Analysing the Dynamic Interaction Between Unbalance and Crack Responses in a Jeffcott Rotor Supported by Foil Bearings: A Numerical Study

Abstract

AbstractThe present paper analyses the vibrational behaviour of an unbalanced and cracked Jeffcott rotor supported by foil bearings. Foil bearings have numerous advantages over rolling element bearings due to their significant operational limitations as well as suitable for only lower speed mechanical and other applications. Incorporating the equivalent stiffness concept of shaft and foil bearing and considering the forces due to inertia, unbalance and crack faults, the dynamic equations for the vibration of an unbalanced Jeffcott rotor with a crack nearby disc at the middle mounted on foil bearings have been derived. The mechanism of a switching crack has been utilized to analyse the crack fault effect which manifests multiple harmonics in the vibrational nature of the system. The displacement responses in transverse directions have been obtained using the Simulink block diagram. Full spectrum data analysis has also been performed to transform the time domain response into the frequency domain, which gives rise to both the forward and backward rotor whirls. The main emphasis of this paper would be to exhibit the interplay between unbalance and crack faults in a Jeffcott rotor system supported by foil bearings.KeywordsVibrationFoil bearingUnbalanceSwitching crack