Problem is diverging. Stiffness matrix will now be reformed

[jksinclair]

Hi,

I am attempting to quantify tibial strains during running. I've attached my model, project and log files here.

https://drive.google.com/drive/folde...m6?usp=sharing

In this FEA, I am boundary constraining the proximal end of the tibia whilst applying a 3D load to the distal end which will be unconstrained. I have included tibial bone modulus and Poisons ratio as Neo Hookean materials.

My mesh passes the mesh diagnostic OK. However, when I run the analysis the issue ''Problem is diverging. Stiffness matrix will now be reformed'' is the model fails to converge until the analysis reaches error termination.

If someone could look at this for me, I'd really appreciate any assistance.

Thank you
Jonnie

[maas]

Hi Jonnie,

It looks like the load is applied to the same node set as the fixed displacement, which is why the model is not doing anything. You'll have to assign the load to a different nodeset.

Best,

Steve

[jksinclair]

Hi Steve,
Thanks for your reply.

I have now revised the model and been able to re-run my analysis which ran to successful termination. The pattern of strain/ stress seems to be good.
However, in comparison to values from the literature for strain where values are typically in the region of 3-5000 microstrains (I've converted my own values to match the literature) and stress also - the values here appear to be well below these, despite having the same materials settings, boundary conditions and input loads at the distal tibia. Is there any reason why my values appear to be much lower.

I've attached my new model and output files.
https://drive.google.com/drive/folde...usp=share_link
Any assistance would be great thank you
Thanks again
Jonnie