ULTRASONIC DEFECT DETECTION | INSTRUMENTATION & CONTROL
Above, figure 3: Portions of received ultrasonic A-scans for each element when one element (labelled C) is fired. The upper (earlier) family of indications (A) are due to the defect tip and the lower (later) indications (B) are due to reflections in the back wall. Here, one channel is pulsed and response signals are recorded on all other elements plus the transmitter element
Trial results and future work During the soak-test, experimental data were collected using the ultrasonic PUMA monitoring system. Defect signals were clearly resolved throughout the trial. With a modification of the TFM applied to data it was also observed that the known defect size was well matched to the TFM result. Comparison of experimental results obtained prior
to heating, during and after the soak-test showed no significant change in array performance and that throughout, the defect could be clearly discerned in the data before, during and after the soak-test with no significant change in signal to noise ratio. As stated, durinh the trial no significant deterioration could be identified in the performance of any of the elements. Experimental and modelled response signals were also
compared. Significant features – timing, pulse shape and amplitude data were well matched between the experiment and model predictions demonstrating that FE could be used as a design tool for array configuration Once data were collected, various analyses could be
performed. TFM-like processing of one entire collection set of 28 x 28 = 784 waveforms matched to a target mesh containing the defect. The TFM peak was located close to (within 1mm) of the buried edge of the synthetic defect. In a full application, we would also suggest use of
differencing tools which look at past and present data and flag differences. The project team will continue to investigate applications
of PUMA technology in areas including: ● More complex component forms
● Anisotropic metals applications, such as dissimilar metal welds
● Different defect types such as stress corrosion cracking ● Further reduction in array density which has been shown to be feasible
The Permanently installed Ultrasonic Monitoring Array (PUMA) high temperature monitoring has been successfully demonstrated to operate for extended periods at temperatures consistent with a water cooled nuclear power plant. This demonstration included revealing constant sensitivity of transducers during the trials with no faults introduced by operation in the defined temperature range from ambient to 370°C with the bulk of the trial at 320- 330°C. The trial duration was in excess of three months. The project also demonstrated the capability for detecting and sizing a synthetic defect throughout the extended trial with no loss or reduction in capability as well as the applicability of KANDE’s monitoring tools and software to the task of detecting and sizing synthetic defects. ■
Acknowledgements This application of monitoring technology was funded by the UK government Game Changer scheme. The authors wish to express their gratitude for that funding. The project also made use of Imperial College’s Pogo FE modelling tool. The authors wish to thank Dr Peter Huthwaite and Professor Mike Lowe for access to Pogo. Jacobs MID department made a piece of SA508 available to the project which was formed into the test specimen used in this project. Again, the authors wish to express gratitude for this.
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