A modelling framework for coupled hydrogen diffusion and mechanical behaviour of engineering components

Professor Edmund Tarleton, with colleagues from the Department of Engineering, proposes a finite element forumulation for solving coupled mechanical/diffusion problems, in this paper published in Vol 66 of Computational Mechanics.

The study focuses on hydrogen diffusion in metals and its impact on their mechanical behaviour (such as embrittlement), and takes into account how the effect of hydrogen in the plastic response, and cohesive strength of different interfaces, can be incorporated.

The formulation adopts a standard Galerkin method in the discretisation of both the diffusion and mechanical equilibrium equations.  This paper explains how the diffusion equation can be expressed in terms of the gradient in chemical potential, which reduces the continuity requirements on the shape functions to zero degree linear functions, compared to the continuity condition required when concentration is adopted.

It is proposed that a consistent interface element formulation can be achieved due to the continuity of the chemical potential across the interface, which leads to straightforward coding of the FE equations.

The details of the physical problem, the finite element formulation and constituitive models, are initially discussed, with numerical results presented for various example problems.