Attenuation and phase compensation for guided wave based inspection using a filter approach

Structural health monitoring (SHM) using guided waves has received great attention recently. However, detecting and characterizing defects in plate-like structures by means of guided waves is complicated due to their dispersive nature. Imaging, e.g. based on compressed sensing, benefits from dispersion compensation due to the reduced computational burden of requiring fewer atoms in the dictionary matrices. We analyze data obtained by a scanning laser doppler vibrometer (SLDV) of an isotropic aluminum plate. We propose a time-domain preprocessing step comprising the generation of a non-dispersive reference signal and a finite impulse response (FIR) filter, which reconstructs the phase (and amplitude) of the measured signal by solving a linear problem involving both signals. The reference signal is modeled as a tone-burst (defined by its center frequency and the number of cycles) and the group velocity is estimated in a data-driven manner from a training set, consisting of an early subset of the measurements acquired shortly after actuating the burst.