Abstract
We have built and tested several focused-arc ultrasonic transducers for use in nondestructive characterization of flaws in thick metal sections. These transducers transmit and receive ultrasonic pulses at frequencies 2.25 or 4 MHz and produce diffraction limited beams at all ranges including the classical nearfield region since the beams are essentially in focus at all ranges. We have used both contact and immersion transducers in conjunction with a mechanical scanner and display package and have produced B-scan images of holes and flaws from 1- to 20-in. depths into metal specimens. Images of patterns of drilled holes have been made demonstrating the resolving of 132- in.-diam holes about 116 in. apart through 212 in. of aluminum. Several other ultrasonic images and comparisons of these with other NDT techniques will be shown. [This work has been supported by the U. S. Navy under contract.]
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