Error Output from CCX

Hengre

Hello

I have a problem solving a model generated and solved in 2018. I just tried to resolve it, but know I'll get the folloing output from CCX:
... The warnings were also in 2018
...
*WARNING in gentiedmpc: no tied MPC
generated for node 268340
no corresponding master face
found; tolerance: 1.2465051363339661E-004
*WARNING in gentiedmpc: no tied MPC
generated for node 268341
no corresponding master face
found; tolerance: 1.2465051363339661E-004

but know I got:

*ERROR in cascade: zero coefficient on the
dependent side of an equation
dependent node: 81776 direction: 1

I tried to remesh the component with node 81776, but the error moved to an new node .
I guess these nodes are unsed in a bonded contact?

I would appreciate any help to get my model running again , thanks

Hengre

i used different versions of CCX (2.14, 2.15, 2.15 paradiso) ...
I also face the problem now in other Prats bonded to the main structure.

I am confused , because the model worked fine in 2018

Victor

That or similar errors can happen with node rotation or fixed support, moment or force (on faces, not nodes) on shells in some cases, particularly if they're curved.

Bonded contact can also fail if it's sharing node with another bonded contact or constraint but I'm not sure what error message appears then. If this is the problem, you can turn on the Elastic option in the bonded contact and give it a very high stiffness per unit area. This option doesn't use MPC equations so it avoids such problems.

I don't know why it would have changed since 2018 but if you send me the file, perhaps privately, I can diagnose it. It might be a new bug.

Hengre

Hello Victor

I am still struggling around with the problem above.

Unfortunately now i found some other model from 2018 (same structure at different stage), but here the Error is
*ERROR in e_c3d: nonpositive jacobian
determinant in element 163463
Strangely enough i found that this error also apeared in the 2018-files with Mecway 8, but I finally still got a result.

Testing that model (with the error) on some of the old Mecway-Versions with different CCX-Versions i found that some give a result - others won't. (see PDF attached).

If you find it worth to have look to the models I can send them to you, but I don't want to bother you to much with that.

Victor

Judging from the number of equations, it looks like you might be bumping up against a memory limit and that might be causing inconsistent failure or success.

The "Solver reports *ERROR" message is simply parsing the error message shown the CCX output and is new since after Mecway v9, so those differences won't be related to the results.

As for why it sometimes produces a result despite the *ERROR message, I'm not sure, but if you have multiple time steps, it might be giving a result for earlier ones then stopping when the error occurs, or it might show the last non-converged iteration in a nonlinear analysis.

The nonpositive Jacobian determinant error means the element is detected as having an impossible shape such as inside-out or self-intersecting. It could be because:

• It's meshed wrong. Usually, the modeler will show a red X in the graphics area in this case.
  
• It's a beam/shell element that's strangely shaped and seems OK in 1D/2D but when expanded to a solid, and connected with its neighbors, turns out to be badly shaped.
  
• In a nonlinear analysis, an element might become badly deformed by the solver after some time steps have successfully completed.
  
• It's very small which can/used to fool CCX into thinking it was badly shaped.
  

I'd like to see the files if you don't mind. Generally, with software, it's easier to diagnose problems by reproducing them instead of just looking at error messages. Error messages often have multiple possible causes which could be trivially eliminated by seeing the file but without it, expand the number of things to consider. There are also unknown causes of error messages which can be discovered by elimination while reproducing it.

Hengre

Thank you Victor,

I have send the model files to your mecway e-mail address