Nonlinear Dynamic Analysis Of Parallel Misalignment Couplings-rotor System

Couplings are widely used in aircraft engines and other rotating machineriesand play an important role in transmitting torque and power in the rotor systems,meanwhile, they have the ability to damp, protect and compensate for clearance forthe rotor system. Misalignment is a common type of fault in rotor system, and about60%of the rotor fault was caused by the shaft misalignment or associated with itaccording to information Statistics. The whole machine vibration fault caused bymisalignment is very significant. A kind of parallel misalignment coupling isinvestigated in this paper, we analyzed the dynamics of the system.Firstly, we used the Lagrange method to build the dynamical equation of thesystem according to the movement of the coupling misalignment characteristics,and we obtained the coupling misalignment parametrically excited vibration systemwith three degrees of freedom for the future theoretical research.Secondly, to get the approximate steady state solutions the average method wasused for solving the equation of the systems, the Taylor expansion was applied forthe nonlinear terms to three times in the truncation to get the bifurcation equationwith6degrees, we obtained the amplitude-frequency response curves by bifurcationequation, and it has the theoretical value for the system parameter design.Finally, the coupling misalignment parametrically excited vibration system andthe rotor system with misaligned rolling bearing were analyzed by the numericalsimulation. The coupling misalignment parametrically excited vibration system ismainly affected by speed, damping factor, the amount of unbalance andmisalignment effects, the system with misalignment fault is quasi-periodic motion.The misalignment fault would have more seriously influence on the rotor systemwith lower speed and higher damping, and the ratio of unbalance and misalignmenthas obvious impact for the vibration response of the rotor system, and the higher theratio was the higher the fundamental frequency component was. Under the influenceof misalignment fault in the rotor system with misaligned rolling bearing, themovement of the system was quasi-periodic and chaotic, the some high-frequencycomponent and significantly sub-frequency component appeared in dynamicresponse. Therefore, it reveals the dynamics mechanism of a couplingmisalignment’ affects for the rotor system in this paper, and it provides a foundationfor the project and the theoretical analysis.