Pressure/force at a hole

About the development of the FEM module/workbench.

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anno15
Posts: 75
Joined: Thu Feb 28, 2019 8:26 pm

Pressure/force at a hole

Post by anno15 »

Hello,

I try to set some fixed constraints an pressure constraints with FEM to calculate it. My part is moved from the zero point.

Project file: https://www.dropbox.com/s/fldelp6ir0fjc ... FCStd?dl=0

Here I have 2 issues?
  • Does the FEM constraint do not support the current position of a part? The constraints are not displayed at the right position. (see image 3.png)
  • How can I set a pressure or force at a hole? The inner 6 holes should be fixed and the outer 4 wholes should be set with an force or pressure constraint but I have no idea how I can set this correctly. (see image 4.png)

Code: Select all

OS: Ubuntu 22.04.2 LTS (ubuntu:GNOME/ubuntu)
Word size of FreeCAD: 64-bit
Version: 0.20.2.29603 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.20.2)
Hash: 930dd9a76203a3260b1e6256c70c1c3cad8c5cb8
Python 3.10.8, Qt 5.15.4, Coin 4.0.0, Vtk 9.1.0, OCC 7.6.3
Locale: English/United States (en_US)
Installed mods: 
  * fasteners 0.4.56
  * sheetmetal 0.2.63
  * Curves 0.6.8
Attachments
3.png
3.png (20.51 KiB) Viewed 524 times
4.png
4.png (27.47 KiB) Viewed 524 times
thschrader
Veteran
Posts: 3129
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: Pressure/force at a hole

Post by thschrader »

It seems that FEM has problems with the part-design body,
the forces/constraints are not attached to the selected positions.
Happens for me too.
I allways use the part-wb for FEM.

Workaround:
Use arch-facebinder tool for extracting the face of the plate.
Run a 2D-FEM with 3 mm shell thickness. Makes meshing/running much easier.
You can adjust the force-direction by selecting edges of the part or other parts,
here the cube. Pressure constraint is allways perpendicular to the selected face.

You can reduce your file size by right-click on mesh in model tree,
select "clear mesh" option.

Test file with cleared-mesh (GMSH):
plate_ts.FCStd
(48.66 KiB) Downloaded 27 times
2D_FEM_facebinder.JPG
2D_FEM_facebinder.JPG (54.15 KiB) Viewed 440 times
force_vector.JPG
force_vector.JPG (41.85 KiB) Viewed 440 times
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