Extraction of Defect Signals in Eddy Current NDE using a DWT Based Method.
IVth International Workshop Advances in Signal Processing for Non Destructive Evaluation of Materials, Québec, Canada, 7-10 août 2001, pp. 119 - 124
In this paper, two defect signal extraction methods were proposed and implemented for the extraction of notch signatures in the context of eddy current testing of steam generator tubes. The methods are based on discrete wavelet transform (DWT) de-noising scheme. The first one uses a firm shrinkage of the wavelet coefficients and the second one uses a wavelet coefficient selection rule based on a multi-scale Maximum Likelihood scheme. The second method shows better extraction results since it permits to take into account the a priori knowledge about the defect signatures to be extracted, at each scale and across scales of the DWT.