Surface loading

About the development of the FEM module/workbench.

Moderator: bernd

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REDAC38
Posts: 4
Joined: Mon Aug 17, 2020 12:24 pm

Surface loading

Post by REDAC38 » Mon Aug 17, 2020 12:42 pm

Hello,
I am new to freecad, I am experimenting with FEM.
When I apply the pressure constraint, there is a parameter (surface load), except there is no unit.
I want to know which unit is applied for this parameter.

Thank you.


My apologies for not following this procedure.



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: French/France (fr_FR)
Attachments
chargement surfacique.png
chargement surfacique
chargement surfacique.png (127.24 KiB) Viewed 689 times
Last edited by REDAC38 on Tue Aug 18, 2020 11:55 am, edited 2 times in total.
jmaustpc
Posts: 10367
Joined: Tue Jul 26, 2011 6:28 am
Location: Australia

Re: Surface loading

Post by jmaustpc » Mon Aug 17, 2020 1:13 pm

Your first post, welcome to FreeCAD. :)


Firstly always post your version data in the manner explained in the forum Rules link above the Help forum. This is especially important for FEM which is currently in development and improves regularly.

If you are not using the latest snapshot release of FreeCAD0.19 or the daily PPA version or similar, then you should do so if you want to use FEM, 0.18.4 is too old.

Jim
REDAC38
Posts: 4
Joined: Mon Aug 17, 2020 12:24 pm

Re: Surface loading

Post by REDAC38 » Wed Aug 19, 2020 5:09 am

Up please.
chrisb
Posts: 28938
Joined: Tue Mar 17, 2015 9:14 am

Re: Surface loading

Post by chrisb » Wed Aug 19, 2020 5:28 am

As mentioned by jmaustpc you should upgrade to 0.19. The current state of this so called development version is indeed more stable than 18.4. In Addition you can have both versions on your system. Just 7-unzip the 0.19 file and place it in an appropriate folder. Please note that with the default configurations both versions share the same config directory.
A Sketcher Lecture with in-depth information is available in English, auf deutsch, en français, en español.
Jee-Bee
Posts: 2145
Joined: Tue Jun 16, 2015 10:32 am
Location: Netherlands

Re: Surface loading

Post by Jee-Bee » Wed Aug 19, 2020 6:23 am

As far as i can see you don't use pressure. You are using Force.
2020-08-19 08_16_52-Clipboard.png
2020-08-19 08_16_52-Clipboard.png (10.31 KiB) Viewed 644 times
2020-08-19 08_14_28-Clipboard.png
2020-08-19 08_14_28-Clipboard.png (13.05 KiB) Viewed 644 times
It is indeed True that no unit is mentioned it is in Englisch so i want consider this as a translation issue

I understand that it is more clear if both (pressure and force) have a more equal look and feel. My personal prefference would be the textline as by pressure. But that is @Bernd
bernd wrote: ping
REDAC38
Posts: 4
Joined: Mon Aug 17, 2020 12:24 pm

Re: Surface loading

Post by REDAC38 » Thu Aug 20, 2020 4:21 am

Hello,

And thank you for your feedback.
Indeed I was wrong, it is indeed a question of force constraint and not pressure constraint.
I see that in both cases on your version 0.19 the units are mentioned.
perfect, the units are well to mention.


I wanted to know how the part went in the case of my bar. the mass (1000N) is distributed over the whole of the bar or occasionally. I would like to simulate the weight of a man standing on the bar.

Thank you all.

OS: Windows 10 (10.0)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.22270 (Git)
Build type: Release
Branch: master
Hash: 45d28c2367f5714cf5463b3373979c2a6f2779bf
Python version: 3.6.8
Qt version: 5.12.1
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: French/France (fr_FR)
Attachments
répartition du poid.png
répartition du poid.png (156.71 KiB) Viewed 567 times
Jee-Bee
Posts: 2145
Joined: Tue Jun 16, 2015 10:32 am
Location: Netherlands

Re: Surface loading

Post by Jee-Bee » Thu Aug 20, 2020 7:53 am

Best method i think is creating a second shape (solid is not necessary i think) thats intersect with your shape and then use one of the splitting tools (i'm not sure what works best).
Then you have a option to select a smaller surface where you put the force on.

https://wiki.freecadweb.org/Part_CompSplittingTools
HoWil
Posts: 1199
Joined: Sun Jun 14, 2015 7:31 pm
Location: Austria

Re: Surface loading

Post by HoWil » Thu Aug 20, 2020 7:13 pm

We had a similar discussion about applying boundary conditions on specific 'sub-surfaces' in FEM before but I cant find the post....
This i how I did it with boolean-fragments... simply draw a sketch onto the surface you need to divide and apply a boolean-fragments to your body and the sketch.
Attachments
Screenshot from 2020-08-20 21-10-57.png
Screenshot from 2020-08-20 21-10-57.png (355.97 KiB) Viewed 497 times
Screenshot from 2020-08-20 21-11-16.png
Screenshot from 2020-08-20 21-11-16.png (279.45 KiB) Viewed 497 times
FEM body with specific region.FCStd
(226.33 KiB) Downloaded 12 times
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bernd
Posts: 10956
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

Re: Surface loading

Post by bernd » Mon Aug 24, 2020 6:41 am

seams all questions have been answered already.

Just for reference. For constraint force the unit has to b N (the input field does not support FreeCAD unit system) and for constraint pressure the unit can be put in by the user. For example MPa, Pa, kPa, N/mm^2 MN/m^2 etc are know units.
REDAC38
Posts: 4
Joined: Mon Aug 17, 2020 12:24 pm

Re: Surface loading

Post by REDAC38 » Wed Aug 26, 2020 7:50 am

Thank you, for all your answer, I continue to experience all this.
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