Inspecting Composite Ceramic Armor Using Advanced Signal Processing Together with Phased Array Ultrasound

摘要

A series of 16-inch square by 2-inch thick, multi-layered ceramic composite armor specimens have been inspected using a 128 element, 10MHz immersion phased array ultrasound system. Some of these specimens had intentional design defects inserted interior to the specimens. Because of the very large changes in acoustic velocities of the various layered materials, ultrasonic wave propagation is problematic. Further, since the materials used in the layers were stacked such that a lower elastic modulus material was on one side and a higher elastic modulus material was on the other, the side selected for ultrasonic insonification became a significant parameter. To overcome some aspects of the issues with the acoustic wave propagation, two digital signal processing methods were employed. These were: 1)- use of fast Fourier transforms (FFT) and 2)-an integrated signal analysis. Each method has strengths and weaknesses with application in part dependent upon the side of sample used for insonification. The results clearly show that use of these methods significantly improves defect detection. This paper presents the details of the samples used, the issues with ultrasonic wave propagation, a discussion of the two digital signal processing algorithms and results obtained.