Abstract: This paper presents a finite element model of a rotor system with
pedestal looseness stemming from a loosened bolt and analyzes the effects of
the looseness parameters on its dynamic characteristics. When the displacement
of the pedestal is less than or equal to the looseness clearance, the motion of
the rotor varies from period-one through period-two and period-three to
period-five with the decreasing of stiffness of the non-loosened bolts. The
similar bifurcation phenomenon can be also observed during the increasing
process of the rotational speed. But the rotor motion is from period-six
through period-three to period-four with the decreasing of the foundation
stiffness. When the stiffness of the foundation is small and the displacement
of pedestal is greater than the looseness clearance, the response of the rotor
exhibits period-one and high order harmonic components with the decreasing of
looseness clearance, such as 2X, 3X etc. However, when the stiffness of the
foundation is great, the spectrum of the response of the rotor will be from
combined frequency components to the continuous spectrum with the decreasing of
the looseness clearance.
Keywords: Nonlinear Vibration, rotor system, pedestal looseness, finite element method
