Abstract

Multiscale microstructural and micromechanical modeling has arisen as a candidate to improve upon the classical methodologies for evaluation of fatigue crack initiation and propagation, both concerning improving our understanding of the fundamental material deformation and damage processes as well as in establishing more accurate design rules for engineering purposes. By exploiting methodologies of multiscale materials modeling, the vision is that engineering material properties can be directly computed based on microstructural scale analysis of single crystal plasticity and damage evolution. The models can then be further used to simulate the various dependencies affiliated with fatigue damage arising from material microstructure, such as the effects of stress triaxiality, compressive loading, and overall complex stress states. The overall goal of these efforts is the general decrease in empiricism, inaccuracy and affiliated uncertainty in the fatigue modeling and design chain. Current work utilizes novel crystal plasticity coupled damage model to evaluate the inclusion of steel microstructure interactions with the objective of better understanding and quantifying the role inclusions play concerning nucleation and growth of microstructure scale fatigue cracks. The approach is microstructural, i.e., material characteristics such as microstructural morphologies, individual phases, and inclusions are included explicitly in the numerical finite element models, and the subsequent behavior concerns single crystal deformation and initiation of fatigue. The analysis uses a micromechanical model where crystal plasticity and damage directly couple. A case study is carried out for primarily martensitic quenched and tempered steel for machine construction. The results suggest potential ways of exploiting multiscale materials modeling in the design of fatigue resistant microstructures, optimization of material solutions and improved fatigue design of products and components.