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In this paper, an unbalanced Jeffcott rotor supported by the roller bearings is modelled, and the dynamic differential equations are obtained by the Lagrange's equations. The fourth order Runge-Kutta method is employed to simulate this system in two cases. Simulation results show the combined effect of the coupled lateral and torsional vibrations and the variable compliance vibration of the rotor. In the case of that only a large and constant radial force is applied, the sum and difference between variable compliance and rotational frequency components of the torsional vibrations of the disk are induced because of the roller bearings' rotation. And when they are near to the natural frequency of the torsional vibration, the resonance peaks appear. In the case of that a large and constant radial force and a harmonic torque are simultaneously applied, the two components, the sum and difference between rotational frequency and the frequency of the external torque, of the lateral vibrations of the disk are induced. When the frequency of the external harmonic torque approximatively equal to a special value, the two frequency band lines, variable compliance and the sum of rotational frequency and the frequency of external torque, intersect near the natural frequency of the lateral vibration, and the vibration may aggravate.

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In this study, composite coatings of polyvinylidene fluoride (PVDF) and epoxy resin deposited with La2O3 and MoS2 nanoparticles on the surface of a Babbitt alloy have been studied in order to improve its tribological performance. A pin-on-disc tribometer was used to evaluate the tribological properties of the Babbitt alloys with and without the composite coatings. The results showed that compared with the polymer-La2O3 composite coating, the polymer-MoS2 composite coating was more effective in reducing the friction coefficient and the wear rate of the Babbitt substrate under both dry and boundary lubrication conditions compared with the polymer-La2O3 composite coating. However, the wear rate of the Babbitt alloy with the polymer-La2O3 composite coating was lower than that of the alloy with the polymer-MoS2 composite coating. The wear scratches were analyzed using a scanning electron microscope (SEM). The worn surface of the polymer-La2O3 coating was much smoother and more continuous than that of the polymer-MoS2 coating, meanwhile transfer films were respectively detected on the pin surfaces. The addition of nanoparticles can reduce the wear rate and friction coefficient of polymer composite coating by forming a transfer film. Hence, the polymer composite coating can protect the Babbitt substrate.

Purpose This paper aims to study different morphology Cu6Sn5 effect on Babbitt alloy tribological properties. Design/methodology/approach Different morphology Cu6Sn5 of Babbitt was conducted by different cooling modes. Bare Babbitt was marked by Babbitt-0, Babbitt modified by first cooling mode (marked by Babbitt-1) and Babbitt modified by second cooling mode (marked by Babbitt-2). The microstructure and microhardness of specimens were tested. Then, tribological properties of Babbitt-0, Babbitt-1 and Babbitt-2 were performed by reciprocating mode under lubricated condition. Findings The results showed that shape Cu6Sn5 of Babbitt was changed from mixed needle and star-like shape to short rod-like or granular shape. The microhardness of Babbitt-1 was highest than that of Babbitt-0 and Babbitt-2. Compared with Babbitt-0 and Babbitt-2, tribological properties of Babbitt-1 were better under lubricated condition due to short rod-like and sparse distribution of Cu6Sn5. Moreover, the simulation result of strain and stress of Babbitt-1 was lowest than that of Babbitt-0 and Babbitt-2. Originality/value Different morphology (shape and distributed) of Cu6Sn5 was obtained by different cooling modes. Modulated different forms of Cu6Sn5 around SnSb was beneficial to improve Babbitt alloy tribological properties.

Purpose This study aims to improve the tribological performance of Babbitt alloy under oil lubricant condition. Thus, the surface was treated into oleophobic state by modifying with low surface energy fluorosilane (1H,1H,2H,2H-perfluorodecyltriethoxysilane). It is believed that the oleophobic surface offered excellent wear resistance of Babbitt-based tribo-pairs. Design/methodology/approach By modifying the Babbitt alloy with low surface energy fluorosilane and measuring the oil contact angle, the wetting behavior was evaluated. Using Pin on Disk tribometer, the tribological properties of bare Babbitt and modified Babbitt were quantified. The samples after the friction test were characterized by scanning electron microscope (SEM) and the anti-wear performance was evaluated under dry and oil lubrication conditions. Findings Results showed that oil contact angle of modified Babbitt was109° which was tripled compared to that of prime surface, which indicates the oleophobic behavior was greatly improved. Under dry conditions, the friction coefficient of the modified surface with different load conditions is slightly lower than that of the bare surface, while the friction coefficient of the modified surface under lubrication conditions is significantly decreased compared to that of the bare surface. Interestingly, under low load and high load, the wear rate of the modified Babbitt alloy surface is only 1/4 and 1/3 of that of the bare surface, respectively. Originality/value The work proposed an effective method to improve the Babbitt tribological performances and will lighten future ideas for the Babbitt alloy bearing with high wear resistance, which is beneficial to improve the service life of sliding bearings and has huge promotion and application value in the manufacture of sliding bearings.