Tie Constraint surfaces

[ladykin]

Hi There,

I am trying to model contact of indenting a circular embryo with a rigid indenter.
The embryo has a outer layer and inner matter. I used solid elements for the inner matter and shell elements for the outer layer. I need to constrain the inner matter follow the outer layer indentation using tie constraint.
The Slave surface is obviously the boundary of the solid part but I am not sure about Master surface. The outer layer has 2 surface and each surface has 2 sides. Can anyone help me with the slave surface of the tie constraint?

Regards,
Ladykin

 

[rstupplebeen]

You can apply a skin to the solid body and no tie constraint will be needed since they will share nodes. I hope this helps.

Rob Stupplebeen

https://sites.google.com/site/robertkstupplebeen/

 

[ladykin]

Dear Robert,

Thanks for your reply. I tried skin, it works perfectly fine but using skin I can not define the thickness of the outer layer. Please let me know if you have any idea.

Regards,

 

[mosgef]

Depending on the preprocessor, you should be able to grab the outer face of the solid, and 'convert to shell'. This should create a layer of shell (S4 or S3) elements that will share nodal connectivity with the solid elements. You can then define the thickness of the outer layer in the section card. I may be imagining the geometry differently, so another thing you could try is to ensure all of your original shell elements share a common outward facing normal. You could then deal with both the tie and indenter contact by defining two surfaces. For example, define the surface on the solid elements (it will show up in your .inp as *SURFACE, followed by a list of solid element numbers and their face identifiers (something like 123, S4)).
You can then define a surface from the SPOS and SNEG side of the elements in your outer layer.
Assign a contact pair with the surface of the outer layer to be indented (the SPOS surface) as a slave surface, and the rigid indenter as the master surface.
Assign a tie pair with the surface made from your solid elements slaved to the master surface on the other side of the outer layer elements (the SNEG surface).
This scheme should allow the indenter to correctly contact the outer layer, and transfer loads into the outer layer and then the solid elements.
One thing to be aware of, the contact routine is very sensitive to master-slave assignments and mesh refinement. You may need to play around with the mesh densities if you go with this method. Good luck.