Research On Dynamic Characteristics Of The Contact Pair In Rolling Element Bearings Under Elastohydrodynamic Lubricate

The dynamic characteristics of single Elastohydrodynamic lubricated (EHL) contact pair, which is the basic structural unit of rolling element bearings, affect the overall performances of the bearings directly. Because of the complicated relationships between the kinematics and dynamics of rolling bearings system, its tribological and dynamical behaviors have been studied seperately in the domain of tribology or dynamics for a long time, but ignoring the coupling effects of tribological and dynamical behaviors. Therefore, there are some limitations in related research results. The performances of rolling bearings are constantly requred to be silence, high-speed and with heavy-load capacity, thus more perfect theories are urgently for the tribology-dynamics design of rolling bearings. Therefore, it is significant in theory and practice to investegate the behaviors of the contact pair in rolling bearing from the viewpoint of coupling of tribology and dynamics, which would improve the accuracy of the theoretical analysis.On the basis of the research status of EHL and dynamics of contact pair of rolling element bearing, the necessity of research on coupling of tribology and dynamics for the contact pair is analyzed. This analysis shows that the behaviors coupling of EHL and dynamics in the contact pair mainly reflect in two aspects. Firstly, the dynamic characteristics of contact pair will affect load-bearing status of the film, and change the film thickness and pressure distribution of EHL Secondly, due to variations of the film status will affect the stiffness and damping characteristics of the contact pair, its dynamic behavior will be affected in turn. Therefore, both tribological effects and dynamic effects should be considered at the same time in the analysis of mechanical properties of the contact pair in rolling element bearings.Based on the composite direct iteration method for solving EHL problems, two kinds of EHL problems, in steady state and unsteady state respectively, are studied in this dissertation. Then, a new fast algorithm for solving the problem of unsteady state EHL in point contact is proposed, which provides an effective tool for coupling analysis of tribology and dynamics of contact pair.The relationships between tribology and dynamics behaviors both in point contact pair and in line contact pair are investigated in this dissertation. Based on the mechanical vibration theory and EHL theory, the coupling models of tribology and dynamics for contact pair have been established under the conditions of both free vibration and harmonic excitation vibration. Taking several bearings as examples, their coupling models have been solved by using the sequential coupling analysis method, and then the time-varying progresses of film thickness and pressure distribution of EHL contact pair together with the vibration responses have been obtained. Then, the equivalent stiffness and damping coefficient of contact pair have been gotten on the basis of the models established under the conditions of both free vibration and harmonic excitation vibration for analysis and calcultion of the stiffness and damping. Furthermore, the coupling mechanism between the tribological behavior and the dynamic behavior of the contact pair is analyzed, and the influence of various factors, such as load, speed and lubricant viscosity under ambient pressure, on the dynamic characteristics of contact pair is studied in this dissertation also.A dynamic model of rolling bearing system in EHL has been established based on the stiffness and damping models of single contact pair between the roller and race. The vibration experiments for qualified bearings and defective bearings have been done by means of the vibration measurement platform to get the vibration responses. Then, the dynamic model of contact pair has been verified through comparative analysis of the vibration responses obtained theoretically and experimentally.