Learning Forum

[ben.gilmour]

I have been attempting to automate the extraction of principal stresses from a beam element model. This seems to be a little tricky, and I’m now having an issue exporting the principal stresses using APDL. I can see the principal stresses mapped onto the nodes in a stress plot, giving me an example maximum principal stress value here of 1.8e5 Pa. Using my APDL script, the principal stress I extract is 0.7e-30 Pa.

I have used this script successfully with shells and understand there is some difficulty in reading nodal stress outputs from beam elements. However, even in this model I have a maximum principal stress of 1.2e8 Pa on my shell node whereas the script picks up -0.2e-2 Pa. Stranger still, it reads the middle and minimum principal stresses fine for the shell.

Anyone know what the problem is here please? 

I will include the script below for reference:

/OUTRES,DATAFILE,TXT

FINISH

/POST1

SET,LAST

 

!   Name a text file and write headers for columns.

FNAME = 'NodeStress'

*CFOPEN,%FNAME%,TXT

*VWRITE,'No.','MaxPrinc','MidPrinc','MinPrinc'

(A,','A,','A,','A)

 

!   Select all nodes, and then call upon the node numbers we're interested in. Name these using an

!   incremental value such that the names can be sequentially read. 

ALLSEL

NS1 = 23

NS2 = 88

NS3 = 426

 

Nos = 3

 

!   'D' is used as an integer describing the number of iterations performed.

D = 1

 

!   Do loop for finding the node, getting the maximum/middle/minimum principal stresses.

*DO,A,1,Nos,1

NSEL,S,NODE,,NS%A%

*GET,Snom1%A%,NODE,NS%A%,S,1

*GET,Snom2%A%,NODE,NS%A%,S,2

*GET,Snom3%A%,NODE,NS%A%,S,3

ALLSEL

 

!   Write the stress values to the text file.

*VWRITE,%D%,NS%A%,Snom1%A%,Snom2%A%,Snom3%A%

(F8.0,','F8.0,','E16.10,','E16.10,','E16.10)

 

!   Increase the iteration count by one before restarting the loop.

D = D + 1

 

*ENDDO

 

!   Close the text file and end script.

/OUTRES

*CFCLOSE

[danielshaw]

The low stress value obtained by *GET probably just means that quantity was not available.  What message was issued to the solve.out file when that *GET was issued? 

1Did you try just issuing *GET for 1 node/element before embedding the *GET commands inside a *DOLOOP?

1Why are you attempting to extract nodal stresses for beam elements?  What is the relevance of the nodal stress from a beam element?  Typically you are interested in the beam results.

 

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