7. Reliability of Structural Ceramics
A high frequency 250 MHz A-scan system has been used for flaw detection. We have been able to detect 25-500 ~m defects of different types (C, Si, SIC, BN, Fe, WC) in a Si3N4 plate. Since it is difficult to determine the defect type and size from the amplitude of the backscattered signal , we have carried out Fourier transforms of the backscattered signal to obtain reflectivity as a function of frequency, and used that information to characterize the size and type of defect. Our ea~ly experiments have been with voids in glass and Si 3N4 and we are able to predict the size of the defects we detect.
Kino, Gordon S.; Khuri-Yakub, B. T.; and Tittmann, Bernard R., "High Frequency Ultrasonics" (1978). Proceedings of the ARPA/AFML Review of Progress in Quantitative NDE, September 1976–June 1977. 40.