Forum: Answers and discussion

Monitor Forum | Start New Thread Start New Thread
FEMLink : read NASTRAN element matrices and deformations [ Reply ]
By: Balmes on 2009-08-23 10:48
[forum:21]

Question 1 : I tried the software a little bit, but somehow I do not get my necessary results. My goal is to read in a nastran op2 result file derived by PARAM,POST,-4 of a direct/modal frequency response calculation, as it  is enclosed in this mail. Especially I need the element stiffness and mass matrices KELM, MELM and the displacement results OUGV1.

 
For PARAM,POST,-4 you need to use the 'buildup' command
 Up=nasread('FileName.blk','buildup')
 
 note that you need to have both the output2 and bulk files with the same root name.
 
The upcom function can then be used to reassemble the model.
 
Question 2:  As far as I can tell, this will give me a condensed and assembled stiffness/mass matrix. My goal is to have the element stiffness/mass matrices for each element of the model. Is this possible?
 
Yes, you have to read through the upcom documentation which tells you how to reassemble matrices. Typically by groups of elements called parameters. But you can easily set up a parameter per element and thus get element matrices.
 

 Question 3: Additionally, I also tried a bigger model (20.000 elements instead of 1.500, 170MB result file) but then I do not get any displacement results at all with command nr. 2. I do get the element matrices with strange entries as mentioned before with command nr. 1. 

The displacement results will be stored in the model Stack Up.Stack entry 'curve','OUG(1)' in most cases (the exact name is given by your version of nastran)

If deformations go over the out of core buffer size (100 MB) they are left in the file until you use them. To see the value use

def=stack_get(Up,'curve','OUG(1)','getdata');
def.def

To read everything in memory. def.def=def.def(:,:);