title: Ultrasonic flaw detection using threshold modified S-transform.
abstract: Interference noising originating from the ultrasonic testing defect signal seriously influences the accuracy of the signal extraction and defect location. Time-frequency analysis methods are mainly used to improve the defects detection resolution. In fact, the S-transform, a hybrid of the Short time Fourier transform (STFT) and wavelet transform (WT), has a time frequency resolution which is far from ideal. In this paper, a new modified S-transform based on thresholding technique, which offers a better time frequency resolution compared to the original S-transform is proposed. The improvement is achieved by the introduction of a new scaling rule for the Gaussian window used in S-transform. Simulation results are presented and show correct time frequency information of multiple Gaussian echoes under low signal-to-noise ratio (SNR) environment. In addition, experimental results demonstrate better and reliable detection of close echoes drowned in the noise.
authors.affiliation: Welding and NDT Research Center (CSC), BP 64, Cheraga, Algeria; Département d'Electronique, Faculté des sciences de l'ingénieur, Université Sâad Dahlab de Blida, BP 120, Route de Soumaa, 09000 Blida, Algeria. Electronic address: Abs_benammar@yahoo.fr.
authors.forename: Abdessalem
authors.initials: A
authors.lastname: Benammar
authors.forename: Redouane
authors.initials: R
authors.lastname: Drai
authors.forename: Abderrezak
authors.initials: A
authors.lastname: Guessoum
mesh_terms: D000465:Algorithms; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008422:Materials Testing / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods*
keywords: Flaw detection; Modified S-transform; Time–frequency signal analysis; Ultrasonic signal