We present a novel computational framework to assess the structural integrity of welds. In the first stage of the simulation framework, local fractions of microstructural constituents within weld regions are predicted based on steel composition and welding parameters. The resulting phase fraction maps are used to define heterogeneous properties that are subsequently employed in structural integrity assessments using an elastoplastic phase field fracture model. The framework is particularised to predicting failure in hydrogen pipelines, demonstrating its potential to assess the feasibility of repurposing existing pipeline infrastructure to transport hydrogen. First, the process model is validated against experimental microhardness maps for vintage and modern pipeline welds. Additionally, the influence of welding conditions on hardness and residual stresses is investigated, demonstrating that variations in heat input, filler material composition, and weld bead order can significantly affect the properties within the weld region. Coupled hydrogen diffusion-fracture simulations are then conducted to determine the critical pressure at which hydrogen transport pipelines will fail. To this end, the model is enriched with a microstructure-sensitive description of hydrogen transport and hydrogen-dependent fracture resistance. The analysis of an X52 pipeline reveals that even 2 mm defects in a hard heat-affected zone can drastically reduce the critical failure pressure.

翻译：本文提出了一种新颖的计算框架，用于评估焊接头的结构完整性。在该模拟框架的第一阶段，基于钢材成分和焊接参数，预测焊接区域内微观结构组成的局部分数。所得的相分数分布图用于定义非均匀材料属性，随后这些属性被应用于采用弹塑性相场断裂模型的结构完整性评估中。该框架特别针对氢气输送管道的失效预测，展示了其在评估现有管道基础设施改造用于输送氢气的可行性方面的潜力。首先，通过对比传统与现代管道焊缝的实验显微硬度分布图，验证了工艺模型的准确性。此外，研究了焊接条件对硬度和残余应力的影响，结果表明热输入、填充材料成分和焊道顺序的变化会显著影响焊接区域的性能。随后，进行了氢扩散-断裂耦合模拟，以确定氢气输送管道发生失效的临界压力。为此，模型引入了对氢传输的微观结构敏感描述以及依赖于氢浓度的断裂抗力表征。对X52管道的分析表明，即使在硬质热影响区中存在2毫米的缺陷，也会显著降低临界失效压力。