Efficiency of time-reversed acoustics for nonlinear damage detection in solids

Time-reversed acoustics (TRA) has been developed in the last few years as a powerful tool for several applications, based on the theoretical properties emerging from the time reversal invariance of the wave equation. TRA is expected to be a good basis for the development of imaging techniques in the field of nondestructive evaluation. For this purpose, however, data processing is necessary to discriminate between images due to defects (in general nonlinear scatterers) and images due to linear inclusions, boundaries, etc. We propose here an approach based on the filtering of the time signals. The image of the scatterer is obtained through numerical simulations of the back propagation in a fictitious reference specimen. We validate the approach using the inversion of synthetic data. We also estimate the robustness of the procedure in the presence of constraints that can occur in any experimental procedure. (c) 2006 Acoustical Society of America.