SUMMARY

The proposed research intends to develop a method to further employ and advance computational micromechanics methods developed over the past few years that consider combined effects of microstructure, residual stresses, inclusions, pores, and notches on the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) behaviors of a powder metallurgy processed polycrystalline Ni-base superalloy, IN100, and a cast single-crystal Ni-base superalloy, Rene' N4. A microstructure-sensitive computational crystal plasticity model will be used to compute the distribution of fatigue indicator parameters (FIPs) within regions of stress concentrators (inclusions, pores, notches) with and without prescribed compressive residual stresses. These FIP distributions will then be used in conjunction with deterministic crack formation and growth algorithms that account for cyclic stress redistribution to estimate fatigue life variability, a new feature of this framework. The general approach can be used to advance integrated computational materials engineering (ICME) by predicting variation of fatigue resistance and minimum life as a function of heat treatment/microstructure and surface treatments for a given alloy system and providing support for design of materials for enhanced fatigue resistance. In addition, this framework can reduce the number of experiments required to support modification of material to enhance fatigue resistance, which can lead to accelerated insertion (from design conception to production parts) of new or improved materials for specific design applications. Elements of the framework being advanced in this research can be applied to any engineering alloy.