Application of micropolar theory to the description of the skin effect due to hydrogen saturation

Abstract

A model is proposed for the description of a highly inhomogeneous distribution of hydrogen within a saturated metal specimen (the so-called skin effect due to hydrogen saturation). The model is based on the micropolar continuum approach and results in a nonuniform stress–strain state of a cylindrical metal specimen due to distributed couples or microrotations. The dependence of the diffusion coefficient on the strain energy is considered in order to model stress-induced diffusion. Accumulation of hydrogen within a thin boundary layer results in a highly nonuniform distribution of hydrogen across the specimen. The mutual influence of the stress–strain state and hydrogen accumulation is taken into account. The estimated thickness of the surface layer containing hydrogen is comparable to the thickness observed in experiments. The predicted average concentration coincides with experimental data.