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[ICEM] Error: Degenerate to an invalid element

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Old   February 26, 2014, 09:54
Default Error: Degenerate to an invalid element
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Hi,

if I load my ICEM mesh in Ansys Pre I get the error message:
"Hexahedral Element 198678 will degenerate to an invalid element: NodeIDs: ..."

How can I find this element in ICEM? As the element number suggests I have got a quite large geometry and by clicking "Mesh" -> RMB -> "Element Numbers" I can't find that element. Is there a possiblity to show just that one element?

I know the mesh quality button and I tried to eliminate negative elements, but the problem somehow persists. I got some prisms in my mesh, although they are not desired. A short google search told me that prisms could be the problem. That's why I want to change my blocking (see attached pictures).
Mistakenly I merged vertices and now I got this "K-style" blocking (picture 1 and 2). Actually I want an "H-style" blocking. I tried it but now the vertices are not correctly connected (picture 3).

Anyone an idea how to do that?

Best regards
G.
Attached Images
File Type: jpg Wrong Merged Vertices.jpg (38.0 KB, 15 views)
File Type: png Wrong blocks.png (4.6 KB, 12 views)
File Type: png My try.png (9.2 KB, 11 views)
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Old   February 26, 2014, 13:07
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Sebastian Engel
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Try out the "split vertices" feature in the split block page.

Attached are pictures which shows which vertices you could try to pick. I don't know which order is the most adviced. You can try out different selection orders.

After you selected the vertices and applied the splitting, click on refresh.

Sebastian.
SplitVertices.jpg
SplitVertices3D.jpg
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Old   February 26, 2014, 13:17
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Hi,

that's what I did already. The result is the "My try" picture in my first post. But then the blocks are not connected correctly. I need to move the middle block to the left, so it is connected with the blocks lying at the surface of the geometry. Currently, the middle blocks are moved inside so that the wrong vertices are connected.

G.
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Old   February 26, 2014, 13:53
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Are you sure it didn't work this way to "unmerge" those vertices.

This is what i get after using the split vertices feature
SplitVertices3DAfterSplit.jpg
the recovered block is skewed but its possible to regain the H-shape by moving the vertices back to the wanted position and check the association of the vertices, edges and faces in this region.
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Old   February 26, 2014, 14:24
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Thanks a lot for your fast response, I'll give it a new try.
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Old   February 28, 2014, 06:01
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Hi,

it really worked the way you explained. What I did before was to split the upper vertices, split the middle block and then split the lower vertices. By doing so the result was the one which can be seen in my earlier screenshot.

Do you also know an answer to my first question: How to show a single element with given number in ICEM?

Best regards.
G.
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Old   March 3, 2014, 07:27
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Well, I found out that it seemed to work according to the edges. But now I can see that the middle block is not created in my case although the edges give rise to the suspicion that there is a block. What could be the problem?

Best regards.
G.
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File Type: jpg Missing block.jpg (49.9 KB, 7 views)
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Old   March 3, 2014, 11:15
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I've solved it myself by creating a block with "Create block" -> "By vertices/faces" and selected the 8 adjoining vertices.
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Old   March 3, 2014, 13:05
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Your case also has blocks in the third direction, i didn't saw that.

To your other question, i also haven't found a way to select an element by ID. Possibly, there is a tcl function for the replay scripts to do that which i haven't found yet.
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