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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of the Korean Society for Nondestructive Testing
Journal Basic Information
Journal DOI :
The Korean Society for Nondestructive Testing
Editor in Chief :
Volume & Issues
Volume 8, Issue 1 - Dec 1988
Volume 7, Issue 2 - Apr 1988
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Split-spectrum Processing for Improved Flaw Detectability by Ultrasound System
Koo, Kil-Mo ; Shim, Chul-Moo ; Ahn, Byeong-Wan ;
Journal of the Korean Society for Nondestructive Testing, volume 7, issue 2, 1988, Pages 8~15
A split-spectrum processing technique for an ultrasonic flaw detection system has been developed, which improves the flaw-to-grain echo ratio in large-grained materials. The enhancement is achieved by partitioning a wide-band received spectrum to obtain frequency shifted bands, which are then processed to suppress the grain echoes with respect to the flaw echo, using a novel signal minimization algorithm. A technique for suppression of grain echoes has also been devised which takes advantage of the fact that the grain echo amplitude changes with the frequency of the incident ultrasound whereas the flaw echo amplitude does not. The combination of this technique and the new flaw detection system greatly improve the capabilities of ultrasonic evaluation of large grain materials.
The Detection of the Steam Generator Tubing Defects in the Sludge Piles by the Eddy Current Testing
Ahn, Byeong-Wan ; Yim, Chang-Jae ; Koo, Kil-Mo ;
Journal of the Korean Society for Nondestructive Testing, volume 7, issue 2, 1988, Pages 16~26
In the in-service inspections for the steam generator tubing of the nuclear power plants by the Eddy Current Testing, the ECT signals are evaluated by their phase. If oxidized copper sludge is piled up in the secondary side, however, big sludge signals occur in large quantities which originate from copper layers forming in the sludge piles due to the pitting mechanism of the steam generator tubing by
, and modulate the defect signals, causing the difficulty in the defect detection. In this research, sludge specimens were prepared considering the formations of the sludge signal sources and multi-frequency ECT mixing experiments by different choices of the mixing standards were performed. The results were found to be 5 to 30% of the tube wall thickness over-estimated. Experiments using the ring-type mixing standards showed the least errors of all, while those with the mixing standards nearing the sludge conditions brought larger errors as a result of the influence of the interference between the defect and the copper layers.
A Study on the Thickness Measurement of Thin Film by Ultrasonic Wave
Han, Eung-Kyo ; Lee, Jae-Joon ; Kim, Jae-Yeol ;
Journal of the Korean Society for Nondestructive Testing, volume 7, issue 2, 1988, Pages 27~34
Recently, it is gradually raised necessity that thickness of thin film is measured accurately and managed in industrial circles and medical world. In this study, regarding to the thickness of film which is in opaque object and is beyond distance resolution capacity, thickness measurement was done by MEM-cepstrum analysis of received ultrasonic wave. In measurement results, film thickness which is beyond distance resolution capacity was measured accurately. And within thickness range that don't exist interference, thickness measurement by MEM-ceptrum analysis was impossible.
Measurement of the Crack Height using the Two-Probe Ultrasonic Diffraction Method.
Lee, Jae-Ok ; Lee, Seung-Kyu ; Kim, Young-Kil ;
Journal of the Korean Society for Nondestructive Testing, volume 7, issue 2, 1988, Pages 35~41
The optimum test conditions of measuring the crack height were determined for the two-probe ultrasonic diffraction method. The applicability and the accuracy of the two-probe ultrasonic diffraction method on the inclined artificial cracks and the fatigue cracks were evaluated. It us possible to measure the height of the normal and inclined artificial cracks with the maximum error of
with the two-probe ultrasonic diffraction method. It was found, however, that the accuracy of this method in meaasuring the height of the fatigue crack depends on the degree of closure of the crack tip. It was desirable to choose a refraction angle as small as possible, but the angle should not be so small that the distortion of the lateral waveform became appreciable.
A Study on the Strength Evaluation of Unidirectional Carbon Fiber Reinforced Plastics by Nondestructive Method
Chang, H.K. ; Lee, J.S. ; Cho, K.S. ; Lee, S.H. ; Park, E.S. ;
Journal of the Korean Society for Nondestructive Testing, volume 7, issue 2, 1988, Pages 42~47
The off-axis tensile strength of the unidirectional carbon fiber reinforced plastic and the residual strength of impact damaged CFRP were measured and compared with the stress wave factor (SWF) of the specimens. The SWF values were measured to be decreased with the strength reduction in both cases and found to be useful for the nondestructive strength evaluation of unidirectional CFRP. The failure behaviour of the unidirectional CFRP during off-axis tensile testing was also monitored by acoustic emission(AE) method. The AE energy release showed the characteristic feature depending on the off-axis angle and this result was analyzed to be caused by the difference of the expected failure mode depending on the off-axis angle. The failure mode of CFRP was found to be analyzed by investigation of the peak amplitude distribution of AE.
UT Flow Measurement
You, Young-Ok ;
Journal of the Korean Society for Nondestructive Testing, volume 7, issue 2, 1988, Pages 48~51
Computer-aided tester for non-destructive determination of material properties
Neumaier, Peter ;
Journal of the Korean Society for Nondestructive Testing, volume 7, issue 2, 1988, Pages 52~57
This article presents a newly developed equipment system for computer-aided, magneto-inductive testing of metals for material properties. The advantages of ultramodern computer technology over conventional test mothods are illustrated, in particular the greatly simplified equipment adjustment and the extended possibilities of test data evaluation. The characterisitics of the new system of equipment are demonstrated by way of practical testing examples.