Transient Torsional Vibration Due to Suddenly Applied Torque

Abstract

Several instances of gear, coupling, or turbine-bucket failures in systems in which the compressors were subjected to extensive periods of heavy surge suggested the possibility that the transient torsional vibration caused by the surge could have contributed to the failures, and led to this investigation. Calculations of transient torsional vibration during acceleration through resonance and for motor or generator sudden short-circuit is treated in reference [1]. The current paper extends this work to the solution of transient vibration resulting from a suddenly applied aperiodic torque. The suddenly applied torque can be a step function representing motor or generator trip-out and compressor surge, or any other aperiodic function of exponential form. Transfer functions for shaft torques due to a sudden change in torque at any point in the system are given for systems with four degrees of freedom. Rules are given for the relatively easy conversion of the transfer functions from the frequency to the time domain. An approximate method of calculating more complex systems is suggested.