[solved] tube connection

About the development of the FEM module/workbench.

Moderator: bernd

thschrader
Veteran
Posts: 3129
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

[solved] tube connection

Post by thschrader »

Hi,
I must calculate a tube connection (R550x12,5 -- R660x16 Steel S235)
under momentum-loading. Meshing works without error, but I cant write
the case. What I am doing wrong? Can someone have a look at this?
Thanks. Thomas
gurbrü_flansch_559_660.FCStd
(415.29 KiB) Downloaded 38 times
gurbrü_flansch_559_660_fem.FCStd
(106.19 KiB) Downloaded 38 times
Done with:
OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.15273 (Git)
Build type: Release
Branch: master
Hash: 4e77cee5ee6efa1b28290c10ccb8b2540b9eecaf
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: German/Germany (de_DE)
pipe_connection_CAD.JPG
pipe_connection_CAD.JPG (50.06 KiB) Viewed 1508 times
pipe_connection_gmsh.JPG
pipe_connection_gmsh.JPG (118.21 KiB) Viewed 1508 times
error.JPG
error.JPG (122.46 KiB) Viewed 1508 times
Last edited by thschrader on Fri Nov 30, 2018 2:06 pm, edited 1 time in total.
thschrader
Veteran
Posts: 3129
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: tube connection

Post by thschrader »

some more info...
site location: Gurbrü, Switzerland
drawing_connection.JPG
drawing_connection.JPG (160.81 KiB) Viewed 1505 times
photo_mast.JPG
photo_mast.JPG (75.82 KiB) Viewed 1505 times
User avatar
bernd
Veteran
Posts: 12849
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland
Contact:

Re: tube connection

Post by bernd »

Seams the ü makes problems. This used to work. Try a file and path name without special character like ü. May be we indroduced this with all the Py3 fixes and broke Py2.
User avatar
bernd
Veteran
Posts: 12849
Joined: Sun Sep 08, 2013 8:07 pm
Location: Zürich, Switzerland
Contact:

Re: tube connection

Post by bernd »

BTW: cool project!
UR_
Veteran
Posts: 1354
Joined: Tue Jan 03, 2017 8:42 pm

Re: tube connection

Post by UR_ »

At first sight, this joint look's more reliable :?

RogersCommission-v1p57.jpg
RogersCommission-v1p57.jpg (77.42 KiB) Viewed 1450 times

But, unfortunately it wasn't :cry:
thschrader
Veteran
Posts: 3129
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: tube connection

Post by thschrader »

bernd wrote: Thu Nov 29, 2018 4:13 pm Seams the ü makes problems.
Yes. After renaming the FC-file everything runs fine.
it_works.JPG
it_works.JPG (77.32 KiB) Viewed 1402 times
thschrader
Veteran
Posts: 3129
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: [solved] tube connection

Post by thschrader »

Did some tests with a cylinder and 2D-shell elements.
You get good results with netgen and 1.-order elements.
The tube connection is based on one sketch and is parametric.
When changing the sketch, netgen does a remesh automatically.
Meshing needs only 20 sec, calculating less than 30 sec.
So I will use this model for my static calculation of the antenna-mast.
shell_model_tube_connection.JPG
shell_model_tube_connection.JPG (100.66 KiB) Viewed 1359 times
User avatar
HarryvL
Veteran
Posts: 1283
Joined: Sat Jan 06, 2018 7:38 pm
Location: Netherlands

Re: [solved] tube connection

Post by HarryvL »

Nice case study Thomas.

I found in other posts that CCX shell stresses (especially at corners and connections) can be very inaccurate. Also: when output is set to 2D then only mid-surface stresses are reported. These do not capture local bending effects.
thschrader
Veteran
Posts: 3129
Joined: Sat May 20, 2017 12:06 pm
Location: Germany

Re: [solved] tube connection

Post by thschrader »

Hi Harry,

thanks for the hint.
But in this case I must live with errors. The problem is:
For the existing mast-structure we get absolutely no documentation
(no construction-plans, no statics, no material-lists, nothing about the foundation...nothing!)
The network-carrier (I forgot the name) gave the whole document-management to the
former general-contractor. XXX forgot to put a passage into the contract,
that the sub must give them all documents after finishing the contract.
Finishing in this case means: they dont like each other anymore...
Now we are the new rider on the horse...
The CAD-drawing from above is from an other more or less similar mast-structure.
We will make a geometry-check at the site. The biggest problem is the foundation.
How can I detect the rebar structure in a massive concrete block?
What about checking the soil under the foundation?
The good news: antenna-masts like this are designed for a minimim deflection.
The radio-mirrors on top only work, when the rotation on top of the mast is less
then one degree under full wind loading. Otherwise the link to the receiver-mirror
(which can be kilometers away) can break. So you need a high tube stiffness, which
automatically gives a stress utilization below 60 %.
Thomas
User avatar
HarryvL
Veteran
Posts: 1283
Joined: Sat Jan 06, 2018 7:38 pm
Location: Netherlands

Re: [solved] tube connection

Post by HarryvL »

thschrader wrote: Sat Dec 01, 2018 3:06 pm ...forgot to put a passage into the contract,
that the sub must give them all documents after finishing the contract.
Uh oh. :shock: Yep I have seen that happen before :D

How did you create the model in FC? I see various tubes and rings. How did you create those surfaces and stitch them together?
Post Reply