COMPARISON OF DIGITAL SIGNAL PROCESSING METHODS FOR THE DETECTION OF ISOLATED FLAWS USING PERPENDICULAR ULTRASONIC TRANSDUCERS

This paper reviews and analyses distinct alternatives for the testing of materials using ultrasonic traces coming from different transducers located on perpendicular radiating planes. Three methods, which uses digital signal processing techniques to combine the A-scans acquired by the transducers involved to form a two-dimensional representation, are compared. Mathematical expressions of the improvements, in a signal-to-noise ratio sense, are shown, and evaluations are carried out to compare the performance of these digital signal processing methods for A-scans combination. Several two-dimensional representations obtained from a common set of ultrasonic traces are displayed at the end of the paper. They have been constructed using several set of parameters for the different signal processing methods applied, and the resulting two-dimensional signal-to-noise ratios are included in each graph