Large Assembly: Unable to solve
Altair EmployeeHello,
We have a large assembly (structural steel frame) including a lot of steel beams and bolts/nuts. The assembly contains fully defined connections and constraints.
After solving the analysis we got the message:
“Unable to solve equation system (status 17, 4276, 0). The structure may not be sufficiently constrained. Do you want to check possible rigid motions?”
After directly checking Rigid motions we get the message:
“The structure is sufficiently constrained. No rigid body motions was found.”
These are conflicting reports. Now i have to check manually every part and connection in the large assembly.
Do you have some tips? Thanks.
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Altair Employee Thank you for reply. Ok i will work through the options and try other connections. unfortunately that it is difficult to find where the problem exactly is.
This is a confidential project. Where can I send the model for verification?
Altair EmployeeWe do not need even the CAD model, just share the ssp any way (Drpbox, google drive, etc.).
Altair EmployeeToday i had remade all connections. First i had set the auto connections at a smaller gap size and higher resolution. Then i got the message again and again with check possible rigid motions, this time it shows the loose components (a lot components and very much bolt/nut/washer sets). It cost a lot of time to set all the contacts manually. I have also suppressed a lot of parts and fasteners because of time consuming (at setting manual contacts).
After analysing again i got now results!
Thank you for helping. I will send you the .ssp file for your info and development of Simsolid. I do a lot of this engineering jobs, also for the future. I hope you continue to develop for efficiency and better automatic contacts at large assemblies.
The reasons for numerical instability can be:
– insufficient contact resolution. Particularly important in case of large frames when the global size is much bigger than size of beams cross-sections (may result in internal hinges). Remedy: increase the resolution in Find Connections dialog
– significant part overlaps which makes connections not physical
– significant distance between connected parts (reduce gap tolerance)
– invalid geometry (you can check geometry quality by launching diagnostics from Assembly toolbar
The best way is to send us the model for investigation.