I created a component mode synthesis model of a cylinder to export the reduced-order mass and stiffness matrices; however, when I compare the matrices to those determined analytically, I see completely different results. This results in two very different solutions to a flexible body dynamics model. The cylinder has two boundary nodes: at the face center of either end. I am using the CBN method of arriving at the matrices. Is this a bug with the software? I confirmed that the matrices determined analytically match what we would expect, so the issue comes from Hypermesh.

Output from hypermesh (mass matrix top, stiffness matrix bottom):


Analytical solution (mass matrix top, stiffness matrix bottom):


Thank you