The study of micro-crack localisation based on vibro-acoustic modulation and time reversal method

The time reversal (TR) method is applied to the localisation of microcrack based on the vibro-acoustic modulation (VAM) which is one of the effective non-linear ultrasonic testing approaches in this paper. The principle of the localisation combining the VAM and TR was analysed and deduced in theory. Then, the VAM experimental system was established and used to detect the aluminium plate and tube containing microcrack. The signals which were produced when the ultrasonic wave and vibration wave interact with the microcrack were received from different positions using the numbers of piezoelectric ceramic pieces. The non-linear components were extracted from the received signals by empirical mode decomposition method. Finally, the non-linear components were reversed in time domain and reloaded into the finite element model of the aluminium plate and tube. The location information of microcrack could be represented in the cloud image of aluminium plate and tube by focusing reversed non-linear signals. The experiment results have been shown that the obtained microcrack location information is closed to the actual location of microcrack in the tested specimen and the localisation method for microcrack is effective.