Detecting Damage Size and Shape in a Plate Structure Using PZT Transducer Array

An algorithm to detect damage size and shape using a lead zirconate titanate (PZT) transducer array for a plate structure is developed in this paper. During the process of detection, the predetermined PZT transducers are chosen as actuators to generate Lamb waves, and others are chosen as sensors to detect the Lamb waves. When there is damage, the Lamb wave reflects at the boundary of the damage. The reflection point is on an ellipse with two foci at the actuator and sensor, and this ellipse is tangent to the boundary curve of the damage at the reflection point. The reflection point can be obtained by finding a special point on the ellipse, and this point has the shortest distance to the center of the curvature of the damage boundary curve. As a result, the damage boundary curve can be determined by finding various reflection points, and the envelope of the identified reflection points is employed to represent the shape of the damage. Experiments are conducted on an aluminum plate with 12 piezoceramic transducers to identify the sizes and shapes of bonded masses, which are considered as simulated damages. The experimental results indicate that the proposed method can obtain the size and shape of bonded masses with a relatively small error.