I am running a SOL 101 linear statics FEA. If I fix down the whole geometry it converges. But anything less than around 90% fix down and it will sit there crunching away at the numbers forever. This is with no other boundary conditions, forces, etc. applied on the system. What is it even trying to crunch? there are no forces on the system! What could be causing my geometry to be "haunted"? How do I go about troubleshooting this?

So far I have been un-fixing down regions of my geometry to try to track down what could be causing the problem, but I am not having much luck. Plus each test takes 10+ minutes so I am hoping there is a better way.

  • $\begingroup$ What happens when you add a force though? Perhaps some elements are bistable? $\endgroup$ Jul 7 at 12:56
  • $\begingroup$ when I add a force it also just crunches away indefinitely. I have tried similar geometries successfully and they ran fine within 10 minutes. I left this one running for 122 hours without any results. $\endgroup$ Jul 7 at 13:23
  • $\begingroup$ Sounds like there is an issue with the mesh, then. Can't really help much without being able to poke around in the software and see what's up 😔 $\endgroup$ Jul 7 at 13:44
  • $\begingroup$ but if there was an issue with the mesh, how would I track it down? $\endgroup$ Jul 7 at 13:46
  • $\begingroup$ Honestly? I'd start by just looking at it through the lens of experience... Unhelpful I know! $\endgroup$ Jul 7 at 14:00

Found the solution. Looks like there is a bug in Nastran where if it doesnt see enough space in your C: drive (even if your scratch directory is in your D: drive), it just hangs. Once I cleared out some space in my C: drive (AND restarted my computer) then it started working.


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