Modal characteristics of rotors using a conical shaft finite element

Abstract A finite element formulation for a rotor-bearing system is presented. The equations of coupled bending and torsional motion of the rotating shaft are derived using the Lagrangian approach. A conical beam finite element for vibration analysis of rotating shafts including shear deformations and rotary inertia is derived. The finite beam element has ten degrees of freedom and accounts for linear tapering. Explicit expressions for the element mass, stiffness, and gyroscopic matrices are derived using consistent mass formulation. The finite element discretization is employed, the generalized eigenvalue problem is defined, and numerical solutions are obtained for a wide range of whirl ratios, spin speeds, and taper ratios. Comparisons are made wherever possible with exact solutions, and with other numerical results available in the literature. Extended numerical results are produced for a wider range of parameters for which solutions were not previously attempted.