06-20-2018 07:44 AM
Dear community,
I am trying to understand the stress output Nastran generates in MES1 in a punch file. As far as I understand, MES1 is the output transformation matrix for stress/strain. To be able to understand this matrix, I have made a simple beam model with 12 DOF. The MES1 generates a matrix of 44x12. As the amount of columns is the same as the amount of DOF (also for other models), I assume the columns correspond with the DOF.
However, I can not make sense of the rows. Can anyone tell me with what information the rows correspond?
I have added the .pch file as a .txt file, as the forum does not accept punch attachments.
Thanks in advance,
Christiaan
06-21-2018 10:13 AM
Is there a way to print the MES1 matrix to the f06 file? I tried the command "STRESS(PRINT) = ALL", but that does not seem to do the trick. I can find some info on the MES1 matrix in the f06 file, but enough:
*** USER INFORMATION MESSAGE 4103 (MATPCH)
MATPCH HAS PUNCHED MATRIX DATA BLOCK MES1 ONTO 31 DMI CARDS.
I also found this topic (https://community.plm.automation.siemens.com/t5/CAE-Simulation-NX-Nastran-Forum/Reducing-the-size-of...) which gave me some more information on this topic, but it did not solve my problem yet.
06-21-2018 10:35 AM - edited 06-21-2018 10:36 AM
STRESS will only write tehe actual stress values (tensor!) to teh .f06 file, no matrice. Uou probaly need to write the data to a punch file (.pch). There might be some DMAP involved with printing matrices. never had to do it so just a "wild" guess
06-21-2018 10:47 AM
I already have the data in a punch file, which I have translated back into a normal matrix. However, that does not explain to me what data is actually in the MES1 matrix, which I'm trying to understand.
06-25-2018 07:47 AM
Alright, it took me quite some time, but I think I figured it out, and I will put my solution here for anyone who ever wants to use the MES1 matrix.
The columns correspond with the DOF's of an element. The columns correspond with stresses, which stresses differ per element type. Information about these stresses can be found by combining the Quick Reference Guide with the Element Library Reference, and can take some effort to find the right stresses. Below you can find 2 examples, for a rod and a beam element.
For a rod element the first stress is the normal stress, the second stress is the torsional stress.
For a beam element the four stresses are the real longitudal stresses at point C to F, as defined in the QRG. The first 4 rows correspond to the first cross section of your beam and the last 4 rows correspond to the last cross section of your beam. The rows in between correspond to cross section defined in between the other cross sections (optional).