ULTRASONIC CORRELATOR FOR NONDESTRUCTIVE CHARACTERIZATION OF MATERIALS

A NEW CROSS-CORRELATION METHOD DEVELOPED FOR MEDICAL DIAGNOSIS AND A NEW FLAT RESPONSE ACOUSTIC EMISSION TRANSDUCER ARE BROUGHT TOGETHER WITH THE PROMISE OF AN IMPROVED, NONDESTRUCTIVE, ULTRASONIC METHOD TO CHARACTERIZE MATERIALS. THE IMPULSE RESPONSE CAN YIELD VALUABLE INFORMATION ABOUT MATERIALS SUCH AS DAMAGE, POROSITY, MICROSTRUCTURE, COMPOSITION, FATIGUE, ETC. THE CROSS-CORRELATION METHOD, NOW USED TO CHARACTERIZE AUDIO SYSTEMS AND TO STUDY LUNG DISEASE TO FREQUENCIES OF 20 KHZ, WILL BE EXTENDED TO THE MEGAHERTZ RANGE. THE FLAT RESPONSE RECEIVING TRANSDUCER WILL BE COUPLED WITH A SIMILAR ULTRASONIC TRANSMITTER; THE TRANSMITTER AMPLITUDE REQUIREMENTS WILL BE MODEST. THE RESULTANT NONDESTRUCTIVE CHARACTERIZATION INSTRUMENT WILL PROVIDE CAPABILITY TO MEASURE THE IMPULSE RESPONSE OF A MATERIALS SYSTEM AND YIELD INFORMATION ABOUT THE TEST OBJECT IN TERMS OF FREQUENCY, PHASE AND GROUP DELAY RESPONSE AND DISPERSION; THESE MEASUREMENTS WILL REVEAL IMPORTANT INFORMATION ABOUT THE STATE OF THE MATERIAL. SUCH INFORMATION IS VITAL IN DETERMINING WHETHER OR NOT MATERIALS SHOULD BE USED OR REMAIN IN SERVICE. THE MEASUREMENT PROMISES TO BE PARTICULARLY USEFUL AS A COMPARATIVE TECHNIQUE TO DETECT EARLY INDICATIONS OF DEGRADATION DUE TO FATIGUE, IMPACT DAMAGE, ETC.; IT WILL BE USEFUL FOR MATERIALS CHARACTERIZATION IN THE PLANT AND IN THE FIELD AND FOR CONTINUED RESEARCH ON MATERIALS. THE NEW TEST INSTRUMENT WILL BE APPLICABLE TO MEASUREMENTS FOR MANY MATERIALS INCLUDING METALS, COMPOSITES, POLYMERS AND CERAMICS.