Calculix sometimes converging

Model setup
1

Hi Guys

Please refer to the link for the .inp file.

The simulation presents a connection where one location has a slotted hole. I am applying a fairly low pretension of 8kN on the bolts over 3 seconds, there is then 2 seconds where nothing occurs, and then I apply an incremental moment to the system for the next 7 seconds.

I am finding that the model will sometimes solve and other times not solve. I initially thought this may be an issue with using 8 cores for the simulation, but I got similar results using 1 core. Using PlastiX I have also set the PASTIX_MIXED_PRECISION to 0 and the issue still presists.

Has anyone experianced something similar or knows why I am having this issue?

2

Abaqus doesn’t want to solve this because of an overconstraint between pretension section and tie constraints. You should add contact there and only tie bolt heads/nuts if necessary.

Without this tie constraint, Abaqus reaches 6.52 s before diverging. However, adding BCs to all DOFs of the reference point apart from the one with moment makes it run to completion, also in CalculiX.

*BOUNDARY
14377, 1, 3
22674, 2, 3