Physics-Based Probabilistic Life-Prediction Model for Advanced Hot-Section Turbine Disk Materials With Gradient Microstructures

The proposed approach will build on existing probabilistic micromechanics model for failure analysis to include gradient microstructures. This effort will develop physics based damage models for the gradient microstructures focusing on complete damage evolution of the transition zone between the bore (fine grain) and the rim (coarse grain). The mechanisms considered will include 1) fatigue, 2) crack growth 3) tensile elongation and 4) creep. These four failure modes represent the primary damage mechanisms active in high temperature turbine rotors. The operating environment of todays jet engine requires high reliability with respect to these damage modes. Improved fatigue and crack growth at the bore and creep in the rim are the primary reasons behind the development of dual microstructure alloys. Particular focus under the proposed effort is to develop microstructural damage models for the transition zone where the stress gradient, temperature gradient along with the microstructure gradient will strongly influence the damage initiation and growth in a multiaxial stress field. The Phase I goal is prove concept feasibility for extending and applying probabilistic microstructure based modeling approaches to life turbine engine components with gradient microstructure. The models will be inherently mechanistic, suitable for application to a broad range of materials. BENEFIT: The New Generation Bomber or Long-Range Strike (LRS) program will revitalize the AF bomber to adapt to the changing operating environment, which includes tougher air defenses, longer flight distances, and time-critical missions. To meet these stringent new requirements of future war fighting scenarios, weapon system must be extremely fuel efficient.  To attain high fuel efficiency the engine thrust-to-weight must be maximized and unnecessary weight must be eliminated while maintaining engine reliability and durability. The technology to be developed from this SBIR will allow for rotor design optimization to reduce unnecessary weight. The turbine rotors will be designed to operate at extreme temperatures to maximize performance and mission flexibility, obtain the lightest weight possible to maximize thrust- to-weight, and do so with enhanced turbine durability. This proposal effort will evaluate the durability of a design configuration which could produce a cost savings from up to 1% increase in fuel efficiency or $500M for a fleet of 1000 engines over 15 years of service.