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*; *; Yabuuchi, Satoshi
JNC TY7400 2000-001, 72 Pages, 2000/03
JNC-TY7400-2000-001.pdf:4.01MB
None
Kawasaki, Hirotsugu; *
JNC TN9400 2000-018, 37 Pages, 2000/03
JNC-TN9400-2000-018.pdf:1.34MB
The damage evaluation for the vessel model on the cyclic thermal transient loading in sodium were performed by the ultrasonic detection method. The wavelet analysis that was an analysis method of the waveform was applied to detect the micro damage before a sign of the crack initiation. The time-frequency analysis by the wavelet transform was performed to evaluate the ultrasonic parameter for the micro damage. As the results, the ultrasonic echo was analyzed by some mother wavelet, and Gabor wavelet was reasonable. The analysis of ultrasonic echo by Gabor wavelet showed drop of the sound velocity at higher frequency than the peak frequency because of attenuation in the high frequency component. The difference of the peak frequency △fp between B1 and B2 echoes increased with the amount of damage, and △ fp was available as a parameter for the micro damage detection. The correlation between the sound velocity and the micro hardness for the amount of damage was also found, and each method suggested to available alternately. ln this study, it was indicated that an ultrasonic wave characteristic value that can detect damaged state before crack initiation was obtained from the wavelet analysis.
Yamamoto, Yoichi
Dai-21-Kai Kaku Busshitsu kanri Gakkai (INMM) Nihon Shibu Nenji Taikai Rombunshu, p.63 - 70, 2000/00
no abstracts in English
Yamamoto, Yoichi
EUR-19943-EN, p.238 - 245, 2000/00
no abstracts in English
; Aoto, Kazumi;
JNC TN9400 99-061, 32 Pages, 1999/07
In this report, reconstruction of magnetic charges induced by mechanical damages in a test piece of SUS304 stainless steel is performed as a part of eforts to establish a passive nondestructive testing method on the basis of the inspection of leakage magnetic field. The approach for solving this typical ill-posed inverse problem is selected as a way in the least square method category. Concerning the ill-poseness of the system of equations, an iteration algorithm is adopted to its solving in which the designations of initial profile, the weight coefficients and the total number of iterations are taken as means of reqularization. From examples using simulated input data, it is verified that the approach gives good reconstruction results in case of signals with a relative high S/N ratio. For improving the robustness of the proposed method, a Galerkin procedure with base functions chosen as the Daubechies' wavelet is also introduced for discretizing the governing equation. By comparing the reconstruction results of the least square method and those using wavelet discretization, it is found that the wavelet used approach is more feasible in the inversion of noise polluted signals. Reconstruction of 1-D and 2-D magnetic charges with the least square strategy and reconstruction of an 1-D problem with the wavelet used method are carried out from both simulated and measured magnetic field signals which are used as the validation of the proposed inversion strategy.
Takase, Hiroyasu*; PeterGr*; Kathery*; *
PNC TJ7281 96-002, 168 Pages, 1996/03
no abstracts in English