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Nitrile Butadiene Rubber (NBR) is widely used in ship water-lubricated stern tube bearings. Sediments in the water would cause a serious effect on friction and wear properties of the water-lubricated bearings. In this study, the tribological performance of water-lubricated rubber bearings under different sediment particle sizes and sand types were analyzed. Two sediment sand types are involved in the research, (i) SiO 2 particles with sizes of 0–25 μm, 48–60 μm, 75–90 μm and 150–200 μm, respectively; (ii) Sediment particles collected from the Yangtze River with sizes of 48–60 μm, 75–90 μm and 120–150 μm, respectively. The friction coefficients and wear volumes as well as surface morphology were measured. It was found that NBR worn by SiO 2 particles was worse than that by the sediment within a certain particle size range. On the other hand, the particle sizes exhibited significant effects on the tribological properties. As the particle size increased, the largest wear volume of NBR occurred at particle size of 75–90 μm, While the friction coefficient grew firstly and then fell down, and reached its maximum at particle size of 48–60 μm. Additionally, the friction coefficient demonstrated a negative correlation with sliding speed regardless of the sediment type and particle size. The particle sizes were prevented from flowing into the friction pair as applied load increased. In conclusion, this research offers a great insight for designing water-lubricated bearings. [ABSTRACT FROM AUTHOR]

Unacceptable vibrations induced by the friction in the water-lubricated bearing-shaft system can seriously undermine the reliability and concealment performance of the ship. The mechanism of frictional vibration and the coupling process with torsional vibration are not yet entirely understood. In this study, a glass shaft is used to form a friction pair with a rubber block. To explore the frictional vibration mechanism and process of coupling with torsional vibration, a high-speed camera records the responses of the rubber, fixer and shaft simultaneously. The frictional vibration in stern shaft system is visually revealed by joint analysis of vibration, noise, friction, and images. Most importantly, the coupling process of frictional and torsional vibrations in the stern shaft system is intuitively displayed. • A transparent glass shaft was used to form a friction pair with a rubber test block. • With the help of a high-speed camera, the dynamic responses of the friction pair were recorded and analyzed. • The mechanism of frictional vibration was explained by joint analysis of vibration, noise, friction and image data. • The coupling process of frictional vibration and torsional vibration was explored visually. [ABSTRACT FROM AUTHOR]