[SOLVED] FEM: elements do not stick together (invalid geometry?)

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Roland
Posts: 224
Joined: Fri Aug 21, 2015 2:20 pm

[SOLVED] FEM: elements do not stick together (invalid geometry?)

Postby Roland » Thu Oct 17, 2019 12:01 pm

Dear Forum,

My FEM calculations misbehave.

This my input:
FEMInput.PNG
FEMInput.PNG (33.82 KiB) Viewed 281 times
This my output:
FEMOutput.PNG
FEMOutput.PNG (61.13 KiB) Viewed 281 times
Obviously, the L-profile is not attached to the bottom plate. How can I arrange that?

Part is a compound made from faces and wires:
FEMCompound.PNG
FEMCompound.PNG (3.86 KiB) Viewed 281 times
Part is invalid, says Part WB (I do not know what that exactly means):
PartValidity.PNG
PartValidity.PNG (27.22 KiB) Viewed 281 times

Do you have any clues for me?

Best regards,

Roland

On:
OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16117 (Git)
Build type: Release
Branch: releases/FreeCAD-0-18
Hash: dbb4cc6415bac848a294f03b80f65e888d531742
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedKingdom (en_GB)
Last edited by Roland on Thu Oct 17, 2019 1:15 pm, edited 1 time in total.
Roland
Posts: 224
Joined: Fri Aug 21, 2015 2:20 pm

Re: FEM: elements do not stick together (invalid geometry?)

Postby Roland » Thu Oct 17, 2019 1:06 pm

I found perhaps part of the answer.
To create a valid part: Select all, PartWB/Boolean/Union. This gives a Fusion that is "valid".

However, now FEM gives errors. I am analyzing this further, and shall revert soon.

Roland
Roland
Posts: 224
Joined: Fri Aug 21, 2015 2:20 pm

[SOLVED] Re: FEM: elements do not stick together (invalid geometry?)

Postby Roland » Thu Oct 17, 2019 1:15 pm

All solved. After the Union command was done and the geo was "valid", I made a FEM mistake of incomplete definitions of shell plate thickness.
The Union command increased the amount of shells. (which I overlooked).

Suggestion: There are multiple FEM wikis around, only one of them mentioned the need of Fusion. Compare:
https://www.freecadweb.org/wiki/Manual: ... M_analyses
https://www.freecadweb.org/wiki/FEM_tutorial

Perhaps make this more uniform (I know ... time ...)

Thaks for this great software!

Roland
User avatar
bernd
Posts: 9246
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

Re: [SOLVED] Re: FEM: elements do not stick together (invalid geometry?)

Postby bernd » Fri Oct 18, 2019 6:15 am

Hi Roland,

welcome to FreeCAD FEM.
Roland wrote:
Thu Oct 17, 2019 1:15 pm
All solved. After the Union command was done and the geo was "valid", I made a FEM mistake of incomplete definitions of shell plate thickness.
The Union command increased the amount of shells. (which I overlooked).

Suggestion: There are multiple FEM wikis around, only one of them mentioned the need of Fusion. Compare:
https://www.freecadweb.org/wiki/Manual: ... M_analyses
https://www.freecadweb.org/wiki/FEM_tutorial

Perhaps make this more uniform (I know ... time ...)
You could get wiki write permissions and just add what you have encountered.


cheers bernd
Roland
Posts: 224
Joined: Fri Aug 21, 2015 2:20 pm

Re: [SOLVED] FEM: elements do not stick together (invalid geometry?)

Postby Roland » Tue Nov 05, 2019 7:51 pm

Thanks, Bernd, for the suggestion to give wiki write permissions.
However, at this stage I am not competent to make proper use of it.
In stead, let me propose some adaptations to the wikis, for others to consider and implement where needed.

Best regards,
Roland