Using cross-correlations of elastic diffuse fields for attenuation tomography of structural damage.

A scanning laser Doppler vibrometer is used to measure, at multiple grid points, the diffuse vibrations (50-150 kHz) propagating over a thin aluminum plate with complex geometry. These diffuse vibrations were generated by a few pulsed laser impacts randomly distributed outside of the measurement grid. The pairwise cross-correlations of the diffuse field recorded at all grid points provided an estimate of the first antisymmetric Lamb mode direct arrival between these grid points. Attenuation tomography imaging of a simulated structural damage is performed based on the relative amplitude variations of these direct arrivals between the damaged and undamaged conditions.