> On 6 Nov 2019, at 10:26, MA Ariza-Gracia <[email protected]> wrote: > > Dear all, > > apologies, I just realized I crossed the subjects of two different (related > questions). Following up using the previous geometry, though. > > The problem is that when you create a volume mesh from some STL surfaces and > export it to an Abaqus INP, the structure of the INP file is as follows: > > ************************************************************************************************** > > *Heading > > *NODE > > <bunch of coordinates and labels> > > *ELEMENT, type=CPS3, ELSET=Surface1 -> This is bad (in my application, of > course) > > <bunch of labels and connectivity> > > *ELEMENT, type=C3D4, ELSET=Volume1 > > <bunch of labels and connectivity> > > ************************************************************************************************** > > The main problem here is that a 2D triangular mesh is generated on top of the > 3D solid mesh which is not the goal. The goal is, for example, to have a > *SURFACE definition in which to apply a pressure boundary condition / contact > definition WITHOUT adding an additional 2D mesh on top. This *SURFACE > definition should be done with the facets of the elements that belong to the > volume but are on the surface (hopefully, it was clear). >
I don't know the Abaqus format well enough to understand this... Two choices : 1) either patch our INP exporter (other people on the list might know better and could help). You could open an issue on our gitlab, as for developer access and create a branch with your proposed changes 2) you can also directly use the API to access all the mesh info, and then write the INP file yourself directly. > > > In Abaqus, the surface definition can be Element-based or Node-based. For the > Element-based, the *SURFACE is defined as a group of element sets and the > facet that should be used for defining the surface. For example, > > > ************************************************************************************************** > > *ELSET, ELSET=test-surface_S6, generate -> This would generate an element > set of 16 elements whose facets are in the boundary of interest > 1, 61, 4 > *SURFACE, type=ELEMENT, name=test-surface -> This would generate the surface > using the previous element 6 and facet S6 of the hexahedra (there is a > convention in Abaqus for this) > test-surface_S6, S6 > > ************************************************************************************************** > > Yesterday, I delved a bit in the source code and I think there is not such an > option (only NSETS and ELSETS) but, if we would be able to retrieve (somehow) > those elements with facets on the surface of interest, we could actually > build the surface with a bit of post-processing (tedious but doable). > > > > So, finally, my question: is there any way of retrieving elements (*ELSETS) > and nodes (*NSETS) of ONLY a volume mesh in Gmsh? Take as an example the > enclosed INP files (geometries in line with my previous email): > > 1) thin-lens-duplicate-geo.inp: this file was exported after meshing the > volume and without a physical group -> "Wrong" file definition > > 2) thin-lens-volume-geo.inp: this file was exported after meshing WITH a > physical group for the volume. Here, there is no wrong additional 2D > elements, but we do not have any information about elements or nodes in a > target surface. -> Can we obtain this information somehow in Gmsh? > > Note: the *.geo files and the *.STL correspond to the ones used for > generating the INP files. > > > > This topic also raised an additional question for me: > > 1) Can we have internal boundaries if there is, for example, an inclusion > inside a lens? E.g., bubble of air. This would help defining internal > contacts or pressures or the like. > Yes, sure - just define this either as CAD entities, or as discrete entities like the 2 exterior surfaces, and build the appropriate volume(s). Christophe > > > Best regards and apologies for the crossed subject once again, > > MA > > <surface-sets-inquiry.zip> — Prof. Christophe Geuzaine University of Liege, Electrical Engineering and Computer Science http://www.montefiore.ulg.ac.be/~geuzaine _______________________________________________ gmsh mailing list [email protected] http://onelab.info/mailman/listinfo/gmsh
