Connection beetween ligaments and bones in Abaqus

[DBeman]

Hi everyone, i should do some analysis to study the mechanical behavior of the plantar fascia, i already have a CAE model of foot bones and plantar fascia, all the bones are disconnected so i have to connect them through ligaments; for that purpose i created a part for each ligament and set them as only tension truss element. Now i have to connect ligaments to bones but i don't know what the best way is. I already tried tie constraints between nodes at the ends of ligament and nodes on the bone surface (node-to-surface) but i have convergence problem and my job aborts, then i tried a coupling constraints between nodes at the ends of ligaments and nodes on the bone surface (kinematic) but in the same way my job aborts and gives me a lot of these error: IS USED MORE THAN ONCE AS A COUPLING NODE IN THE *KINEMATIC COUPLING KEYWORD. REMOVE MULTIPLE USAGE OF THIS NODE AS A COUPLING NODE; although I was careful not to attribute two properties to the same node, so I don't understand why this error occurred.

So i would ask if someone can tell me the correct way to connect ligaments to bones?

I want something like these in therm of stress distribution.

here is a link for the download of the cae model:

https://we.tl/t-uWNjc8hiPJ

I hope someone can help me, thanks.

 

[FEA way]

Check this thread:

https://www.eng-tips.com/viewthread.cfm?qid=456424

The problem in your model is that you have multiple reference (control) nodes per constraint.

 

[DBeman]

FEAway thanks for the hint.
I modified all the contacts by creating a couple constraint for each node at the end of the ligament and the corresponding node on the bone, however now the job aborts due to a numerical singularity problem, which I believe is due to the fact that these nodes are not constrained. How is it possible if i constrained all the degrees of freedom?
How can i solve the problem?

I leave an image with the errors and the setting of the couple constraints

 

[FEA way]

Those are just warnings but I assume that the error is a generic message about non-convergence, judging by the incrementation. Apparently, there are some unconstrained rigid body motions. You can try running a frequency analysis to identify them. Also, such a model may require dynamic implicit step instead of general static.

 

[IceBreakerSours]

Take a big step back. Make an extremely simple yet relevant problem and test your understanding of the kinematic coupling feature. For instance, create a square or a cube (made up of one or more elements) and a reference node. Then, play with the features. Simple tests of this nature run fast and you learn everything there is to learn about the feature very quickly. Be sure to have the relevant documentation open on the side so the 'theory' and practice together make sense.

*********************************************************
Are you new to this forum? If so, please read these FAQs:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083