Methods of signal processing for the determination of the dimensions of objects using focusing ultrasonic probes

Detection of defects using ultrasonic probes must be followed by a characterization of defect types (crack, inclusion, etc) and a determination of their positions and dimensions. Numerical methods have been developed in France for the processing of ultrasonic signals from artificial and natural defects aimed at providing a precise and reproducible determination of their dimensions, and to give a suggestive imaging of their features. The experimental details, the principles and examples of sizing and imaging of defects and the reduction of noise by averaging are discussed. A method for the measurement of short time intervals and its applications is also presented. (U.K.)