Simpel one end fixed beam force in other end

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Oldbelt
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Joined: 24 Dec 2018, 14:15
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Simpel one end fixed beam force in other end

Post by Oldbelt » 11 Jan 2019, 18:12

I have tried to simulate a beam X =1 Z= 0.1 Y= 0.05 m.
one end fixed the other have a force at 2000 N in -Y direction.
Material pine Youngs M 10e9 .
Text book calc. gives a result at 0,065m displament.
Elmer 8.2m!!.
Can any one help to set a proper Equation up for this
very simple case, I am newbee.
SimpeIndspændtBjælke (1).step
(10.88 KiB) Downloaded 61 times

Change to .stp

Kr. Oldbelt

mzenker
Posts: 1962
Joined: 07 Dec 2009, 11:49
Location: Germany

Re: Simpel one end fixed beam force in other end

Post by mzenker » 11 Jan 2019, 18:38

Hi,

looks like a scaling problem.
If your coordinates are in mm in the STEP file, set Coordinate Scaling = 0.001 in Model->Setup.

HTH,
Matthias

Oldbelt
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Re: Simpel one end fixed beam force in other end

Post by Oldbelt » 12 Jan 2019, 01:47

Hej Matthias.
Tank you for your reply.
My CAD model is in m.
My CAD export to .stp is set to m.
You are righ the meshed Beam loaded into Paraview is in mm.
I thought this faulure was corrected since the former edition of Elmer.
Setting the scale to 0.001 gives still a wrong result, insted af 8.2 m as I wrongly read it, it is 8.2mm.
Scaling gives of course 8.2e-3m still 8.2 mm.
I have used a tutorial called : Tutorial 3 Linear elasticity equation - Loaded elastic beam.
But i have made my ovn beam , I can't find the tutorials file called: beam3d.grd.
The solver setting from this tutorial gives the wrong result with my beam.
Please advice how to procede.

KR. Oldbelt.

mzenker
Posts: 1962
Joined: 07 Dec 2009, 11:49
Location: Germany

Re: Simpel one end fixed beam force in other end

Post by mzenker » 14 Jan 2019, 12:40

Hi,

if Elmer calculates the output in mm, the mesh was also in mm. So at some stage between CAD and Elmer mesh, a scaling factor was applied accidentally to the geometry data.
I would first try to reproduce the tutorial exactly using the files linked on the Elmer documentation page: https://www.csc.fi/web/elmer/documentation.
Then I would start to modify things in the direction of my intended use.

HTH,
Matthias

Oldbelt
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Joined: 24 Dec 2018, 14:15
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Re: Simpel one end fixed beam force in other end

Post by Oldbelt » 15 Jan 2019, 00:34

Hi Matthias.
I have downloaded the tutorial 3Dbeam.
and got the right result a deflection at 0.065m.
It isn't a matter of scaling because check of dimensions can be done in paraview, I had m. as dimension.
It seams to be a matter of meshing, my design out of my CAD was meshed with triangles,
the results was a deflection at 8.2m.
The toturial's meshing is with "rectangles and the textbook result was obtained.
The setup of the sif was similar with the two beam's.
Can it be explaned what happens ?
Kr. Oldbelt and thank you for your support.

mzenker
Posts: 1962
Joined: 07 Dec 2009, 11:49
Location: Germany

Re: Simpel one end fixed beam force in other end

Post by mzenker » 15 Jan 2019, 12:57

Hmmm...
So with the exact same settings and same geometry, you set such a big difference? I doubt that it is due to the mesh being in triangles or rectangles.
I would compare the two cases carefully. You can compare the settings in case.sif and the geometry size in Model->Summary. What is the length of the beam? Also have a look at the fineness of the mesh. If, for example, your CAD mesh is much coarser than the one of the tutorial file, that might have an effect on the result.

HTH,
Matthias

Oldbelt
Posts: 11
Joined: 24 Dec 2018, 14:15
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Re: Simpel one end fixed beam force in other end

Post by Oldbelt » 16 Jan 2019, 16:23

Loaded Beam Oldbelt.zip
(102.8 KiB) Downloaded 56 times
Hej Matthias.
I have run the beam with my beam and Toturial3D beam.
The results is in the Zip file.
Comparing SIF show no difference.
Comparing VTU shows great differences.
The scren dumps show the correct textbook result from toturial 3D beam.
I think it's something about the meshing, I can't control the meshing in my CAD,
only export a STP file which when loading in ElmerGUI is translated to a mesh.

If its is meshing , than how to optimise this process?.

By the way there are anither guy at the forum Elmer Post, I have been in touch with
correcting his textbook formula for a loaded beam.

kind regards Oldbelt.

mzenker
Posts: 1962
Joined: 07 Dec 2009, 11:49
Location: Germany

Re: Simpel one end fixed beam force in other end

Post by mzenker » 16 Jan 2019, 16:26

Hi,

you should do the meshing with an external mesher like Salomé or gmsh.
What does Model->Summary say for the beam from the tutorial, and for the beam from you CAD?

HTH,
Matthias

Oldbelt
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Joined: 24 Dec 2018, 14:15
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Re: Simpel one end fixed beam force in other end

Post by Oldbelt » 17 Jan 2019, 12:49

Hi Matthias.
Thank you for your time.
Summery shows a big difference in amount of nodes ect.
How to judge in the situation with a new task, the needed amount of nodes ect ?
My Beam Summery.zip
(92.51 KiB) Downloaded 59 times
.
I am new and used this toturial to get a feeling with ELMER because textbook exsamples
from UNI is at hand.
My next project is about water flow, I forsee a lot a trouble.
Thamk you for your effort to guide me , I have downloaded gmsh and will try it .

mzenker
Posts: 1962
Joined: 07 Dec 2009, 11:49
Location: Germany

Re: Simpel one end fixed beam force in other end

Post by mzenker » 17 Jan 2019, 13:45

Hi,

look at the section "Bounding Box" in the summary. from Elmer's point of view, the tutorial beam has dimensions of of 0.1x0.05x1 m, whereas your beam has 100x50x1000 m. So for your beam, you should write 0.001 in the Coordinate Scaling field. Or draw a beam that has the same dimensions as in the tutorial.

HTH,
Matthias

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