The Finite Element Simulation Of F.C.C Poly-Crystalline Plastic Deformation

The poly-crystal plasticity finite element model at room temperature is set up in this thesis using the Voronoi diagram, based on finite element theories and crystal plasticity mechanics. During the modeling, three primary factors that maybe influence the model are discussed in details. Three primary influence factors are the number of the grains of the poly-crystal, the orientation of the grains and the density of the mesh partition. The model is established by taking into account these factors synthetically. By using the model, this thesis studies the macroscopic stress-strain responses of polycrystalline materials in a simple tensile test at room temperature in the meso-scale. Results of simulation are compared with experiments of the pure copper and GH4169. The following results can be concluded:(i) The Voronoi diagram can be used to describe the microstructure of polycrystalline materials via the geometrical and topological properties in real materials. And it also can be used to compare with the form of crystal core and the growth of crystal randomly.(ii) The influence of the size of the grains is not taken into account in this model. The number of the grains has a biggish influence on the results of the simulation. While increasing the number of the grains, results of the simulation go into better and better. The number of the grains in model should be chosen according to the requirement of the precision.In this thesis, we chose universal type of the mesh and study the affection of the density of the mesh partition. Different density of the mesh partition reflects the amount of the elements that will be calculated during the calculation. Results will be more exact with more discrete elements in the crystal. For the responses of the macroscopic stress-strain, the effect of the density of the mesh partition is very small even if there is only one element for one grain.(iii) Two types of the orientation of grains have been chosen to study the affection of the orientation, random and texture respectively. With different orientations of the grains, the macroscopic stress-strain responses of the poly-crystal have biggish difference. With the increment of the content of texture, the poly-crystal represents its anisotropies mightily. But the difference is not obvious if the orientation of the grains have been chosen random. The choice of the orientation of the grains should be determined by the materials accordingly.(iv) It is showed that the model of this thesis is reliable and effective at simulation of the macroscopic stress-strain responses during plastic deformation of the poly-crystal by comparing with experiments for pure copper and GH4169.