Modelling Hydrogen Embrittlement in Heterogeneous Welded Joints

This study presents the development and implementation of a numerical framework to assess the structural integrity of welded components subjected to hydrogen embrittlement (HE). The framework accounts for heterogeneous material properties and incorporates a hydrogen informed Gurson type damage model. Due to the inherent microstructural heterogeneity across the weld metal (WM) and heat affected zone (HAZ) regions, a spatially varying material response must be considered in numerical analysis. To address this, an element-specific property assignment strategy is adopted. The yield strength and hardening properties in the WM and HAZ regions are derived from a local hardness value, extracted from Vickers hardness maps of pipeline girth welds. Locally derived mechanical properties are assigned to each element in the numerical model to provide a description of the heterogeneous mechanical response. Different hydrogen-related parameters are assigned to the WM, HAZ and base metal, through explicit fusion line definitions based on a macro photograph of the girth welded joint. The proposed numerical framework allows for the detailed study of the HE in heterogeneous welded joints, capturing damage behavior and accounting for local variations in mechanical and hydrogen-related properties. It enhances the predictive capability of finite element simulations for assessing the integrity of girth welded pipelines operating in hydrogen environments.