Finite element modeling of periodic polycrystalline aggregates with intergranular cracks

The present study addresses the prediction of the mechanical response of model polycrystalline aggregates in which the anisotropy of individual crystals induces high internal stresses as well as microcracks. A novel procedure is proposed in order to automatically generate finite element (FE) meshes that conform to the polycrystalline microstructure. The meshes obtained are periodic in 3-D and they contain cohesive zone elements along all grain boundaries. The FE model is applied to two materials with significant elastic anisotropy at the crystal level: stainless steel and graphite. A self-consistent equivalent inclusion solution is shown to produce a valid mean-field estimate of the effective stiffness of the polycrystal. This reference solution is used in order to optimize the assignment of lattice orientations to individual grains prior to the FE simulations. It is demonstrated that relying on such model polycrystals increases the accuracy of FE predictions at an affordable computational cost. The influence of internal cracks on the macroscopic response depends on the anisotropy of individual crystals.