 Boundary condition  Natural frequencies (Hz) at P = 0 and M = 0  Mode 1  Mode 2  Mode 3  Exact [38]  FEM (40 elements)  Exact [38]  FEM (40 elements)  Exact [38]  FEM (40 elements) 
 CF  2.556  2.556  15.995  15.995  44.858  44.858  CC  16.266  16.266  44.858  44.858  87.970  87.970  PP  7.175  7.175  28.718  28.718  64.633  64.633  PC  11.209  11.209  36.351  36.351  75.611  75.611 

