Detection of internal defect in metal plate structures using air-coupled ultrasonic Lamb waves
MENG Xiangzhen;LI Zaiwei;ZHU Wenfa;HE Yuelei;LU Hongyao;College of Urban Rail Transportation, Shanghai University of Engineering Science;
Aiming at the problems of high environmental requirements, low efficiency and high operational difficulty of the contact ultrasonic detection method in the actual engineering detection of defects in the metal plate structures, the Lamb wave detection method of air-coupled ultrasonic was proposed, which can better adapt to the field application environment, improve the detection efficiency and reduce the number of sensors.The finite element simulation and experimental analysis are compared to compare air-coupled ultrasonic testing and the contact ultrasonic testing methods for receiving signals and imaging effects. The results show that in the finite element simulation and experiment, the positioning error of the air-coupled ultrasonic detection method to the defect position is 2 mm and 3.6 mm respectively, and the positioning error of the contact detection method to the defect position is 2 mm and 11.3 mm respectively. The air-coupled detection has a high positioning accuracy. Under the one-side excitation condition, the A0 mode of Lamb wave used to detect the defects in the board is suitable; the air-coupled ultrasonic detection can receive the single mode Lamb wave by adjusting the signal receiving angle to avoid artifact generation. This method can be used as a reference for the subsequent ultrasonic detection of defects in metal plate structure.