Numerical Simulation Of Micro Upsetting Process In Polycrystalline Plasticity Model

The three-dimensional Voronoi polyhedron, which is topologically similar to the mesostructure of real polycrystalline material, has been frequently used to study microforming at mesoscopic-level. In this paper, two models based on the basic principle of Voronoi diagram, smooth model and coarse model, are established respectively. Smooth model is the exact realization of Voronoi diagram. Coarse model is realized by discretizing Voronoi diagram, thus is only an approximation to Voronoi diagram but has computational advantage. The two models are applied to represent the cylindrical billet containing 32, 128 and 512 crystals respectively. Finite element simulations of upsetting within the framework of crystal plasticity theory are performed, and the results are compared in terms of heterogeneity of material flow, deformation resisitance, and inverse polar figure evolution. The comparison indicates that crystal plastic theory is able to account for the heterogeneity of deformation; the modeling of mesostructure significantly affects the simulation results.