ULTRASONIC IMAGE DATA-PROCESSING FOR THE DETECTION OF DEFECTS

Ultrasonic testing is widely used in material inspection. Forming an ultrasonic image helps the operator in decision making. This image, however, can result in common interpretation difficulties during the testing of heterogeneous or noisy zones. A new method of detection of defects located in a noisy medium is presented: it is based on considering the ultrasonic grey-level image from the beginning of the analysis. The data processing used here is searching for a certain determinism in the spatial and temporal evolution of the image in the presence of a defect: a first criterion studies the horizontal stability of the gradients in the image and a second considers the transient temporal nature of the defect echo. Results obtained on artificial defects located in real welds are shown. Conclusions with respect to the quality of this defect detection method are drawn.