Pattern recognition in the ultrasonic imaging of reverberant multilayered structures

Often the existence of reverberations in the ultrasonic pulse-echo imaging of multilayered structure prevents the direct characterization of each layer. The reverberating pattern is governed by the integrity of the layers, and deterioration of these layers can generate complex and unpredictable patterns. Analytical models for the classification of reverberant patterns using both normal and unique angle scanning schemes are presented. The theoretical model has been utilized in the experimental studies of a particular multilayered reverberant environment that exists in the detection of corrosion and/or volatile changes in stem generator tubing used in nuclear power plants. Various reverberant patterns can be recognized that are in close agreement with theoretical predictions.