A Study on Bearing Dynamic Features under the Condition of Multiball–Cage Collision

Cage stability directly affects the dynamic performance of rolling bearing, which, in turn, affects the operating state of rotating equipment. The random collision between the rolling elements and the cage pocket is the main reason for cage instability. In this paper, from the perspective of the relative sliding velocity between the rolling elements and the bearing raceway, the interactions of the rolling elements and the cage pockets were analyzed, and the four zones with different collision features were defined. On this basis, and on the basis of the bearing dynamics model, the interaction of two adjacent rolling elements and the cage pockets in the a’–b’ area is discussed, and the peak impact force of the adjacent two balls and the cage pockets was investigated in terms of the rotation speed, radial load, acceleration/deceleration, and materials. When the ball runs close to the loaded zone, the probability of multiball random collision increases, which leads to an increase in the cage instability. At the entrance of the loaded zone, the peak impact force has the greatest impact on the cage stability during the acceleration process. Compared to the radial load applied to the bearing, the peak impact force is more sensitive to the bearing speed changes. The multiball collision analysis method provides a new idea for the research of cage stability.

Theoretical Study on Compliance and Stability of Active Gas-Static Journal Bearing with Output Flow Rate Restriction and Damping Chambers

The design is considered and theoretical research of operability of the active radial gas-static bearing with restrictors of output flow rate in the form of mobile rings with an elastic supports and the dampers working by Helmholtz acoustic resonator principle is done. The mathematical model of the bearing dynamics and method of calculating its degree of stability are developed. The device is steady against vibrations; it has smaller power consumption compared to the known devices with input regulators, a zero and negative compliance of a gas-lubricated film.

Raceway Defect Frequency Deviation of Full-Ceramic Ball Bearing Induced by Fit Clearance in Wide Temperature Ranges

Full-ceramic ball bearings are widely applied in wide temperature ranges due to their excellent thermal shock resistance, and the condition monitoring and fault diagnosis are mainly conducted through the spectrum analysis based on the defect frequencies. However, the outer ring has a spinning motion in the temperature-related fit clearance, which leads to the deviation of raceway defect frequencies, and is not conducive to the fault diagnosis. In this paper, the temperature-related fit clearance is considered in the dynamic model, and defects are added on the inner raceway and outer raceway. The motions of the rings are calculated and analyzed in the frequency domain, and the trends of peak frequencies with temperature are investigated. Simulation and experimental results show that the spinning speed of the outer ring increases with temperature, and the defect frequencies exhibit obvious deviation in wide temperature ranges. In a temperature range of 500 K, the defect frequencies exhibit deviations of over 3%, which is obvious in the defect frequency identification. The results provide insights on the full-ceramic ball bearing dynamics and help with the fault diagnosis and status monitoring of the relevant devices.

Nonlinear Dynamics Analysis of a Rolling Bearing

A numerical analysis of the nonlinear bearing model about two degrees of freedom has been presented in this paper. The contact between a ball and ring by Hertz theory is described. Influence of the number of balls, shaft rotation and clearance on the acceleration were investigated in detail. Three numbers of balls from 11 to 16 were analyzed. The clearance level in the range of 0-71μm has been studied. It has been shown that the acceleration responses are different, depending on the vibration direction and are usually higher when the radial internal clearance and the shaft speed are increased. The higher ball number caused that the accelerations decreased in both directions. Moreover, two dynamic indicators that can be used for comparison bearing dynamics have been proposed. These obtained results are useful for understanding the vibration response mechanism from a practical point of view.

Model Based Determination of Size and Location of a Crack in a Rotor System Using Wavelet Transformation and Pattern Search Optimization

Real rotor with multiple disks, ball bearings and flexible bearing supports has been considered in the present work. Reduced order model required for simulations of the dynamic system is developed using multi-objective genetic algorithms by matching its dynamic response with full order Finite Element Method based model. This enables us the possibility of including ball bearing dynamics as well as experimental data in model updating. In a rotating machinery, multiple types of faults can be expected during its service life, such as transverse breathing crack, looseness of bearing supports and unbalance. Rotor crack can be quantified by using the dynamic response of the rotor under coast up conditions in open loop situation using Pattern Search optimization. Wavelet transformations are used to denoise the signal and enhance the estimation accuracy.

Quality of Dynamics of a Circular Gas-Static Thrust Bearing with an Elastic Suspended Support Center

A design, a mathematical model are presented and a calculation technique of quality indicators of the gas-static thrust bearing dynamics with the elastic suspended support center is described. It is shown that the application of such improvement allows to eliminate completely essential shortcomings of the quality of dynamics characteristic for a bearing with annular diaphragms and transforms the construction into a dynamic system with optimal dynamic characteristics – high indicators of degree of stability, aperiodic nature of the transient process, values of the oscillation index that are peculiar to ideally damped dynamic systems