Error #941

Altair Forum User

Hello,

 

I am trying to do an encasing simulation but every time i launch optistruct, I am getting this error (ERROR #941); I tried changing the magnitude of the translation but it still doesn't work. Please help.

 

Thank you

 

 

Altair Forum User

Hi @KBE

 

Could you please share the model file, please to find the reasons for non-convergence. 

Altair Forum User

Hi Prakash,

 

Due to the company confidential policy, I can not send you the file. However, I can tell you that I am try to encase two cylinders. See below for the config details:

 

Contact Group:

- DISCRET : S2S

- TRACK = CONSLI

- Property ID = PCONT

 

PCONT details:

- STIFF = SOFT

- MU1 OPTIONS = REAL VALUE

        MU1    =  0.13

- SEPARATION = YES

- FRICESL_opts -- ticked

 

After changing some things around, below is the current message I am getting.

 

 * Friction or STICK can cause more difficult nonlinear convergence - if feasible
   try frictionless gap/contact.
 * This problem has gap elements with friction or stick condition. For more
   intuitive results and often better convergence, set GAPOFFS on GAPPRM card
   to AUTO. (This may violate rigid body balance, especially for unsupported
   structures.) * This problem has elasto-plastic materials and the maximum plastic strain 1.10e+002
   is beyond the limit of small deformation theory. This may be the cause of
   non-convergence. Using fully integrated plastic elements may improve convergence,
   although possibly create overly stiff results.

 

I look forward to your advice

 

Thank you

 

Altair Forum User

Hi KBE,

 

Do you expect large/finite sliding interactions between the cylinders? If not, please change the TRACK field to SMALL.

 

Also, add the below PARAM card and see if that helps

 

PARAM,EXPERTNL,CNTSTB

 

Thanks

Vikas

Altair Forum User

Altair Forum User said:

Hi KBE,

 

Do you expect large/finite sliding interactions between the cylinders? If not, please change the TRACK field to SMALL.

 

Also, add the below PARAM card and see if that helps

 

PARAM,EXPERTNL,CNTSTB

 

Thanks

Vikas

Hi Vikas,

 

thank you but that wasnt the problem. I already had PARAM, EXPERTNL and CNTSTB defined. I dont remember what it wad but I changed something in the PCONT card and it worked. I think i already posted my solution.

 

Thanks again

 

-KBE

FaroukM

Hey All;

 

I had the same error : OptiStruct thinks that a contact problem, but I found that stiffness matrix (MAT9) is not stable ... and that's why the solver didn't converge.

 

Best regards,