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"excessive distortion of element..."

Dare1989

Guest
Good morning to all,

I'm modeling a shell structure using shell181. this structure presents on its edges a change of thickness, necessary to make it work and to have acceptable efforts. in a first grosser modeling I divided the surface of the structure into several areas and to each area I gave the thickness that allowed me to obtain acceptable efforts. I'll explain better and put the image of the deformed here to better understand what I'm saying.Deformée.webpI therefore give more important thicknesses to the edges of the structure and to the junction points of the four ipeberbolic paraboloids from which my structure is composed.
in the first modeling there was a dry passage of thickness, so at the edges I had 20 cm, on the points at the top of conjunction 30 and the rest was all 15 cm. I put another image to better understand.file001.webpThis first modeling did not give me any problem even if there was a jump of 15 cm between one area to another.

then I did a second modeling that best described what I would do in reality, so trying to give it a thickness that would change softly. therefore I have created more areas to pass from a thickness of 30 cm to one of 15 cm, in the sense that between one area to the other I have reduced the thickness jump to 5 cm.
When I launch the calculation, it gives me an error message like "excessive distorsion of element..." and the calculation seems not to converge. Now it seems strange to me that you give me a message like this since it worked first anyway. I thought it was a mesh problem, because the elephants were too irregular.

Can you tell me what the problem is?

thanks in advance,

give rise to
 
the problem arises from the fact that you divided your initial area into several areas of smaller surface. ansys cannot create regular shape elements with the division of the surfaces you created. too distorted elements arise and then communicates that message.
you need to change shape to the areas, or create a border division methodology so as to distort less elements. the thickness does not enter the problematic.
 
the problem arises from the fact that you divided your initial area into several areas of smaller surface. ansys cannot create regular shape elements with the division of the surfaces you created. too distorted elements arise and then communicates that message.
you need to change shape to the areas, or create a border division methodology so as to distort less elements. the thickness does not enter the problematic.
Excuse me, but how do you split the edges?
 
Excuse me, but how do you split the edges?
We are at the beginning of what I see:-).

imagine having a rectangular area: before making the mesh of the area create a division of the boundary lines "ad hoc" in such a way as to have a more regular mesh.

look for a bit on google "mapped mesh!" !
 
We are at the beginning of what I see:-).

imagine having a rectangular area: before making the mesh of the area create a division of the boundary lines "ad hoc" in such a way as to have a more regular mesh.

look for a bit on google "mapped mesh!" !
Okay!
 
We are at the beginning of what I see:-).

imagine having a rectangular area: before making the mesh of the area create a division of the boundary lines "ad hoc" in such a way as to have a more regular mesh.

look for a bit on google "mapped mesh!" !
but it is strange that I make a problem, because my surface is composed exclusively of rectangle areasfile004.webp
 
your geometric entities are not properly partitioned so your mesh is not congruent (fem) which is instead being in the fem1 file.

solution: you have to act with the commands you see in fem2 file

greetings
 

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your geometric entities are not properly partitioned so your mesh is not congruent (fem) which is instead being in the fem1 file.

solution: you have to act with the commands you see in fem2 file

greetings
Thank you very much eih64, now I see where the problem is!
 
your geometric entities are not properly partitioned so your mesh is not congruent (fem) which is instead being in the fem1 file.

solution: you have to act with the commands you see in fem2 file

greetings

ciao eih64,

ho provato a fare come suggerito da te, ma ansys mi da errore, credo che si perché le mie aree non si intersecano, ma sono solo congruenti. ansys mi dice "current ansys geometry failed to support booleans operations. see list error window for details"

the following entities do not support booleans.

use the splot command to examine bad surfaces/areas
format for splot is splot,na1,na2,ninc,meshsize

volume shell area loop line
- - 3 1 45
- - 4 1 68
- - 6 1 70
- - 8 1 72
- - 11 1 6
- - 14 1 79
- - 16 1 24
- - 17 1 80
- - 18 1 81
- - 19 1 31
 
I found how to do it, just use the aglue command instead of the one for the areas that intersect. but I find myself with areas with quite irregular elements
 

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