Intergranular and intragranular behavior of polycrystalline aggregates. Part 1: FE model

The constitutive equations currently used for metallic materials are writte n on a macroscopic scale, using macroscopic criteria and internal stresses to represent hardening. The granular nature of the material is then not rep resented. Since it may be critical in some cases, many attempts have alread y been made to account for it. So a series of modeling have been made in th e framework of models having uniform stress or strain in each (crystallogra phic) phase. As a result, each crystallographic orientation has a different stress-strain state, but the actual microstructure is generally not introd uced (Taylor model, self-consistent approach), so that the heterogenity obt ained is not realistic. The aim of this work is to have a better evaluation of the heterogenity of stress and strain fields in realistic polycrystalli ne aggregates. For that purpose, an aggregate model is generated, and compu ted by finite element technique. The paper is presented in two parts, the f irst one being devoted to the description of the numerical tools, the secon d one showing the results at different scales. The present part includes th e description of the 3D generator of microstructures, able to define any nu mber of grains in a given 3D volume, with arbitrary shapes, and with a moni toring of the volume fraction of each phase. The result of this code will b e taken as a starting point of the modeling, which is performed with a crys tallographic model implemented in a parallel finite element code. Typical v alidation results are shown, with convergence data, on the size of the mesh es and on the geometrical realisations of aggregates. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.