An Applicable Time Reversal Analysis of Guided Waves in Al-Plate with Ultrasonic Immersion Testing

Ultrasonic guided waves are capable of propagating relatively long distances in plate-like structures generates leaky lamb waves from the metal surface, a key phenomenon to characterize the surface defects of metal structures. The general technique of time reversing guided plate waves is advantageous to investigate various kinds of defects. The present research has been focused on the adopted time reversal technique for ultrasonic immersion testing. System’s electromechanical irreversibility effect is a barrier for the time reversal analysis of lamb waves in water medium based immersion testing which cannot be avoided experimentally. In this study, this critical time reversal signal reconstruction problem has been solved using the correction factor calculated from the reference experiment and finite element method (FEM) numerical simulation in a water medium. Two kinds of experiments were conducted, first one is a through-transmission system without the use of specimen for the calculation of correction factor and another experiment is pitch-catch system performed on the aluminum specimen, using two 1 MHz center frequency transducers with a diameter of 12.7 mm. Basically, this paper is intended to investigate a methodical approach applicable to analyze guided plate wave signal reconstruction using time reversal technique in water medium ultrasonic immersion testing. The proposed approach can be applied in any time reversal inspection of a plate and pipe-like structures in ultrasonic immersion system.