Simulation of rotor’s axial rub-impact in full degrees of freedom

Axial rub-impact problem scarcely discussed in the previous literature is investigated based on a full-degree-of-freedom Jeffcott rotor. An axial rub-impact force model corresponding to all the six degrees of freedom is developed according to Coulomb’s friction law. A rotordynamic model of a rotor with unbalances and axial rub-impact is established using Lagrangian equation, with the integration of the axial rub-impact force model into it. The dynamic responses are obtained using ODE solvers in MATLAB. The dynamic behaviors of the rotor are demonstrated by means of waveforms, frequency spectrums, orbit trails, Poincare maps, and bifurcation diagrams. It is concluded that the dynamic behaviors of axial rub-impact are quite distinct from those of radial ones, and that the dynamic behaviors of axial vibration are essential to the diagnostics of axial rub-impact. In addition, an internal bending–torsion coupling phenomenon is disclosed.