This study describes the internal structure of materials used to produce medical stents. A two-level elastoviscoplastic mathematical model, which sets the parameters and describes the processes at the grain level, was developed and numerically implemented. A separate study was conducted to identify the most dangerous deformation modes in the balloon-expandable stent placement using the finite-element method in COMSOL Multiphysics. As a result, the challenging strain state type required for setting the kinematic loading on a representative macrovolume in the two-level model was obtained. A yield surface for different deformation paths in the principal deformation space for stainless steel AISI 316L was obtained and the effect of grain size on the deformation behavior of this material was explored using the developed model.

The paper discusses problems related to the description of grain boundary structure in polycrystalline materials. A mathematical model that describes intergranular boundary formation as a result of bidirectional crystallization is developed and numerically implemented using the molecular dynamics method. The EAM-type interatomic interaction potential is used as a defining relation. Apart from it, the problem of the initial configuration generation of the atomic system is solved which made it possible to ensure the equilibrium of solid and liquid phases. Heat removal from the boundaries of the simulated area is carried out. The obtained structure is analyzed using the central symmetry parameter, as well as by estimating the boundary energy in comparison with the crystalline part of the simulated region. It is shown that the developed model can be used for the simulation of special boundaries.