A high-resolution imaging method based on broadband excitation and warped frequency transform

Lamb wave has received widely attention in structural health monitoring (SHM). However, due to its multi-mode character and dispersion effect, the damage positioning and imaging resolution are limited. Besides Narrowband wave, which is usually adopted as excitation in Lamb wave detecting, broadband signal can also be chosen as excitation, with which plenty of signals can be obtained in one test to strengthen the brightness of damages by superposition. Warped frequency transform (WFT) is a new method based on group velocity dispersion curves, which can directly used to the received signals to suppress the dispersion and turn the signal to distance domain. In this paper, a new high-resolution method is proposed base on warped frequency transform and broadband excitation. The propagation of Lamb waves in damaged aluminum plate is simulated by finite element software ABAQUS, results show that high resolution images can be obtained with the proposed method.