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Converting shell elements to solid elements  

 

saberman12
(@saberman12)
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July 15, 2019 6:54 am  

Hi, I would like to know if there is anyway of changing shell elements to solid elements. When I import my IGES file from SolidWorks into LS-Prepost, my model always use shell elements. I hope you can tell me if there's any method of changing shell elements to solid elements. 


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Negative Volume
(@negativevolume)
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July 15, 2019 2:24 pm  
Posted by: saberman12

Hi, I would like to know if there is anyway of changing shell elements to solid elements. When I import my IGES file from SolidWorks into LS-Prepost, my model always use shell elements. I hope you can tell me if there's any method of changing shell elements to solid elements. 

So you are importing an IGES file into LS-Prepost and then meshing it in Prepost correct? LS-Prepost is pretty limited when it comes to meshing but I believe you can get a simple tetrahedral mesh of a IGES file in the Mesh tab -> Solid Mesh. In order to do this though your solid needs to be enclosed, meaning that there cannot be any free edges. 


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saberman12
(@saberman12)
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July 16, 2019 1:55 am  

Yes, I am importing IGES to LS-Prepost for meshing. I have hypermesh that I can use for meshing as well. However, I want my model in LS-Prepost to use solid element, not shell element. I would like to know if there is any method of converting my shell element to solid element.


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Negative Volume
(@negativevolume)
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July 16, 2019 1:36 pm  

I have moved this to a new topic as it is really relevant to element formulations. 

You cannot "convert" a shell element to a solid element. You can, however, make a solid 3d mesh from a 2d mesh using something like extrude where you pull the shell mesh a certain distance and determine the number of layers of solids you want. You can also take an enclosed 2d triangular mesh and "fill" it with 3d tetrahedral elements. Does either of these seem like something that you are wanting to do? Also, if you have access to Hypermesh, there is no reason why I would try to do this in LS-Prepost. 


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saberman12
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July 18, 2019 3:50 am  

Thank you. For now, I managed to make solid elements using 2D and 3D mesh by meshing my frame model one portion by one portion. However, I am faced with another issue of my mesh not interacting together. I am modelling a frame with a empty space in the center to be subjected to a blast in LS-PrePost but only the two sides of my frame is moving while the top and bottom sides are not. Do you know why is that the case?


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Negative Volume
(@negativevolume)
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July 18, 2019 3:41 pm  

Could you attach a picture of the mesh? I would assume that you have duplicate nodes at the connecting edges of the individual sides that you meshed, meaning that they are not connected. These should also all be in the same part I am assuming, which you can do in the Element toolbar -> Move/Copy and move all of the elements to the same part. If two sides are not moving while the others are, I would check that you don't have any constraints or rigid materials that could be restricting motion. 


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saberman12
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July 22, 2019 9:43 am  

I had checked for duplicate nodes but there are no duplicate nodes at the connecting edges. Would my mesh be better if I copy existing elements to build my mesh?

1563784984-Capture.png

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Negative Volume
(@negativevolume)
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July 23, 2019 7:08 pm  

It's a little hard to see exactly what's going on. You may not have set the tolerance high enough in the duplicate node check. It's going to search for nodes within that distance and highlight them. If you are really struggling then you can send me the model file and I can look at it: contact@feassistant.com


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saberman12
(@saberman12)
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July 24, 2019 2:51 am  

I had set my tolerance to 0.001 to check. There are no duplicate nodes. I generated one portion of my 3D mesh from the front of my frame and one portion of my 3D mesh from the rear of my frame. And I had used the equivalence function to ensure the area where both 3D mesh meets to be equivalence. Perhaps that is the reason why my mesh are not reacting together?


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Negative Volume
(@negativevolume)
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July 24, 2019 3:00 am  

Increase the tolerance to around 1/4 the size of the element edge length and check for duplicates again. In terms of meshing, It’s generally easiest to mesh from connecting surfaces to free surfaces. So you could try to re-mesh it from either the front or the back only to see if that works. 


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arafat_alam
(@arafat_alam)
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September 10, 2020 12:29 am  
Posted by: @saberman12

Hi, I would like to know if there is anyway of changing shell elements to solid elements. When I import my IGES file from SolidWorks into LS-Prepost, my model always use shell elements. I hope you can tell me if there's any method of changing shell elements to solid elements. 

Hello,

Have you find a way to mitigate this issue? Please share. I also have the same issue. 

1599694195-shell_error_1.jpg

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saberman12
(@saberman12)
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October 13, 2020 10:17 am  

@arafat_alam

From what I understand, when I imported a IGES file into Ls-Dyna, the program will automatically convert all faces to shell elements. You could use Element Generation, click on solid element and generate your solid element. You can do that quite easily for the red and blue boxes. However, for the green object, you may need to use the program auto mesh system to generate the solid elements or use a different meshing program.


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