Time-frequency and wavelet transform applied to selected problems in ultrasonics NDE

Type : Publication
Auteur(s) :  Redouane DRAI, Mohamed KHELIL, Amar BENCHAALA
Année :  2002
Domaine : Electronique
Revue : NDT & E International
Résumé en PDF :  (résumé en pdf)
Fulltext en PDF :  (.pdf)
Mots clés :  NDT/NDE, Ultrasonic, time frequency representation, Wavelet transform

Résumé : 

In this paper, we contribute by the development of some signal processing in order to enhance the sensibility of flaw detection, to measure thin materials thickness and to characterize defects in nature (planar or volumetric). Features for discrimination of detected echos are extracted in time domain, spectral domain and discrete wavelet representation. Compact feature vector obtained is then classified by different methods: K nearest neighbour algorithm, statistical Bayesian algorithm and artificial neural network. Mallat decomposition algorithm is also developed in order to enhance flaw detectability. Finally, time frequency algorithms based on STFT, Wigner–Ville, Gabor transform are developed and applied to thickness measurements of materials with small thickness.