Integrated surface and plate acoustic wave sensors for health monitoring

Piezoelectric films sprayed onto metal substrates together with interdigital transducer electrodes form the integrated Rayleigh surface acoustic wave (RAW) transducers to excite and detect RAW. Using integrated longitudinal (L) wave ultrasonic transducers (UTs) and mode conversion from L waves to shear waves symmetrical, anti-symmetrical and shear horizontal types of guided plate acoustic waves have been generated and received in aluminum alloy plates. These transducers can be operated in pulse-echo mode for in-situ non-destructive testing (NDT) and/or health monitoring purposes in a distance of hundreds of mini-meters at 150°C. Examples of using such waves for NDT of defects are also demonstrated.