Three-dimensional constitutive creep/relaxation model of carbon cathode materials

In order to adequately simulate the behavior of a Hall-Heroult electrolysis cell, a finite element model must take into account the properties of each material forming the cell structure and those contained in it. However there is some lack of full knowledge of the mechanical behavior of these materials, e.g., the long term viscoelastic (creep/relaxation) behavior of the carbon cathode. In this present paper a three-dimensional viscoelastic model is devised and proposed, being ready to be implemented in a finite element code. This 3D viscoelastic model was developed from the thermodynamics of irreversible processes, where the selection of the model's internal variables was based on a phenomenological approach. The model has been developed at a particular reference state; therefore, the model parameters are represented by constant constitutive tensors. The model's particular parameters were identified for three different types of cathode carbon, i.e., semigraphitic, graphitic, and graphitized.