured in the 20 trabecular bone samples exhibited high Pearson's correlation coefficients (r) of r = 0.83 and 0.72 with apparent bone density, respectively. The multiple regression analysis with SOS and nBUA as independent variables and apparent bone density as a dependent variable showed that the correlation coefficient r = 0.85 of the multiple linear regression model was higher than those of the simple linear regression model with either parameter SOS or nBUA as an independent variable. These high linear correlations between the ultrasonic parameters and the bone density suggest that the ultrasonic parameters measured in the femur can be useful for predicting the femoral bone mineral density.

Observation of Acoustic Characteristic Change in bubble cloud by Ultrasonic Cavitation (초음파 캐비테이션에 의한 기포군에서의 음향특성 변화관찰)

  • Noh, Si-Cheol;Kim, Ju-Young;Choi, Heung-Ho
    • Journal of the Korean Society of Radiology
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    • v.6 no.5
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    • pp.351-356
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    • 2012
  • Ultrasonic cavitation is a physical phenomenon that generates and collapses microbubbles in media (mainly fluids) under conditions of strong ultrasonic irradiation. In this study, changes in the ultrasonic acoustic characteristics of bubble clouds in relation to ultrasonic irradiation were observed by the quantitative evaluation of cavitation yields. Concave-type single ultrasonic transducers with center frequencies of 500 kHz and 1.1 MHz were used to produce cavitation, and 2.25 MHz interference ultrasonic waves that would traverse any bubble clouds generated were used to analyze the cavitation. The parameters used for the evaluation of cavitation yields (changes in the center frequency, attenuation characteristics, and the propagation time of penetrating waves) were analyzed in relation to the cavitation-generating conditions (irradiation intensity, excitation signal, and center frequency). On the basis of these results, correlations between the changes in the center frequency and irradiation intensity were identified. Although the correlation coefficient was low, notable changes were observed in the center frequency under certain irradiation conditions. Attenuation trends in the interference ultrasonic waves showed high correlations with all the irradiation conditions, and it was noted that these trends were not affected by the forms of cavitation generated. No differences in the propagation time were observed among different irradiation conditions. These findings suggest that bubble yields can be quantitatively evaluated effectively by evaluating the diverse irradiation conditions and that such a quantitative evaluation could be used to study the basic cavitation phenomenon occurring in high-intensity ultrasonic wave treatment.

The Study on the Ultrasound Signal Processing for Estimating the Attenuation Coefficient - The study on the stability of the attenuation coefficient in silicon-made phantom using both homomorphic process and the modified spectral difference method - (감쇠 계수 추출을 위한 초음파 신호 분석 연구 - Homomorphic Process와 수정된 spectral difference방법을 사용하여 얻은 실리콘 팬텀의 감쇠 계수 안정성에 관한 연구 -)

  • 송인찬;민병구
    • Journal of Biomedical Engineering Research
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    • v.12 no.4
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    • pp.249-254
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    • 1991
  • In the study on the quantitative diagnosis using ultrasound, the stability and precision of tissue characterized parameters are important for the clinical application. We estimate attenuation coefficient introducing homomorphlc process Into the modified spectral differnce method about silicon-madu phantom. We compare the results with those estimated uslng the method used for obtaining the attenuation map image before. Homomorphic process has the effect smoothing the reflected echo signal spectrum, therefore eliminat os the random pattern of the signal spectrum generated by the scatterers. As a result, it Is shown that the stability is enhanced

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