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# Hexa mesh of a shaft

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### Hexa mesh of a shaft

Posted by Mattia Piron at June 20. 2018

Hi, I must mesh a shaft with hexa element. This shaft is composed by more cylinder of different radius.

I try to create more divided cylinder, but when I mesh it, the element on the surface of one cyinder doesn't match the element on the surface of the other cylinder. How can I do that?

Thank you

### Re: Hexa mesh of a shaft

Posted by Sergio Pluchinsky at June 21. 2018

I would:

1) Split the main shape in a quarter

2) On that quarter, I would create a partition of the geometry with a cilinder concentric to the shaft (leaving two volumes, will call it exterior and interior)

3) Then, I will create first a 2D mesh of the plane surface to the surface of the shaft exterior volumen, using the Netgen and option "allow quads" to have mainly quads in the mesh. You can add some local refinement on the section changes areas, and add a mesh control on the interior side of the shape to keep element size constant along that edge

4) Revolute this mesh or use some mesh pocedure to create this as a revoluted mesh

5) Now you need to mesh the interior volume of the shaft. If you would mesh it using the same procedure, you'll finish with wedges elements in the center, so in order to have hexas, you need to create a 2D mesh on one of the end plane faces of the shape (take care of matching the element count with the revoluted mesh), and then extrude this mesh along the axis shaft (again taking care of the number of element along the axis of the point 3) to match the nodes)

6) After that, make a compound mesh with the option to glue the coincident nodes in order to match any non coincident mesh that could be left.

7) After that you can "simetrize" your mesh to have a half or the complete geometry meshed.

With this procedure you can have 90-95% of hexas and the rest will be wedges, adding more partitions to the geometry and using some mapped algorithm to create the meshes you could reach 100% hexas, but you must weight if this will worth the extra time.

Regards, and enjoy your mesh!

### Re: Hexa mesh of a shaft

Posted by Mattia Piron at June 26. 2018

I'm sorry, I don't understand.

Point 1 and 2, did I do it right? (see attachment).

Thank you

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### Re: Hexa mesh of a shaft

Posted by Sergio Pluchinsky at July 11. 2018

Yes, you are right. You can work with a quarter of your geometry, the exterior anular volume can be meshed as a six faces volume, and the inner core the same but changing the direction.

Regards