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A rule-based expert system for high-temperature fatigue life estimation (HTF) is currently under development. This system will augment a designer's ability to make preliminary engineering decisions on the durability of high-temperature components. It may also be used as a verification tool, to establish bounds for fatigue life estimates performed using other, perhaps more sophisticated, methods. The system uses an expert system shell (C Language Production System—CLIPS). The rules in the system select appropriate fatigue life models based on the available material properties and the application. The rules and functions in the HTF system incorporate materials property data (sufficient for the fatigue life models used) for a small group of aerospace materials. If the system cannot find the user-specified material in the rule base, the user is queried for the materials property data. The program calculates (or approximates) the required fatigue life model parameters and performs the appropriate life calculation. The lower bound on the predicted life, based on the estimated error in the material properties, boundary condition data, and on experience with the fatigue life model, is determined via a direct Monte Carlo simulation. Fatigue life models incorporated into the system make allowances for the influence of multiaxial stress/strain states and creep-fatigue-environment interactions. The scope of this project is limited to alloys used in high-temperature, high mechanical/thermal stress applications.
expert systems, low cycle fatigue, high-temperature fatigue life models, Monte Carlo simulation, test automation, fatigue (materials), testing methods, data analysis
Research engineer, Vehicle Propulsion Directorate, Army Research Laboratory, NASA Lewis Research Center, Cleveland, OH