Flexible ultrasonic transducers for structural health monitoring of pipes at high temperatures

Piezoelectric films have been deposited by a sol-gel spray technique onto 75 µm thick metal membranes and have been fabricated into flexible ultrasonic transducers (FUTs). Such FUTs were glued and brazed onto steel pipes providing as on-site installation techniques for continuous thickness monitoring purposes at up to 490°C. At 150°C, the thickness measurement accuracy of a pipe with an outer diameter of 26.6 mm and a wall thickness of 2.5 mm was estimated to be 26 µm. Ultrasonic 4 by 16 element arrays were also fabricated and single element performance was measured.