Reference-Free Damage Identification in Plate-Like Structures Using Lamb-Wave Propagation with Embedded Piezoelectric Sensors

Structural health monitoring (SHM) has been adopted in the aircraft and civil industries over the last two decades. The ultrasonic guided wave propagation technique is a promising damage detection approach in airplane thin wall structures because of their long distance traveling ability and low attenuation. In fact, by efficiently designing the pattern of sensors one can effectively pick up the changes that happen in propagated signals due to presence of any kind of structural damage. This detection approach could be effectively assisted by numerical simulation techniques like finite-element modeling. To obtain a damage detection algorithm based on instantaneous baseline data, the finite-element technique is employed for simulation of wave propagation in thin wall structures. Also, the influence of artificial crack (cut-damage) on propagated Lamb waves is investigated. An instantaneous baseline damage detection based on cross-correlation (CC) analysis is carried out to detect the damage, and the results show good agreement with the experimental test results available in the literature. In addition, another proposed instantaneous baseline damage detection technique based on wavelet analysis is examined here. The fast Fourier transform (FFT) and time of flight (TOF) techniques are also used to estimate the size and location of the detected damage instantaneously without the need for prior baseline signals. Conclusively, the numerical simulation can assist in designing an effective a process for damage identification using piezoelectric wafer active sensors. Furthermore, due to the nature of elastic wave velocity in metallic structures, the reported techniques shows that the localization of damage is more accurate than using damage size identification.