J-52 BOLT HOLE REPAIR USING A SHAPE MEMORY ALLOY EXPANSION BUSHING

THIS PROJECT PROPOSES TO REPAIR FATIGUE DAMAGE IN J-52 COMPRESSOR DISCS USING A NICKEL-TITANIUM "SHAPE MEMORY" ALLOY EXPANSION BUSHING. BUSHING INSERTS OF CONVENTIONAL ALLOY MATERIALS CAN RESULT IN SIGNIFICANT IMPROVEMENTS IN FATIGUE STRENGTH AT AMBIENT TEMPERATURES WHEN THE MATERIAL SURROUNDING THE BOLT HOLE IS INITIALLY COLD EXPANDED TO PLACE IT IN COMPRESSION. THE COMPRESSIVE STRESSES SO DEVELOPED WILL RELAX TO SOME DEGREE AT THE ELEVATED TEMPERATURES AT WHICH COMPRESSOR DISCS OPERATE, AND IT CAN BE EXPECTED THAT THE EFFECTIVENESS OF THE CONVENTIONAL BUSHING WOULD DIMINISH OVER A PERIOD OF TIME. IT IS FELT THAT "SHAPE MEMORY" ALLOY BUSHINGS, BY MAINTAINING THIS COMPRESSIVE STRESS, WILL RESULT IN PROLONGED EFFECTIVENESS AT ELEVATED TEMPERATURES. THE USE OF "SHAPE MEMORY" ALLOY BUSHINGS WOULD HAVE SEVERAL OTHER ADVANTAGES, SUCH AS UTILIZATION FOR SMALL HOLES. THIS PROGRAM PROPOSES TO COMPARE THE FATIGUE STRENGTH OF TEST SPECIMENS CONTAINING EITHER CONVENTIONAL OR "SHAPE MEMORY" BUSHINGS, BOTH ASMANUFACTURED AND AFTER ELEVATED TEMPERATURE EXPOSURE.