Finite Element Analysis Of Three-dimension Microstructure Of Polycrystal Materials

Mechanical properties of materials will become independent when the size in micro-scale conditions and size effect is particularly obvious,the doctrine of the original isotropic at the macro scale cannot well explain the size effect and provide less effective guidance,this situation prompted the people focus on the research of material microstructure.The theory of plasticity analysis can make people a better understanding of the mesoscopic mechanism of plastic deformation of polycrystalline materials,upgrade material processing process and improve the quality of product to provide the corresponding reference in Mesoscopic scales.This thesis focuses on the basic theory of crystallography and constitutive relation of the finite element polycrystal implementations,polycrystalline geometric modeling,the RVE model,single or double finite element analysis of the specimens of A6061 aluminum Based on crystal plasticity finite element method(CPFEM),taking alloy crystal orientation and grain morphology etc into consideration,to analyzes the macroscopic plastic deformation,discuss the effects of microstructure deformation on macroeconomic performance,analysis the changes of grain under complex loading condition.The details are as follow:(1)Using the user-defined subroutine of ABAQUS interface and writing UMAT that meet the needs of user and carries on the debugging and application in the polycrystal finite element analysis based on crystal plasticity constitutive relation,the simulation results show that constitutive model is an effective tools and instruments to describe the deformation of the micro material anisotropy.(2)Matlab and Python are both realize the geometrical modeling of polycrystalline based on the geometric principle of Voronoi diagram,given therandom orientation to the grain using the oula angle,complete the finite simulation of polycrystalline in the platform of ABAQUS.The Voronoi polycrystalline can provided the overall appearance and the shape of the polycrystalline grains,which is a effective way of polycrystalline in the finite simulation.(3)The characters of slip system and uneven distribution of the stress and strain have been discussed according to the finite simulation of RVE model,The result illustrate that the stress concentration and contract pressure signification changed around the grain boundary.The effects of grain boundary and initial orientation of grain on the deformation behaviour of the grain are analyzed through the study of single and cruciform specimen tensile.