Modelling Of Double Impulses Phenomenon And Performance Degradation Index Accessment Of Hybird Ceramic Ball Bearing

Rolling bearing is a key foundation part of rotating machinery, mainly used for supporting rotor rotation, and because of bearing most of the energy, it is easy to lead to damage or failure. With the high-speed development of mechanical equipment in recent years, the hybrid ceramic ball bearing, because of its advantages, is widely used in high-end machine tools. However, the research on the hybrid ceramic ball bearing fault diagnosis and damage degree evaluation method is extremely limited at present. By analyzing the double impulse from the bearing vibration signal and realizing the estimation of the length of the fault zone, it provides a reliable way for judging bearing health status and forecasting residual life. In the research, as an example of a single peeling defects in rolling bearing outer raceway, we deeply analyze the elastic deformation between the local defect edges and the rolling element base on Hertzian contact theory when ball passes the different size of defects. The waveform and amplitude of bearing impact pulse is directly related to the shape and the size of race defect. It has an important academic value for the research of the double impulse generation mechanism.Based on the research of the nonlinear vibration mechanism of the bearing fault, there is a elaboration the rolling element passing through the defect in the outer race, including the change of displacement and contact force, and the corresponding time-varying functions are constructed. The effects of the elastic deformation at the edges of the localized defect and the double impulse phenomenon on the vibration characteristic of the rolling element bearing cannot be described by the current localized defect models considering the time-invariant and the time-varying displacement excitation based on single function. To overcome this problem, a new local defect dynamic model considering time-varying displacement and time-varying contact force based on normal rolling bearing dynamic model is proposed in this paper, which broke the limitations of the current localized defect models. The differential equations of fault dynamic model are solved by Runge-kutta numerical integration. Then compared with the test analysis results, it verified the effectiveness of the fault rolling bearing double impulse dynamic model.With the bearing damage accumulation, its performance degradation is a continuous process, and there are several stages from the initial degradation to the final failure, which need seek some characteristic quantities to monitor the degree of performance degradation of bearing. It can be replaced in time when bearing is failure, which can avoid defective appliance. In this paper, the characteristic index, representing the physical condition of bearing, are extracted from time domain, frequency domain and time-frequency domain. In addition, we mainly analyze the principle and algorithm of EMD and EEMD in the time-frequency domain, and introduce the concept of EEMD energy-entropy. Because of the effects of interferences including other parts and noises, vibration signal is preprocessed by the AR filtering pre-whiten algorithm based on the maximum kurtosis to eliminate deterministic signal. To deeply research on the characteristic index reflecting bearing performance degradation, especially the sensitivity of the initial performance degradation and the consistency of the whole degradation process, accelerated life test is carried on.