This paper aims to improve the tribological performance of journal bearings by optimizing the coverage area of circular microtextures in divergent region of the sleeve. A numerical model is proposed to calculate the friction coefficient and bearing load of textured journal bearings. The surface of the sleeve is divided into rectangular squares. Textures that located at the center of rectangular grids are assumed to be present or absent, marked as 1 and 0, respectively. Afterward, different texture coverage area arrangements are evolved and selected based on the genetic algorithm (GA). The area of semi-elliptical shape is obtained as the novel and preferable textured coverage area design for journal bearings. Influences of width and eccentricity ratio are discussed, which confirm the semimajor and semiminor axes of the semi-elliptical shape of texture coverage area equal to one-third of the circumferential length and half of the width of the journal bearing, respectively.

Gallium based liquid metal (GLM) is an amorphous metal that remains liquid at room temperature. It has important characters such as high temperature resistance, high thermal conductivity, good electrical conductivity, favorable radiation resistance and low saturated vapor pressure, thus being an ideal lubricant in the nuclear equipment, aerospace industry and some other engineering fields under extreme operating conditions. Firstly, the physicochemical properties and the factors affecting the lubricity of GLM are reviewed in this paper. Furthermore, the lubrication mechanisms of GLM are elucidated in detail. Followed by is the summarization of the research progress of strategies to improve the lubricity of GLM. After that, the applications of GLM in engineering tribology are also reviewed. Finally, the future developments of GLM as a special lubricant for extreme conditions are prospected.

Controllable wetting of liquid on solid surface is meaningful for advanced science and engineering. Current researches about controllable liquid spreading are generally limited to unidirectional modes, while achieving multi-directional spreading on microstructured surfaces remains challenging. Herein, we propose a novel type of bulk-cusp microstructure, exhibiting 0 to 4-directional spreading of droplet without external energy input. This behavior occurs not only under single-drop deposition but also under continuous liquid injection. The bulk structure is assumed to have cross or square shape, implying relatively high and low coverage ratio of the precursor film, respectively. Owing to the drag effect of the precursor film, the cross-cusp microstructure facilitates controllable spreading of the main droplet, whereas the square-cusp microstructure just has guidance action on precursor film due to its low coverage ratio. Mechanism analysis reveals the capillary forces generated from the narrow gaps between adjacent cusps effectively separate the precursor film. The area coverage ratio of precursor film determined by the shape of the bulk influences the coupling or decoupling of the droplet body and precursor film. Such controllable multi-directional liquid spreading enables applications in lubrication enhancement and smart evaporation cooling.

In this paper, three kinds of polymer, of epoxy resin (EP), phenolic resin (PF), and unsaturated polyester (UP), were used as fillers to prepare the laminated composite surface, and the tribological properties of a composite surface were studied under dry sliding condition. The results showed that: (i) the composites surface without MoS₂ exhibited high friction coefficient and high wear rate at 25 °C, while the friction coefficients were reduced when the temperature increases to 100 °C; (ii) with the addition of MoS₂, the friction coefficient of the epoxy resin composite containing MoS₂ (E1) was below 0.22 under a temperature of 25–150 °C, and the friction coefficient was increased to 0.32 as temperature increased to 150 °C, while the average friction coefficient of the unsaturated polyester composite containing MoS₂ (U1) was very low and below 0.20 under a temperature of 25–150 °C. Analysis of the wear scars indicated that, for the MoS₂-containing composite, the transfer films of the E1 and U1 were smooth and continuous under low temperature, while the transfer film of U1 was comparatively complete than that of E1 under 150 °C. The composites with solid lubrication had excellent high-temperature self-lubricating properties, which was attributed to the synergistic effect of the laminated structure, and the thermal expansion of the polymer, and finally a transfer film was formed on the sliding path.