Nonlinear dynamics of a spinning shaft with non-constant rotating speed

Abstract

Research on spinning shafts is mostly restricted to cases of constant rotating speed without examining the dynamics during their spin-up or spindown operation. In this article, initially the equations of motion for a spinning shaft with non-constant speed are derived, then the system is discretised, and finally a nonlinear dynamic analysis is performed using multiple scales perturbation method. The system in firstorder approximation takes the form of two coupled sets of paired equations. The first pair describes the torsional and the rigid body rotation, whilst the second consists of the equations describing the two lateral bending motions. Notably, equations of the lateral bending motions of first-order approximation coincide with the system in case of constant rotating speed, and considering the amplitude modulation equations, as it is shown, there are detuning frequencies from the Campbell diagram. The nonlinear normal modes of the system have been determined analytically up to the second-order approximation. The comparison of the analytical solutions with direct numerical simulations shows good agreement up to the validity of the performed analysis. Finally, it is shown that the Campbell diagram in the case of spin-up or spin-down operation cannot describe the critical situations of the shaft. This work paves the way, for new safe operational 'modes' of rotating structures bypassing critical situations, and F. Georgiades (B) School of Engineering, College of Science, University of Lincoln, Brayford Pool, Lincoln LN6 7TS, UK e-mail: fgeorgiadis@lincoln.ac.uk also it is essential to identify the validity of the tools for defining critical situations in rotating structures with non-constant rotating speeds, which can be applied not only in spinning shafts but in all rotating structures.

Chaotic Dynamics in Spinning Shafts with Non-constant Rotating Speed Described by Variant Lyapunov Exponents

“…In Ref. [4], the equations of motion of a spinning shaft as Euler-Bernoulli isotropic beam has been derived and dynamic analysis is performed, noted that the model has a similar form with this one obtained in Ref. [3] about rotating blades.…”

“…The equations of motion describing the dynamics are given in Ref. [4] and in Ref. [5] by neglecting the equation of rigid body angular position then a restricted system is arising.…”

“…There is a significant number of articles focused in dynamics of rotating structures with constant rotating speed but the examination of dynamics of rotating structures with a non-constant rotating speed which occurs during spin-up/down operation is very limited [1][2][3][4][5]. In Ref.…”