Dear pgalibrov,
I have tried constraining DOF, however to no avail. The solution is still not converging.
Carl,
your messages are not helping to resolve the problem. Could you please be more specific? have you used the new template? have you constrained the node with 0 forces in it as I explained? Could you provide a screenshot of the applied forces? The error message?
You should get a dynamic equilibrium with the forces that you get from AnyBody. That means that the problem is somewhere else. ‘Not converging’ is not a good descriptor of the problem.
Regards,
Pavel
Dear pgalibrov,
Sorry if I haven’t been specific enough. I am carrying out a simulation of the forces on the L3 vertebra during gait. I have used the new template and the forces were successfully loaded. I have also tried constraining the node with 0 forces on it however the same error still persisted. I think that there is one of the beam elements created that is having excessive force.
I have copied my error file, and some screenshots of the applied forces.
Regards,
Carl
Error file:
*** WARNING *** CP = 1574.892 TIME= 15:33:40
Previous testing revealed that 66 of the 130939 selected elements
violate shape warning limits. To review warning messages, please see
the output or error file, or issue the CHECK command.
*** WARNING *** CP = 1575.095 TIME= 15:33:42
No constraints have been defined using the D command.
*** WARNING *** CP = 1576.515 TIME= 15:33:43
0 constraints specified, but exactly 6 needed for 3-D inertia relief.
Maybe OK if symmetry constraints or internal MPC are included. Check
that the reactions at all constraints are zero.
*** WARNING *** CP = 1594.096 TIME= 15:34:01
Coefficient ratio exceeds 1.0e8 - Check results.
*** ERROR *** CP = 1851.560 TIME= 15:37:48
A small negative equation solver pivot term has been encountered at the
UY degree of freedom of node 3124. Check for an insufficiently
constrained model.
The more information - the easier it is to resolve the problem 
"*** WARNING *** CP = 1576.515 TIME= 15:33:43
0 constraints specified, but exactly 6 needed for 3-D inertia relief. "
Does not look like the constraints were applied correctly. Could you show the code used for these constraints?
Regards,
Pavel
I will attach the generated file from the AnyFe2APDL program then. You can find it here:
Could you point where you imposed the constraint? I could not find it in the code. You need something like:
D,250001,ALL ! constrain node 250001 all 6 degrees of freedom for inertia relief
! 250001 is an extra node created for the load transfer.
Regards,
Pavel
Ohh I see… so should I constraint that particular node? I will try it now and tell u what has happened immediately 
That is an example - you should constrain a node with no forces in.
P.
I have tried constraining a node with no forces in but the same thing happened
Dear Pavel
I have tried constraining the model as you have suggested and I am now loading the file. It looks like it’s going to take a while for ANSYS to load the file and solve.
Right now I am using a computer at a lab in my University, and the lab is going to close, so, I will tell you what happened tomorrow. Thank you for your help
Regards,
Carl
Dear Pavel,
I have constrained my model as you have tolde me (text file attached). However there is still an error, so I have included also the a copy of the error file. I hope this will be of some help.
Regards,
Carl Muscat
Error file:
*** WARNING *** CP = 4777.843 TIME= 17:23:11
Using 1 iteration per substep may result in unconverged solutions for
nonlinear analysis and the program may not indicate divergence in this
case. Check your results.
*** WARNING *** CP = 4780.557 TIME= 17:23:14
Previous testing revealed that 66 of the 130939 selected elements
violate shape warning limits. To review warning messages, please see
the output or error file, or issue the CHECK command.
*** WARNING *** CP = 4801.040 TIME= 08:10:42
Coefficient ratio exceeds 1.0e8 - Check results.
*** ERROR *** CP = 5067.100 TIME= 08:15:09
A small negative equation solver pivot term has been encountered at the
UY degree of freedom of node 2647. Check for an insufficiently
constrained model.
Hi Carl,
Have you solved the problem? I could not see the constraint in the code you sent - so have a feeling that something goes wrong there. But otherwise you could also adjust the last section to have more than one timestep.
Regards,
Pavel
yes solve the problem, sorry but i attached the wrong file by mistake. The problem was something with pivot checking, as soon as I issued the command “pivcheck,off” and solved, the solution converged and results were as expected. Thank you for your time and cooperation
Hi there,
as I saw the license topic was solved a few replies before. I’ve done everything as you mentioned, license renamed and put it right to the exe-file, but the problem is still there. Even if I run it with the DOS Command it says “no valid license…”. I got a Trail-license … could it be that the anyfe3apdl is not released in it?
Regards,
felix
Hi Felix,
yes, that seems to be the case. Please send an e-mail to sales@anybodytech.com with your license file and mention the problem.
Regards,
Pavel
Hi Pavel,
yes, we were right. The trail license is supporting the any3apdl-converter until the next AnyBody release. Thanks for your quick help.
Best regards,
felix
Hi Pavel,
yes, we were right. In the next Anybody release it will be possible to work with the converter with (just) a trail license.
Thanks for your quick help!
Best regards,
felix
Dear Pavel,
Thank you for your kind help and aid in my previous problem. I have successfully solved the system, however, when post-processing in Ansys, I am getting a stress concentration of about 30MPa at the middle of the L3 vertebra. Do you have any idea what might be causing this? could it be that the markers when using MoCap were a little bit misplaced and this is resulting in an exaggerated force? I am saying this because everything seems to be running fine with my model.
Best regards,
Carl
Dear Carl,
Good to hear that there is some progress. This stress concentration is probably due to the joint reaction force being applied to a small area by the default procedure. I think the magnitude may be somewhat within realistic range for a heavy person and a stressful activity (by the way what are those factors?), but the concentration is not very good. You could try to individually adjust application of this load to be distributed more to the area rather than a small area. Ideally this load should be transferred via an adjacent disc and a ‘rigid’ endplate.
But it is, of course, does not harm to check your simulations and see that the motion is ok.
Regards,
Pavel
Dear Pavel,
It is a bit of a problem to manually adjust the forces, this because I am doing an analysis of a gait cycle and seeing what the effects on the spine are. This means that I would have to manually adjust every single force file generated during the gait cycle (approx. 150 files).
When checking the motion, everything seemed alright at first sight. There is however a small problem with penetration of surfaces when I try running the inverse dynamics. I was told that these are of no real concern since they occur before the inverse analysis sequence starts and not when it is running, however now I have my doubts about this. What are your suggestions please?
Thank you once again for your time :), I really appreciate.
Best regards,
Carl