Non-Contact Local and Global Damage Detection with Integrated Ultrasonic Transducers

摘要

Miniature and light weight thick piezoelectric films (>40μm) integrated ultrasonic transducers (IUTs) for bulk longitudinal (L) and shear (S) and plate acoustic waves (PAW) propagation are presented. The unique and distinct advantages of these IUTs are that they can be fabricated, using sol-gel based technique, directly onto sample with complex structures including curved surfaces and require no couplant for operation. Using novel mode conversion methods, the L wave generated by IUTs can be converted to S, symmetric, anti-symmetric and shear-horizontal (SH) PAW. The experimental results agreed well with those obtained by a finite difference based method which solves the 3D visco-elastic wave equations. These IUTs can operate at temperatures at least up to 150°C, at center frequencies ranging from 1 to 20 MHz, and provide damage detection range of tens of centimeters in metallic structures. An inductive coupled technique is used to achieve non-contact measurements with these IUTs.