Abstract:

The propagation characteristics of Lamb waves can be changed when they encounter a defect in plate style waveguides, which has close relationship with the relative distance between defects position and the propagation paths of Lamb waves among the transducer. A defect zone imaging method based on propagation paths analysis is presented to realize defect zone image in composite plates. To obtain enough defects information, a chirp excitation is stimulated by piezoelectric transducers, then abstract tone burst responses those have several of center frequency form the chirp responses. Through comparing the peak values of the signal envelops, the relationships between the defect and propagation paths are acquired. The paths have similar propagation velocities with paths those a defect located are chosen as interested path, then calculating elliptical tracks with the defect scattering signals with the elliptical imaging algorithm. The error tolerance is introduced to select the elliptical tracks calculated with difference frequencies. Detect zone image is realized by fusing the selected elliptical tracks. The feasibility of the proposed method is validated with experiments in a composite material plate.

Key words: Chirp signal, composite plate, data fusion, defect zone imaging, paths analysis