When crack emerges in shaft of rotating machinery rotor, time-varying rotation-whirl phase difference makes crack open and close periodically, which makes transient vibration of rotor different from its steady vibration. The neutral axis method was adopted to determine the crack opening and closing, and the transient vibration response caused by crack breathing of single disc rotor crossing critical speed was calculated numerically, and the influence of crack depth, orientation angle and gravity on speeding-up rotor with linear acceleration, and transient vibration characteristics and stability of system speeding-up with constant power were analyzed. The results show that the sub-harmonic resonance of breathing crack rotor is not obvious in transient process; The deeper crack is, the larger transient amplitude crossing critical speed is; when crack opens near critical speed, intense transient vibration will be excited; When crack rotor accelerates with constant power, if the power is not enough to provide the rotor smoothly through the critical speed, the outside torque and transient vibration will couple over energy, and with big crack in shaft, chaotic vibration may occur.
Key words
neutral axis method /
breathing crack /
critical speed /
single rotor /
transient vibration
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References
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