Mechanistic investigation of weak magnetic internal detection for hydrogen-induced stress damage in pipelines at the atomic scale

Localized hydrogen enrichment within pipeline materials under stress can readily induce the initiation and propagation of internal cracks, which constitutes a major cause of abrupt pipeline failure. Weak magnetic internal detection technology, recognized as an effective method for evaluating early damage in ferromagnetic materials, demonstrates considerable potential for identifying hydrogen-induced damage. This study aimed to explore the formation of hydrogen-induced damage by investigating its underlying mechanism. The critical stress required for atomic slip in the α-Fe-H system was analyzed utilizing the first-principle, and the correlation between stress and magnetization intensity at hydrogen-damaged sites was assessed using magnetoelastic effect. Based on magnetic charge theory, an analysis model for hydrogen adsorption-induced dislocation (AID) magnetic signal was developed. The model facilitated a multi-dimensional analysis of the mechanisms through which hydrogen intensified local stress concentration within the pipeline, leading to abnormal variations in magnetic signals. Relevant evaluation metrics were proposed to effectively characterize hydrogen-induced damage in the pipeline, and conducted systematic experimental verification. The results indicate that the energy barrier required to overcome hydrogen-induced damage varies under different influencing factors. The weak magnetic signal calculated using the AID magnetic signal model can effectively characterize hydrogen-induced damage. Compared to other vacancies, hydrogen located on the slip plane at FractionalXYZ (1.000, 0.500, 0.417) had the most significant impact on the weak magnetic signal, with the signal mean variation (C_average) of 74 %. Among different hydrogen concentrations, high hydrogen concentration exhibited to have a relatively higher impact on the magnetic signal, with an average (D_average) change rate of 65 %.