Imaging method for damage inentification of plate structures detected by single mode Lamb waves

The damage detection of steel plates with prefabricated rectangular through-cracks was carried out by using single mode Lamb waves. The excitation and receiving transducers were arranged in a sparse array on the damaged steel plates. A numerical model of Lamb waves propagation in the steel plate was established based on ABAQUS software, and a corresponding experimental platform was built. Through numerical simulation and experiments, the propagation characteristics of Lamb waves in the steel plate were analyzed. A steel plate damage localization program was developed based on MATLAB. The elliptic trajectory was determined based on differential signals of the excitation and receiving transducer. Then, damage position of the steel plate was determined according to the intersection points of multiple sets of elliptic trajectories. The multiple sets of elliptic trajectories were fused to locate and visualize the steel plate damage. Based on the numerical simulation results and experimental data of the Lamb wave damage detection, the influences of different data fusion methods on the accuracy of steel plate damage localization were further compared. Research results indicate that using an excitation signal frequency of 200 kHz and a bilateral symmetrical excitation method can effectively ensure the single mode characteristics of Lamb waves, thereby avoiding dispersion effects and multimodal interference when Lamb waves propagate. For steel plates with single damage, damage imaging errors for both the amplitude summation method and the amplitude multiplication method are within 5 mm. For steel plates with double damage, imaging results of the amplitude summation method will exhibit an indistinguishable pseudoscopic image, with a damage imaging error up to 30 mm. However, imaging results of the amplitude multiplication method are still close to the true damage location, with a maximum error of only 4 mm. Moreover, the contrast of damage imaging is more obvious, indicating that the amplitude multiplication method has more advantages in predicting multiple damage in the steel plate. The localization error of steel plates with double damages obtained from numerical simulation and experimental signals is within 2 mm, which verifies the good damage prediction accuracy of the numerical model.