LASER SPECKLE INTERFEROMETER FOR SURFACE ACOUSTIC DISPLACEMENT MEASUREMENTS

ADVANCES IN REAL-TIME MEASUREMENT TECHNIQUES FOR CHARACTERIZING STRUCTURAL AND PROPULSION SYSTEM PROPERTIES REQUIRE ACCURATE MEASUREMENT OF DYNAMIC PROPERTIES IMPORTANTTO THE DESIGN OF ADVANCED AERONAUTICAL AND AEROSPACE VECHICLES. THE SPECIFIC INNOVATION ADDRESSED BY THIS PROPOSAL IS THE EMPLOYMENT OF A NON-INTRUSIVE, RUGGED OPTICAL IMAGING METHOD COMPATIBLE WITH ROUGH AND POORLY REFLECTING ADVANCED PROPULSION SYSTEM COMPONENTS. THIS IS AN INNOVATIVE APPROACH BECAUSE SUCH A METHOD BASED ON GUIDEDWAVE PROPAGATION PHENOMENA CAN USE THE LAMB WAVE TECHNIQUE IN WHICH MEASUREMENTS OF ACOUSTIC WAVE SPEEDS CAN BE DIRECTLY RELATED TO MATERIAL STIFFNESS PROPERTIES. IT IS BELIEVED BY THIS RESEARCH TEAM THAT THE PROPOSED APPROACH DETAILED IN THIS PROGRAM CAN ADDRESS THE ASSOCIATED OPTICAL DETECTION PROBLEMS IN THE AREA OF SURFACE ACOUSTICAL MEASUREMENTS EMPLOYING OPTICAL TECHNOLOGY. TECHNICAL OBJECTIVES INCLUDE IDENTIFICATION OF ELASTIC WAVE PARAMETERS AND TESTING REQUIREMENTS, EVALUATION OF A RUGGED MULTI-AXIS ACOUSTIC DISPLACEMENT SENSOR, INTEGRATION OF ACOUSTO-OPTICAL ULTRASONIC (AOU) DETECTION SUBSYSTEMS, ASSESSMENT OF TEST DATA AND DESIGN OF A PROOF-OF-CONCEPT SYSTEM FOR DEVELOPMENT AND TESTING IN THE PHASE II PROGRAM. SUCCESSFUL COMPLETION OF THESE OBJECTIVES WILL RESULT IN THEDEVELOPMENT OF THE PROPOSED AOU INSTRUMENTATION FOR MONITORING THE PERFORMANCE CHARACTERISTICS OF FLIGHT VEHICLES IN NASA'S ADVANCED STRUCTURAL SYSTEMS.