SUMMARY

Hydrogen embrittlement is a long-standing issue in materials science and engineering with a multitude of competing hypotheses and theories. Despite advances in experimental and computational capabilities, common understanding of contributing phenomena has not yet been achieved. Hence, a more complete understanding of hydrogen embrittlement processes operating at multiple length and time scales is still an open challenge that justifies the current research. In this work, a unique approach is taken to incorporate a wide range of experimental, computational, and analytical approaches across multiple length scales to produce a mechanistically motivated hydrogen embrittlement model for fracture and fatigue. This research describes and simulates the complex interplay between hydrogen, hydrogen-related defects, dislocations, and dislocation substructures. The model is developed in a crystal plasticity context and implemented in a finite element framework to simulate the hydrogen embrittlement of austenitic stainless steels, structural materials important in energy applications. The proposed research extends current understanding through the development of: i. a physically-based crystal plasticity model developed to capture the evolution of dislocation substructure and material behavior during cyclic loading, ii. a hydrogen transport and trapping model that considers dislocation-mediated transport mechanisms and a more complete set of hydrogen traps, and iii. a fully coupled chemo-mechanical model to capture the effects of hydrogen in reducing crack tip ductility, leading to embrittlement effects.