DEFECT CHARACTERIZATION BY ULTRASONIC SIGNAL PROCESS TECHNIQUES.

Small defects in structural materials can be successfully characterized if ultrasonic waves scattered from them are captured and analyzed by simple signal processing algorithms. Angular and frequency dependence of the scattered signals give information about the size, shape, orientation and material content of the defects. Depending on how much is already known about a defect, a variety of algorithms can be used to estimate the unknown properties. In particular, a technique for measuring defect size independently of material content by the use of the frequency dependence of the phase spectrum is suggested. Applications of several such algorithms to commercial alloys are shown.