LOW CYCLE FATIGUE ENHANCEMENT OF BLADE ATTACHMENT

THIS PROGRAM WILL DETERMINE THE POTENTIAL FOR LIFE IMPROVEMENT, WEIGHT REDUCTION, AND HIGHER LOAD BEARING CAPABILITY OF AIRCRAFT ENGINE COMPONENTS MADE FROM EMERGING MATERIALS AND MANUFACTURING TECHNIQUES. THE GEOMETRIES TO BE STUDIED, BUT NOT LIMITED TO, ARE BOLT HOLES, BLADES, BLADE ATTACHMENTS, CUTOUTS, AND SCALLOPS. TESTING WILL BE CONSTANT AMPLITUDE CRACK GROWTH UNDER BOTH AMBIENT AND HIGH TEMPERTURE ENVIRONMENTS. SPECIMENS WILL HAVE INITIAL CRACK SIZES CONSISTANT WITH THE REQUIREMENTS OF THE PROPOSED ENGINE STRUCTURAL INTEGRITY PROGRAM (ENSIP). MATERIAL TO BE TESTED WILL BE TI 6AL-2SN-4ZR-2MO. OTHER EVALUATIONS TO BE PERFORMED INCLUDE QUALITATIVE PHOTOELASTIC ANALYSIS AND MEASUREMENTS OF DEFORMATIONS DUE TO THE FATIGUE ENHANCEMENT PROCESSES STUDIED. USE OF THE PATENTED SPLIT SLEEVE COLD EXPANSION (CX) SYSTEM AND SYSTEM VARIATIONS WILL BE THE METHOD BY WHICH BENEFICIAL RESIDUAL COMPRESSIVE STRESSES ARE IMPARTED INTO THE METAL AROUD STRESS CONCENTRATORS. THE RESIDUAL STRESSES LOWER THE EFFECTIVE TENSILE STRESSES WHICH PROPAGATE CRACKS. THE PROCESS HAS BEEN USED WIDELY FOR LIFE EXTENSION OF NEW AND IN-SERVICE AIRFRAMES. THESE SYSTEMS HAVE NOT BEEN FULLY EVALUATED FOR GAS TURBINE ENGINE APPLICATIONS.