50 MHZ LIQUID COUPLED ULTRASONIC SHEAR WAVE IMAGING SYSTEM FOR NONDESTRUCTIVE EVALUATION OF CERAMICS

THEIR OUTSTANDING PHYSICAL PROPERTIES ARE CAUSING CERAMICS TO BECOME IMPORTANT STRUCTURAL MATERIALS. THEIR SUSCEPTIBILITY TO FAILURES INITIATED BY VERY SMALL DEFECTS HAS LED TO A NEED FOR HIGH RESOLUTION FLAW DETECTION. EXISTING TECHNIQUES HAVE NOT DEMONSTRATED ADEQUATE ABILITY TO DETECT DANGEROUS DEFECTS. WE PROPOSE TO MODIFY AND EXISTING ULTRASONIC C-SCAN SYSTEM TO USE 45 DEG INCIDENCE SHEAR WAVES AND LIQUID COUPLING. TH USE OF SHEAR WAVES WILL DOUBLE THE RESOLUTION OBTAINABLE AT A GIVEN FREQUENCY, AND ENHANCE SENSITIVITY TO CERTAIN TYPES AND ORIENTATIONS OF DEFECTS. THE 45 DEG INCIDENCE WILL ELIMINATE THE NEAR-SURFACE DEAD ZONE OF TYPICAL ULTRASONIC SYSTEMS, AND WILL PERMIT THE USE OF LIQUID COUPLING. THIS WILL ALLOW RAPID SCANNING OF THE SAMPLE, IMPORTANT FOR PRACTICAL, ECONOMIC TESTING SYSTEMS. P.A.D. POSSESSES UNIQUE EXPERTISE IN THE FABRICATION OF TRANSDUCERS AND ELECTRONIC EQUIPMENT FOR THIS PROJECT, AND HAS AVAILABLE A SCANNING SYSTEM WHICH CAN BE USED AS A TEST BED TO DEMONSTRATE THE VIABILITY OF THE TECHNIQUE. OUR CONSULTANT, PROF. B. T. KHURI-YAKUB OF STANFORD UNIVERSITY, HAS MADE IMPORTANT CONTRIBUTION TO THE FIELD OF NDE OF CERAMICS. WE ARE IN A UNIQUE POSITION TO DEMONSTRATE AN EFFECTIVE TESTING MODALITY FOR STRUCTURAL CERAMICS, AND TO DEVELOP A COMMERCIALLY SUCCESSFUL TESTING SYSTEM.