Wavelet time-frequency analysis of torsional vibrations in rotor system with a transverse crack

Based on simple hinge crack model and local flexibility theorem, the modified function of torsional vibrations in cracked rotor system is presented, and the torsional stiffness variation with crack depth is studied. The corresponding dynamic equation for torsional vibration is modelled; the numerical simulation solutions of rotor system with a switching crack or a deep crack are obtained, the parametric excitation and the subharmonic resonance are discussed. By wavelet time-frequency analysis, the time-frequency features of torsional vibrations in cracked rotor system are investigated, and numerical simulation shows that the time-frequency features of torsional vibrations in cracked rotor system are unique, which can be used as the criteria for identification of crack.