Based on the actual working condition of the cycloidal gear on the RV reducer, the maximum normal contact load of gear tooth and mesh tooth pair for varied quantity of plus equidistant modification and minus radial-moving modification were analyzed. By considering the macroscopic geometry, the contact load, and the real tooth surface roughness and transient effect of the contact area between pinwheel and cycloidal gear, a mixed lubrication model was established. The effects of normal load, curvature radius at the meshing point, fillet radius, as well as the speed on the lubrication condition were discussed. The results suggest that load, fillet radius, and speed have different degrees of influence on the lubricating conditions while the change of curvature radius in a small range has no significant effect on the lubrication, which also helps in the optimization of cycloidal gear tooth profile modification, therefore, to obtain better comprehensive performance of RV reducer.

Water-lubricated bearings usually operate under severe environmental conditions, most likely in the mixed regime, in which surface contact between the drive shaft and the bearing sleeve is often significant. This presents great challenges to bearing design, especially material selection. The Tenmat, Thordon, and Rubber are common water-lubricated bearing composites. In this paper, by using a block-on-ring test apparatus, the Stribeck curve, wear rate, and vibration characteristics of three kinds of polymer materials in water-lubricated bearings (Tenmat, Thordon SXL, and Ben Teng Group (BTG) Rubber) under low speed and heavy load were studied. The experimental results show that, under the same working conditions, BTG rubber has excellent tribological properties and vibration properties. The research method in this paper can provide references for the selection of materials used for friction pair, improvement of working performance and vibration reduction of water-lubricated bearings in the future.

The vibration noise generated by water-lubricated rubber bearings (WLRBs) seriously reduces the concealment of a ship’s navigation. The purpose of this study was to obtain the relationships between friction-induced vibration and the friction coefficient, specific pressure, temperature, and stiffness of the bearing support during the shutdown process of WLRBs. Using transient dynamic analysis (Abaqus/Standard), the shutdown process of the bearing system was simulated by setting a friction coefficient curve, and with the fast Fourier transform (FFT), the data in the time domain were then converted to the frequency domain. In addition, an orthogonal table was applied to select the best level for each factor. The results show that proportionally increasing the friction coefficient and specific pressure caused higher vibrations, and the effect of the specific pressure on vibration is more prominent than that of the friction coefficient. Higher temperatures led to an increase in the peak frequency of noise (squeal) and the virtual value of acceleration. Increasing the stiffness of the bearing support decreased the higher-frequency squeal but dramatically increased the lower-frequency chatter. The results of the study are of guiding significance for the improvement of research methods and the optimization of the materials and structures of WLRBs.

By considering the effects of multiple grooves, rubber deformation, and actual boundary conditions, the steady elastohydrodynamic lubrication mathematical model and the dynamic Reynolds equation of water-lubricated rubber bearings are presented. The Reynolds equation is solved numerically by the finite difference method, and the stiffness and damping coefficients are calculated from the real and imaginary parts of the integrated pressure. Analysis results suggest that angular velocity, eccentricity ratio, groove configuration, and radial clearance have significant effects on the steady state and dynamic stiffness as well as damping characteristics, which also help in designing proper structure parameters of water-lubricated rubber bearings to obtain better dynamic performance.

Purpose: The research purpose of this paper is to obtain a transition process of lubrication condition of water-lubricated rubber bearing (WLRB) by investigating Stribeck curve of WLRB with either straight grooves or spiral grooves using a comparison experiment and providing guidance for structure optimization and application extension of WLRB. Design/methodology/approach: This study tested the Stribeck curve of WLRB with either straight or spiral grooves using a comparison experiment; the variables used are rotary speed and external load. Findings: Stribeck curves of WLRB with straight or spiral grooves under varied load are obtained with the experiments, and the speed turning points when the lubrication condition of WLRB transit are acquired. Research results indicate that the transition of the speed turning point for lubrication condition of WLRB with spiral grooves is smaller than that of WLRB with straight grooves. Besides, it was found that within the whole speed range, the friction coefficient of WLRB with straight grooves decreases with the increase in load under the same speed. However, Stribeck curves of WLRB with spiral grooves show that the coefficient increases first and then decreases with the increase in load and finally comes to a steady value. Under the same rotary speed and external load, the friction coefficient of WLRB with spiral grooves is smaller than that of WLRB with straight grooves, claiming that the WLRB with spiral grooves has better lubrication properties. Originality/value: By testing the Stribeck curve of WLRB with straight grooves or spiral grooves using the comparison experiment, lubrication properties of the WLRB are obtained. The transition mechanism of the lubrication condition for WLRB is acquired, revealing the effects of speed and load on the lubrication property. The research offers a scientific basis for the structure optimization of WLRB.