DEVELOPMENT OF NOVEL PIEZOELECTRIC ULTRASONIC TRANSDUCERS FOR COUPLANT-FREE NONDESTRUCTIVE TESTING

Experiments are presented from a 5 MHz centre frequency normal inciden ce longitudinal wave ultrasonic transducer that does not need a coupla nt. The transducer is novel in that it operates at 5 MHz, which is a m uch higher frequency than has been possible in previous 'dry coupled' probes. It is based on a conventional approach, using a new low loss, synthetic rubber delay line and is shown to give good results when use d in the pulse-echo mode on various samples of industrial interest.