i am trying to find normal modes of simple ideal circular membrane.
I chose strecutral steel as material, and geoemtry is: diamater is 0,391mm, thickness is 0,0035mm.
However, i got "double" modes: every two modes are very very similar - with the almost same value of frequency.
i got same answer with other commercial program.
I tried to chcange mesh, i tried do model my geomtry as solid and also as a shell/surface but i got the same problem.
see pictures: mode 4 and mode 5 is only ONE mode in reality. Why i got this result?