I am a relatively new user of Mecway, but have some nonlinear FEA experience with other codes.
What is the best strategy for generating hex meshes within Mecway? I tried creating a 3D model within FreeCad and exporting the STEP file, but when I used "Automesh3D" I got all tetrahedral elements.
As another approach, I tried to export just the 2D sketch from FreeCad (for an axisymmetric part) with the idea maybe I could create a quad 2-D mesh in Mecway and then revolve it to get the 3D part, but the 2D sketch did not seem to import into Mecway at all (I'm not sure it even exported correctly from FreeCad).
What is the best strategy to create a hex mesh with Mecway? My problems usually involve extensive plasticity and contact, and will be solved in CCX. Tet elements don't perform well in plasticity, so I'd really like to end up with a hex mesh.
I'd welcome guidance on how best to approach this.
Thanks,
-Robert
Comments
Make a surface in FreeCAD and export it (not the sketch) as STEP and import to Mecway. Under Meshing Parameters, check Surface mesh and Quad dominant. That won't always be 100% quads, but mostly. From there, you can extrude it into hex's. See picture of loop.
Export a 2D shape as DXF. Not sure if/how FreeCAD does this. Then import to Mecway and use Automesh 2D to make a quad dominant mesh.
If it's a simple shape, make it directly in Mecway. For example, you can start with Quick cube then refine and delete elements to carve out the geometry you want. (see attached picture) If it's curved, make a coarse mesh using quad8 elements placed by hand with curved sides, then use Mesh tools -> Refine custom to effectively make a mapped quad-only mesh out of them. (see attached picture)
There are also free hex meshers. I haven't tried them but Gmsh and IA-FEMesh (https://www.ccad.uiowa.edu/MIMX/projects/IA-FEMesh) are two.
Regards
-Robert
What I have found productive for simple parts is export the solid as IGS (faces) from the CAD suite, and then mesh with pure cuads in Roshaz one face of the geometry and then export as Abaqus inp and import on Mecway to extrude/revolve/simetrie and have nices hexas....
At the first tries you will find a little ugly the Roshaz interface, but after doing the same work several times you will start to understand it.
Regards!
Since I use the FEA to drive design iterations, I don't like to get too many steps or too much manual labor in the CAD->FEA process or it really slows everything down. The manual labor is really the biggest issue, so if I can easily create the mesh somewhere and bring it into Mecway for loads, BCs, and generation of the CCX input file that may be a good solution.
Regards
(Images attached from IA-FEMesh manual)
Thanks
For simple parts can be a kind of "almost fully hexa mesh".
1) We need a wireframe view and possibility of select hiden surfaces to then invert selection and delete elements. Guess that the best will be every surface identified and their mesh also identified separately. As was really dificult (or impossible) to select the hiden surfaces, I has solved exporting in the CAD only the surfaces that I need to mesh (this adds an extra step of planning the mesh secuence)
2) For the bosses of the second part I try by revolute the elements, we need a possibility of select the position of the revolution axis (now is only possible in the global coordinate system axis, but for features not in the center the rotation can't be done.
3) I have tried to swep in place of rotate, it works when I use 2D element edges as guide/paths, but not when the guides are 3D element edges (I have solved creating a set of 1D elements over the edge of the 3D elements.... now how I could delete it?) Even that the sweep don't conect the nodes that are not in the path or guide, and the faces of the last element loose the normal direction, so I make a lot of manual node reposition to merge with the existent elements.
4) Still I didn't find a way to make a symetric copy of the mesh as the symetry plane is not an ortoghonal one. I have tried the point option but it makes a rotated copy, not simmetric
This is my first tries with hexa meshes in mecway, surely the practice would improve. Guess that having the option of just mesh by selected surfaces would improve a lot, and if can be with only quads even better.
Having hexa mesher capacity will be a great plus for Mecway, even more now that people will start to use as prepro for CCX.
Regards
Happily I was able to mesh all the part, and found very usefull the sweep command (more than extrude or revolve) as it permit to keep the element spacing along the path. Extrude or revolve will make perfectly evenly separate elements, but sweep use the path as reference for spacing, and this important to match with the nexted meshed volumes.
Again, will be a great help to have the possibility of using 3d element edges as path/guide and not have to add extra 2d elements. The best would be some kind of "autoselect" for the element edges by tangency or conectivity to avoid selecting one by one.
Another improvement would be that when the 2D meshes were created, is the possiblity of have every surface mesh grouped automaticly (is just create a named selection for every surface), so then sweep/extrude/revolve operations become more easy
The grey elements are those that I was forced to delete and recreate (on 2D meshing before sweeping) to keep the node conectivity. First I tried to move the nodes manually, but is quicker, easier and precise (to don't lose the plane) to delete and recreate manualy.
I'm really impressionated by the things that can be done with Mecway!
Regards
Regards
Regards
Guess that the next step will be meshing in IA-FEMMesh also.
Then, in production, when you mesh a part for first time you must plane how the model must be cleaned (some features will not be possible to mesh with hexas) and divided in order to get the "swepable" volumes, and do the mesh. In the next desing iteration the mesh must be done from the begining (yes, normally the "update mesh" just strugle your model), but now as you know hot to do it so it takes a fraction of the time.
On the other side, this meshes are for complex analysis (contact, no lineal, hyperelastic materials...), so not switable for last minuts requests :-)
I have tried to mesh in IA-FEMMEsh this same part (obviolusy usin multiblock), but I didn't get a usefull mesh in the few minuts that I have to try.
Regards!
Don't know how much it costs. I think a lot of these tools are cost prohibitive. I like that Mecway is low cost for home use. Adding features like this are likely to be very expensive. Pretty sure these are the meshing libraries ANSYS has used for a long time.
Im preparing a simple workshop to import structured mesh from salome platform, exporting in .med then converting in .msh in GMSH. Please let me know if this can be of your interest.
Best Regards,
Stefano
Regards
For reference:
http://onlinelibrary.wiley.com/doi/10.1002/cnm.485/abstract