The Dynamic Analysis And Study Of Cracked And Rub-impact Rotor

In the condition of the bending-torsional coupled vibration, the cracked rotor and rub-impact rotor contain complex non-linear dynamic characteristic. Based on the rotor dynamics and nonlinear dynamics theory, dynamic characteristics of the cracked rotor and rub-impact rotor, especially the nonlinear dynamics characteristic, are investigated in this paper.The dynamic model of Jeffcott rotor with a transverse crack is built, then considering the unsymmetric stiffness, the differential equation of motion is established. Through computer simulation, the influences of the speed, the angle, and the depth of the crack on the vibration are studied. And the breathing characteristic of the crack is also analyzed. Using numerical integral method, bifurcation diagrams, Poincare mapping and spectrum diagrams are used to analyze the nonlinear dynamic characteristics of the system. It is found that 1/3X and 1/2X sub-syntonic resonances occur with the cracked rotor accelerated both in flexural and torsional vibration, and the non-linear movement of flexural vibration is restrained by the torsional vibration.By the same method, the characteristic of rub-impact rotor is studied. The movement of rub-impact rotor is very complex, and appears quasi-periodic and chaotic phenomenon, so the nonlinear feature and the region of instability are primarily studied in this paper. Through the bifurcation diagrams, Poincare mapping, the vibration characteristics and nonlinear characteristics are analyzed. It is shown that the movement of rubbing rotor with torsion is more complex, and the nonlinear feature is also much more notable, the speed period of complex movement is wider too. In general, the movement with torsion is much move unstable. But as the speed increased, the periodic movement and complicated movement appear at intervals both in flexural vibration and torsional vibration.Finally, through the running orbit and the waterfall diagram, the experimental data are analyzed. And the answer validated the theoretical results. So they can be used as guidance to practice. And the analysis of flexural and torsional vibration together is much more suitable for the fault diagnosis.