simtk.org

Hi Ahmet,
Thanks so much for this fantastic educational and research resource!

I'm attempting to run the tf_joint.feb file using FEBio v.1.8, and things appear to run without any major problems until approximately time=2.3, at which point the error message below is generated and convergence is not obtained.

I'm wondering:
(1) Have you tested things with v.1.8?
(2) Do you have a version which is compatible with FEBio v.2.0?

Cheers,

Todd




7
Nonlinear solution status: time= 2.32984
stiffness updates = 0
right hand side evaluations = 16
stiffness matrix reformations = 7
step from line search = 1.000000
convergence norms : INITIAL CURRENT REQUIRED
residual 1.074068e+12 nan 1.074068e+11
energy 1.329068e+05 nan 1.329068e+03
displacement 3.997864e+03 4.016463e+02 4.879025e-01
Reforming stiffness matrix: reformation #7

===== reforming stiffness matrix:
Nr of equations ........................... : 184062
Nr of nonzeroes in stiffness matrix ....... : 7200717

8
*************************************************************************
* FATAL ERROR *
* *
* NAN Detected. Run aborted. *
*************************************************************************


N O N L I N E A R I T E R A T I O N I N F O R M A T I O N

Number of time steps completed .................... : 95

Total number of equilibrium iterations ............ : 993

Average number of equilibrium iterations .......... : 10.4526

Total number of right hand evaluations ............ : 3182

Total number of stiffness reformations ............ : 1012

Time in solver: 5:10:28


Elapsed time : 8:23:19


E R R O R T E R M I N A T I O N

Hi Todd,

Thank you for your message.

tpataky wrote:
(1) Have you tested things with v.1.8?

No, we did not have a chance to test the model with version 1.8. Your feedback is much appreciated. It seems like the problem (based on the error message you provided) is related to FEBio not being able to calculate a convergence norm. I am not certain why this may be the case. It may be beneficial to ask FEBio folks as well.

tpataky wrote:
(2) Do you have a version which is compatible with FEBio v.2.0?

Not at this moment. We have focused our recent efforts on development of specifications for specimen testing and modeling of Open Knee(s) - Generation 2. Nonetheless, the time to upgrade the Generation 1 model (which is the only one available) to newer versions of FEBio is due. Other users also had similar interests in using Open Knee - Generation 1 with FEBio v2.0. I am suspecting that we will have a chance to focus on this during the fall.

Best,

Ahmet

Todd,

I am working with Ahmet and have recently updated the openknee (gen1) model [tf_joint.feb] to FEBio v2. I used PreView v1.14.0 import/export to do so and have committed a new version in the respository [tf_joint_FEBio_v2.feb] at:

https://simtk.org/websvn/wsvn/openknee/ ... __gen1_src_

I got a few warnings on import, but the simulation converges using FEBio v2.0.1 with 'Normal Termination', which I'm not sure was even the case in the FEBio v1 compatible model.

Let us know if you have feedback. Thanks!

Craig Bennetts

Principal Research Engineer
Computational Biomodeling (CoBi) Core
Department of Biomedical Engineering
Lerner Research Institute
Cleveland Clinic
Cleveland, OH