Effect of piezoelectric sensor debonding failure on structural health monitoring system based on lamb wave signals

The piezoelectric sensor in the structural health monitoring (SHM) system may be debonded due to complex service environment. However, there are little attention on the debonding behavior of piezoelectric element, which could affect the reliability of the monitoring network. This paper considers the effect of left and right debonding of sensor on receiving signal with different debonding length (2, 4, 6 and 8 mm, respectively) and debonding directions (which are 90 degrees, 180 degrees and 270 degrees, respectively). A finite element model was established to simulate the interface debonding between piezo disc and Aluminium matrix, and both an experimental investigation using a real Aluminium plate is made to further comparison with the simulation results. The characteristic parameters including the amplitude and phase of time domain receiving Lamb wave signals were extracted. The simulation results show the voltage distributions of piezoelectric sensor under different debonding length and direction. In addition, receiving signal indicates that there is not a monotonic downward trend of signal amplitude with the increase of right debonding length of the sensor. And when the wave propagation direction is parallel to the sensor debonding direction (180 degrees), the signal amplitude of the sensor is greater than that perpendicular to the debonding direction (90 degrees and 270 degrees).