ERROR #312 - NEGATIVE COMPLIANCE
Altair EmployeeHi everybody,
I am running a non-linear quasi static analysis in Optistruct. This analysis features a partial fan structure, with several components kept in place only by mutual contact with other elements. and various bolts wich keep together the parts via preload.
In particular:
-ALL COMPONENTS ARE MODELLED VIA 3D ELEMENTS (FIRST ORDER TETRA)
-ALL BOLTS HAVE FREEZE CONTACT. OTHER PARTS ARE MODELED WITH CONTACT CARDS USING MU=0.1. ALL Contact surfaces match node by node.
-The gap between every contact surface is zero. There is NO GAP between one surface and another.
-MY INPUT ENTRIES ARE (AS LISTED IN MY .FEM FILE):
PARAM,AUTOSPC,YES
PARAM,CONTFEL,YES
PARAM,EXPERTNL,CNTSTB
PARAM,PRGPST,ALL
That being said, I obtain the following warnings at the end of the run:
*** WARNING # 312
In static load case 2
the compliance is negative or large -2.49893e+010.
Optimization/buckling analysis cannot be performed.
due to possible rigid body mode.
*** INFORMATION # 942
Apparently some contributions to negative compliance come from
gap/contact elements. This can happen in case of initial interference (U0<0)
or significant attractive force (KB>0). To ignore gap/contact contributions
to compliance, set GAPCMPL to NO on the GAPPRM card.
My question is:
Since all displacements seem ok and stresses seem to be consistent with the applied loads and preload seem to work properly, should I ignore contact contributions or they might be invalidating all my results?
Thank you in advance for any reply.
Answers
-
Hi,
Not sure where this extra compliance. Can you share some results and also .out file?
0 -
Unfortunately I can't share too much. But the .out file should do. If you need more information please just ask.
0 -
Hi,
Did you notice this warning message?
*** WARNING # 5912
On TIE and FREEZE contact interfaces, 11 slave nodes are
not tied, these nodes are exported in SETs in the file
named test_nontied.fem.Can you please check if this is the reason?
0 -
Hi!
Yeah, I noticed it and tried to fix it by increasing the searchdist length. However, nothing happened. Do you have any suggestion about a way to take care of this issue?0 -
0
-
Dear Prakash,
thank you for your reply. I will rearrange the model accordigly!
0