Laplacian wavenumber filtering for improving damage visualization in fast non-contact inspections

Full acoustic wavefield data acquired over large areas may provide a unique insight about the presence of defects in the monitoring of shells and plates. However, full wavefield imaging techniques have some limitations, including slow data acquisition and lack of accuracy. This research addresses both of these challenges and presents a fast and robust non-contact wavefield imaging method based on the Compressive Sensing (CS) approach, as a mean to speed up the acquisition process, and a novel analysis tool to process recovered wavefield data in the wavenumber/ frequency domain. The proposed strategy is based on the removal of the injected wave from the overall response, in order to highlight the presence of reflections associated with damage. This strategy is based on the application of the (3DFT) to the CS reconstructed wavefields to produce the frequency wavenumber representation. The frequency-wavenumber coefficients are then thresholded, and, finally, a Laplacian filter is applied to enhance the discontinuities. This concept was tested over multiple experiments with different panels. Tests were performed on aluminum and composite plates, and the defect was simulated with an attached mass. The results demonstrate the capability of the technique for enhancing damage visualization while reducing the original number of scan points.