Numerical and experimental study on quantitative assessment of multiple fault parameters in a warped internally damped rotor with a transverse fatigue crack integrated with an active magnetic bearing

Abstract

This work aims to apply experimental data in the multi-fault identification algorithm developed for an internally damped warped cracked rotor system integrated with an auxiliary active magnetic bearing (AMB).A quantitative assessment of additive stiffness due to crack, unbalance, and residual bow with their orientations, multiplicative fault due to residual bow and crack, external and internal (rotating) damping, and AMB parameters that affect the dynamics of the system is done. The rotor experiences multiple harmonics in rotation due to the effect of crack and multiplicative bow-crack fault. To overcome the drawback of removal of residual bow at only 1X harmonic in signal processing, the present work addresses the simultaneous estimation of crack, bow, and multiplicative faults. Measurements of vibrational signalsof shaftand control current from PID controller are taken from the rotordynamic test bench. The multi-harmonic full spectrum amplitudes and phases of forward and backward whirl extracted from the measured test data are fed to theidentification algorithm which estimates fault and system uncertain parameters of fatigue cracked rotor system.This technique can effectively identify simultaneous rotor faults with prior knowledge of some characteristics of the rotor system. The novelty of this work is the identification of shaft residual bow with additive stiffness of crack where the additive crack stiffness is the direct indicator of crack and the magnitude of residual bow is of the permanent bend in rotor defining their severity.