• Title/Summary/Keyword: Acoustic Nonlinear Parameter

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Evaluation of Degradation of 2.25Cr-1Mo Materials using the Nonlinear Acoustic Effect (초음파 비선형성을 이용한 2.25Cr-1Mo 강의 열화도 평가)

  • Choi, Yun-Ho;Kim, Hyun-Mook;Jhang, Kyung-Young;Park, Ik-Keun
    • Proceedings of the KSME Conference
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    • 2001.11a
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    • pp.222-227
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    • 2001
  • Nonlinear acoustic effect has been considered as an effective tool for the evaluation of material degradation. In this paper, the applicability of nonlinear acoustic effect to the evaluation of degradation of 2.25Cr-1Mo steel is investigated. Firstly, a number of 2.25Cr-1Mo steel samples were heat-treated, and their damage mechanism was examined. Secondly, Ultrasonic nonlinear parameter was measured. Nonlinear acoustic parameter was found to be clearly sensitive to the material degradation.

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Estimation of Nonlinear Parameter in Water - saturated Sandy Sediment by using Difference Frequency Acoustic wave (수중 모래 퇴적물에서 차 주파수 음파를 이용한 비선형 변수 추정)

  • Kim Byoung-Nam;Lee Kang Il;Yoon Suk Wang;Choi Bok Kyung
    • Proceedings of the Acoustical Society of Korea Conference
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    • autumn
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    • pp.429-432
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    • 2004
  • Nonlinear acoustic responses of water-saturated sediments are very important to understand nonlinear phenomena of gassy ocean sediments. Especially, the second harmonic, the sum and the difference frequency acoustic waves in water-saturated sediments can provide practical criteria to estimate the nonlinear parameter of gassy sediments. In this paper, the difference frequency acoustic wave in water-saturated sandy sediment was observed in a water tank experiment with a pulse transmission technique. Its pressure level was 12 dB higher than the background noise level at a maximum undistorted driving pressure of source acoustic transducer. The experimental results were compared with a theoretical estimation of the parametric acoustic array. The nonlinear parameter of water-saturated sandy sediment was also estimated as 73 with their comparison. This value can be utilized as the background information to estimate gas void fraction in the water-saturated gassy sandy sediment.

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Evaluation of Surface Fatigue Degradation Using Acoustic Nonlinearity of Surface Wave (표면파의 음향비선형 특성을 이용한 표면 피로열화 평가)

  • Lee, Jae-Ik;Lee, Tae-Hun;Jhang, Kyung-Young
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.5
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    • pp.415-420
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    • 2009
  • This paper reports the results of a case study for the evaluation of surface damage by using acoustic nonlinearity of surface wave. In this study, the experimental system was constructed to measure the acoustic nonlinear parameter of surface wave in an Aluminum 6061 T6 specimen of which surface was damaged by the three point bending fatigue test, and magnitudes of nonlinear parameter measured before and after the fatigue test were compared. Especially, since the surface fatigue damage by the three point bending is concentrated at the central position of loading, the change in the nonlinear parameter around this position was monitored. Experimental results showed that the measured nonlinear parameter at the outside of this position after the fatigue test was almost same as the initial value before the fatigue test, since the fatigue damage at this position was little. However, clear increase in the nonlinear parameter was noticed after the fatigue test at the central position of specimen where the surface fatigue damage is expected to be concentrated.

