Nastran Displacement Coordinate System

[stresscalcs]

[tt]Hi

Anybody able to help me and tell me

1) where do I find a definition of "Displacement Coordinate System"?
ref. 2004 Nastran Reference Manual page 42.

2) Can you define it somewhere in Patran?

I have been unable to find anything meaningful.

TIA
Richard[/tt]

 

[brianabreugomes]

Hi Richard,

I know nothing about PATRAN but the displacement coordinate system is defined on the GRID ID output coordinate system. Whatever that coordinate system, the *.f06 file should print the displacements. You should be able to define this in PATRAN. Run some tests. Define the GRID in global coordinate system (I think it is "0)" and then define the output in a different coordinate system. Compare the *.f06 file displacement output. Should be different. As far as viewing it in PATRAN, you might have to change something in the viewing option for the results when creating a contour plot.

Cheers,
Brian

 

[stresscalcs]

Hi Brian

Thanks for the input.

I have now done some testing of my own (as you suggested and it is a most necessary thing to understand MSC's software, as the documentation is so sadly lacking or misleading) and further information has come to light.

It has become apparent that Patran has no "displacement coordinate system", only Nastran has it.
Patran has an "analysis displacement coordinate system" which appears to be and my MSC contact has confirmed is the same thing. Notice I originally made reference to the Nastran Manual.

Most people use an "as installed" Patran and then any Nastran input data decks created and run will produce a F06 file in the Nastran "basic coordinate system" (you and almost everybody calls this the Global system which is not the correct Nastran name, see again pages 41 & 43 of Nastran Manual).

Use of the Patran "analysis displacement coordinate system" will allow you change the axes system of the F06 file, but beware that element offsets then appear to be corrupted. That was what I was investigating when I posed the question.
I still have to complete my investigation.

Best Regards
Richard