Generation mechanism and safety state identification of hydrogen-induced cracking in ultra-high strength steel wires

The ultra-high strength steel wires of large-span bridge cables are subjected to high stress during long-term service in coastal or river environments. Hydrogen generated by electrochemical corrosion and during Zn/Zn–Al alloy electroplating can adsorb and diffuse into the wire, leading to hydrogen-induced damage. To investigate hydrogen embrittlement (HE) susceptibility and hydrogen-induced crack initiation and propagation, acoustic emission (AE) signals from hydrogen non-charged and charged 1670, 1770, and 1860 MPa steel wires were monitored during slow strain rate tensile (SSRT) tests. Hydrogen charging significantly reduced elongation, section shrinkage, and fracture ductility. The HE susceptibility indexes (Iδ, Iψ, and Iε), calculated from elongation, section shrinkage, and true strain, increased with strength. Ductility reduction caused abrupt micro- and macro-crack initiation and restricted dislocation deformation. Hydrogen bubble evolution was identified as the main AE source, resulting in increased cumulative energy and hits. AE hits and cumulative energy rose sharply at brittle fracture. K-means clustering classified AE signals into three clusters, revealing correlations between AE characteristics and their sources.