I use the APDL command "debug,-1,,,1" to extract the element stiffness matrix, and I use the APDL command "HBMAT" to extract the full stiffness matrix. However, the elements number are 640 in debug mode, and the elements number are 1280 in HBMAT mode. This problem puzzles me.

I want to use the element stiffness matrix to assemble the full stiffness matrix, and I can not find the reason.

The element stiffness matrix contains: 640 matrices for stiffness and 640 matrices for mass.