Multiphysics Modeling of Stress–Hydrogen Diffusion Interaction in X80 Pipeline Steel Containing Double Notches

With the increasing deployment of hydrogen pipeline transportation, hydrogen embrittlement (HE) of high-strength pipeline steels such as X80 has become a critical concern for structural integrity. In service, surface defects such as notches formed by manufacturing imperfections or mechanical damage can significantly accelerate hydrogen ingress under combined mechanical loading and hydrogen exposure. In this study, a coupled multiphysics finite element model integrating solid mechanics and hydrogen diffusion was developed in COMSOL to investigate stress-assisted hydrogen transport in X80 pipeline steel containing double surface notches. The effects of notch geometry (angle, depth, and shape) and spatial configuration (spacing) on stress distribution and hydrogen accumulation were analyzed. The results show that smaller notch angles and sharper defects produce higher stress concentration and stronger hydrogen localization, while increasing notch depth enlarges high-stress and hydrogen-rich regions. Reduced notch spacing causes stress field superposition and multi-center hydrogen accumulation, increasing embrittlement susceptibility.