Advanced Modeling Tools for Processing and Lifing of Aeroengine Components

Lifing is one of the main challenges for aeroengine manufacturers. For fatigue prediction, attention has been focused on the crack initiation mode depending on stress level and initial microstructure. Microstructure prediction during the component manufacturing, especially for final heat treatments and final forging operations, is required if it is to be included in fatigue analysis. Reliable tools are now available for basic nickel-based alloys such as Inconel 718. For other alloys, notably gamma/gamma' alloys, research is still being performed in close partnership with academia. Globally, two main trends are emerging; first, one of our main interests is to develop the modeling capability for the entire manufacturing process, including ingot conversion and billet forging. Second, new approaches are still under development by introducing more physical considerations through full-field models, which are very useful for a better understanding of specific issues such as heterogeneous grain growth. From a component lifing point of view, the initial state of stress is also a key parameter to be considered. One method for the control of residual stresses is application of a pre-spinning process. Finally, a standard lifing methodology is explained and improvements are proposed; in particular, size effect is used to model notch specimen life considering surface or internal initiation.