Omnidirectional guided wave PWAS phased array for thin-wall structure damage detection

Widely used 1-D guided wave phased arrays can only scan within 0°~180° range due to the intrinsic structural limitation. To overcome this limitation, multiple installations are unavoidable. However, by using 2-D configuration phased arrays, large structural interrogation can be conducted from a single location with a single scanning covering the entire 0°~360° range through omnidirectional beamforming. Based on the developed generic PWAS Lamb wave phased array beamforming formula, this paper aims to bring up the practical implementation of an 8x8 PWAS array and present analytical and experimental results concerning the omnidirectional damage detection ability. The theoretical beamforming of 2-D rectangular PWAS configuration will be presented at first based on the generic PWAS phased array beamforming formulation. Then, an 8x8 rectangular PWAS array is installed on the target aluminum specimen. Laboratory experiment is set up next and conducted various crack damage detection. Specimens include: (1) a single crack positioned at 90º; (2) a single crack positioned at 270º; (3) a single hole positioned at 180º; 4) a crack at 90 º and a hole at 180 º, respectively. The experiments will demonstrate the 360º damage finding ability of the 2-D PWAS array and the multiple damage detection ability as well. We finally end up with discussions on the practical application and come up with plans for future work on various 2-D array developments.