Investigation of Ultrasonic Guided Waves Interacting With Piezoelectric Transducers

Ultrasonic guided waves (UGW) can be used to inspect and monitor a structure from a single test location. Piezoelectric transducers are commonly dry-coupled with force to the surface of the waveguide in order to excite UGWs. These UGWs propagating within the waveguide will interact and reflect from known features, thus possible damage could be detected. In this paper, the interaction of UGWs with piezoelectric transducers is reported and investigated. A Finite Element Analysis (FEA) approach has been used to conduct a parametric study in order to quantify the effect of the waveguide diameter on the guided wave response. Laboratory experiments are carried out to measure the effect of the force on the dry-coupled piezoelectric transducers and the corresponding guided wave response, including reflections and mode conversions. A test rig is used to apply and measure the force on the piezoelectric transducers. For verification, a 3D Laser Doppler Vibrometry (3D-LDV) scan is performed on the waveguide in order to quantitatively identify the modes of interest. The conclusions reached this paper, particularly with respect to the quantification of the wave mode properties, lead to useful recommendations which may contribute to field inspection scenarios.