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Order of stresses in pch-file in nastran

Hello everyone,

 

I'm quite new in this community, but I couldn't find an answer to this question, which is why I'm asking here.

I'm calculating the nodestresses, which occure in the eigenforms of a component. I can display these in NX. The problem is the following: when I put the nodestresses into a pch file it seems like they are always printed in a different order, differing with which kind of element is used in the fe-net. Can I somehow get them in a special format like xx, yy, zz, xy, yz, xz? Or is there a documentation that displays where in which elementtype which nodestress is printed?

 

I hope the discription was understandable and detailed enough. If there are open questions I will of course answer them. Thank you very much.

4 REPLIES

Re: Order of stresses in pch-file in nastran

The order of data in the punch file matches the order of the data in the .f06 file printout. The .f06 is more "human readable" with column headers, page breaks, etc. The punch file has all of this formatting removed and just contains the data values.

 

The stress conponents avaialble and their order does depend on element type. This is due to the fundamental differences in formation between shells, solids, beams, etc.

 

 

Re: Order of stresses in pch-file in nastran

Thank you very much for the fast answer. It helped a lot!

Re: Order of stresses in pch-file in nastran

Hi JimB,

 

I was googling a similar question and stumbled upon your answer which was very helpful, thank you.

 

I am actually using Autodesk Nastran Editor, but I understand (think/assume) that the results files should be the same in all Nastran solvers (NX, Patran, MSC..). 

 

I requested the stress results to be printed out in the punch file, and I am now comparing the values with the values from an Autodesk output file which has the same structure as a .f06 file.

 

In this case I'm talking about a CHEX (67) element.

 

In the output file (f06) I can see which values are stresses in X, Y, Z, XY ect.. as well as the direction cosines.

If I then compare these results to the values in the punch files, in the order they are printed (as you mentioned). The stress values corrsponds exactly, but the cosine direction values are not the same. (Some are equal but some are deviating by up to 30%. Should be noted that I only checked for one element.)

 

Do you know if the cosine directions are represented differently in the punch file and the f06 file?

Re: Order of stresses in pch-file in nastran

The output in the punch file is described in the "Chapter 7 : Item Codes" of the QRG (quick reference guide).