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Keep running into meshing errors and long runtime

Posted Jun 8, 2012, 3:57 p.m. EDT MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Mesh, Studies & Solvers Version 4.2 3 Replies

Doyle Baker
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I want to find the area on the device with the greatest stress and strain yet I keep running into errors and I'm not sure where to begin in solving it. I am a new user with not much in terms of resources of people who know how to use COMSOL so I have been doing this on my own for a while. I have constrainded the sides and added a load perpendicular to the surface but when I mesh the device I kepp getting errors. Any help would be appreciated.

side note: the part that it keeps saying it cannot mesh is the strontium titanate (STO) It was a user defined material since it was not in the materials library. Im sure this may have something to do with it

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3 Replies Last Post Jun 11, 2012, 4:01 p.m. EDT
Amro Elshurafa
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Posted: 1 decade ago Jun 9, 2012, 12:48 a.m. EDT
This sometimes happens when the dimensions are too small, and your mesh/element size you choose is too big for that small dimension.

Try to make the mesh size smaller. So, instead of 'Normal', go to 'Fine', and 'Finer', etc, and work your way up until it meshes.

If this does not work, you should probably create a mesh in 2D and then extrude the mesh to make it 3D. There is a good explanation of this in the documentation. Search for mapped meshing.
This sometimes happens when the dimensions are too small, and your mesh/element size you choose is too big for that small dimension. Try to make the mesh size smaller. So, instead of 'Normal', go to 'Fine', and 'Finer', etc, and work your way up until it meshes. If this does not work, you should probably create a mesh in 2D and then extrude the mesh to make it 3D. There is a good explanation of this in the documentation. Search for mapped meshing.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jun 9, 2012, 5:28 a.m. EDT
Hi

I can only say I that that is "my way" to takle meshing too.
But I have one more trick I try: (apart from removing small features when I can on the CAD) it is to detect the "small edges" (you have some analysis tols in the geometry section), then to select these and mesh them as edges or surfaces first, then mesh the rest with a normal or even coarser mesh.

Meshing strategies is more an art than a science so it's "by doing" you become the best, so do not give up ;)

--
Good luck
Ivar
Hi I can only say I that that is "my way" to takle meshing too. But I have one more trick I try: (apart from removing small features when I can on the CAD) it is to detect the "small edges" (you have some analysis tols in the geometry section), then to select these and mesh them as edges or surfaces first, then mesh the rest with a normal or even coarser mesh. Meshing strategies is more an art than a science so it's "by doing" you become the best, so do not give up ;) -- Good luck Ivar
Doyle Baker
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Posted: 1 decade ago Jun 11, 2012, 4:01 p.m. EDT
Thanks both you you for your help. I am trying to run it now as smaller mesh size to see if that works. Crossing my fingers.
Thanks both you you for your help. I am trying to run it now as smaller mesh size to see if that works. Crossing my fingers.

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