Damage Detection Using Guided Waves and Piezoelectric Wafer Active Sensor Arrays

This paper presents our research work on using the guided waves for damage detection generated by piezoelectric wafer active sensors (PWAS) arrays that are permanently attached to the structure. The data collection and processing is performed using the embedded ultrasonics structural radar (EUSR) concept. Research objectives includes: (a) improving damage detection in the array near field; (b) designing optimized phased-array patterns; (c) exploring the application of the to compact specimens with complicated geometries. Firstly, a generic formulation for the EUSR phased array directional beamforming was deduced using the exact traveling wave’s formulation without the limiting parallel-rays assumption used by other investigators. The analytical deductions have been followed by the proof-of-concept experimental results. Secondly, the beam forming and steering characteristics of linear PWAS arrays was studied for optimal array design. The influence of several geometric parameters, such as the number of elements in the PWAS phased array, the spacing between adjacent PWAS, and the steering angle, was discussed. Extensive simulation studies have shown that wellbehaved directional beamforming can be achieved with judicious array design. Thirdly, the possibility of applying the guided wave phased array to compact specimens was investigated and a design of using miniaturized PWAS phased arrays was proposed. The paper ends up with discussion and conclusions regarding the beamforming optimization and implementation of the guided wave PWAS phased arrays, followed by suggestions for further work.