Recent advances in the study of structural materials compatibility with hydrogen.

Hydrogen is a ubiquitous element that enters materials from many different sources. It almost always has a deleterious effect on mechanical properties. In non-hydride-forming systems, research to date has identified hydrogen-enhanced localized plasticity and hydrogen-induced decohesion as two viable mechanisms for embrittlement. However, a fracture prediction methodology that associates macroscopic parameters with the degradation mechanisms at the microscale has not been established, as of yet. In this article, we report recent work on modeling and simulation of hydrogen-induced crack initiation and growth. Our goal is to develop methodologies to relate characteristics of the degradation mechanisms from microscopic observations and first-principles calculations with macroscopic indices of embrittlement. The approach we use involves finite element analysis of the coupled hydrogen transport problem with hydrogen-assisted elastoplastic deformation, thermodynamic theories of decohesion, and ab initio density functional theory calculations of the hydrogen effect on grain boundaries.