Convergence problem
Convergence problem
(OP)
Hello, I am running a simple curved sandwhich panel with large displacements on. the boundary conditions are : it is pinned on one end and allowed to translate on the other.I have applid pressure to the inner surface of the beam. It is a non-linear analysis and i am not able to get it converged. Could anyone give me some idea please. Thanks for yout time.





RE: Convergence problem
First try a linear analysis, second increase the number of loadsteps and print everything. Then you can follow the solution and perhaps find the problem.
However, a thought, curved panel pinned at one end and free at the other. Isn't that a mechanism, the first end can rotate and the second does not stop global rotation.
Run a frequency analysis to find any free-body motion.
Good Luck
Thomas
RE: Convergence problem
RE: Convergence problem
Garland E. Borowski, PE
RE: Convergence problem
Also, does a nonlinear analysis without "large deflection work"? In other words, is that the problem?
Also, which Nastran do you use (MSC NX, NEi etc)?
Regards
Thomas
RE: Convergence problem
RE: Convergence problem
Then I would set the k6rot value to default.
Also, do you get any results, you say a few steps. The error messages in the .f06 file can indicate what goes wrong.
Unfortunately all I can do is some "blind" guessing.
Good Luck
Thomas
RE: Convergence problem
RE: Convergence problem
As for the "crumbling" of elements I don't know what you mean so no ideas right now, sorry.
Regards
Thomas
RE: Convergence problem
RE: Convergence problem
So your system without compressive load converges but not with the compressive load.
A few ideas:
First try with only the compressive load. You might have some kind of buckling instability present.
Another method is to first create a loadcase with internal pressure only and then a second loadcase where you add the compression.
Since you don't mention it I guess this is not a case of plastic faliure.
You can also "play" with the convergence criteria. If you set them "wrong" you might be able to get a incorrect solution that can indicate what the problem is.
Good Luck
Thomas