Spatial patterns of the transient ultrasonic field radiated by a dual-transducer NDE probe

Abstract

In some Non Destructive Evaluation applications, a particular type of probe having two separate transducer elements, for emission and reception purposes, is used looking for a practical improvement in sub-surface flaw detection and lateral resolution. These probes (named dual-element transducers or twin T/R probes) are intended for an operation in which only one of the transducers is specifically radiating an ultrasonic field. In this work a T/R NDE ultrasonic probe is investigated when it is radiating into water. A preliminary analysis to check possible radiation problems associated with such probe, when it is non-conventionally operated in order to actuate as two similar emitters, is here presented. Experimental plots of field patterns generated in transient regime by both transducers, in separated and simultaneous way, are gate-detected and comparatively evaluated. Some differences between cross-sectional and longitudinal patterns produced by the two twin transducers contained inside the T/R probe are evidenced. Some possible origins of these probe asymmetries are commented.