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A crystal plasticity FEM code used to determine bulk constitutive properties of metals
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README.md

ExaConstit App

Author:

Date: Aug. 6, 2017

Updated: Oct. 11, 2019

Description:

The purpose of this code app is to determine bulk constitutive properties of metals. This is a nonlinear quasi-static, implicit solid mechanics code built on the MFEM library based on an updated Lagrangian formulation (velocity based).

Currently, only Dirichlet boundary conditions (homogeneous and inhomogeneous by dof component) have been implemented. Neumann (traction) boundary conditions and a body force are not implemented. A new ExaModel class allows one to implement arbitrary constitutive models. The code currently successfully allows for various UMATs to be interfaced within the code framework. Development work is currently focused on allowing for the mechanical models to run on GPGPUs.

The code supports either constant time steps or user supplied delta time steps. Boundary conditions are supplied for the velocity field applied on a surface. It supports a number of different preconditioned Krylov iterative solvers (PCG, GMRES, MINRES) for either symmetric or nonsymmetric positive-definite systems.

Remark:

This code is still very much actively being developed. It should be expected that breaking changes can and will occur. So, we make no guarantees about stability at this point in time.

Currently, the code has been tested only using monotonic loading with an auto-generated mesh that's been instantiated with grain data from some voxel data set. MFEM natively supports a variety of different mesh types and those should work, but we have not tested them to ensure the grain instantiation part works.

While we plan on the ExaCMech models and FEM builds run on the GPU, we currently have no plans for doing the same for UMATs.

See the included options.toml to see all of the various different options that are allowable in this code and their default values.

A TOML parser has been included within this directory, since it has an MIT license. The repository for it can be found at: https://github.com/skystrife/cpptoml .

Example UMATs maybe obtained from https://web.njit.edu/~sac3/Software.html . We have not included them due to a question of licensing. The ones that have been run and are known to work are the linear elasticity model and the neo-Hookean material. Although, we might be able to provide an example interface so users can base their interface/build scripts off of what's known to work.

Note: the grain.txt, props.txt and state.txt files are expected inputs for CP problems, specifically ones that use the Abaqus UMAT interface class under the ExaModel.

Installing Notes:

  • git clone the LLNL BLT library into cmake directory. It can be obtained at https://github.com/LLNL/blt.git

  • MFEM will need to be built with Conduit (built with HDF5). The easiest way to install Conduit is to use spack install instruction provided by Conduit

    • You'll need to use the exaconstit-dev branch of MFEM found on this fork of MFEM: https://github.com/rcarson3/mfem.git
    • We do plan on upstreaming the necessary changes needed for ExaConstit into the master branch of MFEM, so you'll no longer be required to do this
  • ExaCMech is required for ExaConstit to be built and can be obtained at https://github.com/LLNL/ExaCMech.git.

  • Create a build directory and cd into there

  • Run cmake .. -DENABLE_MPI=ON -DENABLE_FORTRAN=ON -DMFEM_DIR{mfem's installed cmake location} -DBLT_SOURCE_DIR=${BLT cloned location} -DECMECH_DIR=${ExaCMech installed cmake location} -DRAJA_DIR={RAJA installed location} -DSNLS_DIR={SNLS location in ExaCMech} -DMETIS_DIR={Metis used in mfem location} -DHYPRE_DIR={HYPRE install location} -DCONDUIT_DIR={Conduit install location} -DHDF5_ROOT:PATH={HDF5 install location}

  • Run make -j 4

Future Implemenations Notes:

  • Multiple phase materials
  • Evolving loading conditions
  • Code ported over to the GPU
  • Commonly used post-processing tools either through Python or C++ code

CONTRIBUTING

ExaConstit is distributed under the terms of the BSD-3-Clause license. All new contributions must be made under this license.

Citation

ExaConstit can be cited using the following bibtex entry:

@misc{ exaconstit,
title = {{ExaConstit}},
author = {Carson, Robert A. and Wopschall, Steven R. and Bramwell, Jamie A.},
abstractNote = {The principal purpose of this code is to determine bulk constitutive properties and response of polycrystalline materials. This is a nonlinear quasi-static, implicit solid mechanics code built on the MFEM library based on an updated Lagrangian formulation (velocity based). Within this context, there is flexibility in the type of constitutive model employed, with the code allowing for various UMATs to be interfaced within the code framework or for the use of the ExaCMech library. Using crystal-mechanics-based constitutive models, the code can be used, for example, to compute homogenized response behavior over a polycrystal. },
howpublished = {[Computer Software] \url{https://doi.org/10.11578/dc.20191024.2}},
url = {https://github.com/LLNL/ExaConstit},
doi = {10.11578/dc.20191024.2},
year = {2019},
month = {Aug},
annote = {
   https://www.osti.gov//servlets/purl/1571640
   https://www.osti.gov/biblio/1571640-exaconstit
}
}

LICENSE

License is under the BSD-3-Clause license. See LICENSE file for details. And see also the NOTICE file.

SPDX-License-Identifier: BSD-3-Clause

LLNL-CODE-793434

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