Reaction force request
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Reaction force request
Any one knows how to calculate reaction forces on FEM FreeCAD 0.17? Thanks!
Re: Reaction force request
FreeCAD does not read reaction forces into results yet
You need to add RF to the *Node file card and the ccxinputwriter.py
http://web.mit.edu/calculix_v2.7/Calcul ... de159.html
Then on the freecad side read the results in in the ccxfrdreader.py file and pass them to VTK
This is not a difficult one for you to add yourself
Thanks for the contribution
You need to add RF to the *Node file card and the ccxinputwriter.py
http://web.mit.edu/calculix_v2.7/Calcul ... de159.html
Then on the freecad side read the results in in the ccxfrdreader.py file and pass them to VTK
This is not a difficult one for you to add yourself
Thanks for the contribution
Re: Reaction force request
Hi Poimsm, welcome to the forum.
You can request reaction forces in .frd file by
or in .dat file - where it is practical to limit them on some nodeset
this prints reaction forces in x, y, z for all nodes. For me it is practical to ask for total reaction forces
You can easily add this into your .inp file after similar lines when you generates it in FreeCAD, when you insert nodeset(s) which names you can find under *BOUNDARY card in the generated .inp file - something like "FemConstraintFixed".
if TOTALS=YES then you get it in nodes and also totals
However, there are some difficulties with reaction forces. I doubt it is possible to get reaction moments. From http://web.mit.edu/calculix_v2.7/Calcul ... #nodeprint
You can request reaction forces in .frd file by
Code: Select all
*NODE FILE
RF
Code: Select all
*NODE PRINT,NSET=FemConstraintFixed
RF
Code: Select all
*NODE PRINT,NSET=FemConstraintFixed, TOTALS=ONLY
RF
if TOTALS=YES then you get it in nodes and also totals
However, there are some difficulties with reaction forces. I doubt it is possible to get reaction moments. From http://web.mit.edu/calculix_v2.7/Calcul ... #nodeprint
So if you apply loads through rigid body elements, then reaction forces are wrong. If you apply load on fixed node, then this load (e.g. portion of pressure on element face) is not counted to reactions.The external forces are the sum of the reaction forces, concentrated loads (*CLOAD) and distributed loads (*DLOAD) in the node at stake. Only in the absence of concentrated loads in the node and distributed loads in any element to which the node belongs, the external forces reduce to the reaction forces. Forces induced by multiplpoint constraints are not calculated. Since single point constraints defined in transformed coordinates are converted into multiple point constraints in the global rectangular system, the force in a node in which a SPC is defined in local coordinates are not correctly delivered upon using the RF key in combination with the *NODE PRINT keyword card.
Re: Reaction force request
The newer manuals of ccx like version 2.11 have an extra section regarding reaction forces. Have a look here: http://www.feacluster.com/CalculiX/ccx_ ... de177.html
Ulrich
Ulrich
Re: Reaction force request
Hello,
I am not very familiar with FEM FreeCAD and Calculix. I use FreeCAD 0.18 on Windows 10
I try to compute the reaction force on fixed constraint nodes using
RF
as FandaL said.
First question: After generating the .inp file with the write command, I can edit the file directly in FreeCAD , but how to save it directly in FreeCAD?
So I search in my "C:\Users\julien\AppData\Local\Temp\" folder and save the file manually.
Second question:
I calcule the modified .inp file but I don't know where to see the reaction force results. I don't anaything under the CalculiX_static_results node in FreeCAD
Sorry for the basic question.
Julien
I am not very familiar with FEM FreeCAD and Calculix. I use FreeCAD 0.18 on Windows 10
I try to compute the reaction force on fixed constraint nodes using
RF
Code: Select all
*NODE PRINT,NSET=FemConstraintFixed, TOTALS=ONLY
RF
First question: After generating the .inp file with the write command, I can edit the file directly in FreeCAD , but how to save it directly in FreeCAD?
So I search in my "C:\Users\julien\AppData\Local\Temp\" folder and save the file manually.
Second question:
I calcule the modified .inp file but I don't know where to see the reaction force results. I don't anaything under the CalculiX_static_results node in FreeCAD
Sorry for the basic question.
Julien
Re: Reaction force request
see https://forum.freecadweb.org/viewtopic.php?f=18&t=12212
If you would use 0.19 the dat file will be written. The dat file contents will be in the tree in FreeCAD in this dat file content will be the reaction forces.
cheers bernd
If you would use 0.19 the dat file will be written. The dat file contents will be in the tree in FreeCAD in this dat file content will be the reaction forces.
cheers bernd
Re: Reaction force request
Thank you bernd,
Yes I see by myself the improvement with the dat file. This is very good.
Does the reaction force is automatically computed on each BC with fixed constraints condition in 0.19 ? Because I have not add any command in the .inp file and I can see a result.
Is it possible to add some command in the .inp file and have the results in the dat file in FreeCAD?
How can I save directly modification when editing the file .inp via FreeCAD?
Julien
Yes I see by myself the improvement with the dat file. This is very good.
Does the reaction force is automatically computed on each BC with fixed constraints condition in 0.19 ? Because I have not add any command in the .inp file and I can see a result.
Is it possible to add some command in the .inp file and have the results in the dat file in FreeCAD?
How can I save directly modification when editing the file .inp via FreeCAD?
Julien
Re: Reaction force request
Yes reaction forces are added automatically in 0.19
If you use the solver task panel you can edit the inp file before run the inp file. Furthermore the use of the splitted inp file option makes sense in this regard.
No the edit can not be saved ATM.
If you use the solver task panel you can edit the inp file before run the inp file. Furthermore the use of the splitted inp file option makes sense in this regard.
No the edit can not be saved ATM.
Re: Reaction force request
Hi all! I have freecad 0.19 on My Macbook and in .dat file I have only these 2 lines (instead of reaction force for all nodes)
total force (fx,fy,fz) for set FEMCONSTRAINTFIXED and time 0.1000000E+01
1.885456E-01 -3.685454E-02 -3.500000E+03
might be a difference between .dat file in Linux and Mac?
Best
Re: Reaction force request
in FreeCAD the file is just read, means there is no difference. If there is one in ccx run is difficault to say since I have never run ccx on mac. But I would not exclude it ...hex41434 wrote: ↑Fri Jul 30, 2021 8:37 amHi all! I have freecad 0.19 on My Macbook and in .dat file I have only these 2 lines (instead of reaction force for all nodes)
total force (fx,fy,fz) for set FEMCONSTRAINTFIXED and time 0.1000000E+01
1.885456E-01 -3.685454E-02 -3.500000E+03
might be a difference between .dat file in Linux and Mac?
Best
If you post the file I could test on Linux and Windows.