# Symmetry Region vs. Frictionless Support

• 1.8K Views
• Last Post 01 August 2018
jonsys posted this 30 July 2018

In a symmetric structure, what is the difference between using:

• "Insert Symmetry Region" in Model
• applying "Frictionless support - Static structural" at the face where the model is cut due to symmetry?

rgpatchi posted this 30 July 2018

Hi Jonsys,

If the face (where the model is cut) is geometrically flat, then, Frictionless Support is equivalent to applying a Symmetric Region.

Best regards,

-Rohith

jonsys posted this 30 July 2018

Hi Rohith,

What if it is not flat, which one should be used? (even though I can't think of any cutting that is not flat)

rgpatchi posted this 30 July 2018

Hi Jonsys,

When the cut surface is not flat, Symmetry is not applicable.

In such cases, if a Frictionless Support is applied, this results in a constraint in the surface normal direction. For example, if the frictionless support is applied on a cylindrical surface, the nodes are constrained in the radial direction (similar to a Cylindrical Support in Mechanical, with radial fixed, but, Axial and Tangential directions free).

Best regards,

Rohith

jonsys posted this 30 July 2018

Hi Rohith,

thank you for the explanation of the frictionless support.

So, since the surface is always flat (for the symmetry to be applicable), this means that "Symmetry Region" and "Frictionless support" will always be the same?

Regards,

peteroznewman posted this 30 July 2018

Hi Jon,

You are only thinking of flat surfaces. A good example where Frictionless Support is used is on the cylindrical surface of a hole to represent that hole being mounted to a rigid shaft, which is not in the model, and gives the body with the hole rotational and axial freedom about the hole axis.  I don't think you can do that with Symmetry Region.

Regards,

Peter

• Liked by
rgpatchi posted this 30 July 2018

Hi Jonsys,

"So, since the surface is always flat (for the symmetry to be applicable), this means that "Symmetry Region" and "Frictionless support" will always be the same?"

-Yes, that is correct.

Best regards,

Rohith

• Liked by
SandeepMedikonda posted this 30 July 2018

Just to add to the discussion, here's a relevant thread from an older XANSYS forum.

• Liked by
jonsys posted this 01 August 2018

Peter, Rohith, Sandeep,

thank you very much

Regards,
Jon