Coupled damage-stress corrosion cracking (SCC) modelling in buried pipelines

For buried pipelines, stress corrosion cracking (SCC) is a scenario of degradation where pipeline steel is under stress in a corrosive environment. In these conditions, the progressive damage is strongly coupled with plastic deformation and electrochemical corrosion. In order to evaluate the coupling between those mechanisms, a model is proposed in the framework of Continuum Damage Mechanics (CDM). The description of features of the SCC process is briefly presented. Instead of trying to reproduce all fine details of this degradation process involving complex interactions, it is supposed to be more reasonable to introduce some internal variables (damage parameters), reflecting only the main features of mechanical damage accumulation. This approach to creep in metals was first used by Kachanov in 1958 [introduction to Continuum Damage Mechanics, (Kluwer Academic Publishers, 1986)]. The objective of this work is to generalize this kind of approach for SCC conditions and to analyze, from this point of view, some features of failure in buried pipelines. The main originality of the approach resides in the fact that the model considers mechanical and electrochemical actions simultaneously and their mutual actions. A preliminary example of finite element computations illustrates the application of the model.