Sinulation of Crack Identification in Elastic Solids using Surface Signals

Piezoelectric actuators/sensors are quick in response, highly linear, small, non-invasive, inexpensive and easily wired into sensor arrays. As a result, many researchers have studied the technique of generating and collecting diagnostic elastic waves using piezoelectric materials and thus realizing continuous monitoring of structural integrity. The current presentation will present a numerical technique for damage detection based on the signals from thin-sheet piezoelectric actuators/sensors bonded to elastic materials. A theoretical model is developed to simulate the dynamic load transfer between the actuators and the host medium and the resulting elastic wave propagation. Simulation is conducted to detect embedded cracks quantitatively using high frequency elastic waves. The received surface signals, in response to an applied dynamic excitation, are used to determine the position and geometry of embedded cracks based on a reverse elastic wave method. The identification of cracks is achieved from the following three steps: (i) the image of a specific point in the material is formed by extracting the amplitude of the scattered wave at that point at the moment when the incident wave arrives, (ii) both P (longitudinal) wave and S (transverse) wave are used to generate different images of the material, and (iii) false images of cracks are removed. The method developed has been used to identify cracks of different sizes and shapes based on simulated sensor signals. Typical results are shown in Figure. The results show the feasibility of the technique to determine positions and shapes of embedded cracks using surface actuators/sensors.