Grid point stress output 1

[Robr123]

Hi!

I would like to print as output both the stress at each grid point ( the average one obtained through GPSTRESS ) and the Root mean square kind of error obtained through GPSDCON. I am completely new to the Nastran world, I only started last week using Femap, so for sure I am doing something wrong but I can't understand what I am missing.
I have created a really small model using Femap then I exported the input file, I added the two lines GPSTRESS=ALL and GPSDCON=all to the case control section and finally run the analysis on MSC NASTRAN but the f06 is exactly the same with and without the two lines I added.
I have attached the .dat input file. The model is a simple rectangle made of few plate elements, the left side is fixed and the right side is pulled.
The kind of analysis is a static one ( should be the sol 101 )
P.S. Hoping that I will be able to obtain that output, I would also like to normalize the GPSDCON output with the GPSTRESS one, is there a way to ask it as input or I will have to do it post-processing?

Thanks in advance !!

 

[dmapguru]

Hi Roberto,

There is much elaboration on this subject in the MSC Nastran Reference Manual in Chapter 8 entitled "Element Data Recovery Resolved at Grid Points".

When you use the GPSTRESS output command, MSC Nastran needs to know which elements are going to participate in the averaging procedure to compute the unique stress values at the GRID points. In addition, geometric discontinuities must be handled appropriately (like edges, T sections, branches, etc.), so the interface is for a general capability. You provide these data on a SURFACE (for 2D elements) or a VOLUME (for 3D elements) command. The SURFACE and VOLUME commands appear in the OUTPUT(POST) section of the input file, which appears between the end of the SUBCASE control and BEGIN BULK.

GPSDCON needs the additional case control request STRFIELD if you want printed output to the f06 file. I am not aware of a way to renormalise the outputs.

So, in short, for your flat plate example, you need to add these commands (or variations thereof) just before BEGIN BULK:

STRFIELD = ALL $ for GPSDCON output to f06
OUTPUT(POST)
SET 9 = 1,THRU,25 $ these are the elements participating in the averaging
SURFACE 10 SET 9 NORMAL Z

DG