A comparative finite element study of stress-assisted and non-stress-assisted hydrogen diffusion at a triangular notch in API 5L X52 steel

• A novel finite element model compares stress-assisted and non-stress-assisted hydrogen diffusion in API 5L X52 steel. • The study reveals that stress-assisted diffusion leads to significantly higher and more localized hydrogen concentrations at a triangular notch compared to non-stress-assisted models • A comprehensive parametric study systematically investigates the influence of notch angle, aspect ratio, and prescribed displacement on hydrogen accumulation and stress profiles. • Hydrostatic stress is identified as the primary driving force for hydrogen transport, with its magnitude directly correlating with applied displacement. • The maximum hydrogen concentration of 12.611 arbitrary units was achieved at a notch angle of 10°, an aspect ratio of 0.1, and a prescribed displacement of 0.1 mm. • Quantitative findings provide critical data for predicting and mitigating hydrogen embrittlement, offering valuable insights for the safety and integrity assessment of pipeline infrastructure. This research presents a comprehensive model and simulation to analyze hydrogen concentration at the triangular notch of API 5L X52 steel, critical for understanding its susceptibility to hydrogen embrittlement. The study employs both stress-assisted and non-stress-assisted diffusion models within COMSOL Multiphysics, concurrently solving Solid Mechanics and Diffusion in Solids interfaces. A parametric study systematically investigates the influence of the triangular notch angle ( θ ), varied from ( 10 o ) to ( 90 o ), and an aspect ratio ( a r , fracture height to steel height) ranging from 0.1 to 0.4. Prescribed displacements ( P d ) of 0.025 mm, 0.05 mm, and 0.1 mm are applied to the right end of the steel to evaluate its mechanical response and hydrogen ingress over a two-hour time-dependent analysis. Results clearly demonstrate the profound influence of mechanical stress on hydrogen accumulation. The stress-assisted diffusion model consistently predicts significantly higher and more localized hydrogen concentrations at the notch tip, particularly under increasing prescribed displacements, compared to the more uniform and lower concentrations observed with the non-stress-assisted model. The study identifies specific parameter combinations that yield peak values for key variables, as summarized in the accompanying tables. Notably, the maximum von Mises stress of 965.56 MPa was observed with θ = 45°, a r = 0.1, and P d = 0.1 mm. Similarly, the highest hydrostatic stress, reaching 659.62 MPa, occurred at θ = 60°, a r = 0.1, and ​ P d = 0.1 mm. Crucially, the maximum hydrogen concentration at the fracture tip, 12.613 (mol/m 3 ), was achieved with θ = 10°, a r = 0.1, and P d ​ = 0.1 mm.