Research On Multi-fault Mechanism Andvibration Model Of Rolling Element Bearings

Rolling ele ment bearing is one of the most widely used general machinery part in all kinds of rotating machineries. Its running state directly affec ts the performance of the whole sets of mechanical equipment. The fault mechanism is considered to be the theoretical foundation of fault diagnosis of rolling e lement bearing. The research on fault mechanis m can simulate the producing and coupling of the fault signa l and provides the theoretical support for the research on the method research. With the development of the fault diagnosis method, research on fault mechanism attached more and more attent ion of the researchers.Firstly, this paper expended the theoretical model wit h signal defect to the model considering mult i-defects. The basic characterist ics of the signal defect and multi- defects is acquired by theoretical analys is. When the mult i-defects locates on the same ring, the fault signa l has peaks at the fault characteristic frequency and its mult iple. The amplitudes of the peaks are decided by the phase angle of signals. The phase angle is decided by the relative posit ion among defects. When the defect exists on inner and outer ring respective ly, t he multi- fault signal is compounded by two signal defect signals.Based on Hertz contact theory, a dynamic model for rolling element bearing considering impact force has been developed. In this model, the contact between rolling elements and races are cons idered as springs. Unlike the previous studies, in which the stiffness was rather simply calculated in one direction, the stiffness parameters were calculated separately in horizontal and vertical directions in the present study. The simulation of defects has been devided into two parts. The one is the abrupt change of the contact deformation. When the ball pass through the defect area, the contact deformation changes leading to the change of the contact force. The other is the impact between balls and defe cts. In this model, the impact process between rolling elements and defective races, which is affected by velocity, was studied in detail. And the formulat ion of impact force is given. The signa l defect and mult i-defects model is developed in this paper. The characteristics of the simulated signal agree with the result of theoretical analysis model. C ompared with the experimenta l signal, the simulated signa l can highlight the fault characterist ic frequency and the frequency doubling part successfully. The amplit ude error is within 30% for signal defect. And the this model can simulate the coupling mechanism for mult i-defects wit h good stability.