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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
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Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 19, Issue 6 - Dec 1999
Volume 19, Issue 5 - Oct 1999
Volume 19, Issue 4 - Aug 1999
Volume 19, Issue 3 - Jun 1999
Volume 19, Issue 2 - Apr 1999
Volume 19, Issue 1 - Feb 1999
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Dimension Measurement of Nuclear Fuel Rods Using an Image Processing Technology
Koo, D.S. ; Min, D.K. ; You, G.S. ; Shin, H.S. ; Hong, K.P. ;
Journal of the Korean Society for Nondestructive Testing, volume 19, issue 2, 1999, Pages 79~84
An image processing technology was developed to measure the dimension of nuclear fuel rods and the diameter of nuclear fuel rods was measured by this method. It was confirmed that parameters such as camera-to-specimen distance. camera location, light intensity and light characteristic would affect dimension measurement of nuclear fuel rods. The percent relative error and percent standard deviation of measuring the diameter of nuclear fuel rods using image processing method were 4.88%,
while the percent relative error and percent standard deviation using conventional method were 12.7%,
, respectively. The accuracy of diameter measurement of nuclear fuel rods using image processing method was about 3 times as high as that using conventional method.
Application of Bispectral Analysis to Estimate Nonlinear Acoustic Parameter
Kim, K.C. ; Jhang, K.Y. ;
Journal of the Korean Society for Nondestructive Testing, volume 19, issue 2, 1999, Pages 85~92
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
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
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.
Development and Application of the Visual Test Instrument for Spent CANDU Fuel Bundle Serial Number Identification
Na, Won-Woo ; Lee, Young-Gil ; Yoon, Wan-Ki ; Kwack, Eun-Ho ; Park, Seung-Sik ;
Journal of the Korean Society for Nondestructive Testing, volume 19, issue 2, 1999, Pages 93~99
SCAI(spent CANDU fuel bundle serial number identifier) was developed to read serial numbers of spent fuel bundles in the spent fuel storage. For the purpose of effectively identifying the serial number of fuel bundle. SCAI was composed of underwater camera & light part. guiding & supporting part and control & monitor part. So it is easy to assemble and disassemble, and operate. It was tested to read serial numbers of spent fuel bundles loaded in basket during the recent spent fuel transfer campaign at Wolsong Unit 1. And it was also applied to read serial numbers of spent fuel bundles discharging from the initial core at Wolsong Unit 3 by slight change of camera and light. Inspectors could easily operate SCAI after several practices in the storage pond, which was a user friendly. And SCAI provided clear and immediate picture for identification of serial numbers of spent fuel bundles. It was interally evaluated that SCAI greatly contributed to cut inspection efforts for national and international safeguards at Wolsong power plant.
Development of a Method for Characterizing Single-Fiber Composite Interphase from Frequency-Domain Characteristics of Ultrasonic Scattered Waves
Kim, Woong-Ki ; Yim, Hyun-June ;
Journal of the Korean Society for Nondestructive Testing, volume 19, issue 2, 1999, Pages 100~109
A method is proposed to characterize single-fiber composite interphases from the frequency-domain characteristics of scattered ultrasonic waves, and its feasibility is investigated theoretically. It has been shown that the locations and magnitudes of the peaks and valleys in the frequency domain are affected significantly by the interphase properties, which may indicate the effectiveness of the proposed method. Although the frequency-domain behavior is basically associated with the resonance of the fiber-interphase system, it is not dominantly affected by the scatterer's resonance unlike that in the case of acoustic wave scattering. Therefore, the conventional acoustic resonant scattering theory is not directly applicable to the characterization of composite interphases. In order to solve the inverse problem of predicting the interphase properties from the frequency-domain characteristics of the ultrasonic scattered waves, an artificial neural network has been constructed. This approach has demonstrated reasonable accuracy in most cases considered in this study.
Ultrasonic Nondestructive Evaluation of Creep-Induced Cavities
Jang, Young-Su ; Jeong, Hyun-Jo ;
Journal of the Korean Society for Nondestructive Testing, volume 19, issue 2, 1999, Pages 110~117
In order to ultrasonically evaluate creep cavities pure copper samples were subjected to creep test and their microstructures were examined. Ultrasonic velocities. frequency-dependent magnitude spectra and attenuations were measured on a series of copper samples obtained from the different stages of creep test. Velocities measured in three directions with respect to the loading axis decreased and their anisotropy increased as a function of the creep-induced porosity. The anisotropic behavior could be attributed to the progressive change of pore shape and preferred orientation as the creep advanced. The 2% porosity by volume decreased the longitudinal and shear wave velocities by 11% and 4%, respectively. Furthermore, both velocities decreased nonlinearly with the porosity. As the creep damage developed, the magnitude spectra lost high frequency components and their central frequencies shifted to lower values. The attenuation showed almost linear behavior in the frequency range used. Normalized velocity, central frequency shift and attenuation slope were selected as nondestructive evaluation parameters. These results were presented and showed good relations with the porosity content.
Measurements of Ultrasonic Velocity and Attenuation by Signal Processing Techniques in Time and Frequency Domains
Jang, Young-Su ; Kim, Jin-Ho ; Jeong, Hyun-Jo ; Nam, Young-Hyun ;
Journal of the Korean Society for Nondestructive Testing, volume 19, issue 2, 1999, Pages 118~128
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.
Material Degradation and Life Assessment in Mechanical Equipment and Structure
Kim, K.Y. ;
Journal of the Korean Society for Nondestructive Testing, volume 19, issue 2, 1999, Pages 129~144