Innovative Design of Residual Stress and Strain Distributions for Analyzing the Hydrogen Embrittlement Phenomenon in Metallic Materials

Round-notched samples are commonly used for testing the susceptibility to hydrogen embrittlement (HE) of metallic materials. Hydrogen diffusion is influenced by the stress and strain states generated during testing. This state causes hydrogen-assisted micro-damage leading to failure that is due to HE. In this study, it is assumed that hydrogen diffusion can be controlled by modifying such residual stress and strain fields. Thus, the selection of the notch geometry to be used in the experiments becomes a key task. In this paper, different HE behaviors are analyzed in terms of the stress and strain fields obtained under diverse loading conditions (un-preloaded and preloaded causing residual stress and strains) in different notch geometries (shallow notches and deep notches). To achieve this goal, two uncoupled finite element (FE) simulations were carried out: (i) a simulation by FE of the loading sequences applied in the notched geometries for revealing the stress and strain states and (ii) a simulation of hydrogen diffusion assisted by stress and strain, for estimating the hydrogen distributions. According to results, hydrogen accumulation in shallow notches is heavily localized close to the wire surface, whereas for deep notches, hydrogen is more uniformly distributed. The residual stress and plastic strains generated by the applied preload localize maximum hydrogen concentration at deeper points than un-preloaded cases. As results, four different scenarios are established for estimating a la carte the HE susceptibility of pearlitic steels just combining two notch depths and the residual stress and strain caused by a preload.

Automated summary

This study analyzed the stress and strain fields under different loading conditions and notch geometries to investigate the influence of these factors on hydrogen diffusion and susceptibility to hydrogen embrittlement. The results showed that hydrogen accumulation is localized near the surface in shallow notches, while it is more uniformly distributed in deep notches. The residual stress and strain generated by preload caused maximum hydrogen concentration at deeper points. Four different scenarios were established to estimate the hydrogen embrittlement susceptibility of pearlitic steels.