I wrote a matlab code which gives the natural frequencies of a 12 Degree of Freedom Beam (2 Node).
6 dof at first node and 6 dof at second node (displacement x, y,z and rotation x, y z)
When i try to validate my code , ıt's seen form the table below, the first four natural frequencies is so close but the others are totally different. Because of this, i also did a static analysis and applied Force at the free end. The deflection for Ansys and Matlab is equal. So i expect that the stiffness matrix in my code is same with the stiffness matrix Ansys used. Is my expectation right? when i try to compare the stifness matrices they are different. But they give the same result.
what am i missing?
what makes the differences between natural frequency values after four mode bigger?
Table. Left Side-1 Element Used Right Side-10 Element Used