Neper: Polycrystal Generation and Meshing

Neper is a software package for polycrystal generation and meshing. It can deal with 2D and 3D polycrystals with very large numbers of grains. Its primary features are:

  • Generation of polycrystals from (experimental) morphological properties

    • Distributions of grain sizes, shapes, etc.
    • Individual grain data such as obtained by synchrotron X-ray diffraction (3DXRD, DCT, HEDM…): grain centroids/volumes or full polycrystal image.

    Standard approaches (regular, Voronoi or Laguerre tessellations) are also available.

  • [NEW] Generation of multiphase microstructures

    Phases can be defined and assigned specific fractions and morphological properties for the cells. This allows to model complex microstructures encountered in steels, titanium alloys, etc.

  • Generation of multiscale microstructures

    Each cell of a primary tessellation is partitioned into a new tessellation, and the process can be repeated any number of times. This allows to model complex microstructures such as bainitic steel, lamellar Ti-6Al-4V, etc. See examples.

  • Generation of periodic or semi-periodic microstructures

    The tessellations (and their meshes) can be prescribed periodic or semi-periodic conditions to avoid free-surface effects or reduce the RVE size.

  • Generation of polycrystals in non-convex domains

    Once generated, tessellations can be cut by a series of geometric primitives, such as half-spaces, cylinders, elliptic cylinders or spheres, to generate non-convex domains. See examples.

  • Generation of uniform orientation distributions

    Orientations can be uniformly distributed (flat ODF) for any number of orientations and any crystal symmetry. Some orientations can even be prescribed. See examples.

  • Meshing into good-quality elements

    Meshing involves specific methods called regularization, multimeshing and remeshing. The mesh size can be uniform or defined on a per-grain basis. Cohesive elements can be inserted at interfaces.

  • [NEW] Simulation-related capabilities

    Simulation results (from FEPX) are arranged in a simulation directory, and new results can be computed.

  • Visualization of the tessellations, meshes and simulation results

    The tessellation, mesh and results to visualize can be set in great detail for publication-quality rendering as PNG images. VTK files can also be generated for interactive visualization.

Neper is built around four modules: generation, meshing, simulation and visualization. All the input data are prescribed |non-interactively, using command lines and / or ASCII files. Neper is written in C/C++, and can be compiled (via CMake) and run on any Unix-like system (including MacOS).

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[NEW] Neper now has a companion program, FEPX.

Neper now works hand in hand with FEPX, a new free / open-source finite element software package for polycrystal plasticity. Neper’s output meshes can be readily used by FEPX for simulation, and FEPX’s output results can be processed by and visualized using Neper.

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