TO BEGIN

GEOMETRY : UNIT-CELL DESCRIPTION

Definitions

A heterogeneous Unit-cell consists of one (or more) Material, and each Material consists of one (or more) Zone. They are defined as follows:

  • All the voxels of the 3D uniform grid define the Unit-cell.
  • Within a Material, all the voxels have the same behaviour law.
  • Within a Zone of a Material, all the voxels have the same material properties (coefficients of the behavior law).

Note

The description of a unit-cell is often not unique (see example below). If so:

  • avoid large number of Materials
  • looking at outputs proposed by AMITEX_FFTP may help you to choose an appropriate description

MaterialID and ZoneID integer fields

AMITEX_FFTP needs two integer fields (or one if the other is a homogeneous field of ‘ones’) as inputs, each one representing the spatial distribution of materials and zones within materials.

This example considers a unit-cell with two materials, and one material is devided into two zones (same behavior law but with different coefficients). The corresponding MaterialID and ZoneID fields are represented here:

 _images/materialID_zoneID.png

Example of a non-unique description

Assuming a composite material with elastic isotropic matrix and inclusions, the N inclusions having the same elastic coefficients, AMITEX_FFTP is able to take into account the FIVE following descriptions:

  1. 1 material with 2 zones
  2. 1 Material with N+1 zones
  3. 2 materials with 1 zone per material
  4. 2 materials with 1 zone for the ‘matrix’ material and N zones for the ‘inclusions’ material (one per inclusion)
  5. N+1 materials with 1 zone per material
 _images/composite_Nincl.png

Depending on the required outputs, the recommanded descriptions are:

  • Description 1 will be the most efficient with very few outputs
  • Description 4 will provide per material (‘matrix’ and ‘inclusions’) statistical quantities and, on demand at given times, per inclusion statistical quantities

HOW TO LAUNCH AMITEX_FFTP

Once installed (see Installation), to use AMITEX_FFTP, you must set the environment variable AMITEX_PATH, PATH (and LD_LIBRARY_PATH since v8.18.x).

For example in a file env_amitex.sh:

#!/bin/bash
export AMITEX_PATH=(amitex)
export PATH=$AMITEX_PATH/libAmitex/bin:$PATH
export LD_LIBRARY_PATH=$AMITEX_PATH/libAmitex/lib:$LD_LIBRARY_PATH

And then

$ source env_amitex.sh

If you have compiled GCC and/or openMPI and/or fftw3, and used them for compiling AMITEX_FFTP (see GCC, openMPI, fftw, mfront), be sure that their respectives bin and lib (or lib64) folders are added to the PATH and LD_LIBRARY_PATH variables in the env_amitex.sh

Interactively or within a batch script (for the job manager available on your machine), a simulation is launched with one of the following command lines

MATEVTK="path_to/materialID.vtk"
ZONEVTK="path_to/zoneID.vtk"
MATEXML="path_to/material.xml"
LOADXML="path_to/loading.xml"
ALGOXML="path_to/algorithm.xml"
RESDIR="path_to/results/

#WARNING : you must create the folder "results" before launching amitex_fftp

0. help
mpirun amitex_fftp -help  ! OR SIMPLY :  amitex_fftp -help

1. General case
mpirun amitex_fftp  -nm $MATEVTK -nz $ZONEVTK -m $MATEXML -c $LOADXML -a $ALGOXML -s $RESDIR/output_file

2. One material (assumes materialID.vtk full of 1)
mpirun amitex_fftp  -nz $ZONEVTK -m $MATEXML -c $LOADXML -a $ALGOXML -s $RESDIR/output_file

3. One zone per material (assumes zoneID.vtk full of 1)
mpirun amitex_fftp  -nm $MATEVTK -m $MATEXML -c $LOADXML -a $ALGOXML -s $RESDIR/output_file

4. One material with one zone per voxel (assumes zoneID.vtk varying from 1 to the number of voxels) with dx=dy=dz=1.
mpirun amitex_fftp    -m $MATEXML -c $LOADXML -a $ALGOXML -NX nx -NY ny -NZ nz -s $RESDIR/output_file

5. One material with one zone per voxel (assumes zoneID.vtk varying from 1 to the number of voxels)
mpirun amitex_fftp  -m $MATEXML -c $LOADXML -a $ALGOXML -NX nx -NY ny -NZ nz -DX dx -DY dy -DZ dz -s $RESDIR/output_file

Depending on your MPI version and/or installation, you may have to specify explicitely the number of processes and replace mpirun by mpirun -np number_of_processes.

The five possible command lines listed above correspond to the five following cases :

  1. The materials and their corresponding zones are defined by materialID.vtk and zoneID.vtk.
  2. The unit-cell consists of a unique material with different zones defined in zoneID.vtk.
  3. The different materials defined by materialID.vtk have a unique zone (all the voxel within a material have the same properties).
  4. The unit-cell consists of a unique material with one zone per voxel (the voxel dimensions are set to 1x1x1).
  5. Same as 4. but the user provides the voxel dimensions

In the example above :

  • the material properties, the loading & outputs and the algorithm parameters are defined in the xml files : material.xml, loading.xml and algorithm.xml (see respectively MATERIALS, LOADING&OUTPUTS, ALGORITHM).
  • the rootname of the output files is output_file