In this paper, the developed finite element model of the shaft-cylindrical roller bearing–bearing housing system is established considering the temperature effect and clearance change. The displacement, raceway stress, and bearing stiffness characteristics of the inner and outer rings of the bearing are systematically investigated. The proposed finite element model is validated through adjusting mesh size of the bearing and the comparison of the elastic deformation of the bearing with the experiment. The influence of load, clearance, and temperature expansion on the displacement distribution of the inner and outer rings of the bearing, raceway stress, and stiffness characteristics are all discussed. The obtained results indicate that an appropriate selection of thermal expansion stress can obtain desirable working ambient temperature of the bearing under different clearances, which can serve as an efficient tool in the design of bearing parameters.

Cage rotating and whirling inside rolling bearings involve conical motion and easily lead to excessive wear if the cage exists unexpected unbalances. In this study, the cage motions affected by its unbalance in a ball bearing are investigated analytically and experimentally, which helps to understand the bearing dynamics and cage wear. Firstly, a dynamic model of angular contact ball bearing with the unbalanced cage is established to simulate the cage motions as a function of typical cage unbalances over a range of operating speeds. Then, an experimental approach is proposed to measure the spatial motions of the cage with various prescriptive unbalances on a test rig. Finally, the trajectories, waveforms, and spectra of cage motions are constructed and compared to elucidate its diversified patterns under various cage unbalances. The experimental observations of the cage motions agree well with the theoretical predictions and reveal that the whirl motions of cage are evidently affected by its unbalances. The increment of cage unbalance mass makes the trajectories of cage center more regular and enlarges the whirl radii. It is also observed that the amplitudes of the axial and radial motions of the cage, particularly corresponding cage rotating frequency and the wear extent of the cage guiding surface increase with the increment of cage unbalance.

Purpose: The oil film thickness provides a key performance indicator of a ball bearing lubrication condition. This paper aims to propose an approach to calculate and measure the oil film thickness of the bearing. Design/methodology/approach: On a specially designed test rig, measurement of the capacitance is used to monitor the oil film thickness of ball bearing. A corrected film thickness formula taking account of the influences of non-Newtonian shear thinning and thermal is introduced to predict the oil film thickness of ball bearing. And then the film thickness distribution and the corresponding capacitances are calculated. Findings: Measurement and calculation of oil film thickness in a ball bearing are carried out under various rotating speeds and external loads. By comparing the calculated capacitances with measured results, it can be concluded that the calculated results obtained by the amended film thickness formula are much closer to the test findings than the classical computed values according to Hamrock–Dowson. Originality/value: A new corrected film thickness formula is introduced in predicting oil film thickness of ball bearing and verified by the series of experiments according to capacitance method.

A theoretical model with 5 degrees of freedom (DOF) is derived for a rigid rotor system supported by two ball bearings considering the changes of the bearing stiffness due to misalignment. And then radial and axial vibrations of the rotor system and its bearing reactions under different misaligned offsets are investigated with theoretical and numerical analysis. Then, the effects of misalignment on the vibrations of rotor and the bearing, the variation of stiffness and reaction characteristics of the misaligned ball bearing are predicted theoretically. It is concluded that angular misalignment may cause axial vibration and parallel misalignment can bring out extra moment loads for misaligned bearing.

Oil lubrication is widely adopted in rolling bearings, the characteristics of which affect the oil film formation and friction state, and also the heat generation and dissipation characteristics. However, it is difficult to measure the internal lubrication of rolling bearings in practice, which is of great importance for lubrication and structure design. In this work, one measurement system for lubricant distribution was built and installed on a test rig to obtain original pictures of the lubricant in bearings. Grayscale images were obtained by picture processing to characterize the lubricant distribution, and the image pixels were evaluated for the characterization of lubricant volume. Finally, the measurement of the lubricant distribution in the angular ball bearing was carried out under different lubrication and cage groove conditions, and their influences were investigated. The results show that the lubricant distribution is affected by the oil jet nozzle angle, operating speed, and cage structure. The lubricant capacity among balls and the cage pocket in bearings gradually increased with the increase in the nozzle angle and the depth of the cage grooves, but decreased with the increasing operating speed. The experimental results are helpful to provide a basis for the structure and lubrication design of ball bearings.

A misaligned rigid rotor system with flexible supports differing from the traditional flexible rotor system, which refers to its practical rotating center line determined by supports offset from the theoretical one, often suffers support structure damage risk. In the present work, the dynamic characteristics of a misaligned rigid rotor system with flexible squirrel cage supports are focused, and the vibrations and the stress of its support structures under different misaligned offsets are investigated with experimental and simulated analysis. The finite element model for a rigid rotor system with flexible supports in a scaled test rig is established, and its strain energy distribution is analyzed to find that the first two modes of the system are referred to rigid‐body modes and the strain energy is mainly distributed on the squirrel cage supports. Based on the analysis results, a rigid‐flexible coupling dynamic model is proposed through a data exchange between ADAMS and ANSYS and validated by measurements. The misaligned conditions are focused on, and the influences of misalignment on the vibrations of the rigid rotor system and the reaction force and stress of its support structures are investigated analytically and experimentally. The results from simulation agree very well with the measurements and reveal that the static stress of squirrel cage increases just about proportionally with misalignment levels, but the vibration displacement amplitudes and stress amplitudes show very little change. The more serious the misaligned condition, the higher the static stress of the squirrel cage. Because misalignment will bring out the additional reaction forces in the misaligned direction, it will further result in higher stress and even more serious damage risk for the flexible supports than other parts in the rigid rotor system.