In this present work, we show that pouring water into the interface of SiC sliding against the same SiC material makes the friction coefficient far exceed that governing initial dry friction, and a subsequent load increase causes a dramatic abnormal friction force decrease. With the load further increasing to a critical value, friction force sharply increases again. The small amounts of water in the interface generates a large capillary force, the capillary bridges break to cause micro-separation of interface increase to allow bulk water to enter the friction interface, and a squeezing out of the water film to form a strong adhesion force between SiC-SiC materials, are considered to be responsible for the three stages, respectively.

Purpose: This paper aims to present the slip/no-slip design in two-dimensional water-lubricated tilting pad thrust bearings (TPTBs) considering the turbulence effect and shifting of pressure centers. Design/methodology/approach: A numerical model is established to analyze the slip condition and the effect of turbulence according to a Reynolds number defined in terms of the slip condition. Simulations are carried out for eccentrically and centrally pivoted bearings and the influence of different slip parameters is discussed. Findings: A considerable enhancement in load capacity, as well as a reduction in friction, can be achieved by heterogeneous slip/no-slip surface designs for lubricated sliding contacts, especially for near parallel pad configurations. The optimized design largely depends on the pivot position. The load capacity increases by 174 per cent for eccentrically pivoted bearings and 159 per cent for centrally pivoted bearings for a suitable design. When slip zone locates at the middle of the radial direction or close to the inner edge, the performance of the TPTB is better. Research limitations/implications: The simplification of slip effect on the turbulence (definition of Reynolds number) can only describe the trend of the increasing turbulence due to slip condition. The accurate turbulence expression considering the boundary slip needs further explorations. Originality/value: The shifting of pressure center due to the slip/no-slip design for TPTBs is investigated in this study. The turbulence effect and influence of slip parameters is discussed for large water-lubricated bearings.

With the development of modern industry, rotary lip seals are applied to more complex working conditions. For lip seals with larger or smaller radial force and lip seals with incomplete motion such as robot joint seals, it has been found that the traditional reverse pumping theory has a certain scope of application. Therefore, in this study, a mixed lubrication model based on deterministic surface microdeformation is proposed to calculate the tangent deformation of lip surface asperities without presetting the reverse pumping effect and then assess the effect of reverse pumping behavior. The radial force, contact width, friction torque, leakage rate, static contact pressure, and tangential deformation were either measured or calculated. The results obtained by this study can be used as guidelines for the design and optimization of rotary lip seals.

In some application fields, for example, the automotive industry, lip seals operate over a wide temperature range. Under such conditions, oil temperature plays an important role in determining the efficacy of lip seals. In order to simulate the lip seal’s behavior with ambient temperature change, this paper improved the traditional simulation approach by characterizing the rubber material property regarding temperature dependency in the model. The effect of oil temperature on the sealing performance of lip seals was investigated through numerical simulation and experiments. The static contact pressure, radial force, reverse pumping rate and friction torque was calculated as a function of oil temperature. The simulation results were verified by bench testing.