FREQUENCY STEERABLE TRANSDUCERS WITH 360° DIRECTIVITY FOR GUIDED WAVES INSPECTIONS IN PLATE-LIKE STRUCTURES

摘要

Directional Transducers for Guided Waves generation and sensing are achieved by patterning the piezoelectric material lay-out and the electrodes. The peculiar electrodes' shape produces a spatial filtering effect which is frequency-dependent, so that a direct relationship can be established between the direction of propagation (wavenumber) and the spectral content of the transmitted/received signal. This kind of transducer has been named Frequency Steerable Acoustic Transducers (FSATs). FSAT dedicated signal processing algorithms enable localization of acoustic events in 2D spaces by processing two differential output of a single device, i.e. using only two acquisition channel thus allowing for a drastic hardware simplification and cost reduction of Guided wave based systems. In this work, a new generation of FSATs is proposed, which allows steering the wave direction of propagation in the whole angular range [0°; 360°] with improved directivity and sidelobes reduction.