Hilbert-Huang Transform versus Fourier based analysis for diffused ultrasonic waves structural health monitoring in polymer based composite materials
Résumé
The use of time-frequency distributions for analysis of diffused signals, which takes into account the non-stationarity of these signals, may be vital for structural health monitoring applications. Although this type of analysis may bring new information into the signals analysis, the interpretation of a time-frequency distribution may not be simple, which may affect the damage identification. In addition, the large number of available tools for time-frequency analysis with different assumptions about the signal features (i.e. assumptions about linearity, stationarity, etc.), may cause a problem when selecting the most appropriate technique for signal analysis, and then may affect the interpretation of results. In this paper, induced holes in a Glass Fiber Reinforced Polymer (GFRP) composite plate, considered as damages, are visualized on different time-frequency representations. In particular, representations obtained from traditional Fourier based analysis methods like spectrogram are compared to that provided by the Hilbert-Huang transform, recently developed. Such a comparison of these techniques can be very useful to justify the accuracy of the HHT and for guiding the choice of the appropriate monitoring strategy of a given process.
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