Is ANSYS APDL’s geometric stiffness matrix for solid elements wrong?

- October 14, 2024 at 3:03 am
  
  3343534645
  Subscriber
  
  I derived Cook's theory and also rewrote Borst's theory. When they introduced the calculation formula for the geometric stiffness matrix of solid elements, the matrix had zero elements. Why is the geometric stiffness matrix output by ANSYS APDL entirely composed of non-zero elements? Was the calculation incorrect?
- October 14, 2024 at 3:12 am
  
  3343534645
  Subscriber
  
  Thank you to all the experts for reviewing and replying! I am very interested in this issue.
- October 15, 2024 at 8:54 am
  
  3343534645
  Subscriber
  
  Why haven't any ANSYS staff responded to me? Recently, I also tried Němec's theory (http://creativecommons.org/licenses/by/4.0/). However, the geometric stiffness matrix calculated from the theoretical formulas still doesn't match the one in ANSYS APDL. What could be the reason for this? I sincerely hope that someone knowledgeable can resolve this long-standing confusion for me.