Partitioning a sphere into concentric spheres for meshing

[rogersma]

Hi all,

I have been using Abaqus for ~1 year, mostly for 2D simulations (plane stress) but have recently started using 3D meshes. My problem is fairly simple, and hopefully someone can answer it.

My model geometry is a solid sphere with a spherical hole (easy enough to create using the revolution tool in Abaqus). I put a pressure on the inner hollow sphere and Abaqus calculates stresses. These stresses closely match the analytical dynamic solution for a Heaviside pressure pulse on hollow sphere albeit with tons of noise which I think is due to funny mesh geometry.

Because I am using an Abaqus Explicit VUMAT (dynamic damage mechanics VUMAT), I am limited to the different types of elements I can use for my analysis. I am currently using C3D10M elements but as I mentioned before, I have a lot of noise in my results. I would like to limit the noise by partitioning my spherical mesh into smaller concentric spheres and then using those smaller spheres to seed in order to obtain a more uniform mesh without so much noise. I know how to do this in 2D (partition sketch --> draw a circle) but it seems to be much more involved in 3D. Does anyone know how to partition a spherical sketch into several different concentric spheres? Any help is greatly appreciated.

- rogersma

 

[corus]

Partition a 2D section of the sphere and sweep the partition round.

 

[rogersma]

Hi corus,

Would you mind explaining how to partition the spherical sketch in 2D? Is it some sort of view option? I haven't done much meshing in the past year as I've been altering my VUMAT to match theoretical and experimental results for simple 2D geometries. If you could briefly outline how to do so that would be great!

- rogersma

 

[corus]

Partition the sphere with a plane that cuts through the centre. That'll be the 2D plane from which you can sketch on the concentric circles. Sweep those round using an arc of the sphere as the direction.

 

[rstupplebeen]

I often simulate eyes and contact lenses therefore, spherical and significantly spherical shapes are quite common. For a ball I suggest partitioning into 1/8 sections. Please see the image below and attached CAE file. I hope this helps.

Rob

Thank you.

Rob Stupplebeen
OptimalDevice.com
My Personal WP

 

[rogersma]

Thanks for the reply rstupplebeen!

I haven't looked at the attached CAE file yet because I am not at my main computer. Do you know if your mesh would work with Abaqus Explicit? Would you mind attaching your .rpy file so I can try to follow the same procedure for a sphere? Thanks again!

- rogersma

 

[rogersma]

Can anyone please explain step by step how to do this? I gave up on this a while ago but now need to do it again. I want to create a sphere with a spherical hole in the middle (I know how to do this easily by "Create new part --> 3D Deformable Solid Revolution --> Draw half a sphere with another half sphere in the middle and then revolving 360 degrees. My problem is that I need to create an inner surface which I can seed around the hollow sphere in the center of my part to use as an edge to seed in order to control the graduation in element sizes. Does anyone know how to do this and can someone explain step by step how to do so?

 

[rogersma]

I figured out a solution eventually, I'm sort of surprised no one else could offer it as it was very simple.

The easiest way to do this is to simply make multiple parts (concentric spherical shells - not shell element type - in my case), combine them together while preserving the boundaries and then to use those inner boundaries as seeding surfaces. I was able to properly refine my mesh as desired, giving me better element shape control, etc.

If anyone else has this problem and would like more details as to the specific steps, please let me know.

This link outlines how to merge parts and preserve boundaries, section 13.9.11 "Merging or cutting part instances" of the Abaqus manual.

- rogersma