Coupled hydrogen diffusion simulation using a heat transfer analogy

Abstract

Simulations of Hydrogen Assisted Cracking (HAC) in metals and alloys include hydrogen concentration as a crucial variable. With this objective, phenomenological diffusion models that consider chemical potential gradients as the driving force for diffusion are described. Equations are then modified to include the influence of the stress-strain state and trapping.A crack tip, whose field of stresses and displacements is described by fracture mechanics, is modelled while diffusion equations are implemented through subroutines in the commercial program ABAQUS by means of the analogy between diffusion equations and heat transfer. Effects of trapping on hydrogen transport are then discussed. Moreover, hydrogen induces a lattice dilatation and a modification of the local plastic flow; this coupled behaviour is also modelled through the heat transfer analogy. Finally, stress-dependent boundary conditions are implemented, representing hydrogen entry in a more realistic way.