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Everything posted by Alucard

  1. Hi Rahul, Thanks for the reply. I've checked the document, but it doesn't specify the exact way to determine the beam diameters. On page 5, it says the diameters are proportional to the density value. So if I have an edge between two elements and each had a different density value (say 0.4 and 0.5). How would I determine the diameter at each node? Thanks
  2. Hi, I've been learning how to use optistruct in lattice optimization and I've come across this tutorial. https://forum.altair.com/applications/core/interface/file/attachment.php?id=881 After following the tutorial, I noticed once the initial lattice is generated (before sizing optimization) that strut has it's unique diameter. Is there any reference on how the diameters are determined initially? Thanks
  3. Hi, I would like to know if it's possible to create a clean 3d mesh from an STL file as shown in the image below. I tried the mesh wrap option in 2D and checked the create solid (all tetra) option. But I encountered several problems. The mesh most of the times can jump of the boundaries of the STL file, some elements with very poor quality for FEM analysis are generated (even though I'm using a reasonable size for the elements). Is there a way to do this?
  4. My issue isn't about memory or computational time though. It's about manually having to add the conduction elements internally to get the result that I wanted. If I Was to select all elements, Hypermesh will only add the elements to the external faces of the mesh. So in the case of my 100x100x100, I had to mask every other column and then added the conduction elements. This allowed me to have at least one face in every element that is attached to a conduction element. If I didn't do this, I wouldn't get the results that I'm looking for. Is there another efficient way I can do this? @wumindao Yes, the file Prakash shared with me is able to obtain the same results. QBDY1 load has to be applied to the slave conduction elements. And two cards needs to be defined (OPTI_DEBUG and CASE_UNSUPPORTED_CARDS). I sent you both the 2d and 3d files. I did try Top3d but Matlab ran out of memory when I tried to run a larger model.
  5. So I ran a 100x100x100 3d model with an element size of 2mm and I had to manually add the surface elements one layer at a time just to ensure that I have conduction elements at least touching one face of the internal elements (So not all faces if an element has those elements attached). And I did get the results I was expecting as you can see below from the mid section view and full view. But, this was a time consuming process. Is there an efficient way to do this? If I was to only add the surface elements to the outside face, and add Qvol to the internal elements, I end up getting the shape shown below. If I was only to add the surface elements on the outside faces (Without internal QVol), I get the shape below. And it doesn't match what I should be getting. Thanks
  6. Thanks, Prakash! The model is working fine now. I do however wonder about the two cards OPTI_DEBUG and CASE_UNSUPPORTED_CARDS. What is the use of these cards? Also, if I wanted to do the same for a 3d model. It wouldn't be possible to add the conduction elements in between the internal elements.
  7. Sure. I've also checked wumindao's file. He set the temperature to 1 instead of 0. That gave me some results, but it still doesn't match with the one in the paper that wumindao linked in his first post. I also noticed when I zoomed into the pictures, that the elements seem to have a convection elements included, which isn't allowed for topology optmization. Also, according to another paper https://www.sciencedirect.com/science/article/pii/S0168874X08000905 I should be able to optimize the structure with 0 temp boundary condition on the outer edge without convection included (like in the image below). Planar.fem
  8. How are you able to get that? When I do the optimization process, all elements get removed. What I did was add a 0 temp boundary condition on the middle nodes, and then added a QVOL flux over all elements. I then set the Obj function to min thermal compliance under a volume constraint of 30%. The entire mesh was set as design variables. But it still ends up trying to remove all elements.
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