Estimation of Fracture Toughness Degradation of High Temperature Materials by Nonlinear Acoustic Effects (비선형 음향효과에 의한 고온 재료의 파괴인성 열화도 평가)

  • Jeong, Hyun-Jo;Nahm, Seung-Hoon;Jhang, Kyung-Young;Nam, Young-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.5
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    • pp.424-430
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    • 2000
  • In order to develop an ultrasonic evaluation method for properties degradation of high temperature materials, a number of Cr-Mo-V steel samples were heat-treated and their damage mechanism was examined. Ultrasonic parameters such as velocity, attenuation, and more recently developed nonlinear acoustic parameter were measured. The nonlinear acoustic parameter was found to be most sensitive to material degradation mainly attributed to the precipitation of impurities in grain boundaries. When compared to the electrical resistivity results, the nonlinear parameters showed similar behavior. There existed a relatively good correlation between the nonlinear parameter and the fracture appearance transition temperature (FATT) obtained by Charpy V-notch impact test. Based on the relationship between the FATT and the fracture toughness ($K_{IC}$), correlation between the nonlinear parameter and $K_{IC}$ was established.

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Application of Bispectral Analysis to Estimate Nonlinear Acoustic Parameter (음향 비선형 파라미터의 추정을 위한 바이스펙트럼 해석법의 적용)

  • Kim, K.C.;Jhang, K.Y.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.2
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    • pp.85-92
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    • 1999
  • The fact that material degradation can be evaluated by measuring nonlinear acoustic effect has been proposed by previous studies. The most conventional method to measure nonlinear acoustic effect is to measure the absolute magnitude of fundamental and $2^{nd}$ order harmonic frequency component in the propagated ultrasonic wave. For this aim, power spectral analysis technique has been used widely. However, the power spectral analysis has fatal disadvantage that the gaussian additive noise superimposed in the wave signal remains in the power spectrum domain. Moreover, the magnitude of $2^{nd}$ order harmonic frequency component generated by nonlinear effect is so small that it may be suppressed by the noise remained in the power spectrum. In order to overcome this problem, this paper proposes an alternative method using bispectrum analysis, which can reduce the effect of addictive gaussian noise and. the nonlinear parameter can be obtained more stably. Simulations showed that the proposed method can obtain the value of nonlinear parameter near to the true value in the case of low SNR signal. Also, in order to confirm the usefulness of our method in actual case, we compared the nonlinear parameter obtained by using both of power spectral and bispectral analysis for several specimen intentionally degraded by fatigue load.

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Acoustic Nonlinearity of Surface Wave and Experimental Verification of Characteristics (표면파의 음향 비선형성과 실험적 특성 검증)

  • Lee, Jae-Ik;Kwon, Goo-Do;Lee, Tae-Hun;Jhang, Kyung-Young
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.4
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    • pp.344-350
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    • 2009
  • The goal of this study is to introduce the theoretical background of acoustic nonlinearity in surface wave and to verify its characteristics by experiments. It has been known by theory that the nonlinear parameter of surface wave is proportional to the ratio of $2^{nd}$ harmonic amplitude and the power of primary component in the propagated surface wave, as like as in bulk waves. In this paper, in order to verify this characteristics we constructed a measurement system using contact angle beam transducers and measured the nonlinear parameter of surface wave in an Aluminum 6061 alloy block specimen while changing the distance of wave propagation and the input amplitude. We also considered the effect of frequency-dependent attenuation to the measurement of nonlinear parameter. Results showed good agreement with the theoretical expectation that the nonlinear parameter should be independent on the input amplitude and linearly dependent on the input amplitude and the $2^{nd}$ harmonic amplitude is linearly dependant on the propagation distance.

Nonlinear Scattering of Difference Frequency Acoustic Wave in Water-Saturated Sandy Sediment (수중 모래퇴적물에서 차주파수 음파의 비선형 산란)

  • Kim Byoung-Nam;Lee Kang Il;Yoon Suk Wang;Choi Bok Kyoung
    • Proceedings of the Acoustical Society of Korea Conference
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    • spring
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    • pp.347-348
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    • 2004
  • Nonlinear scattering of difference frequency acoustic wave in a water-saturated sandy sediment was investigated. Difference frequency acoustic wave was observed to be scattered due to the nonlinearity of water-saturated sandy sediment when the collinear acoustic waves with two different fundamental frequencies are incident on the sediment. The pressure level of the difference frequency acoustic wave was 6 dB higher than the background noise level. It seems very useful to evaluate the nonlinear parameter of water-saturated sandy sediment without disturbing the sediment. Such nonlinear acoustic response of water-saturated sandy sediment can be used as background acoustic data for estimating the gas void fraction in marine gassy sandy sedimen.

