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Local damage detection by nonlinear coda wave interferometry combined with time reversal
N Smagin1, A Trifonov1, O Bou Matar1
1Univ. Lille, CNRS, Centrale Lille, ISEN, Univ. Valenciennes, UMR 8520 - IEMN, LIA LICS/LEMAC, F-59000 Lille, France.
Ultrasonics
|July 24, 2020
Summary
This study combines coda wave interferometry (CWI) with time-reversal (TR) to detect flaws. Pulsed TR focusing enhances nonlinear interactions, enabling sensitive defect detection in complex media.
Area of Science:
- Nonlinear acoustics
- Ultrasonic testing
- Materials science
Background:
- Coda wave interferometry (CWI) is a sensitive ultrasound technique for detecting subtle changes in complex media.
- Current CWI methods are primarily used for global inspection of structures like concrete.
Purpose of the Study:
- To enhance CWI by integrating time-reversal (TR) techniques for localized flaw detection.
- To investigate nonlinear pump-probe interactions for improved defect localization and characterization.
Main Methods:
- A nonlinear modification of CWI using a high-frequency probe coda and a low-frequency pump wave.
- Combining CWI with time-reversal (TR) to focus the pump wave onto specific areas.
- Analyzing coda wave mixing in both continuous and pulsed pump modes, with a focus on pulsed TR.
Main Results:
- Experimental observation of nonlinear interaction between pulsed pump and probe waves sufficient for defect detection using TR.
- Demonstrated that TR focusing, even with a single transducer, provides sufficient contrast to differentiate intact and damaged zones.
- Successful localization of flaws through nonlinear CWI enhanced by TR focusing.
Conclusions:
- The integration of TR with nonlinear CWI offers a significant advancement for localized defect detection.
- Pulsed TR is crucial for achieving the necessary spatio-temporal wave compression for effective pump focusing.
- Nonlinear CWI combined with TR is a promising technique for sensitive and localized inspection of damaged zones in complex structures.
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