Laser Ultrasonic Lamb Wave Damage Detection Method Based on the Single Transmitter and Multiple Receivers Circular Array

Laser ultrasonic Lamb wave detection technology provides technical support for noncontact and online large plate/shell structure detection. Improving detection accuracy and efficiency has always been the goal of inspection personnel. In this paper, we have built a noncontact laser ultrasonic Lamb wave detection platform to achieve rapid localization of abnormal damage in aluminum alloy plates. First, analyze laser ultrasonic Lamb waves’ modal types and wavelength components. Design and optimize a circular laser array based on near-field beamforming theory, with a single transmitter at the center and multiple receivers around the circumference. After extracting single-frequency components using wavelet transform, the azimuth of the scattering wave is estimated using the near-field 2D multiple signal classification(2D-MUSIC). The advantage is that there is no need to collect the reference signal or add window filtering to intercept the wave packet. The results indicate that damage within the 900 cm2 area can be localized within 0.7 s, and the orientation error is within 6°. This method is an efficient method to achieve damage orientation in a large area. However, the problem of the low resolution and artifact interference in multi-damage estimation presented by this method is urgent to be solved in the future.