Gmsh unknown error

About the development of the FEM module/workbench.

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PeterII
Posts: 21
Joined: Sat Aug 14, 2021 8:53 am

Gmsh unknown error

Post by PeterII »

Hello,

I am trying to mesh this part. First I fuse it and then I try to mesh it using Gmesh. Each time I did it i got unknown error. I have checked geometry and it seams fine.
I also tried different min mesh sizes, to no effect.
Can someone provide me with some insight please?

Kind regards,
Peter

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.4 (GitTag)
Build type: Release
Branch: releases/FreeCAD-0-18
Hash: 980bf9060e28555fecd9e3462f68ca74007b70f8
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: Slovenian/Slovenia (sl_SI)
sticks_1.step
(641.79 KiB) Downloaded 50 times


EDIT: Bernd ... Gmsh insead of Gmesh


.
Attachments
Sticks.png
Sticks.png (11.04 KiB) Viewed 2686 times
Kind regards,
Peter
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NewJoker
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Re: Gmesh unknown error

Post by NewJoker »

This structure consists of many very thin bars modeled as solids. It will be hard to mesh it (and achieve sufficient mesh density) because you would need lots of very small tetrahedrons. In such a case it's highly advisable to model the structure with lines and mesh it using 1D (beam/truss) elements.

Also, your FreeCAD version is quite outdated. I suggest switching to the newest release (0.20, currently a dev version). FEM module changed a lot since then.
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Kunda1
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Re: Gmesh unknown error

Post by Kunda1 »

PeterII wrote: Thu Apr 21, 2022 4:13 am Version: 0.18.4 (GitTag)
https://forum.freecadweb.org/viewtopic.php?f=18&t=12212
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PeterII
Posts: 21
Joined: Sat Aug 14, 2021 8:53 am

Re: Gmesh unknown error

Post by PeterII »

Hi,
Sorry for my ignorance. I will redo thproces in 0.20 and post replay.

Regards,
Peter
Kind regards,
Peter
Danial Iskhakov
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Location: Україна/Ukraine
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Re: Gmesh unknown error

Post by Danial Iskhakov »

For such geometry better to use beam FEs with assign cross section to them. Calculix supports round and rectangle cross sections.
Make schime from lines, results of calculation will be the same.
PeterII
Posts: 21
Joined: Sat Aug 14, 2021 8:53 am

Re: Gmesh unknown error

Post by PeterII »

Hi,

I have re done everything in FreeCAD v0.20. Mesh is done this time although with an error. However when I try to asign the material to it I get the error:

22:41:16 Single click on a Face or Edge which belongs to one Solid will add the Solid to the list!
22:41:25 Selection: Compound Fusion Edge1
22:41:25 Selection variable adapted to hold the Solid: Compound Fusion Solid1
22:41:25 Multiple shape types are not allowed in the reference list.
22:43:45 Traceback (most recent call last):
File "C:\Program Files\FreeCAD 0.20\Mod\Fem\femguiutils\selection_widgets.py", line 613, in addSelection
self.parseSelectionFunction(self.added_obj)
File "C:\Program Files\FreeCAD 0.20\Mod\Fem\femguiutils\selection_widgets.py", line 488, in selectionParser
selection[0].Shape.ShapeType,
<class 'AttributeError'>: 'FeaturePython' object has no attribute 'Shape'

Can anyone makes any sense of it?

Regarding the solution with using lines, what is the best way of doing that? Should I use Sketcher, what would you suggest?

Kind regards,
Peter

OS: Windows 10 Version 2009
Word size of FreeCAD: 64-bit
Version: 0.20.27422 (Git)
Build type: Release
Branch: master
Hash: d938733eaf2c2ce7cb18d1cbb56147185c473530
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.3
Locale: Slovenian/Slovenia (sl_SI)
Kind regards,
Peter
thschrader
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Location: Germany

Re: Gmesh unknown error

Post by thschrader »

PeterII wrote: Sat Apr 30, 2022 9:30 pm ...
Regarding the solution with using lines, what is the best way of doing that? Should I use Sketcher, what would you suggest?
...
You can put different 1D-objects (sketches, draft-lines) in a "Part/Boolean-Fragment" object
to mesh/run the simulation. See example:
frame_example.FCStd
(88.08 KiB) Downloaded 44 times
Danial Iskhakov
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Re: Gmesh unknown error

Post by Danial Iskhakov »

PeterII wrote: Sat Apr 30, 2022 9:30 pm Regarding the solution with using lines, what is the best way of doing that? Should I use Sketcher, what would you suggest?
In my opinion better to use Draft Workbench and instead of Circle, for more correct meshind, use Polygon. To see in results cross sections dimensions in Calculix properties "Beam Shell Result Output 3D" shold be set "true". See example
шпр_балка.FCStd
(111.37 KiB) Downloaded 35 times
PeterII
Posts: 21
Joined: Sat Aug 14, 2021 8:53 am

Re: Gmesh unknown error

Post by PeterII »

Hi,

thank you for your answers. I am now working on lines model, however, I have to place a thin membrane in front and I want to apply pressure on it. How can I do it for the model made out of 1D elements? Should I extrude just the arc? How should I mesh it all together?
membrane in front.png
membrane in front.png (6.2 KiB) Viewed 1990 times
Kind regards,
Peter
Danial Iskhakov
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Re: Gmesh unknown error

Post by Danial Iskhakov »

PeterII wrote: Sun May 08, 2022 6:50 am How should I mesh it all together?
For now FreeCAD doesn't support different FE in one mesh. Only you can do it's calculate membrane apart, using shell FE. Then add it like a load to your 3d truss.
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