TABLE OF CONTENTS To verify the damage detection ability of the 2D-EUSR algorithm, two rectangular PWAS arrays (a 4 8 array and an 8 8 array) were used. The 4 8 PWAS array was used to detect a crack in an aluminum plate placed in front of the array and parallel to it. Such a crack would act as a specular reflector and send the echo signal directly back to the array.
The 8 8 PWAS array was used to detect a more difficult situation. The crack was again placed in front of the array, but its orientation was inclined at 45 . This inclined crack sends its specular reflection signal away from the array and thus makes the detection more difficult. What the 8 8 array detects is the secondary signals resulting from scatter at the crack ends.
A rectangular 4 8 phased array, with a total of 32 PWAS elements, was installed in the center of a 1-mm thick 2024 T3 aluminum alloy plate. The phased array was fabricated from a large 0.2-mm thick PZT plate that was diced into an 4 8 pattern. Each element in the array was a 7-mm square PWAS with an element spacing d = 8 mm. The aluminum plate was of square shape with a nominal dimension of 1220 mm (4-ft). The damage to be detected was a 20-mm through-the-thickness simulated...
