Modeling of the interaction between corrosion diffusion and mechanical behavior of metallic alloys by FEM coupling

Abstract

This work aimed at the modeling the interaction between corrosion diffusion and the mechanical behavior of metallic alloys, by the development of a coupling finite element method model. A non-fickian diffusion process was considered to interact with a two-dimensional mechanical model, assuming a plane stress state. Both models were coupled in a linear differential system solved by an approached implicit integration scheme.

The validation of the model was performed based on experimental results of metallic alloys submitted to hot corrosion, without mechanical loading. The numerical predictions matched the experimental results with a maximal error reaching 25%.

Corrosion induced damage was modeled by a damage law, modeling a linear degradation of the Young's modulus with the corrosion rate. The diffusion of the corrosion was therefore inducing stress redistribution around the softened material, which in turn increased the peak of hydrostatic pressure. Stress-driven diffusion, whose amplitude was conditioned by a pressure factor, was found to accelerate or decelerate the natural corrosion diffusion process depending on the nature of the stress. This phenomenon was specifically observed in zones submitted to high gradient of hydrostatic pressure.