Experimental dynamics research on a rotor bearing system with two rub-impact faults

In this paper, a finite element model of a nonlinear rotor-bearing system with two rub-impact faults is established, and the bifurcation and instability characteristics are analyzed along with the changing of rubbing clearance. To verify the results of the theoretical analysis, a rotor-stator rubbing experimental system is established, which contains a pair of oil lubrication cylinder bearing and two disks. With monitoring the rubbing state by a designed electronic device, some qualitative analysis have been done on the rubbing response with different rotor-stator clearance. With investigation of the experimental response in time and frequency domain, some conclusions have be found: for the low eccentricity, when the rubbing clearance decreases, the rubbing fault makes the oil whirl take place earlier, the system of instability speed will decrease slightly, and lost instability through a period-doubling bifurcation. When the rubbing clearance increases, the instability speed will increase slightly, and the rotor system shows a quasi-periodic bifurcation. when the system is in a low speed state, due to the existence of the rubbing fault, the frequency domain appeared multiple frequency components, when the rotating speed is higher, because of the strong "oil whip", multiple frequency components are not obvious. In addtion, due to the existence of the rubbing fault, the "oil whirl" and "oil whip" of the system become more obvious. The results of the study in this paper will provide some theoretical reference for the characteristic analysis and vibration control of similar rotor-bearing system.