Title: Improvement of Damage Detection with the Embedded Ultrasonics Structural Radar for Structural Health Monitoring

2 Structural health monitoring is used to monitor the onset and progress of structural damage such as fatigue cracks and corrosion. The occurrence of the damage can be detected as reflections from it by using ultrasonic phased array technique, which applies time delays to steer a focused beam around the inspected area. The embedded ultrasonic structural radar (EUSR) uses ultrasonic guided Lamb and Rayleigh waves generated with tuned piezoelectric wafer active sensors (PWAS) that are permanently attached to the structure. It can interrogate large structural areas from a single location by using the steering ultrasonic beam concept. This paper aims to bring together several aspects of the application and implementation of Lamb-wave phased array to structural damage detection. The objective of our research is to improve the design of embedded phased arrays for structural health monitoring in three aspects: (a) improving the near field damage detection, which is a known drawback of phased-array radar systems; (b) designing optimized phased-array patterns, which improve the detection for all steering angles in the range 0º through 360º; (c) applying the EUSR method to compact specimens with complicated geometries and multiple boundaries. 1