ABSTRACT
The modern, pulsed ultrasonic circuit has evolved largely from the electronics advances achieved in World War II. As reported in Refs. 1 and 2, the primary successes before that were analytical with few reports of experimental work. In 1945, Erwin 22 reported pioneering work on ultrasonic thickness measurement and discussed the limitations of contemporary equipment on ultrasonic research. Shortly thereafter, Firestone 23 , 25 and Simmons 24 reported results describing the use of pulsed circuits in materials inspection. It was from these early researchers that the modern ultrasonic pulse-echo nondestructive evaluation system evolved.