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Evaluation of Ultrasonic Nonlinear Characteristics in Heat-Treated Aluminum Alloy (열처리된 알루미늄 합금의 초음파 비선형 특성 평가)

  • Kim, JongBeom;Cheon, Chung;Jhang, Kyung-Young;Kim, Chung-Seok
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.2
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    • pp.193-197
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    • 2013
  • In this study, ultrasonic nonlinear characteristics in the heat-treated aluminum alloy have been evaluated. The nonlinearity of ultrasonic wave has been measured as the acoustic nonlinear parameter ${\beta}$, depending upon the amplitude ratio of the second-order harmonic and the fundamental frequency component of ultrasonic wave propagating through the materials. The parameter ${\beta}$ measurement has been carried out with the reflected signals from the back-wall of specimens at the same plane using the contact-type transducers. The heat-treatment, aging, has been achieved at $300^{\circ}C$ for various durations in the range of 1 to 50 hours. The tensile strength and elongation are obtained by the tensile test and then compared with the parameter ${\beta}$. There is a peak of the acoustic nonlinear parameter ${\beta}$ on 5 hours aging and the ${\beta}$ decreases thereafter, exhibiting closed relations with tensile strength and elongation. Also, the heat-treatment time showing peak in the parameter ${\beta}$ was identical to that showing severe change in the ${\sigma}-{\varepsilon}$ curve. These results suggest that the acoustic nonlinear parameter ${\beta}$ can be used for monitoring the strength variations with aging of aluminum alloys.

Application of Non-linear Acoustic Effect for Evaluation of Degradation of 2.25Cr-1Mo Steel (2.25Cr-1Mo 강의 열화도 평가를 위한 비선형 음향효과 응용법)

  • Choi, Y.H.;Jhang, K.Y.;Park, I.K.;Kim, H.M.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.2
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    • pp.170-176
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    • 2002
  • Nonlinear acoustic effect has been considered as an effective tool for the evaluation of material degradation. In this paper, the applicability of nonlinear acoustic effect to the evaluation of degraded 2.25Cr-1Mo steel is investigated. Firstly, artificial aging was performed to simulate the microstructural degradation in 2.25Cr-1Mo steel arising from long time exposure at $540^{\circ}C$. Secondly, ultrasonic nonlinear parameter was quantitatively measured by bi-spectrum and power spectrum. Nonlinear acoustic parameter from bi-spectrum was found to be clearly sensitive to the aging time.

The Evaluation of Partially Degraded Material Using Nonlinear Propagation Characteristics of Ultrasonic Wave (초음파 비선형 전파특성을 이용한 부분 열화 재료의 평가)

  • Kim, Kyung-Cho;Jhang, Kyung-Young;Hisashi, Yamawaki
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.2
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    • pp.214-219
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    • 2001
  • In this paper, the nonlinear behavior of ultrasonic wave in partially degraded material is considered. For this aim, FDM(finite difference method) model for the nonlinear wave equation was developed with the restriction to the 1-D longitudinal wave motion and how the partial degradation in material contributes to the detected nonlinear parameter was analyzed quantitatively. In order to verify the rightness of this simulation method, the relation between the detected nonlinear parameter and the continuous distribution of degradation obtained from simulation was compared with experiment results and the simulation and experiment results showed similar tendency. It can be known from simulation result that the degree of degradation, the range of degradation and the continuous distribution of degradation have strong correlation with the detected nonlinear parameter. As it was possible in these simulations that only special part is assumed as degraded one, the quantitative evaluation of partially degraded material may be obtained by using this method.