TABLE OF CONTENTS In this section, we will describe the 2-D embedded ultrasonics structural radar concept that was developed from the original EUSR concept that uses 1-D PWAS arrays. We achieved the 2-D EUSR using 2-D planar PWAS arrays (Giurgiutiu and Yu, 2006). Though the results presented here are specific to rectangular grid PWAS phased arrays, they can be easily adapted to other array configurations (rectangular fence, circular ring, circular grid). The benchmark crack detection situations to be discussed in this section are presented in Fig. 11.47.
As different from the 1-D implementation of the EUSR algorithm, the implementation of a 2-D analysis requires that we define the front and the back of the 2-D array. That is to say, we need to establish numbering rule for setting up the firing order in the array. The numbering used in 1-D situation started from left to right (such that the front side is determined). Extending to the 2-D situation, the rule of numbering still starts from left to right and then moves from the back to front. By this means, the front side of the array can be determined. If the 0 direction (or front side of the array) is determined, the numbering of the N M array will start from...
