Woodruff School of Mechanical Engineering

Mechanical Engineering Seminar


Ultrasonic Guided-Waves Characterization with Warped Frequency Transforms


Dr. Luca De Marchi


University of Bologna, Dept. of Electronics, Computer Sciences and Systems


Friday, January 22, 2010 at 3:00:00 PM


MRDC Building, Room 4211


Dr. Karim Sabra


Guided waves (GWs) dispersion curves can be analyzed by means of time-frequency representations(TFRs). Unfortunately, any TFR is subjected to the time-frequency uncertainty principle. This, in general,limits the capability of TFRs to characterize multiple, closely spaced guided modes from a time-transient measurement, over a wide frequency range. To overcome this limitation, a warped frequency transform (WFT) can be implemented. Such transformation presents enhanced modes extraction capabilities in force of a more flexible tiling of the time-frequency domain. The proposed transformation is fast, invertible, and covariant to group delay shifts. The results obtained on simulated and experimental data show that the proposed WFT limits interference patterns which appears with others TFRs and produces a sparse representation of the Lamb waves patterns that can be suitable for identification and characterization purposes.


Dr. Luca De Marchi is in the Department of Electronics, Computer Sciences and Systems at the University of Bologna in Bologna, Italy.