Learning Forum

[Diona Çejku]

Hello everyone, 

I've been working on extracting mass matrices from Ansys APDL using the following code for analysis:

ANTYPE,MODAL 

MODOP,LANB,10

/STATUS,SOLU

/SOLU

OUTPR,BASIC,1

/OUT,SCRATCH

SOLVE

 

/POST1

SET,FIRST

 

*dmat, m0, D, import, full, file.full, mass

*print, m0, matm.txt   ! Exports Mass to Text File

*export, m0, mmf, matmMMF.txt ! Exports Mass as MMF

 

/OUT

FINISH

However, I've encountered an issue where the extracted matrix is not diagonal. I've double-checked my code and inputs, but I'm still unable to identify the source of the problem. I would highly appreciate if anyone could help to resolve this issue. 

Thanks :)

[mrife]

Hi Diona

Why would the mass matrix be diagonal?  My guess is that you are assuming a lumped mass formulation...if so please see the help on the Mechanical APDL command LUMPM.  You may also want to read the MAPDL Theory Guide, chapter 12.5 (Element Reference -> Lumped Matrices) as there are some caveats to using this.

Mike