Nastran fatal error 9050

[fender21121987]

Hi everybody. I'm doing a static analysis on a part of an aircraft. Te part is already meshed and if I run the analysis with the applied loads everything works. However to perform my analysis I have to remove some elements from the mesh to simulate a damage on the skin. After removing these elements the .f06 file gives me a fatal error:
USER FATAL MESSAGE 9050 (SEKRRS)
^^^ RUN TERMINATED DUE TO EXCESSIVE PIVOT RATIOS IN MATEIX KLL
^^^ USER ACTION: CONSTRAIN MECHANISMS WITH SPCI OR SUPORTI ENTRIES OR SPECIFY PARAM,BAILOUT,-1 TO
CONTINUE THE RUN WITH MECHANISMS.

The problem is that the elements specified in the fatal message are really far away from the ones that I removed and the fatal shouldn't appear. Obviously I cannot block them with SPC1 and neither use the PARAM, BAILOUT, -1 because the results would be incorrect. In my office everybody has no idea of the reason of the fatal error. Does anybody of you know what could be the problem?

Thanks in advance,
Philipp

 

[Edubya]

Since you had a previously stable model and you deleted elements, I'd suspect you've got unattached nodes...

If that doesn't work I'd try the 6-dof run constrained and free. That'll make the mechanism really obvious

 

[Naffoussi]

Hi fender,

1) perform a free-free analysis
2) check if the deleted elements does not represent a constraints that you defined and then your model is unconstrained
3) delete unattached nodes related to the deleted elements
4) you can also use the PARAM,BAILOUT,-1. that will just help you to see where is the problem...

 

[ZeroExperience]

FATAL 9050 is a very common message. Here is a cheat sheet:

http://www.mscsoftware.com/support/...essive_Pivot_Ratios Cheatsheet_2011_11_10.pdf

 

[almpunk]

Hi to all,
Have you tried to launch a modal analysis?? it will help you to identify if you have any unconnected elements. Also I will recommend you to make a GROUNDCHECK to check the DOF of your structure.
Have a nice day!!

 

[ZeroExperience]

FATAL 9050 is a very common message. Here is a cheat sheet:

http://www.mscsoftware.com/support/...essive_Pivot_Ratios Cheatsheet_2011_11_10.pdf