A wavelet-time frequency analysis on torsional vibration response of a rotor with a switching crack and a dominant twisting torque

A parametric excitation due to a crack on a rotor shaft in torsional vibration is the core of the investigation in this paper. A coherent hinge model derived on the basis of local flexibility theory and fracture mechanics is adopted to represent the cyclic and the nonstationary signal of a deep breathing crack in an uncoupled transient torsional vibration of a rotating cracked rotor shaft. A special treatment of the system governing equation for a deep switching crack under a dominant twisting torque is presented. Consequently, a wavelet time-frequency technique is employed to explore the cracked rotor system response. The numerical simulations results are consistent with existing literature and offer a sufficient criterion for crack identification. Interesting scenarios including sub harmonic resonance are discussed to emphasize the investigation.

1 Introduction

Research on online condition monitoring and fault diagnosis of cracked rotors is a subject of considerable interest in turbo-machinery. Fatigue- inflicted cracks may lead to catastrophic failure if undetected [1]– [10]. However, research in this area is still at a theoretical stage.