High Fidelity Reduced Order Modeling of Polycrystalline Materials

Air Force Office of Scientific Research, Multi-Scale Structural Mechanics and Prognosis

The objective of this research is to reduce the prohibitive computational cost associated with the mathematical homogenization of polycrystalline materials. Eigenstrain based representation of the inelastic response field is employed to approximate the microscale boundary value problem using an approximation basis of much smaller order. The reduced order model takes into account the grain-to-grain interactions through influence functions that are numerically computed over the polycrystalline microstructure. The proposed approach is also endowed with a hierarchical model improvement capability that allows accurate representation of stress and deformation state within subgrains. Two orders of magnitude efficiency is achieved compared with computational homogenization, which allows accurate macro analysis of polycrystalline structures.

Crystal Plasticity Finite Element Modeling of Fatigue and Creep-Fatigue of Alloy 617 at High Temperature

U.S. Department of Energy (DoE), Nuclear Energy University Programs (NEUP) initiative

The objective of this research is to understand the deformation and failure mechanisms Nickel-based super alloy Inconell 617, which is a candidate structural material for very high temperature reactor (VHTR) intermediate heat exchangers. In the collaborative project, we aimed at developing a experimentally validated microstructure-based creep fatigue model, to investigate the creep-fatigue interaction and ultimately achieve the life prediction capability. To achieve this goal, crystal plasticity constitutive laws are used to characterize the dislocation slip of the grains while cohesive zone models are adopted to capture the intergranular damage, both of which are incorporated into a finite element framework on fully discretized statically representative microstructures.