NONDESTRUCTIVE EVALUATION OF CERAMIC USING SYSTEM IDENTIFICATION

CERAMIC MATERIALS ARE UNDER CONSIDERATION FOR STRUCTURAL COMPONENTS IN ADVANCED HEAT ENGINES FOR SEVERAL REASONS. THE PRIMARY MOTIVATION IS THEIR HIGH STRENGTH UNDER SIGNIFICANTLY INCREASING OPERATING TEMPERATURES. THE USE OF THESE HIGH TEMPERATURE MATERIALS WILL PERMIT BETTER FUEL EFFICIENCY AND REDUCE COOLING SYSTEM REQUIREMENTS. DUE TO THEIR ATOMIC STRUCTURE, CERAMICS INTRINSICALLY EXHIBIT LOW STRAIN TOLERANCE AND LOW FRACTURE TOUGHNESS. LOW TOUGHNESS, WHEN COMBINED WITH DESIRED TENSILE STRESS STATES, USUALLY RESULTS IN VERY SMALL CRITICAL FLAW SIZE. THE PROGRAM CONSISTS OF TESTING STRUCTURAL ELEMENTS OF SIMPLE CONSTRUCTION. IT WILL BE DETERMINED WHETHER THE RANDOM DECREMENT (RANDOMDEC) TECHNIQUE CAN CORRECTLY ASSESS DAMAGE LEVELS, CONSISTENT SIGNATURES, AND DAMPING AS A FUNCTION OF FREQUENCY FOR THESE STRUCTURAL ELEMENTS.