Self contact in FEBio

[Yunm]

Dear all,

I am trying to model a self-contact problem in FEBio. First I used a cell growth model to a beam to generate a snake-shape configuration, and then I applied a prescribed compression strain to make it self contact, similar to the problem in https://forums.febio.org/showthread....-search_radius.

There are two contact interfaces, one for the top surface and another for the bottom surface of this snake. For both contact interfaces, the slave and master surfaces are the same (thus, a self-contact problem). The contact was defined as "sliding-elastic" with the following parameters:

<laugon>0</laugon>
<tolerance>0.2</tolerance>
<gaptol>0.1</gaptol>
<penalty>10</penalty>
<auto_penalty>1</auto_penalty>
<two_pass>0</two_pass>
<search_tol>0.01</search_tol>
<symmetric_stiffness>0</symmetric_stiffness>
<search_radius>0.01</search_radius>
...

The simulation stops when the surfaces start to self-contact. I also tried with contact type of "sliding-node-on-facet", but got the same results.

Can someone help to take a look at this?

Thanks,
Yunm

[ateshian]

Hi Yunm,

I was able to make your model run until time t=1.459 by making the following changes:

- Increase max_retries from 5 to 10
- decrease penalty from 10 to 1 in both contact interfaces
- turn two-pass on (switch from 0 to 1)

The contact interfaces engage significantly in that case. However, I suspect that the mesh would need to be refined in order to run the analysis to completion.

Please keep in mind that this beam buckling model is highly nonlinear. The buckling mode is very sensitive to small numerical roundoff errors. For example, when I switched max_refs from 25 to 50 the buckling mode changed (you can try it yourself). Refining the mesh will likely alter the buckling mode as well.

Best,

Gerard