LASER-BASED ULTRASONIC EXCITATION AND SPECKLE INTERFEROMETRIC DETECTION SYSTEMS FOR NONDESTRUCTIVE EVALUATION OF HIGH-TEMPERATURE CERAMICS

THE USE OF ADVANCED MATERIALS SUCH AS CERAMICS, CERAMIC COMPOSITES, AND HIGH TEMPERATURE COATINGS HAS LED TO IMPROVED PERFORMANCE OF CRITICAL HEAT ENGINE AND ENERGY-RELATED COMPONENTS AND SYSTEMS. HOWEVER, THE REQUIREMENTS FOR NONDESTRUCTIVE EVALUATION (NDE) OF CERAMIC MATERIALS RESULTING FROM COMPLEX GEOMETRY, INHOMOGENEITY, REDUCED FLAW SIZE, AND ADVERSE PROCESSING ENVIRONMENTS HAVE PRODUCED LONG INSPECTION TIMES AND HAVE REDUCED CONFIDENCE IN ESTIMATING COMPONENT INTEGRITY AND LIFETIME. ONE CLASS OF NDE SENSORS, BASED ON PHOTOACOUSTIC GENERATION AND ACOUSTO-OPTIC DETECTION OF ULTRASOUND, OFFERS IMPORTANT ADVANTAGES OVER CONVENTIONAL NDE TECHNIQUES. THIS PROGRAM INVOLVES A NOVEL LASER-BASED EXCITATION SYSTEM EMPLOYING PHOTO-ACOUSTIC GENERATION COMBINED WITH LASER SPECKLE INTERFEROMETRIC DETECTION. SPECIFIC PROGRAM OBJECTIVES INCLUDE THE LASER GENERATION OF ULTRASOUND IN ADVANCED MATERIALS; INVESTIGATION OF METHODS TO ACHIEVE A HIGH SPEED,HIGH RESOLUTION LASER EXCITATION SYSTEM FOR INTEGRATION WITH SENSITIVE ULTRASONIC IMAGING SYSTEMS; ACQUISITION OF FAMILIES OF TEST DATA FOR COMPARISON WITH OTHER NONCONTACTING NDE METHODS; AND DESIGN OF A PROTOTYPE SYSTEM.THE PHASE I PROGRAM SHOULD PROVIDE A NONCONTACTING, IN-PROCESS CHARACTERIZATION TECHNIQUE FOR LASER-BASED NDE OFADVANCED CERAMIC MATERIALS FOR EXTENSIVE DEVELOPMENT AND TEST WITH STRUCTURAL COMPONENTS IN HIGH TEMPERATURE HEAT ENGINES DURING PHASE II OF THE PROGRAM.