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Showing papers on "Time-of-flight diffraction ultrasonics published in 1989"



01 Mar 1989
TL;DR: In this article, the accuracy of several ultrasonic flaw sizing techniques was measured using thick-walled mock-ups simulating typical reactor pressure vessel weld and clad configurations, which contained intentional flaws representing three major classes of defects: cracks under the cladding, embedded defects in welds, and lack-of-fusion defects in nozzle-to-shell welds.
Abstract: The accuracy of several ultrasonic flaw sizing techniques was measured using thick-walled mock-ups simulating typical reactor pressure vessel weld and clad configurations. The evaluated techniques were: backward-scattering tip-diffraction, time-of-flight diffraction (TOFD), dB-drop (with three different amplitude thresholds), and large-diameter focused probes. For the amplitude-based dB-drop technique, amplitude thresholds of 6 dB below peak, 50 percent DAC, and 20 percent DAC were used, and the effect of correcting for the spreading of the ultrasonic beam was also evaluated. The mock-ups contained intentional flaws representing three major classes of defects: cracks under the cladding, embedded defects in welds, and lack-of-fusion defects in nozzle-to-shell welds. Approximately 200 measurements were made. The results showed that for sizing near-surface and embedded defects in thick welds, TOFD and the backward-scattering tip-diffraction techniques were far more accurate than the amplitude-based techniques. Beam-spread corrections reduced the mean sizing errors for the 20 percent DAC sizing method, but made negligible reduction in the scatter of the data. Even after beam-spread corrections were made, the sizing errors of the amplitude-based method remained much greater than the tip-diffraction measurement error. For small-bore nozzles, focused probe measurements were substantially more accurate than unfocused probe measurements. 21 refs., 43 figs., 2 tabs.

2 citations


Book ChapterDOI
01 Jan 1989
TL;DR: In this article, the authors present some of the important developments and outstanding problems highlighted by the review and present a review of the most important developments in the field of time-of-flight diffraction.
Abstract: SUMMARY The ultrasonic energy diffracted from the tips of cracks has been used in the sizing and evaluation of defects for some 20 years. Industrial application is now possible by means of the time of flight diffraction (TOFD) technique developed by one of us (MS) at Harwell and the focussing, echodynamic time-of-flight (FET) technique developed by the other authors at the Ecole Centrale. We have recently jointly reviewed progress in this field1 and this paper presents some of the important developments and outstanding problems highlighted by the review.

1 citations


Journal Article
TL;DR: Precision de la localisation d'un defaut ponctuel en controle par ultrasons avec la technique de diffraction et temps de vol is presented in this paper.
Abstract: Precision de la localisation d'un defaut ponctuel en controle par ultrasons avec la technique de diffraction et temps de vol

1 citations


Book ChapterDOI
01 Jan 1989
TL;DR: In this paper, the authors used the Time-of-Flight Diffraction (TOFD) technique to monitor the heights of defects in welds of a vessel that has been in operation for 25 years.
Abstract: SUMMARY The Time-of-Flight Diffraction (TOFD) technique has been used to monitor the heights of defects in welds of a vessel that has been in operation for 25 years. Regular monitoring of defect height provides a check that the defects are stable. Satisfactory results mean that the vessel can be kept in operation for a further period. The TOFD technique has been selected for its high sizing accuracy, as this allows a high level of reproducibility to be achieved. This presentation will describe the approach to this monitoring problem, as well as the preparations and the formulation of the criteria used to judge future results on the presence of growth.