XtalMesh Toolkit: High-Fidelity Mesh Generation of Polycrystals

A method for generating high-fidelity, boundary conforming tetrahedral mesh of three-dimensional (3D) polycrystalline microstructures is presented. With growing interest into subgrain scale micromechanics of materials, crystal plasticity finite element (CPFE) models must adapt not only their respective constitutive laws, but also their model geometry to the finer scale, namely the representation of grains and grain boundary junctions. Additionally, with the increasing availability of microstructure datasets obtained via 3D tomography experiments, it is possible to characterize the 3D topology of grains. From these advancements in experiment emerge both an opportunity and challenge for researchers to develop model microstructures, specifically finite element meshes, which best preserve grain topology for the accurate representation of boundary conditions in polycrystalline materials. To accomplish this, an open-source code called XtalMesh was created and is presented here. XtalMesh works by smoothing input voxel microstructure data using a feature-aware Laplacian smoothing algorithm that preserves complex grain topology and leverages state-of-the-art tetrahedralization code fTetWild to generate volume mesh. In this work, the workflow and associated algorithms of XtalMesh are described in detail using a synthetically generated example microstructure. For demonstration, we present a case study involving mesh generation of an experimentally obtained microstructure of nickel-based superalloy Inconel 718 (IN718).