Huang S., Tsai C.

A rotor system composed of flexible shaft, unbalanced disks, elastic supports and shaft coupler with parallel offset was investigated. The authors first derived the transfer matrix method for rotating shafts and discovered that the boundary shears were mutual coupling and time dependent in two perpendicular directions due to rotation. The coupling shears affected the shaft's critical speeds up to 50%. The transfer matrix of a flexible coupling with parallel offset was then derived and its effects on critical speeds and whirling response were particularly focused on. Numerical results showed that the flexibility of couplings significantly influenced the rotor-bearing critical speeds. The parallel offset, yet, played as an excitation force to rotor system as unbalance. The coexistence of disk unbalance and shaft offset revealed that the offset appeared more significant effects at rational speeds but the unbalance increased its weight when rotation speed increased due to the centrifugal force. Response amplitude and whirl orbits across the shaft offset were illustrated as well and it was discovered that in certain rotation range the shaft whirled asynchronously across the offset.