Passive technique for acoustic emission location based on compensated lamb waves and low-profile PZTs

A methodology for acoustic source location in plates based on dispersion compensated Lamb waves is proposed. Dispersion compensation is achieved by means of a Warped Frequency Transform once the dispersion curves of the propagating waves have been predicted for the plate. Next, the cross-correlation between two compensated signals is used to extract the difference in traveled distance between the source point and the two receivers. This information, computed for at least two couple of sensors, is used to feed an hyperbolic position algorithm aimed at identifying the source location. The advantages of the proposed procedure over competitor strategies are several. First, the procedure works in a total passive manner without knowing the time of impact. Procedures based on dispersion compensation, in fact, are usually applied to active monitoring techniques, as they require the knowledge of the time of impact to effectively compensate the guided waves dispersive behavior. Second, low-profile piezoceramic PZT sensors, generally used for the structural health monitoring (SHM) of aerospace structures, can be used without recurring to complex anisotropic transducers. Finally, since the computational time required by the WFT to perform signal compensation is comparable to that of the Fast Fourier Transform (FFT), the procedure could be used in load tracking strategies to follow a moving wave source over the waveguide domain. An application of impact localization in an isotropic flat plate is presented to show the technique capabilities. Future studies include the extension of the approach to non flat plates and anisotropic plates.