Prestrain solution convergence

[bracamontej]

Greetings!

I'm working with cardiovascular mechanics and I'm very interested in using FEBio prestrain plugin to run our simulations considering arterial wall residual strain and starting from a preloaded condition (diastole).

First I'm getting familiar with the Prestrain plugin through the examples included in the plugin folder. Now this is the problem I'm dealing with:

I run the test_9_ps_wc.feb file which prescribes the "prestrain update rule" by including the prestrain constraint. I added an output logfile that prints the resulting deformation gradient tensor per element (Fp). What I understood from documentation is that the resulting deformation gradient is adjusted to be compatible with the reference geometry.

Next step was to run the same problem but using the resulting deformation gradient field from previous step (F0=Fp). I would expect it to converge rapidly to the same (or very close) result as the prescribed deformation gradient as prestrain is already compatible with the geometry. Nevertheless it did not converged, and showed the following error:

************************************************** ***********************
* ERROR *
* *
* NAN Detected. *
************************************************** ***********************

Summarizing:
I run test9_ps_wc.feb , obtained Fp adjusted.log, pasted it as the new prestrain in test9_ps_wc_Fp.feb
test9_ps_wc.febFp adjusted.logtest9_ps_wc_Fp.feb

I also tried to use the resulting deformation gradient as initial condition for a forward analysis getting the same type of error.

Could someone please let me know what is wrong with this procedure?

Thanks and regards,

Johane Bracamonte

[bracamontej]

I realized I posted this in the wrong section. I re-posted in the Plugin User Forum, so I'm closing this one.

Best regards,

Johane Bracamonte