A numerical investigation into the effect of the supports on the vibration of rotating shafts

Vibration is typically encountered by rotating equipment during its start-up, running operation and shutdown. The severity of the oscillation, which depends on the critical speed and natural frequencies of the system, could cause serious malfunction of the device and affect its operating performance. A simplified lumped parameter model of a rotor system is typically used for the study of the shaft dynamics of a single rotor on bearing supports. Bearing supports are the means of connecting a device between the rotor and supporting structure, which are of different forms and designs. They can be a simple bushing, rolling-element or journal types for light, medium and large load applications respectively. Particularly in this work, flexible supports made of rubber are considered by implementing viscoelastic material into the rotor bearing system. Viscoelastic material is well known to be a good choice for use within isolation systems, due to it being easily available and possessing high damping characteristics over a wide temperature and frequency range. However, the change of mechanical properties with frequency and temperature makes it difficult to design a viscoelastically device that works over a large range of operating conditions. Thus numerical analysis, which focuses on the simple rotor model supported on a range of different flexible supports, will be presented and compared.