ACCELERATION THROUGH CRITICAL SPEEDS OF AN ANISOTROPIC, NONLINEAR, TORSIONALLY STIFF ROTOR WITH MANY DEGREES OF FREEDOM

It is well known that the amplitude of the unbalance response of a rot or which runs through a critical speed can be reduced by increasing th e value of the acceleration. However, the models which are used for th e computation of the unbalance response can be used only for constant speed running, and the solutions dealing with accelerating rotors whic h can be found in the literature refer to very simple geometrical layo uts. The aim of the work reported here is to extend the usual mathemat ical models based on the finite element method to the study of the dyn amic behaviour of rotors with non-constant angular speed, Both the non -linear behaviour of the rotor and its geometrical or inertial anisotr opy have been taken into account. The case of a torsionally stiff roto r running with a given law omega(t) is studied in detail. Several exam ples, including a practical one dealing with a complex rotor running o n non-linear bearings, conclude the work.