Novel composite transducer for ultrasonic NDE of concrete

Ultrasonic inspection of concrete structures is practicable only at relatively low frequencies because of multiple scattering caused by the aggregate. Conventional techniques used in ultrasonic nondestructive evaluation (NDE) are less effective below 500 KHz, and new methods of transducer design are needed. Experimental results for a novel transducer, based on the principles of composite acoustic waveguides, used both as a point source transmitter or as a receiver capable of operation at arbitrarily low ultrasonic frequencies, are reported