Residual stress redistribution in pipeline welds resulting from laboratory-scale specimen extraction determined by neutron diffraction

Welding processes used in pipeline construction are known to introduce residual stresses that can significantly impact their fatigue and fracture properties. Environmental factors such as corrosion or hydrogen embrittlement can further exacerbate this issue leading to premature failure. While mechanical testing on full-scale pipe welds is ideal, it is often impractical, especially when large data sets are required. The fatigue and fracture group at the National Institute of Standards and Technology (NIST) has performed extensive mechanical testing on pipeline welds in hydrogen environments to assess weld qualification and effects of hydrogen embrittlement. However, the degree to which residual stress is affected by machining and preparing small-scale test specimens and how their mechanical properties are representative of real-world pipelines remains a topic of debate. Here, we present neutron diffraction results that characterize the redistribution of residual stress in a pipeline weld when extracting specimen geometries commonly used in laboratory-scale mechanical testing. Such findings provide insights into the role of residual stress on laboratory measurements of fatigue and fracture and the implications for future standards development.