Time Reversal Methods for Structural Health Monitoring of Metallic Structures Using Guided Waves

摘要

Time reversal methods for ultrasonic guided waves are being investigated for detecting damage in metallic plate structures. According to this method the input signal to a system can be reconstructed if a response signal obtained from another point is emitted back to the original point after being reversed in time. Damage diagnosis lies in the premise that the time reversibility breaks down when a certain type of defect such as nonlinear damage exists along the wave propagation path. The defect can then be sensed by correlating the reconstructed signal with the original signal. The difficulty of direct application lies in the fact that ultrasonic guided waves disperse while propagating, thus they will not totally reconstruct the original signal. Overcoming this difficulty is examined in a finite difference model with narrow and broadband excitation of guided waves in a metallic plate with damage simulated as a shallow notch. Results show that narrow band excitation is somewhat more sensitive than broadband excitation to notch depth.