CROSS-CORRELATION OPTICAL STRAIN SENSOR FOR WIND TUNNEL TEST INSTRUMENTATION

AEROSPACE STRUCTURES/MODELS ARE SUBJECTED TO HIGH TEMPERATURES AND STRONG AERODYNAMIC FORCES UNDER CAREFULLY CONTROLLED ENVIRONMENTAL CONDITIONS DURING INSTRUMENTED LABORATORY TESTING. WIND TUNNEL TESTING REQUIRES INSTRUMENTATION WHICH IS RUGGED, RELIABLE, ACCURATE AND PROVIDES TEST DATA QUICKLY TO THE TEST OPERATOR. MEASUREMENTS OF STATIC AND DYNAMIC STRAINS AND PROOF TESTING ON AEROSPACE STRUCTURAL MODELS ARE PERFORMED IN VARIOUS TYPES OF WIND TUNNELS. THE TYPICAL STRAIN USED IN SUCH APPLICATIONS INHERENT LIMITATIONS IN VERY HIGH TEMPERATURES, SUCH AS SIGNAL REPRODUCIBILITY AND INCOMPATIBILITY WITH THE TEST SURFACE. THE PROPOSED LASER SPECKLE-BASED, CROSS-CORRELATION STRAIN SENSOR ADDRESSES THESE PROBLEMS BY PROVIDING A FLEXIBLE, NONCONTACTING SYSTEM FOR EVALUATING THE LARGE STATIC AND DYNAMIC STRAIN FIELDS ON THE SURFACE OF ADVANCED STRUCTURAL MATERIALS AT TEMPERATURES OF 1100 CENTIGRADE AND HIGHER. PHASE I OBJECTIVES INCLUDE IDENTIFICATION OF HIGH-TEMPERATURE HIGH-LEVEL STRAIN MEASUREMENT REQUIREMENTS, CONFIGURATION OF RUGGED INTERROGATING OPTICS, INTEGRATION OF SOLID-STATE IMAGING DEVICES, ASSESSMENT OF TEST DATA AND DESIGN OF A PROOF-OF-CONCEPT CROSS-CORRELATION OPTICAL STRAIN SENSOR FOR DEVELOPMENT AND EXTENSIVE TESTING IN THE PHASE II PROGRAM. SUCCESSFUL COMPLETION OF THESE OBJECTIVES WILL RESULT IN A RESEARCH TOOL FOR MONITORING THERMO-MECHANICAL STRAIN FIELDS AND MECHANICAL PROPERTIES OF MODEL AEROSPACE STRUCTURES AT VERY HIGH OPERATING TEMPERATURES AND LOW/HIGH STRAIN RATES. THE NONCONTACTING MEASUREMENTS OF HIGH LEVEL STRAINS AT ELEVATED TEMPERATURES AND HOSTILE ENVIRONMENTS CAN ULTIMATELY BE USED TO DETERMINE THE FATIGUE LIFE OF THE AEROSPACE STRUCTURAL SYSTEMS.