Numerical investigation of hydrogen embrittlement effects in pipelines under varying constraint conditions: Implications for structural integrity in hydrogen transport

This work addresses the influence of hydrogen embrittlement on the fracture resistance and structural integrity of high-strength pipeline steels under conditions representative of high-pressure hydrogen transport. A finite element framework incorporating hydrogen transport and stress-assisted diffusion is employed to quantify the coupled effects of crack-tip constraint, plasticity, and hydrogen accumulation in cracked pipeline geometries. Comparative analyses with a standard compact tension specimen are conducted to establish correlations between laboratory-scale measurements and full-scale structural behavior. The numerical results are then interpreted within the context of Fitness-for-Service (FFS) methodologies, using the Failure Assessment Diagram (FAD) approach prescribed in API 579 and ASME B31.12, to evaluate the implications of hydrogen-assisted degradation on flaw tolerance and safe operating limits. Overall, the study provides an engineering-oriented assessment framework that bridges detailed numerical modeling with practical integrity evaluation procedures for pipelines in hydrogen service. • Finite element framework couples hydrogen diffusion with fracture mechanics. • Analyses quantify crack-tip constraint effects in hydrogen-exposed pipelines. • Comparison with compact tension specimen links lab data to pipeline behavior. • Results interpreted within Fitness-for-Service (FAD-based) methodology. • Practical implications for hydrogen pipeline integrity assessment.