FEM Preferences

From FreeCAD Documentation

The preferences screen of the FEM Workbench are found in the Preferences Editor, Edit → Preferences → FEM.

There are several tabs in the FEM workbench preferences, starting with the General configuration of the workbench. The rest of the tabs control how FEM interacts with supported external solvers.

The current supported external solvers are:

General

On the General tab you can specify the following:

Name Description
Working directory In what directory the mesh and solver files should be stored
Create mesh groups If there are several meshes they will be grouped
Keep results on calculation re-run Existing Result objects will be kept, otherwise overwritten by a new solver run
Restore result dialog settings If checked, the Show result dialog is opened with the last used dialog settings
Hide constraints when open result dialog The constraints will be hidden in the model view when the Show result dialog is opened
Default solver Default solver to be added when adding an Analysis container. (introduced in version 0.21)

Gmsh

On the Gmsh tab you can specify the following:

Name Description
Search in known binary directories If checked, FreeCAD will look for the binary of Gmsh in known (usual) directories
Gmsh binary path The path to the the binary of Gmsh

CalculiX

On the CalculiX tab you can specify the following:

Elmer

On the Elmer tab you can specify the following:

Name Description
ElmerGrid: Search in known binary directories If checked, FreeCAD will look for the binary of the grid writer utility of the Elmer in known (usual) directories
ElmerGrid binary path The path to the the binary of the grid writer utility of the Elmer
ElmerSolver: Search in known binary directories If checked, FreeCAD will look for the solver binary of Elmer in known (usual) directories
ElmerSolver binary path The path to the the solver binary of Elmer
CPU cores to be used The number of CPU cores that will be used to perform the solving.

Important: Elmer divides the mesh into portions. The number of portions is equal to the number of CPU cores used. This can result in side-effects:

  • Depending on your mesh a smaller number of CPU cores can run faster than using more cores.
  • In some cases using e.g. 12 cores does not converge while 8 cores will work fine. The reason is that at some point the mesh portions become too small.

So it is often necessary to adjust the number of cores, depending on the mesh.

Known limitation: For some simulation types you first need to install Elmer modules to enable multi-threading. Check the Elmer report for info about this. A typical case is that for direct solving one has to install the MUMPS module.

Filter results The mesh volume regions processed by each CPU core will be merged to make the volume boundaries invisible.

Mystran

On the Mystran tab you can specify the following:

Name Description
Search in known binary directories If checked, FreeCAD will look for the binary of the Mystran in known (usual) directories
Mystran binary path The path to the the binary of the Mystran

Z88

On the Z88 tab you can specify the following:

Name Description
Search in known binary directories If checked, FreeCAD will look for the binary named z88r of the Z88 solver in known (usual) directories
z88r binary path The path to the the binary named z88r of the Z88 solver
Solver method The solver method used by the Z88 solver for new simulations.
Max places in stiffness matrix This is relevant when the solver method Simple Cholesky is used. After starting the solver, it might tell you that you need to increase the MAXGS value. In this case increase the max places and re-run the solver.
Max places in coincidence vector This is relevant when one of the iterative solver methods is used. After starting the solver, it might tell you that you need to increase the MAXKOI value. In this case increase the max places and re-run the solver.

Material

On the Material tab you can specify the following:

Name Description
Use built-in materials The cards built-in to FreeCAD will be listed as available.
Use materials from Materials directory in user's FreeCAD preference directory The cards from FreeCAD's preferences directory will be listed as available. On Windows, that would for example be this folder:

C:\Users\<username>\AppData\Roaming\FreeCAD\Material

Use materials from user defined directory Also material cards also from the specified directory will be listed as available.
Delete card duplicates Duplicate cards will be deleted from the displayed material card list.
Sort by resources Material cards will appear sorted by their resources (locations). If unchecked, they will be sorted by their name.