NONSTATIONARY OSCILLATIONS OF A NONLINEAR ROTOR DURING ACCELERATION THROUGH THE MAJOR CRITICAL SPEED - INFLUENCE OF INTERNAL RESONANCE

The Jeffcott rotor is the most widely used theoretical model in the an alysis of rotor systems. This model satisfies the condition of 1: (-1) internal resonance, and we clarified the effect of this internal reso nance on nonlinear steady-state oscillations at the major, twice the m ajor and three times the major critical speeds in previous papers. In this study, we investigated nonstationary oscillations during accelera tion through the major critical speed in the Jeffcott rotor and other rotor systems which almost but not exactly satisfy the 1: (-1) interna l resonance relation, and investigated the influence of internal reson ance. The following are clarified theoretically and experimentally. (a ) Nonstationary oscillations of the Jeffcott rotor and other rotor sys tems whose natural frequencies almost satisfy the 1: (-1) relation are influenced by the internal resonance. (b) It is easier to pass the ma jor critical speed of a rotor system with internal resonance than that of a rotor system with no internal resonance. (c) When the system has slight discrepancies among critical speeds, that is, almost satisfies the relation of internal resonance, the rotor can pass the major crit ical speed very easily with small amplitude even if the acceleration i s small.