Reaction forces

About the development of the FEM module/workbench.

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mthulson
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Joined: Wed Jun 05, 2019 6:06 pm

Reaction forces

Postby mthulson » Wed Jun 05, 2019 7:01 pm

I just started using the FreeCAD FEM module and managed to analyze a part I've designed. I fixed one face and constrained the displacement of an edge. The results look good, but I need reaction forces at the edge I've displaced, and that's not included in the results. I found a discussion that sounds like what I need (https://forum.freecadweb.org/viewtopic. ... =4&t=20664), but unfortunately I don't understand how to implement the suggestions. Can anyone help and/or point me toward a tutorial designed for idiots that will help me figure this out?
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PrzemoF
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Re: Reaction forces

Postby PrzemoF » Wed Jun 05, 2019 8:09 pm

@bernd: is it something that could be done easily or there is some coding required?
UR_
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Re: Reaction forces

Postby UR_ » Thu Jun 06, 2019 5:33 am

I think an appropriate example can be found here:


https://forum.freecadweb.org/viewtopic. ... on#p167047


Example file is some days old, perhaps updating is necessary :?

EDIT: updated files

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.16921 (Git)
Build type: Release
Branch: master
Hash: 39e748229e67fa93e924e355c0ce0897c870d756
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: German/Germany (de_DE)


Ringauge.FCStd
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Last edited by UR_ on Thu Jun 06, 2019 7:16 am, edited 1 time in total.
chrisb
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Re: Reaction forces

Postby chrisb » Thu Jun 06, 2019 6:46 am

Moved to FEM.
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bernd
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Re: Reaction forces

Postby bernd » Thu Jun 06, 2019 7:15 am

would be a nice addition to FEM ... has been a feature request for years ... issue #2934
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bernd
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Re: Reaction forces

Postby bernd » Thu Jun 06, 2019 11:54 am

How about adding an option to create reaction forces for every restrained boundary condition? This would be easy to implement. Still one would need to open the dat file anyway to get the forces but it is no longer needed to edit the input file.

bernd
mthulson
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Re: Reaction forces

Postby mthulson » Thu Jun 06, 2019 3:45 pm

I'm afraid I'm missing something fundamental (and probably obvious to everyone but me). I gather that .inp, .dat, and/or .frd files define the problem and output the results. I set the problem up and solved it using CalculiX in the FreeCAD FEM module, but can't find .inp, .dat, or .frd files anywhere.

What am I missing? Sorry to be so obtuse.
UR_
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Re: Reaction forces

Postby UR_ » Thu Jun 06, 2019 5:52 pm

mthulson wrote:
Thu Jun 06, 2019 3:45 pm
... but can't find .inp, .dat, or .frd files anywhere ...
Please have look at Edit->Preferences->FEM->General

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bernd
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Re: Reaction forces

Postby bernd » Thu Jun 06, 2019 7:16 pm

activate on view -> panels -> report view. Run the analysis, there will be printed a lot in report view, one of the last lines is the path to the dat file ...
mthulson
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Re: Reaction forces

Postby mthulson » Fri Jun 07, 2019 4:33 am

I figured out that if I double click on CalculiXccxTools in the tree view, I get a Mechanical Analysis dialog where I can set the working directory, then write the .inp file, then edit it, then run CalculiX. When I add the lines in the example from UR_, the reaction loads are included in the .dat file. Previously, I was using the "Runs the calculations for the selected solver" button.

For some reason, setting the working directory in edit -> preferences -> FEM didn't seem to work. When I open the report view as bernd suggested, I see "FEM preferences working dir is not set, the solver working directory is used."

Anyway, it's working now. Thanks for the help!