SEVERE PLASTIC DEFORMATION BY KOBO METHOD – ESTIMATIONS AND MODEL

Abstract

A new phenomenological model for the description and simulation of  Severe Plastic Deformation (SPD) is developed based on the inverse dependence of the material's viscosity on the concentration of point defects (the higher the concentration, the less the viscosity). In this  case,  the  local  concentration  of  point  defects  is  determined  by  (1)  the  intensity  of deformation, (2) the annihilation of interstitial defects and vacancies, (3) the absorption of defects  at  dislocations,  (4)  diffusiveredistributionof  defects.  The  solution  of  the corresponding system of nonlinear differential equations for the field of defect concentrations and the differential equation for the velocity field at a given rate of deformation at the boundary of the sample providesa non-equilibrium phase transition -a jump in viscosity and a jump in the concentration of defects at a certain distance from the surface. In this case, the width of the zone of reduced viscosity and increased defect concentration is proportional to the surface velocity of the deformation. It is in this zone that it makes sense to consider the material as a viscous medium.