Hi, sometimes is usefull mesh solid parts with 2D elements, in order to use as shell in the calculus, would it be possible in future releases???
Are you talking about taking the outer surface of a 3D model for meshing with shell elements (something like shell from solid feature in Abaqus) instead of extracting the midsurface ? Currently, the easiest way would be to downgrade and then upgdrade the model in FreeCAD’s Draft workbench.
Yes, you could create a surface mesh, and then in modeling just delete the elements not needed to create the shell part. Is a dirty way to create a shell model without using the CAD to create midsurfaces, or delete surfaces.
So a feature “Solid to Shell” and a feature “Delete shell faces” would be needed. Is that correct? I think that would not be so hard to do.
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Maybe in the actual mesh dialog, in the case of solid parts an option to choose to mesh only the faces (so "mesh 3D (by default) / mesh 2D), and in FE Model, under the Mesh menu a new entry with “Delete elements”, and with the usual way of choosing elements (by surface, angle…). The deletion of elements can be done with the actual tools, but the user needs to create an element sets, transform to part and then delete the part.
Deletion of selected elements from mesh could indeed be quite useful. But maybe instead of mesh 2D option (which could be somewhat confusing) it would be better to add a solid to shell (and possibly also shell to solid) tool.
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A generic approach would be for solid parts:
- optional mesh settings for selections of faces and edges (just for truss elements, beams would require a lot of added infrastructure)
- optional suppression of the volume mesh
and for surface parts:
- optional mesh settings for selections of edges
- optional suppression of the surface mesh
If I understand it correctly, then netgen creates edge and surface meshes anyways. one just has to convey the requested ones to the database.
You are right. Netgen creates and stores all three steps of the mesh: edges, surfaces and solids. All of them are imported into PrePoMax and then only the one that is needed is kept. The other two are removed.
But I still think that something like that should be done before meshing. So first prepare the geometry in the right way and then mesh it. I this way the user can later change the mesh sizes and remesh the part with ease.
A natural place to specify which entities to mesh would be the Sections branch of the model tree.
Currently, you only can apply Section specs to already existing elements.
One could go a step further and specify mesh settings in that branch, may be including element sizes.
If all other entities can be specified based on geometry, meshing would be the final step before actually issuing the simulation job.
maybe in the Geometry module tabs the face of a part can selected and extracted. creates new face part to be possible in meshing 2D, later in FE Model an offset of shell element can be set to match original solid models.
but it’s not common workflow, many external pre-processor do extract 2D face from mid side of solid models.
another problems at the plate intersection, there will be a gap in sloped or perpendicular position. an option can be extend to match the neighbor plate (more complex) or simple using bonded tie approach.
That is true for geometries meshed inside PrePoMax. But users also import the mesh from other tools, and I wish to keep the workflow for both possibilities the same. So I think it has to happen before the meshing.
Yes, this is the idea. I really do not have the time to develop a CAD program.
I understood that is a hard work dealing with the CAD geometry. Maybe if the mesher would have the option to mesh only the faces of the solids, and, in the model environment an option to easily select elements do delete manually, then it will be enough for creating shell models from solid parts, without developing a CAD program.
Change from solid to shell should not be hard to do. Since the CAD kernel I am using is the same as in Salome, and this feature is available in Salome, I can recreate the procedure. That is not a problem. A problem is getting the mid surface. And probably from shell to solid Is the same.
But I’m not talking about generating a midsurface, with this procedure we´ll impor the part as a solid, then mesh as shell (all the surfaces), and in the model, we’ll select which side we want (or is better due to boundary conditions) to keep, upper or lower, and delete all the rest element (there we need a way to select and delete element directly, today we could make it creating components and then delete components). After that we should use an appropiate shell ofsset to compensate the fact that the mesh is not exactly the midsurfaces. Some preprocessos even have an option to tell directly that the mesh is upper/mid/lower side, so the user doesn´t have to think (well, thickness/2…).
As far as I see, if you can include the shell meshing, all can be done with the actual tools.
i see, Salome itself has no features to extract mid surfaces from solid part. only have an option to extract of face (sub-shapes) from solid part by exploding.
when interested, may this approach is enough to avoid difficulty at implementation in PrePoMax
I understand what you mean @SergioP1975. And it is doable since when meshing a volume, the surface mesh always exists.
But I think that from a point of view of a workflow, it makes more sense to have appropriate geometry first. Such a process then better fits in the workflow that already exists. And a tool to delete faces can also come in handy in other scenarios.
I think both solutions will take a similar time to develop so this is also not a factor.
Having the midsurfaces is the canonical way to solve sheet metal parts, but very often the designer doesn´t have the time, software or skills to get it, that’s why that alternative method is very common.
Obviously, having a tool to delete and move/offset the surfaces in the CAD module of Prepomax would be amazing.
Hmm, I was talking only about a tool to delete faces or maybe move them. Offset is another matter 