strange result from the constraint transformation

About the development of the FEM module/workbench.

Moderator: bernd

S-Y.Chen
Posts: 11
Joined: Tue Aug 27, 2019 4:33 pm

strange result from the constraint transformation

Postby S-Y.Chen » Fri Nov 08, 2019 8:29 am

I tried to work on the example on this thread https://forum.freecadweb.org/viewtopic.php?t=20238
in which the pin support on the both ends was transformed to cylindrical coordinate system, and the radial displacement is suppressed.

After the analysis, the result of the deformation seems a little strange. The shape of the pin holes remains circles, but it is deformation in the radial direction (the holes become larger).

Did I do anything wrong ? Or this is just the numerical error that cause it looks like the holes are enlarging ?

Regard
S-Y. Chen
User avatar
bernd
Posts: 8475
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland

Re: strange result from the constraint transformation

Postby bernd » Fri Nov 08, 2019 10:36 am

would you post your FreeCAD file and your FreeCAD version info?
S-Y.Chen
Posts: 11
Joined: Tue Aug 27, 2019 4:33 pm

Re: strange result from the constraint transformation

Postby S-Y.Chen » Fri Nov 08, 2019 4:34 pm

Here it is.

Try to scale up the deformation, you will see the holes are enlarged.

>>>>>> Version info
OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.16131 (Git)
Build type: Release
Branch: releases/FreeCAD-0-18
Hash: 3129ae4296e40ed20e7b3d460b86e6969acbe1c3
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: Chinese/Taiwan (zh_TW)
>>>>>> Version info

Regards
S-Y. Chen
Attachments
Test_beam.fcstd
(715.53 KiB) Downloaded 11 times
S-Y.Chen
Posts: 11
Joined: Tue Aug 27, 2019 4:33 pm

Re: strange result from the constraint transformation

Postby S-Y.Chen » Fri Nov 22, 2019 4:20 am

anyone has any idea about this problem ?

Regards
S-Y.Chen
fandaL
Posts: 342
Joined: Thu Jul 24, 2014 8:29 am

Re: strange result from the constraint transformation

Postby fandaL » Fri Nov 22, 2019 8:36 pm

As regards model settings I don't see any mistake.
Enlarging holes in the deformed view (especially when scaled) are due to way of displaying deformation. Transformation to constrain radial displacement around holes created local cylindrical coordinate system. However, by default *.frd file (output from CalculiX) contains results in the global coordinate system, so the tangential displacement is shown in the rectangular c.s. which appears as a rotation and a bit of hole diameter increase.
radial_hole_constraint.png
radial_hole_constraint.png (72.84 KiB) Viewed 132 times
UR_
Posts: 1013
Joined: Tue Jan 03, 2017 8:42 pm

Re: strange result from the constraint transformation

Postby UR_ » Sat Nov 23, 2019 1:35 pm

Screenshot 006.png
Screenshot 006.png (61.95 KiB) Viewed 104 times