A coupled mechanical-diffusion model for hydrogen-driven ductility degradation

Abstract

The permeation of hydrogen atoms into metallic structures leads to a variety of unfavorable mechanisms, which result in a reduction in the material's lifespan and unpredictable mechanical failures. In this context, the objective of this work is to model the nonlinear mechanical response of metallic materials as hydrogen diffuses through them. The present investigation is conducted within a fully coupled, thermodynamically consistent mechanical-diffusion framework that incorporates vis-coplasticity and damage, and captures the influence of lattice and trapped hydrogen on the mechanical response. As a case study, the model parameters for Inconel 718 are identified and the results are validated using experimental data from literature. A parametric study is carried out to examine the interaction between hydrogen concentration, loading rate, and mechanical responses, with particular emphasis on the ductility loss under increased hydrogen exposure. The results provide clear insight into how hydrogen diffusion interacts with stress, viscoplasticity, and damage, and they enhance our understanding of how the coupling between hydrogen diffusion and ductile mechanisms leads to ductility degradation in the material.