Accelerated insertion of metallic structural materials

Accelerated insertion of metallic structural materials

Keywords: Materials, Aircraft, Engines, Design

Development of metallic structural materials for advanced systems such as aircraft engines is a long and costly undertaking that often extends up to 15 years. Failure to provide fully characterized, production-ready materials on time has disrupted engine development, greatly increased system development costs, and now hampers development and limits insertion opportunities for new materials. The Accelerated Insertion of Materials (AIM) initiative was conceived and sponsored by the Defense Advanced Research Project Agency to combat this problem. AIM provides the opportunity to reduce the materials development cycle time by up to 50 percent and thereby lessen the lead time required for new materials.

General Electric (GE) Aircraft Engines has initiated research under the AIM program in collaboration with academia (Georgia Tech, Harvard University, Ohio State University, Princeton, and the University of Wisconsin) and industry(Boeing-Rocketdyne, Howmet, IIT Research Institute, Ladish, and Questek). AIM is generically extensible to other materials systems, however, the GE team will use a nickel-based superalloy turbine disk to develop, validate, and demonstrate the initial AIM system. The program is founded upon bringing about three systemic changes.

• revolutionize the way designers and materials engineers interact;

• achieve a leap forward in the application of computational materials science and integration with design engineering tools; and

• create an environment where the design/ materials team can learn from and build on previous developments.

These three changes will enable continual improvement in development productivity.

The AIM initiative embraces a new process for integrating design and materials engineering and a number of supporting strategies to accelerate acquisition of materials data. However, the centerpiece of the AIM system is the designer knowledge base. This computer system provides a framework for managing experimental data; executing linked models describing processing,microstructure, properties, and producibility (cost); and calculating confidence bounds for system predictions. The designer knowledge base informs design engineers about material performance, producibility, and cost and transfers materials information to design engineering computer-based analysis systems. The GE team will establish a materials representation, models, and uncertainty methods for integration within the designer knowledge base.

Materials representation – accurate modeling depends on the effective extraction and storage of processing and microstructural information, whereas the interoperability of these models to predict material system performance requires unambiguous information flow. The GE team will build a representation to accommodate the usual disparity among the time and length scales of materials phenomena, the path dependencies of microstructural evolution, the interactions among materials phenomena, and the variation of microstructure and properties as a function of location within a part. Representation of microstructure will use both stereological and advanced image feature extraction techniques.

Materials models – acceleration from the integrated AIM system depends on models with sufficient fidelity and robustness to confidently predict processing, microstructure and mechanical properties. The GE team will use available and emerging models to predict the effects of key process parameters on microstructure and properties. Models will emphasize those that capture the physics governing material-system behavior. Some of the commercially available modeling tools include ThermoCalcTM (thermodynamics), DICTRATM (kinetics),ProCASTTM (solidification), DEFORMTM (large strain deformation).

Uncertainty – the design of a complex system, such as an aircraft engine, must account for uncertainty inherent in materials behavior and manufacturing processes. The GE AIM team will apply Monte Carlo analysis and other advanced mathematical techniques to calculate the uncertainty produced by variations in processing history, microstructural features, defect content,measurement errors, or inadequacy of physically-based models.

The GE team will test the fully integrated designer knowledge base by comparing the mechanical property and cost projections against historical results for a fielded nickel-base superalloy, Rene88DT. This test and subsequent demonstration will be carried out to determine the accuracy of the system,provide proof-of concept, identify improvement opportunities, and assist in defining the AIM transition plan.

When developed and applied to materials development, accelerated insertion of materials will have lasting benefit for material dependent industries such as the aerospace sector. Overall and most important, the streamlined development process will significantly reduce development time and cost and thereby progressively erode the disparity between the materials and engine development cycles. Changes will be pervasive and permanent. This will decrease insertion risk, increase the number and frequency of newly introduced materials, and avoid research and development on non-essential materials and processes. As a consequence, materials will contribute more and help advance propulsion technologies and other industries.

Details available from: Dan Backman, Principal Investigator GE Aircraft Engines. Tel: +1 781 594 4554; Fax: 781 594 1691.