Request for help meshing and and analysing a part {Solved}
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Request for help meshing and and analysing a part {Solved}
I have run into 4 "jac" errors meshing this part and analysing it. (I don't know what they are to be quite frank)
I am a FEM novice and no doubt I am making an elementary mistake.
Any help pointing out where I am going wrong and pointers in the right direction will be greatly appreciated.
I am a FEM novice and no doubt I am making an elementary mistake.
Any help pointing out where I am going wrong and pointers in the right direction will be greatly appreciated.
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- 65 SHS x 4 x1358 Chord 1500 Grid 18mm Holes(Checked).FCStd
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Last edited by Laurie Hartley on Tue Feb 01, 2022 2:54 am, edited 1 time in total.
Re: Request for help meshing and and analysing a part
It’s just hard to obtain a sufficient quality solid mesh for this thin-walled part. The error that you get means that your mesh has nonpositive jacobians. Try with finer mesh or another mesher (Netgen). If this doesn’t work, consider simplifying this part and using shell elements.
Update: It seems that Gmsh yields correct mesh and the analysis runs to completion when max element size is set to 3 or 4.
Update: It seems that Gmsh yields correct mesh and the analysis runs to completion when max element size is set to 3 or 4.
Re: Request for help meshing and and analysing a part
Have you tried to set second order linear? This helps a lot and you do not need to make a very fine mesh.
https://wiki.freecadweb.org/FEM_MeshGms ... _Jacobians
if you use the run button the non positives are green.if there are only a few a local finer mesh or improving the geometry could be an option as well.
bernd
https://wiki.freecadweb.org/FEM_MeshGms ... _Jacobians
if you use the run button the non positives are green.if there are only a few a local finer mesh or improving the geometry could be an option as well.
bernd
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Re: Request for help meshing and and analysing a part
Thanks Bernd - I will try this as well as new jokers suggestion above and post the outcomes tomorrow.bernd wrote: ↑Tue Aug 10, 2021 9:53 am Have you tried to set second order linear? This helps a lot and you do not need to make a very fine mesh.
https://wiki.freecadweb.org/FEM_MeshGms ... _Jacobians
if you use the run button the non positives are green.if there are only a few a local finer mesh or improving the geometry could be an option as well.
bernd
I tried both methods and was able to get a clean mesh but encountered another problem probably best explained by uploading some screen shots - see below. (No modes found in Frd file)
For New Jokers suggestion I set gmsh "from shape" the maximum node size to 3mm and min to automatic.
For you suggestion bernd I set gmsh "2D" and the shell geometry thickness to 4mm. (not sure if I have interpreted your instructions correctly)
I ran an analysis on another part successfuly so I don't think I have broken FreeCAD.
Code: Select all
OS: Debian GNU/Linux 10 (buster) (XFCE/xfce)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.19.2)
Hash: 7b5e18a0759de778b74d3a5c17eba9cb815035ac
Python version: 3.8.8
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: English/Australia (en_AU)
Code: Select all
[code]
System: Host: <filter> Kernel: 5.8.0-3-amd64 x86_64 bits: 64 compiler: N/A
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Repos: No active apt repos in: /etc/apt/sources.list
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Active apt repos in: /etc/apt/sources.list.d/debian.list
1: deb http://deb.debian.org/debian buster main contrib non-free
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Active apt repos in: /etc/apt/sources.list.d/megasync.list
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Active apt repos in: /etc/apt/sources.list.d/softmaker.list
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Info: Processes: 271 Uptime: 6h 16m Memory: 13.61 GiB used: 2.55 GiB (18.7%) Init: SysVinit
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- Attachments
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- No modes found in Frd file_3mm_max_from_shape.png (72.61 KiB) Viewed 42105 times
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- No modes found in Frd file_2D_shell_4mm_output_true.png (128.54 KiB) Viewed 42105 times
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- No modes found in Frd file_2D_shell_4mm-output_false.png (75.76 KiB) Viewed 42105 times
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Re: Request for help meshing and and analysing a part
Here is a sim with 2D-shell elements. I eliminated the fillets in the MSH-profileLaurie Hartley wrote: ↑Tue Aug 10, 2021 11:21 am For you suggestion bernd I set gmsh "2D" and the shell geometry thickness to 4mm.
with the defeaturing-wb. With fillets I get a weird mesh.
For 2D-meshing you must produce a 2D-surface from your solid.
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Re: Request for help meshing and and analysing a part
How to produce the 2D-body from the solids?
Steps:
Defeaturing-wb
1+2+3+4: select inner fillets of strut
5: press button, faces are added to list
6: press button, fillets are removed
Arch-wb:
Select all inner faces from the MSH-solid, tube-solids
Press facebinder-tool
Steps:
Defeaturing-wb
1+2+3+4: select inner fillets of strut
5: press button, faces are added to list
6: press button, fillets are removed
Arch-wb:
Select all inner faces from the MSH-solid, tube-solids
Press facebinder-tool
Re: Request for help meshing and and analysing a part
Hi thomas,
which FC Version did you use for your simulaton?
which FC Version did you use for your simulaton?
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Re: Request for help meshing and and analysing a part
LP-built
OS: Windows 10 Version 1909
Word size of FreeCAD: 64-bit
Version: 0.20.25065 (Git)
Build type: Release
Branch: master
Hash: 4de2ad46b2b9c78ac2721a0dbea7c19306261095
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.0
Locale: German/Germany (de_DE)
Re: Request for help meshing and and analysing a part
It’s a really nice way for solid to shell FEA model conversion in general. However, one has to keep in mind that offset is needed for it to be actual midsurface shell modeling. Is it possible to do it in FreeCAD ? Facebinder’s offset option seems to work differently.thschrader wrote: ↑Wed Aug 11, 2021 10:16 am How to produce the 2D-body from the solids?
Steps:
…
Arch-wb:
Select all inner faces from the MSH-solid, tube-solids
Press facebinder-tool
Btw. Facebinder in Draft workbench is the same tool, right ?