ELECTROMAGNETIC DETECTION OF STRESS AND CRACK PROPAGATION IN CRITICAL AIRCRAFT COMPONENTS

NON-DESTRUCTIVE TESTING RESEARCH HAS BEEN PRIMARILY CONCEREND WITH DEFECT DETECTION AND CHARACTERIZATION WITH RELATIVELY LITTLE EFFORT ON NDT TECHIQUES FOR MEASURING STRESS, PREDICTING FATIGUE DAMAGE PRIOR TO CRACKING AND MONITORING OF CRACK PROPAGATION IN CRITICAL AIRCRAFT COMPONENTS. THESE PROBLEMS ARE OF SIGNIFICANCE TO THE AIRCRAFT INDUSTRY AND TO THE NAVY BECAUSE OF THE POTENTIAL FAILURE DUE TO STRESS CORROSION CRACKING, INTER- GRANULR ATTACK, THERMAL SHOCK AND OTHER SERVICE INDUCED MODES. THIS PROGRAM DETECTION AND MEASUREMENT OF STRESS AND CRACK PROPAGATION IN FERROMAGNETIC AND NON-FERROMAGNETIC MATERIALS. INITIALLY, CONVENTIONAL EDDY CURRENT PROBES WILL BE USED TO DETECT IMPEDANCE CHANGES AS MATERIALS ARE MECHANICALLY LOADED IN A MATERIAL TESTING MACHINE. A MAJOR OBJECTIVE OF THE RESEARCH WILL BE THE CORELATION OF PROBE IMPEDANCE CHANGES WITH BOTH STRESS LEVEL AND CRACK GROWTH. IN ADDITION, SEVERAL LESS-CONVENTIONAL ELECTROMAGNETIC MEASURING TECHNIQUES WILL BE INVESTIGATED. SUCCESSFUL COMPLETION OF THE PROJECT OBJECTIVES WILL PROVIDE THE AIRCRAFT INDUSTRY WITH A COST- EFFECTIVE, RELIABLE METHOD OF DETERMINING BOTH STRESS LEVELS AND CRACK GROWTH IN CRITICAL AIRCRAFT COMPONENTS.