SUMMARY

Ni-base superalloys are widely used in hot sections of gas turbine engines due to its high resistance to fatigue and creep at elevated temperatures. Due to the demands on improved performance and efficiency in applications of the superalloys, new materials are successively developed by manufacturers. Constitutive relations for the new materials need to be formulated accordingly to predict behaviors of the components under various loading conditions. Hierarchical multiscale modeling is a desirable way in many aspects to represent deformation mechanisms of these materials. The goal of this work is to develop a framework for hierarchical multiscale modeling network by linking several fine scale models and incorporate the microstructure attributes into the framework to improve the predictability of the constitutive model. The length scales used in this scheme range from nanometers of phase field model to meters in engine components level. The phase field method employs the microtwinning mechanism, and the critical stresses obtained from this model are used as inputs to a grain scale crystal plasticity model. The crystal plasticity model incorporates its microstructure attributes by homogenizing them and bridges the subgrain and the macro scale models. The flow rule and hardening laws comprise the constitutive relations of this material, and the grain scale crystal plasticity model can be calibrated to experimental data for a range of microstructures. The macroscopic ISV model parameters are determined based on the stress-strain-time data using an optimization scheme which provides the linkage from the microstructures to stress-strain-time responses and then to the ISV model parameters. This framework should provide a better physical based interpretation of material behaviors and an improved adaptability to a broader scope of materials covering an extensive range of microstructures with relatively smaller number of experiments conducted.