The simulation of an in-service material behavior accounting for impurities leads to the introduction of complex couplings between mechanics and diffusive processes. The numerical treatment of these phenomena combined may be complex, especially when strong interactions are involved, as in the case of hydrogen embrittlement of metals (Hirth 1980), or in the effect of moisture on polymers (Sar et al. 2014), where molecules are absorbed, transported through the material, and trapped on specific sites, the density of which might be time and space dependent (McNabb and Foster 1963; Carter and Kibler 1978), e.g, due to plasticity in the case of hydrogen in metals (Sofronis and McMeeking 1989). Mechanical fields, furthermore, may be affected by theses impurities, because of induced deformations or modified mechanical properties (Bernstein 1970). 

If there are numerous works to account for such interactions in finite element codes (Charles, Nguyen, and Gaspérini 2017a; Charles, Nguyen, and Gaspérini 2017b), there are hardly few developments that include more than one diffusive species in the computations, especially in commercial softwares. However, such a feature could be of importance, e.g., to model the behavior of structures subjected to the presence of both impurities and temperature variations.

The aim of this work is thus to introduce original developments to introduce mechanical- multi -diffusion computations in Abaqus. 

The multi-diffusion implementation strategy is first presented. Some academic examples are then considered, mainly based on chemical reaction-diffusion processes (Gray and Scott 1983; Gray and Scott 1984).

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