A New Generation of Piezoceramic Frequency Steerable Acoustic Transducers for the Rapid Inspection of Large Areas of Metallic Plate Structures

This study introduces a new type of directional transducer designed for Ultrasonic Guided Waves (GWs)-based Structural Health Monitoring (SHM) applications. GWs inspection typically involves controlling several piezoelectric transducers placed on the component being inspected. However, the deployment of such systems is impeded by weight penalties, complex circuitry, and maintenance concerns arising from extensive wiring. To address these challenges and simplify hardware while reducing costs, shaped transducers with inherent directional capabilities such as Frequency Steerable Acoustic Transducers (FSATs) can be utilized. FSATs make use of spatial filtering that varies with frequency, establishing a direct correspondence between signal propagation direction and the spectral characteristics of transmitted or received signals. The new generation of FSATs eliminates the 180° ambiguity issue present in previous FSATs, enabling 360° surface scanning for defect detection through excitation frequency variation with minimal software/hardware requirements in a quick manner. Finite Element (FE) simulations along with experimental validations using Scanning Laser Doppler Vibrometer (SLDV) were carried out to validate the transducer performance, showing a robust frequency-dependent unidirectionality of the proposed device.