Study on whirling motion and torsional vibration of the power-transmission shaft systems

論文翻譯標題: 動力傳遞軸系之旋動與扭轉振動問題的研究
  • 林 福堂

學生論文: Doctoral Thesis


Abstract The vibration analyses of the ship propulsion system including axial vibration torsional vibration transverse vibration and whirling motion etc are the critical issues for its design and all the ship-design engineers must face this problem carefully In which both the torsional vibration and whirling motion are associated with the shaft rotation it is obvious that the gyroscopic moment on the propeller flywheel and flanges etc will vary periodically when a torsional vibration occurs in the ship propulsion system and any initial-displacement-induced non-synchronous precession could be critical In the existing literature the dynamic characteristics of whirling motions of the shaft-disk systems are usually analyzed by using the TMM or FEM The results of the last methods are the approximate solutions and the exact solution concerned is rare For this reason this thesis presents an analytical method for yielding the exact whirling speeds and mode shapes of a distributed-mass shaft mounted by arbitrary rigid disks In theory the whirling motion of a shaft-disk system is three-dimensional however if the transverse displacement in the xy-plane and that in the xz-plane are combined by using a complex number and the effects of each rigid disk on the shaft are replaced by a lumped mass together with a frequency-dependent equivalent mass moment of inertia then the whirling motion of a rotating shaft-disk system will be similar to the two-dimensional transverse free vibration of a stationary beam Therefore after the foregoing manipulations some techniques for the free vibrations of a stationary beam carrying various concentrated elements will be available for the whirling motions of a rotating shaft mounted by arbitrary rigid disks Based on the above theory some practical examples are illustrated Numerical results reveal that when a shaft-disk system is put into a spinning motion about its longitudinal axis each of its natural frequencies of stationary transverse free vibrations will split into forward whirling speed and backward one furthermore the characteristics of whirling motions are significantly dependent on the slopes of the associated natural mode shapes at the positions where the rigid disks located In order to confirm the reliability of the presented theory and the developed computer programs most of the results obtained from the presented method are compared with those obtained from the existing literature or the FEM and good agreements are achieved
獎項日期2015 七月 23
監督員Heiu-Jou Shaw (Supervisor)