FRACTURE TOUGHNESS TESTING OF ENGINEERING MATERIALS USING HYBRID QUANTITATIVE NONDESTRUCTIVE TECHNIQUES

NONDESTRUCTIVE TECHNIQUES RELATED TO THE QUANTITATIVE CHARACTERIZATION OF MECHANICAL PROPERTIES ARE OF HIGH INTEREST FOR DEVELOPING BETTER MODELS OF DAMAGE MECHANICS AND FAILURE PROCESSES IN VARIOUS TYPES OF ENGINEERING MATERIALS UNDER A VARIETY OF LOADING AND ENVIRONMENTAL CONDITIONS. TRADITIONAL MATERIAL TESTING TECHNIQUES REQUIRETHE DESTRUCTIVE EVALUATION AND REPETITIVE EXAMINATION OF THELABORATORY TEST SPECIMENS WHICH ARE NEITHER DESIRABLE NOR ECONOMICAL FOR IN SITU ASSESSMENT OF STRUCTURAL INTEGRITY AND SERVICE DEGRADATION. A MAJOR CONCERN IS THE NEED FOR SUITABLE, INEXPENSIVE AND ACCURATE NONDESTRUCTIVE METHODS FOR DETERMINING CRITICAL LOADS AND FLAW SIZES BY PROVIDING ABETTER INFORMATION BASE FOR FRACTURE MECHANICS AND LIFE PREDICTION WITHOUT REQUIRING SPECIAL SAMPLE PREPARATION. THE PROPOSED INSTRUMENTATION USING THE COMBINED ULTRASONIC ATTENUATION AND SPECKLE IMAGE CORRELATION STRAIN MEASUREMENTTECHNIQUES ADDRESSES THESE PROBLEMS BY PROVIDING A COMPACT, RAPID AND ROBUST NONDESTRUCTIVE EXAMINATION SYSTEM FOR EVALUATING THE MATERIAL MACROSCOPIC PROPERTIES AND SURFACE CRACK-OPENING DISPLACEMENTS AT CRITICAL LOCATIONS ON THE FULL SCALE OPERATING STRUCTURES. PHASE I OBJECTIVES INCLUDEEXTENSION OF THE FUNDAMENTAL CORRELATION BETWEEN ANALYTICAL ULTRASONIC NONDESTRUCTIVE EVALUATION AND MECHANICAL PERFORMANCE, EVALUATION OF A RUGGED ULTRASONIC ATTENUATION MEASUREMENT SYSTEM, INTEGRATION OF A SPECKLE CORRELATION-BASED STRAIN SENSING DEVICE, DEMONSTRATION OF A FRACTURE TOUGHNESS TESTER AND DESIGN OF A PROOF-OF-CONCEPT SYSTEM FOR DEVELOPMENT AND TESTING IN THE PHASE II PROGRAM. SUCCESSFUL COMPLETION OF THESE OBJECTIVES WILL RESULT IN ESTABLISHMENT OF SAFETY ASSURANCE, RELIABILITY AND ECONOMY IN DESIGN OF COMPONENTS OR STRUCTURES.