The resonance of a vertical rotor containing a transverse crack

In this paper, the numerical calculation and the method of multiple scales are used to investigate the vibrational behavior of a vertical rotor containing a transverse crack with unbalanced excitation. It is found that resonance will occur when the spin speed of the rotor is close to 2/3_c or 2_c ( _c is the critical speed of the rotor without crack). It is believed that the phenomenon of parametric resonance may be a basis for crack diagnosing.