Nonlinear Dynamics Analysis Of A Rolling Bearing-Rotor System With Typical Fault

Rotating machinery is widely used in aerospace, energy, transportation, manufacturing and other fields, where bearing-rotor system as its core component plays an irreplaceable role. Mechanical system, especially rotating machine inevitably generates vibration that has an adverse impact on efficiency and lifetime at work and fault will lead to the aggravation of vibration and even accident in a short time. From Ihe perspective of nonlinear dynamics, there is a close relationship between the more complex behavior of rotating machinery and the fault type, fault degree and fault evolution process. So, it’s necessary to analyze dynamical behavior of the system with typical fault to announce the law of generation and development and to provide theoretical basis for design, maintenance and fault diagnosis of rotating machinery.In Chapter2, the steps of solving bearing stiffness based on Hertz contact theory are introduced as well as the basic idea of Runge-Kutta method. The process of solve and analysis the nonlinear system is given by taking Duffing system as an example.In Chapter3, the response of a rotor supported on ball bearings which considering nonlinearity such as surface waviness, internal radial clearance and Hertz contact force is analyzed and the result is presented in the form of bifurcation diagram, time-domain waveform, frequency spectrum, phase diagram and Poincare map. The effect of maximum amplitude of waviness and speed on the dynamic of the rotor response is mainly studied and the characteristic frequency of surface waviness is analyzed.In Chapter4, a modified nonlinear dynamic model of a rolling bearing-rotor system with localized defect is presented, which considers variation of the contact stiffness when the rolling elements pass the defect and the nonlinearity is due to internal radial clearance and Hertz contact force. The numerical integral method is used to solve the model with various defect, the nonlinear dynamic of the system is analyzed by means of frequency spectrum, Poincare map and bifurcation diagram. The effect of defect size, rotating speed and some system parameters is studied, mechanism of intermittency and qusi-period loop breaking have been observed as the routes to chaos.In Chapter5, as the characteristic quantities having good performance in reflecting the nonlinear dynamics of rolling bearing in different fault conditions, a method of fault diagnosis of rolling bearing based on correlation dimension, largest Lyapunov exponent and information entropy is proposed. The classification abilities of each feature are evaluated by using support vector machines, as well as the combination of two quantities. It shows that each type of quantity contains the different fault information and the combination of these can significantly improve the recognition rate. The experimental results show that these three characteristic quantities can effectively identify the different types of fault and also the same fault with different levels.Finally, the research issues are summarized in Chapter5, and some possibly developing directions in this subject are pointed out.