Role of residual stresses and strains after preloading in notch-induced hydrogen embrittlement of cold-drawn pearlitic steel wires for prestressed concrete structures

Abstract

[EN] Prestressing steel wires exhibit a high susceptibility to hydrogen embrittlement (HE). This failure is caused by localized hydrogen accumulation that promotes hydrogen assisted microstructural damage (HAMD) resulting in catastrophic fracture. The key phase of this phenomenon is hydrogen diffusion, a process highly dependent on non-uniform stress and plastic strain fields. Accordingly, the hydrogen diffusion kinetics and HAMD can be controlled by modifying these states. In this study, different stress and strain states are generated by modifying the wire geometry with round notches and producing residual stress and plastic strains by applying a preload. Thus, different hydrogen diffusion conditions causing diverse HAMD are analyzed. To achieve this goal, two finite element (FE) analysis were carried out in four cases of study considering two notched geometries (varying the notch depth) in a high-strength prestressing steel wire under two loading sequences: (i) a constant load and (ii) a preload (causing plastic strains and a residual stress state) followed by a constant load. Firstly, the FE simulation of mechanical loading was developed for obtaining the stress and strain distributions and these results were considered in the second FE simulation of the hydrogen diffusion assisted by stress and strain for revealing the hydrogen concentration distributions. According to the obtained results, four different scenarios for the analysis of hydrogen diffusion and hydrogen accumulation in prestressing steels are found combining the notch depth and the preload-induced residual stress and plastic strain.