FATIGUE CRACK GROWTH RETARDATION/ACCELERATION EFFECTS IN ELEVATED TEMPERATURE ENVIRONMENTS

AN EFFORT IS PROPOSED TO DEVELOP A FRAMEWORK FOR THE MODELING OF FATIGUE CRACK GROWTH RETARDATION AND ACCELERATION IN THERMALMECHANICAL AEROSPACE FLIGHT ENVIRONMENTS. THE PROPOSED TASKS INCLUDE REVIEW OF EXPECTED LOAD/STRESS AND TEMPERATURE PATTERNS, CANDIDATE MATERIALS AND AVAILABLE MATERIAL PROPERTIES; DEVELOPMENT OF A CANDIDATE CRACK GROWTH MODEL; DEFINITION OF THE TEST PROGRAM NEEDED TO VALIDATE THE MODEL; AND DEVELOPMENT OF A SOFTWARE SPECIFICATION TO INCORPORATE THE MODEL INTO CURRENT ANALYTICAL TOOLS. THE END PRODUCT OF THE RESEARCH, PHASE I AND II, WILL BE A SOFTWARE PACKAGE FOR PREDICTING FATIGUE CRACK GROWTH BEHAVIOR THAT ACCOUNTS FOR THE EFFECTS OF CRACK GROWTH RETARDATION AND ACCELERATION IN ELEVATED TEMPERATURE, THERMO-MECHANICAL ENVIRONMENTS.