title: Double-channel, frequency-steered acoustic transducer with 2-D imaging capabilities.
abstract: A frequency-steerable acoustic transducer (FSAT) is employed for imaging of damage in plates through guided wave inspection. The FSAT is a shaped array with a spatial distribution that defines a spiral in wavenumber space. Its resulting frequency-dependent directional properties allow beam steering to be performed by a single two-channel device, which can be used for the imaging of a two-dimensional half-plane. Ad hoc signal processing algorithms are developed and applied to the localization of acoustic sources and scatterers when FSAT arrays are used as part of pitch-catch and pulse-echo configurations. Localization schemes rely on the spectrogram analysis of received signals upon dispersion compensation through frequency warping and the application of the frequency-angle map characteristic of FSAT. The effectiveness of FSAT designs and associated imaging schemes are demonstrated through numerical simulations and experiments. Preliminary experimental validation is performed by forming a discrete array through the points of the measurement grid of a scanning laser Doppler vibrometer. The presented results demonstrate the frequency-dependent directionality of the spiral FSAT and suggest its application for frequency-selective acoustic sensors, for the localization of broadband acoustic events, or for the directional generation of Lamb waves for active interrogation of structural health.
authors.affiliation: School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA, USA. ebaravelli@arces.unibo.it
authors.forename: Emanuele
authors.initials: E
authors.lastname: Baravelli
authors.forename: Matteo
authors.initials: M
authors.lastname: Senesi
authors.forename: Massimo
authors.initials: M
authors.lastname: Ruzzene
authors.forename: Luca
authors.initials: L
authors.lastname: De Marchi
authors.forename: Nicolò
authors.initials: N
authors.lastname: Speciale