Dynamic stability of a rotating shaft embedded in an isotropic winkler-type foundation

The dynamic instability of a rotating shaft subjected to axial periodic forces and embedded in an isotropic, Winkler-type elastic foundation is studied by the finite element technique. The equations of motion for such a rotating shaft element are formulated using deformation shape functions developed from the Timoshenko beam theory. The effects of translational and rotatory inertia, gyroscopic moments, bending and shear deformation are included in the mathematical model. The numerical results show that the elastic foundation can shift the regions of dynamic instability away from the dynamic load factor axis and thus reduces the sizes of these regions, whereas the effect of gryoscopic moments is to shift the boundaries of the regions of dynamic instability outwardly and, therefore, increases the sizes of these regions.