Journal bearings are important supporting elements of mechanical equipment, characterized by stable performance, low noise, convenient manufacturing processes, and diverse types. However, under heavy-load, low-speed and impact conditions, journal bearings are prone to friction and wear problems such as abrasive wear, scratching and scuffing. Boundary slip can significantly regulate interfacial friction dynamics. Studying the mechanism of boundary slip is critical to improve the performance of journal bearings. To investigate the mechanism by which composite slip affects the tribological performance of journal bearings, a composite sliding surface combining slip and non-slip was designed on the surface of the journal bearing. Based on the modified Reynolds equation and the binary slip model, a numerical analysis model of journal bearings with slip boundary condition was established and solved considering cavitation effect. By comparing the tribological performance of different types of composite slip journal bearings, the mechanism and effect of composite slip on improving the tribological performance of journal bearings were revealed. In order to further verify the correctness of numerical simulation, tribological experiments were conducted on different composite slip surfaces. The experimental results and numerical simulation results were compared. In addition, the cavitation effect of the composite slip journal bearings and the synergy effect of slip and cavitation on the tribological performance of the bearing were also analyzed. The results showed that the boundary slip had a significant effect on the tribological performance of journal bearings. Because the boundary slip made the near-wall lubricating oil obtain a higher flow velocity, the flow rate of lubricating oil increased to a certain extent, and the hydrodynamic pressure effect of bearings was improved. To analyze the effect of the slip area ratio on the tribological performance of bearings, five types of composite slip (A, B, C, D, E) with the ratio of the slip area on the stationary surface of the bearing as a variable were designed. The tribological performance of five types of composite slip journal bearings was compared. It was found that the composite slip of E slip type with 28 mm axial length and semicircle length could better improve the tribological performance of bearings. By comparing the tribological performance of the composite slip journal bearing without and with cavitation, it was found that the bearing capacity of boundary slip journal bearing considering cavitation was higher than that without considering cavitation, and the friction coefficient was smaller than that without considering cavitation. Under cavitation, the maximum oil film pressure of the composite slip journal bearing further increased, the hydrodynamic lubrication of the oil improved further, the bearing's load-carrying capacity was enhanced, and the oil film rupture position moved backward, thereby further expanding the bearing's positive pressure zone. Through pin-disk tribological experiments, it was verified that the E-type composite slip had a better effect on improving the tribological performance of journal bearings, which was consistent with the conclusions of numerical simulations, confirming the accuracy and reliability of the numerical simulations.This work has important reference significance for the application of boundary slip in journal bearings and the design of composite slip surface of journal bearings.
Key words
journal bearing /
composite slip /
cavitation effect /
tribological performance /
numerical analysis
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Funding
National Natural Science Foundation of China (51965038)
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