Completely confused - Multi Body Meshing

About the development of the FEM module/workbench.

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dth2m5
Posts: 1
Joined: Fri Jan 31, 2020 9:14 pm

Completely confused - Multi Body Meshing

Post by dth2m5 » Fri Jan 31, 2020 10:10 pm

Hello,

I need help. The GUI is confusing to me and I'm pouring over tons of threads, but something isn't working. Sorry if this isn't in the right part of the forum.

I am trying to assess von misses forces. It's a wheel. I'm trying to look at axial and radial forces to see points of failure. It is a multi-body FEM with different materials attached.

I have no clue what to do. Can someone help provide a step by step process? I can't get the Calculix to run because I can't seem to get it to mesh correctly. I can't seem to mesh the model correctly.

I created it in Solidworks and exported as a STEP. The parts are validated to be solids.

So I try to create a CompSolid through Boolean Fragment, but when I select Compsolid, I get some little red flag.

Here: Image

I know FreeCad doesn't support multiple meshes, so my next thought is to make it one unit.
  1. So I select all the solids and apply Boolean Union (seems most suitable... IDK! everything else ends up creating an error when I get to Boolean Fragment).
  2. I check that it creates a single compound and all the parts are still solid. Check. By this time it has created something called "Fusion" in the model tree. However, it has created a compound, but now it is one single solid, which doesn't seem correct.
  3. Then, I select "Fusion" and all the separated parts under the "Fusion" character tree and apply Boolean Fragment.
  4. Then, I select "CompSolid" from "Standard"
  5. Then, I select "BooleanFragments" and apply "CompoundFilter".

    The geometry check yields "Wheel_FEA_Part_III.CompoundFilter:
    VERTEX : 798
    EDGE : 1340
    WIRE : 637
    FACE : 580
    SHELL : 6
    SOLID : 6
    COMPSOLID : 1
    COMPOUND : 0
    SHAPE : 3368"

    Which seems correct now.
    What is the right step by step process to get the model ready for meshing?

    I really appreciate your help.

    Doug
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    bernd
    Posts: 9310
    Joined: Sun Sep 08, 2013 8:07 pm
    Location: Zürich, Switzerland

    Re: Completely confused - Multi Body Meshing

    Post by bernd » Fri Jan 31, 2020 10:34 pm

    Hi doug, and welcome to the world of FreeCAD FEM.

    the little red exclamation mark indicates an problem in the shape of the boolean fragment. Did the geometry check returned an error?

    Would you post your geometry? it is difficault to find errors in your geometry if we do not know your geometry :mrgreen:

    Depending on your aim to reach you could use a fusion or a compound too. Same as above, we would need more informations what would you like to analyse.

    cheers bernd
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    bernd
    Posts: 9310
    Joined: Sun Sep 08, 2013 8:07 pm
    Location: Zürich, Switzerland

    Re: Completely confused - Multi Body Meshing

    Post by bernd » Fri Jan 31, 2020 10:36 pm

    BTW: SolidWorks should be able to create a CompSolid too. But than you need to export it to brep, because step might not know about compsolids.
    Jee-Bee
    Posts: 1992
    Joined: Tue Jun 16, 2015 10:32 am
    Location: Netherlands

    Re: Completely confused - Multi Body Meshing

    Post by Jee-Bee » Mon Feb 03, 2020 7:11 am

    the deepcopy macro works a lot for me. that one can hlep too
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