node ordering stiffness and mass matrix

- December 11, 2018 at 3:29 pm
  
  LisDeb
  Subscriber
  
  Hi all,
  
  I have a model (made up of solids with 3 degrees of freedom at each node) from which I extracted the stiffness (and mass) matrix unsing APDL Math commands:
  
  *DMAT,MatKD,D,IMPORT,FULL,file.full,STIFF
  
  *PRINT,MatKD,KDense.matrix
  
  This works, however when I tried multiplying the stiffness matrix with the displacements I got from a static solution (I got the displacements in all 3 directions from list results--> nodal solution) to make sure this corresponds to the external force vector, it occured to me that the node ordering cannot be consistent since almost every node has a nonzero value, while I only applied loads on two nodes.
  
  Does this have to do with the fact that *DMAT works with BCS ordering (https://www.sharcnet.ca/Software/Ansys/17.0/en-us/help/ans_apdl/apdldofordering.html) while the displacement exports that i got have a different nodal ordering? how can I transform the stiffness matrix in order to make it match the displacement results I exported?
  
  Thank you!!
- December 12, 2018 at 2:46 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  Hi,
  
  Can you check out example 4.2 in the ANSYS Parametric Design Language Guide? *SMAT with NOD2BCS looks like what you need.
  
  Please do not share any sharcnet links. Use ANSYS Help or the Help Packaged with your installation. I also recommend you to upgrade to 19.2.
  
  Guidelines to the Student Community
  How to access ANSYS Help
  
  Regards,
  Sandeep