Wigner-Ville distribution enhancement for 2D-flaws location

A transmitted wide beam of ultrasonic pulse is able to increase the visible region of the transducer. If a single wide-beam transducer operating in the pulse-echo mode, is mechanically moved along a known linear path and at each step the echoes are detected and stored, an image of the ultrasonic reflectivity can be produced. Once these signals are recorded, a composite digital process is applied to the envelopes of the received signals. This composite technique consists os Wigner-Ville time frequency distribution and envelope beamforming. The Wigner-Ville distribution allows the time-frequency behaviour of the signals being computed, where the time marginal represents the instantaneous energy of signals. This information concentrates the energy in regions where a possible in-homogeneity is present. Then these post-processed signals are time shifted and summed by the time-delay beamformer producing an intensity matrix, where the regions of maximal amplitude give the in-homogeneities location.