Image Processing Reference
In-Depth Information
Two types of experiments have been performed to evaluate these techniques. Results of the
first type, involving simulated noisy signal traces, have confirmed the accuracy of our
theoretical SNR expressions proposed for the three combination variants. The first type
experiments also demonstrate a great capability for accuracy detection of internal flaws.
Results from the second type, using an experimental ultrasonic prototype, permit to validate
the proposed methods in a real NDE context.
More concretely, the three combination methods described and applied in this chapter,
based on different processing tools (the Hilbert, Wigner-Ville, and Undecimated Wavelet
packet Transforms) produce accurate 2D displays for isolated-flaws location. Additionally,
these methods drastically improve the SNR of these 2D displays in relation to the initially
acquired traces, very especially with the two latter processing cases, being the best flaw
discrimination results obtained with the WVT option, but with a mayor computational cost
than the wavelet technique, which also offers a good performance.
These good results for isolated-flaws patterns could be not directly extended to other more
complicated testing situations with flaws very close among them, because some ambiguous
flaw indications could be produced. In a future work, this particular restriction will be
addressed by means of a specifically extended imaging procedure.
7. Acknowledgment
This work was supported by the National Plan of the Spanish Ministry of Science &
Innovation (R&D Project DPI2008-05213).
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