Learning Forum

[Ulvi]

Hi. I have the following questions:

1. When applying symmetry region to the model below do I need to define frictionless support along the symmetry surfaces?

2. Analysis results are saying that ''One or more MPC contact regions or remote boundary conditions may have conflicts with other applied boundary conditions or other contact or symmetry regions. This may reduce solution accuracy. Tip: You may graphically display FE Connections from the Solution Information Object for non-cyclic analysis. Refer to Troubleshooting in the Help System for more details.''

I assume it is because my symmetry region shares a few mutual nodes with MPC based remote displacements. How do i check accuracy of the analysis?

3. I applied anti-symmetry plane to the same surface and results showed gap between the supports along the anti-symmetry region. Why is that?

 

Thanks,

Ulvi

[Sandeep Medikonda]

Hello Ulvi, 

You might find this discussion from another post useful.

Can you post a snapshot of the gap you are seeing and the other contacts you have defined in your model?

~Sandeep

 

[Ulvi]

Thanks for the reference. That helped a lot!

 

In regards with anti-symmetry gap, please see below

 

[peteroznewman]

Hello Ulvi,

I have used Symmetry a lot, but I have never used Anti-Symmetry so I was curious to investigate.

Here is what ANSYS 19.1 Help has to say about Anti-Symmetry.  This explains why you can expect a gap.

I built my own small model to see this for myself.

Regardless of the gap, I expected one arm to go up and the other to go down, but that is not what happened. I can add Frictionless Support along the split line to prevent the gap, but that prevents the essential non-symmetric response I want to see.  If I had used a Symmetric BC without the Frictionless support, the image below is what I would have gotten.

Here is a full model with opposite loads.

Here is the deformation.

That is totally different than the half model with Anti-symmetric BC. Was this the sort of effect you were looking for?

I guess I will continue not using Anti-Symmetric boundary conditions and just use a full model.

Regards,

Peter

[Ulvi]

Thanks Peter. The last one is what I am looking for. Very strange that Ansys can not apply normal constraint in Anti-Symmetry plane

[Sandeep Medikonda]

Hi Peter, Ulvi,

  I've looked into this and was able to replicate what you were seeing.

Symmetry:

Anti-Symmetry:

I am not surprised with the opening as only the normal rotations are constrained but yes the representation of the force in the documentation doesn't match what we are observing here. I suspect it to be a misrepresentation in the documentation and will file a bug request to get it fixed on Tuesday.

Thank you for digging into this.

Regards,

Sandeep

[BenjaminStarling]

Hi All,

It appears that your Anti-symmetry is working. It is simply the graphical expansion that cannot show the anti-symmetry accurately. As far as I am aware no FE package currently allows anti-symmetry graphical expansion.

Apologies if I am interpreting the problem incorrectly.

As per Peters work, the displacement in both of these is nearly exactly the same. The "centerline" of your model is also in the same position.