Virtual Test Bench with Heavy Wall Pipe

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HarryvL
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Virtual Test Bench with Heavy Wall Pipe

Postby HarryvL » Fri Feb 02, 2018 10:00 pm

Hi all,

I analysed a heavy wall pipe with FEM work bench.

PIP3_Mesh_BC.jpg
PIP3_Mesh_BC.jpg (100.76 KiB) Viewed 2216 times

With this set up I aim to create uniform bending moment in the center span. This is just a first test before I try to analyse composite pipe-in-pipe assemblies. The work flow of creating Booleanfragments, Compoundfilter, etc. etc. I explain in a Tutorial, here:

https://www.freecadweb.org/wiki/FEM_She ... site_Block

So far the results are encouraging.

PIP1_Deformed_Mesh.jpg
PIP1_Deformed_Mesh.jpg (97.19 KiB) Viewed 2216 times

The displacements are within 2% of what I get with simple beam theory.

Please forgive me, but I still use Paraview to get the really glossy pictures.

PIP3_Deformation_Stress.png
PIP3_Deformation_Stress.png (84.33 KiB) Viewed 2216 times

Above picture shows uniform bending stresses in the central span ... hooray ... and next picture shows stresses that are in line with bending theory.

PIP3_Normal_Stress.png
PIP3_Normal_Stress.png (41.55 KiB) Viewed 2216 times

Next challenge, real pipe-in-pipe on this virtual test bench :D

As always, comments and suggestions welcome :!:

Harry
Last edited by HarryvL on Thu Feb 08, 2018 8:28 am, edited 2 times in total.
thschrader
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Re: Virtual Test Bench with Heavy Wall Pipe

Postby thschrader » Sat Feb 03, 2018 8:35 am

Hi Harry,
the "virtual test bench" is a nice idea. Would be interesting to see how a
test-case behaves with the different solvers/meshes and on different
machines/OS. Why have you put the vertical loadings nearby the fixings
into the model?
Thomas
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HarryvL
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Location: Netherlands

Re: Virtual Test Bench with Heavy Wall Pipe

Postby HarryvL » Sat Feb 03, 2018 8:56 am

Hi Thomas,

Yeah it would be fun to test different models and solvers.

I put loads at the free surfaces (faces) of the support in equilibrium with the "external" loads to prevent stress concentrations at the fixed supports. The supports need to hinge at both sides and slide at one. This means that I can only fix the edges of the supports. So if I don't apply reaction forces then all the load is transferred to the edge of the support and this would create huge stress concentrations, spoiling all the stress plots and causing spurious deformations.
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HarryvL
Posts: 1071
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Location: Netherlands

Re: Virtual Test Bench with Heavy Wall Pipe

Postby HarryvL » Tue Feb 06, 2018 8:38 pm

HarryvL wrote:
Fri Feb 02, 2018 10:00 pm

Next challenge, real pipe-in-pipe on this virtual test bench :D
Thanks to help received from HoWil (https://forum.freecadweb.org/viewtopic. ... 7&start=20), I now have a robust work flow for assigning properties to internal regions. So I finally managed to model and analyse the pipe-in-pipe assembly (two concentric pipes bonded together with grout) :D

PIP6_Model.png
PIP6_Model.png (200.93 KiB) Viewed 1781 times
PIP6_Def_End_cut.png
PIP6_Def_End_cut.png (222.96 KiB) Viewed 1781 times

Mid-span stresses in the outer tube are reduced from ~34MPa to ~25MPa due to the contribution from the inner tube. This is in line with what I get from beam theory, using a composite second moment of inertia.

PIP6_Ver_Slice_Mid_Szz.png
PIP6_Ver_Slice_Mid_Szz.png (71.35 KiB) Viewed 1781 times

... but near the ends of the inner tube, stresses are fully transferred back to the outer tube. Again, stresses are in line with beam theory. The behavior of the assembly in the transition zone near the end of the inner tube and the length of this zone can only be obtained from FEA.

PIP6_Ver_Slice_End_Szz.png
PIP6_Ver_Slice_End_Szz.png (55.94 KiB) Viewed 1781 times

Radial stresses in the grout can also be extracted from the model (not shown here).

All-in-all a fun learning experience !
Last edited by HarryvL on Fri Feb 09, 2018 6:52 am, edited 3 times in total.
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sgrogan
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Re: Virtual Test Bench with Heavy Wall Pipe

Postby sgrogan » Wed Feb 07, 2018 1:15 am

HarryvL wrote:
Fri Feb 02, 2018 10:00 pm
The work flow of creating Booleanfragments, Compoundfilter, etc. etc. I explain in a Tutorial, here:
@HarryvL did you see this thread? https://forum.freecadweb.org/viewtopic.php?f=8&t=26759
Your work would be excellent to show FEM :)
HarryvL wrote:
Fri Feb 02, 2018 10:00 pm
Please forgive me, but I still use Paraview to get the really glossy pictures.
This illustrates FreeCAD FEM's integration with other FOSS projects!
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HarryvL
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Location: Netherlands

Re: Virtual Test Bench with Heavy Wall Pipe

Postby HarryvL » Wed Feb 07, 2018 4:39 am

sgrogan wrote:
Wed Feb 07, 2018 1:15 am

@HarryvL did you see this thread? https://forum.freecadweb.org/viewtopic.php?f=8&t=26759
Your work would be excellent to show FEM :)
Thanks @sgrogan, I am happy to support ...

By the way, here a few more pleasing pictures. First a combined view of model and deformation

PIP6_Model_and_Def_Combined.png
PIP6_Model_and_Def_Combined.png (240.63 KiB) Viewed 1659 times



and a few to show the integration with CalculiX CGX pre-processor in my work flow, which I use to review the quality of internal meshes before running the analysis. The file names give the context.


PIP6_CGX_Inner_Tube_1.png
PIP6_CGX_Inner_Tube_1.png (94.37 KiB) Viewed 1659 times

PIP6_CGX_Grout_1.png
PIP6_CGX_Grout_1.png (81.04 KiB) Viewed 1659 times

PIP6_CGX_Outer_Tube_1.png
PIP6_CGX_Outer_Tube_1.png (154.02 KiB) Viewed 1659 times

PIP6_CGX_Supports_1.png
PIP6_CGX_Supports_1.png (59.95 KiB) Viewed 1659 times