Best way to create conformal mesh for linear elasticity?

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jandyman
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Best way to create conformal mesh for linear elasticity?

Post by jandyman »

Hello,

I'm a complete newbie both to Elmer and FEM. Forgive my ignorance, I'm learning as fast as I can.

I would like to model bass guitar neck stiffness using various type of carbon reinforcement inside a wood neck. I've looked at some similar efforts and they don't cover what I'm interested in.

Looking over the workflow for FEM, it seems the first steps are to create meshes for the wood and carbon elements, and get them into Elmer. And it seems from what I gather that in order for things to work smoothly, the meshes need to be "conformal", so that the two elements combine properly. Then I need to somehow convey that the elements are bonded (in this case the bond can be considered "perfect", the main deformation will be in the wood and carbon). Then I need to learn how to set up the simulation.

Is this more or less correct?

If so, then the initial challenge is creating the conformal meshes. I do my modeling in Fusion 360, and I'm thinking it will not export these types of meshes - you basically select one "body" at a time for export so there is probably no linkage between the meshes. If that's right, then I'd either need to somehow "fix up" the meshes, or use some other tool to create the meshes instead of Fusion 360. I saw Salome mentioned here and that might work. My shapes are not simple extrusions, but if I were able to define two cross section sketches at the neck endpoints, and loft between them, that would be good enough for this modeling.

I'd be grateful for an advice on how to go about this task. Is Salome the right path? If not, then what? Oh, one more possibility. If Elmer or another tool could "subtract" two meshes, then I could create a mesh for the entire neck in Fusion 360, then one for the internal carbon reinforcement, then create the conformal meshes by subtracting the carbon mesh from the total mesh. Hope that makes sense.
kevinarden
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Re: Best way to create conformal mesh for linear elasticity?

Post by kevinarden »

Yes you are on the right track. If you are comfortable with your meshing tool then you an export each mesh one at a time. However the nodes where they conform need to be coincident. You can then, using ElmerGrid merge the two and the coincident coincident nodes using the -merge flag.
In order to assign different materials each one has to be a body in Elmer. If you your tool you can have it all in one mesh but assign the two different material types, then you can export it as one mesh. Elmer inputs the following mesh formats:
1) .grd : ElmerGrid file format
2) .mesh.* : Elmer input format
3) .ep : Elmer output format
4) .ansys : Ansys input format
5) .inp : Abaqus input format by Ideas
6) .fil : Abaqus output format
7) .FDNEUT : Gambit (Fidap) neutral file
8) .unv : Universal mesh file format
9) .mphtxt : Comsol Multiphysics mesh format
10) .dat : Fieldview format
11) .node,.ele: Triangle 2D mesh format
12) .mesh : Medit mesh format
13) .msh : GID mesh format
14) .msh : Gmsh mesh format
15) .ep.i : Partitioned ElmerPost format
16) .2dm : 2D triangular FVCOM format
kevinarden
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Re: Best way to create conformal mesh for linear elasticity?

Post by kevinarden »

I was able to loft between to cross sections in salome using the shaper module and mesh it. I usually use the geometry module, so I am not very experienced with the shaper module.
loft.PNG
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jandyman
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Re: Best way to create conformal mesh for linear elasticity?

Post by jandyman »

kevinarden wrote: 03 May 2023, 13:24 I was able to loft between to cross sections in salome using the shaper module and mesh it. I usually use the geometry module, so I am not very experienced with the shaper module.
That's great, I'm guessing it is the path of least resistance, but I'll look a bit longer to see if Fusion 360 can export two bodies as one mesh.
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