Periodic Boundary Conditions

[mcgeadyh]

Hi,

I was wondering is it possible in to apply periodic boundary conditions in Preview, so that two parallel surfaces will follow the same deformation? And if it is possible how is it done? I was told it was but cannot seem to find any mention of it anywhere in the manuals?

Thanks,

Hugh

[maas]

Hi Hugh,

Yes, periodic boundary conditions are available in FEBio although they are not yet supported in PreView. I will add it soon, but in the mean time this would be a work-around: setup a sliding interface between the two periodic surfaces in PreView. After you saved the input file edit the file manually and make the following changes. Find the sliding contact definition and replace the type attribute with "periodic boundary".

<contact type="periodic boundary">

This type of contact interface only supports the following parameters:
- laugon: use augmented lagrangian contact enforcement (=1) or penalty method (=0)
- tolerance: augmentation convergence tolerance (only used when laugon=1)
- penalty: penalty parameter (use by penalty method and augmented lagrangian method)
- two_pass: uses two-pass contact enforcement (=1) or not (=0).

Make sure you remove all other sliding contact parameters. Please give it a try and let me know if you run into any problems.

Cheers,

Steve.

[mcgeadyh]

Hey Steve,

The steps you outlined worked fine for creating periodic boundary conditions for me.

Thanks,

Hugh

[rfagan]

Hi,

I'm also interested in periodic boundary conditions, but I want the stress tensors to be the same on the two parallel surfaces in addition to the displacements. Does this contact type cover this?

Thanks,
-Rob

[maas]

Hi Rob,

For the periodic boundary condition only periodicity of the displacements is enforced, not of the stress. If this is something you are interested in, feel free to make a feature request for this on our forum.

Cheers,

Steve

[siboles]

Hi Steve,

I tried using periodic BCs in version 1.8.0.5066 (linux 64bit) and get a Segmentation fault. I've attached the model.

Regards,
Scott

EDIT: The attachment uploader isn't working for me, so I've emailed you the model.