Influence of non classical friction on the rubbing and impact behavior of rotor dynamic systems

A nonlinear finite element model for simulating the effects of rubbing and impact on rotor dynamics has been developed. The nonlinear model is used to conduct a series of forced transient analyses of a rotating system under the influence of rubbing and impact using the modal and the Average Acceleration direct numerical integration methods. The modal method is shown to be more efficient than the Average Acceleration method.; The first approach for modeling the friction forces is the application of Coulomb friction law. Simulation results show the rotating system to be unstable for all ranges of Coulomb coefficient of friction. In contrast, experimental results have shown that the system under study is stable under the influence of rubbing and impact for the simulation conditions.; A second approach for modeling the friction forces is employed for the purpose of investigating the differences between the experimental and the simulation results. The second approach consists of an artificial simulation of a Stick-Slip phenomenon by setting the Coulomb coefficient of friction to a value of zero for certain time intervals. The artificial Stick-Slip simulation has a stabilizing effect on the system.; The third approach for modeling the friction forces is the application of an advanced friction model simulating the Stick-Slip phenomena. The system appears to be completely stable for a dry metal to metal rubbing and impact condition. The results of the simulation using the advanced friction model are close to experimental results. The surface finish of the contacting metals were found to have a negligible effect on the results of the simulation.