Mesh generation problem

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escolano
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Re: Mesh generation problem

Postby escolano » Wed May 09, 2018 7:48 pm

about the question
So, I would like to ask that if the model is correct, but the mesh is wrong (partially), would it affect on the results after FEM analysis?


It if is the related graphic card problem, (that show a wrong mesh just after meshing, but the mesh seems ok simply reopening the file)
then the mesh is really Ok in GiD, what seems that is corrupted is the copy of nodes coordinates that is stored in the graphic card memory.
in this case it won't affect any FEM analysis, because the input file is written from the RAM data of GiD, that is not corrupted.
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escolano
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Re: Mesh generation problem

Postby escolano » Wed May 09, 2018 7:58 pm

About following a tutorial,
If do you want to prevent possible small deviations from the behavior of the tutorial I recommend you to use a official GiD version (current last is 13.0.4).
Developer versions (current last is 13.1.11d) could have some (small) difference related to the tutorials (that were written for the official version)

In a month the last developer will become the next 14.0 official, and its tutorials will be updated to fit the current behavior
pamelissa
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Joined: Fri Feb 16, 2018 10:01 am

Re: Mesh generation problem

Postby pamelissa » Tue May 29, 2018 7:01 am

I have a problem about a tutorial exercise of the GiD-SAFIR software. The "tutorial for GID-SAFIR 3D Structural Analysis - exercise n°9 Hall 2 3D" (12/2011). I was able to do exercise n°8 correctly but as far as exercise n°9 is concerned, there is an error message when I generate the messages

"Condition 'Beam-Load' has flat 'on body elements' and maybe it needs flat 'on face elements' in the .cnd file in the problem type
Condition 'Mass_on_Beam' has flat 'on body elements' and maybe it needs flat 'on face elements' in the .cnd file in the problem type
Error when transfering condition 'Beam-Load' from geometry to mesh in line 10. It has notbeen transferredError when transfering condition 'BEAM_Cross_section' from geometry to mesh in line 10. It has not been trasnferredError when transfering condition 'Mass_on_Beam' from geometry to mesh in line 10. It has not been transferred. "

I do not understand the error, I don't know how to solve it. I did the autorail many times to be sure to don't forget anything, but it still doesn't work. if you have any idea of the problem, thank you for your help.
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escolano
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Re: Mesh generation problem

Postby escolano » Tue May 29, 2018 4:24 pm

The error/warning message mean than the condition named 'Beam-Load' was declared (defined in the .cnd of the problemtype) to be applied 'over lines' of geometry, and 'over body element' of mesh.

And the condition in applied to a geometric line that is not generating any '2-nodes line element', and then the element to apply the condition doesn't exists.
The line is not generating a 'line-element' because belong to a surface, and are generated quadrilaterals/triangles, and then by default GiD delete the lower-level line elements.
If the condition were defined 'over face element' then will be applied to some face of some quadrilateral/triangle with and edge over the line.
In this case is defined 'over body element' and then expect that the line element explicitly exists.

To force having the line-elements of a line that belong to a surface you must explictly say to do it, there are two ways:
1) assign the the desired line
Mesh->Mesh criteria->Mesh->Lines
and select the lines you want to force.

2) enable a global variable that say that 'all lines' must be forced to be meshed.
This is the option that is explained in this tutorial of SAFIR 2016 (I've just downloaded to have a look)
Do you have missed this point of the tutorial:
10.Generate Mesh
From the pull down menu select preferences [ ], open the meshing tab and
select [ ] (beam) as “Mesh always by default” (in the bottom of the window)


The option could be in different place depending on your GiD version.
Now it is located in Utilities->Preferences...
Meshing->Other-Mesh always by default
select the icon of lines and press apply to accept the change.
komayyamok
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Joined: Tue Aug 21, 2018 1:52 pm
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Re: Mesh generation problem

Postby komayyamok » Tue Aug 21, 2018 2:14 pm

KaniTo wrote:
escolano wrote:Try re-opening the file, How look the mesh then?
(without re-mesh, in some case seems that the mesh really is internally ok, but its representation inside the graphic card become wrong)

Check also that do you have only a volume, maybe there are more than one with the same surfaces as boundary



Thank you very much for your suggestion PhenQ
It seems to be o.k. after I re-opened the program.

May i ask you one more question?
Now, i am leaning how to use GID
I try to follow the instruction, but sometimes the error was found after I generated mesh. (please see the attach file)
In my opinion, the program should automatically generate the uniformly and symmetry mesh. (my opinion may be wrong)
So I would like to ask you that in case I did some thing wrong during drawing the model, which cause the wrong mesh generation.
What should I do? can I correct the model without re-drawing.

Thank you,

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