I am trying to use FreeCad to differentiate the Body and boundary elements on a mesh ( A PCB I design)
I use KiCad to export the PCB.
I use FreeCad to create the mesh, then the GMSH groups/faces
And then I import them to ElmerGUI.
I try to understand how to handle Body and boundary properties. If the mesh is simple/doesnt have a lot of edges/solid components its easier to select the faces/solids. Now I try to use a more complex mesh and when I manage to differentiate the solids shown in Elmer, my boundaries go "bad" and vise versa. I have questions in order to generate my mesh more professionally and correctly:
-in FreeCad there are FEM mesh boundary, region and group options and in each of them I can select either Face or Solid parts of my mesh. Which one creates the body and which the boundary for Elmer?
-Say I make a FEM mesh group. When and should(?) I put both a solid and face(s) in the same group?
-Can the GMSH element size negatively affect the body/boundaries set? (aka can there be a bug if the element size of the mesh is too big, and two bodies unite for example?)
(image link: https://i.sstatic.net/jtEPKG4F.png)
For now I try to use only FEM mesh group, as it looks like it can generate both body and boundaries for elmer. I do some trial and error for now, I think Im getting there, but I am unable to find a proper tutorial for elmer+KiCad about this specific topic, for -more-complex meshes.
I attach the step, the FreeCad project and the .unv export if someone needs to take a look at the shape/play around with it or show me something. I try to make the antenna and GND place as one body, and the FR4 as a second body. At the same time I need boundary for antenna signal input and boundary for the GND/bottom layer.
FreeCad FEM mesh: boundary, region and group. Which one and when?
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FreeCad FEM mesh: boundary, region and group. Which one and when?
Last edited by Basilisvirus on 15 Apr 2024, 20:55, edited 4 times in total.
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Re: FreeCad FEM mesh: boundary, region and group. Which one and when?
In 3d groups of solid elements become bodies, groups of plate elements become boundary surfaces. 1D elements are eliminated if you use -autoclean. ElmerGUI uses -autoclean by default.
In 2D models groups of plate elements become bodies, groups of 1D elements become boundaries.
In 2D models groups of plate elements become bodies, groups of 1D elements become boundaries.
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Re: FreeCad FEM mesh: boundary, region and group. Which one and when?
Lets start with this:
I export to .unv
But when I import them to Elmer I see 3 bodies, where when I select them I do not see anything selected on the visual mesh/model and when I select the one boundary it has, the whole mesh is selected.:
I attach you the files I used. (I redid the mesh to be smaller in size so I can upload it) -Why I have 3 bodies in Elmer, while I specified only two?
I selected two parts of my mesh and made them two bodies:In 3d groups of solid elements become bodies
I export to .unv
But when I import them to Elmer I see 3 bodies, where when I select them I do not see anything selected on the visual mesh/model and when I select the one boundary it has, the whole mesh is selected.:
I attach you the files I used. (I redid the mesh to be smaller in size so I can upload it) -Why I have 3 bodies in Elmer, while I specified only two?
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Re: FreeCad FEM mesh: boundary, region and group. Which one and when?
Depending on how the mesh gets saved out of gmsh (all elements or just grouped elements) , elmer makes each group a body, but any solid elements not grouped are sent to the additional group/body of everything not grouped. However, there are flags in gmsh to save all, or just save groups.