Multi-time Lamb waves space wavenumber imaging method based on ultrasonic-guided wavefield

Ultrasonic-guided waves full wavefield scanning technology can realize non-destructive testing with non-contact. The damage detection method based on ultrasonic-guided waves’ full wavefield data is widely used in thin-walled plate structures. The defect imaging method based on full wavefield data faces the challenge of simultaneously obtaining the defect contour and thickness direction information. Based on the ultrasonic-guided waves full wavefield scanning detection technology, this paper proposes a multi-time Lamb waves space wavenumber imaging method. In this method, the analytic signal of Lamb wavefield at each moment is constructed by Hilbert transform, and the phase unwrapping is carried out by amplitude sorting and multi-clustering method. Then the wavenumber information is obtained by calculating the phase gradient. The wavenumber at different times of each measurement point is arranged in descending order, and the median wavenumber is extracted as the wavenumber at each measurement point. Based on the dispersion relationship of the tested specimen, the quantitative detection of the plate thickness in the detection area is realized. This method is first applied to the simulation model. Then it is applied to the defect imaging and quantitative detection of aluminum plates with rectangular groove defects and carbon fiber reinforced plastics (CFRP) plates with delamination defects. In simulation and experiment, the local wavenumber imaging method, the frequency domain instantaneous wavenumber imaging method, and the multi-time Lamb waves space wavenumber imaging method are used for defect imaging and quantification. The imaging results are compared and analyzed. The result shows that the multi-time Lamb waves space wavenumber imaging method can restore the morphology of groove defects in aluminum plates and delamination defects in CFRP plates, and accurately estimate the depth of groove defects and the location of delamination defects.