Quantitative evaluation of corrosion-thinning defect by an instantaneous wavenumber multi-shot fusion method based on laser ultrasonic guided wavefield detection

The thickness loss caused by corrosion is a vital factor that threatens the health of shell structures. It is significant to perform a non-destructive quantitative evaluation of corrosion-thinning defects in plate structures. Based on the laser ultrasonic guided wavefield scanning technology, this paper proposes an instantaneous wavenumber multi-shot fusion method, which improves the performance of the instantaneous wavenumber imaging method. The guided wave mode and excitation parameters are selected through quantitative analysis. A simulation analysis revealed the interaction between guided wavefield and defect with local thickness loss under multiple excitation positions. The results show that a more accurate wavenumber estimation of the defect area can be achieved by utilizing the abundant wavefield information from multiple-point excitations. In addition, the imaging accuracy between single and multiple excitation techniques is compared and analyzed quantitatively in the experiment. It shows that the proposed method can improve the imaging accuracy in the defect area and suppress the imaging noise in the non-defect area, which verifies its effectiveness.