Explicit implementation of hydrogen transport in metals

Abstract

Hydrogen embrittlement prediction demands a numerical framework coupling a damage model with local hydrogen concentration. The inherent nonlinearity in hydrogen-stress-damage interactions challenges convergence in implicit schemes. To address this limitation, we propose a novel chemical potential-based explicit formulation for simulating hydrogen transport in metals. Our approach exploits a heat transfer analogy, linking mechanical and hydrogen transport via inelastic energy as a heat source. By employing chemical potential rather than lattice concentration, our method eliminates the need for user-defined boundary conditions and hydrostatic stress gradient determination. We integrate a VUMATHT subroutine for diffusion modelling and a VUMAT subroutine for material behaviour, coupling stress and strain rates as a heat source for diffusion. Validating against a classical benchmark, we compare our explicit approach with hydrogen concentration-based methods in ABAQUS Standard and Comsol Multiphysics. Stability conditions are assessed for different mesh sizes and mass scaling densities and the capabilities of our approach are showcased for 3D simulations of notched tensile specimens. Our framework offers a novel and efficient pathway for integrating hydrogen transport with user-defined material behaviour, promising advancements in hydrogen-informed damage models.