四乗の非線形復元カをもつ偏平軸および非対称回転体の非線形強制振動 : 第1報,分数調波・超分数調波振動の共振曲線の変化と不安定振動の発生

This paper deals with the subharmonic oscillations of order l/4 and the ultra-subharmonic oscillations of orders 3/2 and 2/3 in an unsymmetrical shaft system and an unsymmetrical rotor system with nonlinear spring characteristics involving quartic nonlinear terms in addition to quadratic and cubic terms. The former system is constituted by an unsymmetrical shaft and a symmetrical rotor and the latter by a round shaft and an unsymmetrical rotor. We theoretically analyzed the effects of the directional differences of shaft stiffness or rotor inertia on these oscillations, paying attention to the nonlinear components represented by the polar coordinates. By numerical calculations, resonance curves of each oscillations are presented. As a result, it is clarified that unstable vibrations occur in particular types of oscillations. In experiments, we observed these unstable vibrations in the unsymmetrical shaft system and the unsymmetrical rotor system, where the shafts were supported by cylindrical roller bearings.