Stress-assisted hydrogen diffusion in the presence of trapping sites in elasto-plastic materials

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Title: Stress-assisted hydrogen diffusion in the presence of trapping sites in elasto-plastic materials
Author: GRYSAKOWSKI, Bartosz; OPTASANU, Virgil; MONTESIN, Tony; DEJARDIN, Steeve; GRUNENWALD, Thierry; NAAS, Philippe; MOLL, Géraldine
Abstract: The quantification of the diffusion of hydrogen in metals is of very high interest for many industrial applications. Particularly, the evaluation of the influence of defects that can occur during material processing is important. For this work very simple defects such as incomplete welding joints have been studied. The influence of stress and pressure on hydrogen concentration profiles in Al7020 (AZ5G) aluminium alloy, as well as hydrogen mass flow rate, total hydrogen loss, J-integral values have been calculated with the use of commercial FEM software ABAQUS for pure elastic and elasto-plastic material models. The results show significant increase of hydrogen concentration in the vicinity of the crack tip, as expected, and different hydrogen distribution around the defect. The ABAQUS software does not provide any built-in model for full coupling between mass diffusion and stress field, in other words, the hydrogen concentration field has no influence on the mechanical parameters of the host metal or the stress field. This problem has been solved with the use of Fortran subroutines (e.g. UMAT), in which a mechanical and diffusion/reaction models can be defined. The hydrogen-trapping model, which is based on chemical reaction kinetics and on extended diffusion laws, has been proposed and implemented in Fortran programming language in order to use this code as ABAQUS subroutine.
Subject: stress-assisted hydrogen diffusion; stress-diffusion coupling; FEM; Couplages multi physiques (S8)
Publisher: AFM, Maison de la Mécanique, 39/41 rue Louis Blanc, 92400 Courbevoie, France(FR)
Date: 2013-12-20

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