Title :
Ultrasonic guided-waves characterization with Warped Frequency Transforms
Author :
De Marchi, L. ; Caporale, S. ; Speciale, N. ; Marzani, A.
Author_Institution :
Dept. of Electron., Comput. Sci. & Syst., Univ. of Bologna, Bologna
Abstract :
In this work a new time-frequency procedure for the extraction of multimodal and dispersive guided waves (GWs) from a recorded time-waveform is presented. The proposed ldquoWarped Frequency Transformrdquo (WFT) is based on a time-frequency domain tiling chosen to match the spectro-temporal structure of the different propagating guided waves by selecting an appropriate warping map which generates non-linearly frequency modulated atoms. The WFT transformation is fast, invertible, covariant to group velocity-delay shifts and, in force of the more flexible tiling, presents enhanced modes extraction capabilities. An application to Lamb Waves propagating in an isotropic plate is presented to show the potential of the proposed procedure.
Keywords :
aluminium; discrete Fourier transforms; frequency modulation; plates (structures); structural acoustics; surface acoustic waves; time-frequency analysis; ultrasonic dispersion; ultrasonic propagation; Al; Lamb wave propagation; WFT transformation; appropriate warping map; dispersive guided waves extraction; inverse discrete-time Fourier transform; isotropic aluminum plate; multimodal waves extraction; nonlinearly frequency modulated atoms; spectro-temporal structure; time-frequency procedure; ultrasonic guided-wave characterization; velocity-delay shifts; warped frequency transform; Acoustic materials; Acoustic propagation; Acoustic waveguides; Computer science; Discrete Fourier transforms; Dispersion; Fourier transforms; Frequency modulation; Structural engineering; Time frequency analysis; Group-delay Covariance; Lamb Waves; Time-Frequency Representations; Warped Frequency Transforms;
Conference_Titel :
Ultrasonics Symposium, 2008. IUS 2008. IEEE
Conference_Location :
Beijing
Print_ISBN :
978-1-4244-2428-3
Electronic_ISBN :
978-1-4244-2480-1
DOI :
10.1109/ULTSYM.2008.0046
