The aim is to describe behaviour of the metal under severe plastic deformation (SPD). In the presented approach the material is treated as a highly viscous, incompressible, anisotropic fluid which flows through an adjustable crystal lattice. The detailed description of the model is provided.

We consider the High Pressure torsion experiment in which specimen under presence of a high hydrostatic pressure together with large shear strains, exhibits significant changes in the internal structure. Such conditions causes improvement of important physical properties of the metals or alloys.

Mixed finite element approach and non-linear Newton solver was used to solve appropriate strongly non-linear system of equations. We compare several approaches to modelling such phenomena, namely investigate different types of constitutive assumptions, carriers of plastic deformations (particularly dislocations) and elasticity.