Defect Characterization in Ceramics Using High Frequency Ultrasonics

A high frequency A-scan system (150-450 MHz longitudinal, 150-300 MHz shear) has been used to characterize defects in ceramics. An Indium bonding technology has been developed to make broadband, and efficient transducers. Defect characterization is done by comparing the time domain backscattered signals from defects to theory. A Wiener filter is used in order to correct the response of the transducer and the propagating medium, and thus give the impulse response of real defects. A good agreement between theory and experiment is obtained for inclusions such as voids, WC, and SiC in Si3N4