Hydrogen diffusion characteristics and behavior in cracked metal: A numerical analysis approach

This study examines the influence of defect geometry on hydrostatic stress and hydrogen accumulation at crack tips during hydrogen diffusion in metallic materials, specifically iron, aluminum, and titanium. A coupled stress–diffusion framework is employed to evaluate how variations in defect width and length affect stress distribution and hydrogen transport under different environmental conditions. The results indicate that defect geometry plays a critical role in hydrogen embrittlement behavior, with defect width exerting a stronger influence than defect length. Wider defects reduce crack-tip hydrostatic stress, leading to lower hydrogen accumulation and a decreased risk of hydrogen-induced cracking, while increased defect length shows a comparatively moderate effect. In addition, environmental pH significantly affects hydrogen diffusion, with acidic conditions promoting hydrogen accumulation and neutral to alkaline environments mitigating embrittlement susceptibility. Material-dependent diffusion behavior is also observed, highlighting the combined effects of mechanical stress, defect geometry, and environmental factors. Overall, the findings emphasize the importance of controlling both geometric and environmental parameters to minimize hydrogen embrittlement and enhance the structural integrity of metallic components. This study investigates the effects of defect geometry (width and length) on hydrostatic stress and hydrogen concentration at the crack tip during hydrogen diffusion in metallic materials (Fe, Al, and Ti). Increasing defect width significantly reduces hydrostatic stress and hydrogen accumulation, whereas defect length has a weaker effect. Widening the defect from 0.3 mm to 0.9 mm reduces hydrostatic stress by 42.3% and hydrogen concentration by 27.1%, while increasing defect length from 8 mm to 12 mm leads to an approximately 10% reduction in hydrogen concentration. Environmental pH strongly influences hydrogen behavior, with acidic conditions promoting accumulation and neutral or alkaline environments mitigating embrittlement. Iron shows lower hydrogen accumulation due to its higher diffusion rate. As a representative example, graphical results illustrate hydrostatic stress and hydrogen flux in the deformed configuration (a: 0.3 mm; c: 0.6 mm; e: 0.9 mm) and hydrogen concentration with hydrogen flux (b: 0.3 mm; d: 0.6 mm; f: 0.9 mm) after 2 hours.