Life Prediction Methodologies for Aerospace Materials Annual Report, 2003
Interim rept. 25 May 2002-24 May 2003
DAYTON UNIV OH RESEARCH INST
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The ability to predict turbine-engine-materials behavior under operating conditions is an important facet of Phase 0 DARPA Prognostics programs. Studies of nickel-based superalloys - Rene 88DT, IN-100, and Waspaloy -- have been undertaken to assess a baseline mechanical props. of material extracted from retired turbine disks, b microstructures of each alloy using optical microscopy and SEM, including OIM, c environment and load-history effects on FCG props., and d capability of fracture surface marking for crack-front location during spin-pit testing. Studies of retained residual stresses from surface treatments such as shot peening and material processing and service, i.e., bulk residual stresses, have been undertaken to incorporate residual stresses into future damage-tolerance based life management programs. Capabilities directed at integration of experiment and analysis are new test software, enhanced thermal imaging system at elevated temperature, and improved crack length measurement techniques. Analytical models have been developed for the relaxation of shot peening-induced residual stresses as a result of thermal exposure, and for simulating the shot peening process in detail to estimate both residual stress and plastic strain distributions in processed parts. Using statistically based data for the size, shape and spacing of typical defects, Monte Carlo simulations were performed to determine probability distributions for localized stress amplification factors in bulk samples of IN100.
- Properties of Metals and Alloys
- Jet and Gas Turbine Engines