who particularly is working on FEM module?

[roozbehg]

I have some experience of FEM programming and really want to participate just want to talk to some head developer for FEM module and get some idea.

[pperisin]

Hi,

jrheinlaender recently asked something about FEM module. It might be a good idea to ask there, since he did not declare if he is woking on something or not:

viewtopic.php?f=10&t=2931


Regards,
Petar

[jrheinlaender]

Hi,

I'm not working on the FEM module (and I'm not a head developer for FEM either).

I was missing some functionality (a DocumentObject for defining loads on a part) and if nobody does it sooner, I might implement that some time.

But I won't be upset if someone else goes ahead, since I only wanted this functionality because I need it for something else I am working on (shaft design wizard, in Part Module)

Jan

[mrlukeparry]

I think what would be a good idea is to find out what you would be interested in helping develop and what your potential ideas are for developing the FEM Module. For example do you want to create the whole workflow or concentrate on a particular area such a meshing, post processing etc?

I may be wrong, but here's my brief view on this: A lot of the pre and post processing is done in opensalome (meshing can be achieved using netgen) and then we would create plugins for different FE solver. These solvers would be run in different threads / processes to prevent locking. Then the entire workflow could be kept within FreeCAD and obviously provide an intuitive GUI for this. A lot of the stuff already exists but it's integrating this all together and keeping it both simple but flexible which is what I think is important.

[roozbehg]

pperisin , jrheinlaender and mrlukeparry

thanks for your response. from what I see here we have long road to go. first thing first we really need a good mesh generator which can be achieved using either tetgen or netgen and then when we get to that point we'll be able to talk about the next steps. but now my suggestion is to focus on mesh generator. what do you think?

couple of questions,
1- what SMESH does right now in the FEM module?
2- how can someone have access to object's or meshes parts inside FEM project (i.e. nodes and faces and their connectivities) to create input file for tetgen?
3- what does user get right now when he/she clicks on "create fem mesh"?

[pperisin]

HI,

About mesh generator - there is "Create mesh from shape" in Part workbench (I think). Also, I think OpenCasCade has "tessellate" method in solid. There is also mesh module in FreeCAD, but I do not know if it is using OpenCascade fo that or not.

Best would be if werner would answer this.

Regards,
Petar

[mrlukeparry]

It seems like you have a good idea and concentrating on the mesher seems achievable!

I definitely recommend you contact wmayer because he has experience with meshing and knows what the current state of the module is.

My only view as far as external meshing goes is that it should allow different meshing programs, whether it's through SMESH or a plugin system using tetgen or netgen.

[wmayer]

For meshing we are using Salome's SMESH module. There is a SF project of this which we included into our repository.
The meshing algorithms works with so called hypotheses where you can e.g. decide if you only want quad meshes and a maximum edge length. Or if you have a solid you can create a volume mesh out of it and so on.

I think the framework is pretty mighty and I for myself only experimented a bit with triangle and quad meshes. With the framework you can also invoke external meshers like Netgen via plugins. However, I don't know how exactly it works.

To get a feeling of how the Salome mesher works you can have a look at the commands "Create shape from geometry" and "Create shape from shape". The first one uses OpenCascade's built-in mesher which creates a quite course triangle mesh, i.e. with a lot of malformed triangles. For display purposes the quality is sufficient but for further mesh.processing stuff you may have a lot of numerical problems.
The second command uses the Salome mesher where you get well-formed triangles and a maximum edge can be set.

In the Fem workbench there is a similar command which creates quad meshes.

To have some code examples of how to use the API check the files src/Mod/MeshPart/App/Mesher.cpp or src/Mod/Fem/App/FemMesh.cpp

[shoogen]

I'm sorry, but i got problems to understand what this type of meshing has to do with FEM. The meshes i was able to create where all hollow. Like those for an stl or obj file.
But what i learned from FEM is that mesh should describe a number of basic elements like rods, beams, plates or (tetraedic or cubic) volumes.
For rods beams and plates that would mean that non-mainfold meshes have to be allowed. And for volumes this would mean that the would be internal faces that delimit the volume elements.
Is there something i missed?

[roozbehg]

dear developers,

please correct me if I'm wrong.

from what I understood, the current FEM module command "create fem mesh" only generate surface meshes which is mixture of quads and triangles (from what I see) !! is this correct?
if so, as shoogen mentioned what we need at this point is a volumetric mesh generator to generate tetrahedral or hexahedral meshes.

and couple of suggestions,
despite all the affords you guys are putting to create this amazing free source code one thing that really is missing is one document that explains major knowledge that a new developer needs to know such as:
1- how to have access to different parts of geometry and which header files is really needed for this.
2- how to add new plugins, dlls or project.
3- etc. ...
long story short this project really needs a programming documentations and I'd believe with the power this program has, having such a documents would really absorb more developers from different field to contribute.