Modelling of Hydrogen-Induced Failure in Polycrystalline Materials through a Strain Gradient Crystal Plasticity Framework

Hydrogen-induced failure, which affects a wide range of metals, occurs when hydrogen particles diffuse within the lattice structure of materials exposed to hydrogen-rich environments. Various studies on hydrogen-induced failure has demonstrated that the presence of hydrogen atoms significantly affects crack initiation and propagation, leading to reductions in ductility, strength, tough- ness, and fatigue life. Several theories have been proposed to explain the mechanisms involved in hydrogen-induced failure, such as hydrogen-enhanced plasticity and hydrogen-enhanced decohesion. These mechanisms connect hydrogen-induced damage to the interactions occurring between hydrogen and imperfections within the material. This study is used to model the hydrogen- enhanced decohesion mechanism, focusing on hydrogen-induced intergranular failure as the primary failure mechanism. Presented novel framework integrates a strain gradient crystal plasticity model with a potential-based mixed-mode cohesive zone formulation and a stress-driven hydrogen transport model. To explore size and nonlocal effects on hydrogen-induced failure, 3D polycrystalline representative volume elements (RVEs) with different initial hydrogen concentrations are simulated. The findings show that incorporating strain gradient effects significantly increases hydrogen accumulation near grain boundaries, altering the failure path.