Numerical investigation of an unbalanced rotor system with bearing clearance

The nonlinear vibrations of a rotor system with bearing clearance are considered. The model consists of an unbalanced shaft with two d.o.f connected to a nonrotating massless housing by linear springs and dashpots. The clearance occurs when the housing (modelled as a ring) has a radius less than the stator. The behaviour of this system has been investigated with the use of time histories, Poincaré maps, bifurcation diagrams, Lyapunov exponents, phase portraits, cell mapping and design space. Numerical simulations have achieved these results. The main objective was to find possible causes of failure in machines containing this type of clearance. The existence of subharmonic, quasi-periodic or even possible chaotic motion has been found. It is shown that these motions may give raise to bouncing modes, which results in high bearing forces and hence can be a possible cause of failure.