Pipe Analysis

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Outsourced
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Pipe Analysis

Post by Outsourced »

Hello FC,
Please see the attached Video, https://youtu.be/sj2NKQf8TiA
Two questions I pose in FEM
1, Beam Section Analysis - is this Anna Struct does that need to be installed prior, examples?
2, Shell Plate Thickness is the way I am doing it right? why doesn't the 3d view update?
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NewJoker
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Re: Pipe Analysis

Post by NewJoker »

What is Anna Struct and what do you mean by beam section analysis ? Calculating moments of inertia and other properties for arbitrary beam cross-sections ?

Shell thickness is not visualized in preprocessing, you can only see it in results when shells are expanded to solids by CalculiX.
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Re: Pipe Analysis

Post by thschrader »

Outsourced wrote: Fri Jan 27, 2023 8:51 am ...
2, Shell Plate Thickness is the way I am doing it right?
Yes, using 2D-shell elements is a good way.
You should use the mid-plane of the tube as facebinder,
which has a radius of 36,75 mm instead of 38,05 mm as shown in your video.
Your tube is a little bit too stiff.

Beam theory gives 33 MPa stress, 0,7 mm deflection,
FEM gives 35 MPa at 0,7 mm deflection.

You should always check the resulting forces in ccx-dat result.
tubeFEM.FCStd
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tube_calc.JPG
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Outsourced
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Re: Pipe Analysis

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NewJoker wrote: Fri Jan 27, 2023 2:56 pm What is Anna Struct?
Here is a link a thread https://forum.freecadweb.org/viewtopic. ... 3&p=337543 2d Analysis
NewJoker wrote: Fri Jan 27, 2023 2:56 pm what do you mean by beam section analysis ?
Correction 'Beam Cross Section' https://wiki.freecadweb.org/FEM_ElementGeometry1D is vague is there any examples or tutorials?
NewJoker wrote: Fri Jan 27, 2023 2:56 pm Calculating moments of inertia and other properties for arbitrary beam cross-sections ?
That would be handy, how?
NewJoker wrote: Fri Jan 27, 2023 2:56 pm Shell thickness is not visualized in preprocessing, you can only see it in results when shells are expanded to solids by CalculiX.
Are you refering to https://wiki.freecadweb.org/FEM_FemMesh2Mesh ?
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Re: Pipe Analysis

Post by Outsourced »

thschrader wrote: Fri Jan 27, 2023 4:29 pm
You should use the mid-plane of the tube as facebinder,
which has a radius of 36,75 mm instead of 38,05 mm as shown in your video.
Maybe that was lost in translation a little? When I use your file with corrected Dimensions Calculix returns the values you speak of. I mesh the Facebinder which is the circumference of the tube. The midplane would be cutting a longitudinal section.

I think its important for future readers to understand the Corrected Bending Stress of 35MPa is not the final result you will still need to complete the calculation of Total Fibre Stress to understand the stresses. Would you agree?
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Re: Pipe Analysis

Post by thschrader »

Outsourced wrote: Fri Jan 27, 2023 6:05 pm ...
I think its important for future readers to understand the Corrected Bending Stress of 35MPa is not the final result you will still need to complete the calculation of Total Fibre Stress to understand the stresses. Would you agree?
I agree. Go ahead! :)
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Re: Pipe Analysis

Post by thschrader »

https://wiki.freecadweb.org/Macro_FCInfo

for calculating cross-section parameters (and other stuff)
like moment of inertia, area...
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NewJoker
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Re: Pipe Analysis

Post by NewJoker »

Outsourced wrote: Fri Jan 27, 2023 5:43 pm Here is a link a thread https://forum.freecadweb.org/viewtopic. ... 3&p=337543 2d Analysis
Thanks, so it’s actually a Python library for 2D FEM of trusses and frames. And it’s actively developed. Together with FreeCAD GUI it could make a really handy tool.

Outsourced wrote: Fri Jan 27, 2023 5:43 pm Correction 'Beam Cross Section' https://wiki.freecadweb.org/FEM_ElementGeometry1D is vague is there any examples or tutorials?
This is just a definition of dimensions of a few standard beam cross-sections that can be used for beam elements in CalculiX.

Outsourced wrote: Fri Jan 27, 2023 5:43 pm That would be handy, how?
There’s another Python library for this purpose: https://github.com/robbievanleeuwen/section-properties
Unfortunately, there’s no GUI for it yet.

Outsourced wrote: Fri Jan 27, 2023 5:43 pm Are you refering to https://wiki.freecadweb.org/FEM_FemMesh2Mesh ?
No, that’s something completely different, meant for exporting the deformed mesh obtained from FEA. The visualization that I’m talking about should happen automatically, provided that the OUTPUT parameter of the *EL FILE keyword is set to 3D. This can be controlled directly in FreeCAD - make sure that "Beam Shell Result Output 3D" is set to true in CalculiX solver settings.
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Re: Pipe Analysis

Post by Outsourced »

NewJoker wrote: Fri Jan 27, 2023 8:44 pm

This is just a definition of dimensions of a few standard beam cross-sections that can be used for beam elements in CalculiX.
It Can? I can't! wouldn't it just be a matter of selecting a wire, edge or other then defining the cross-section & then run the analysis - There's no more info on this anywhere. Beam Cross Section in FEM is Vague, we need an example.
NewJoker wrote: Fri Jan 27, 2023 8:44 pm

There’s another Python library for this purpose: https://github.com/robbievanleeuwen/section-properties
Unfortunately, there’s no GUI for it yet.
It sounds like Anastruct, Section Properties, & FEM Cross Sections are made for each other. May the Dev's be blessed with an eternity of Covid restrictions & Lock downs. Joking........'mostly'. Thanks for your work.
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Re: Pipe Analysis

Post by NewJoker »

Outsourced wrote: Sat Jan 28, 2023 3:17 am It Can? I can't! wouldn't it just be a matter of selecting a wire, edge or other then defining the cross-section & then run the analysis - There's no more info on this anywhere. Beam Cross Section in FEM is Vague, we need an example.
The usage section describes all the necessary steps - just pick the type of cross-section, specify the dimensions (one or two, depending on the section type) and optionally select wires to which this cross-section definition will be applied. By default, it’s simply applied to all wires.

You can find some example files on this forum and there are also YouTube tutorials like this one: https://youtu.be/JMRuhY5ICqs
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