Search Results (293)

Water-lubricated bearings (WLB), due to their pollution-free nature and low noise, are increasingly becoming critical components in aerospace, marine applications, high-speed railway transportation, precision machine tools, etc. However, in practice, water-lubricated bearings suffer severe friction and wear due to low-viscosity water, harsh conditions, and contaminants like sediment, which can compromise the lubricating film and shorten their lifespan. The implementation of micro-textures has been demonstrated to improve the tribological performance of water-lubricated bearings to a certain extent, leading to their widespread adoption for enhancing the frictional dynamics of sliding bearings. The shape, dimensions (including length, width, and depth), and distribution of these micro-textures have a significant influence on the frictional performance. Therefore, this study aims to explore the coupling effect of different micro-texture shapes and distributions on the frictional performance of water-lubricated sliding, using the computational fluid dynamics (CFD) analysis. The results indicate that strategically arranging textures across multiple regions can enhance the performance of the bearing. Specifically, placing linear groove textures in the outlet of the divergent zone and triangular textures in the divergent zone body maximize improvements in the load-carrying capacity and frictional performance. This specific configuration increases the load-carrying capacity by 7.3% and reduces the friction coefficient by 8.6%. Overall, this study provided critical theoretical and technical insights for the optimization of WLB, contributing to the advancement of clean energy technologies and the extension of critical bearing service life. Full article

Aiming at the engineering problems of the severe wear and limited service life of mandrels during the hole extrusion strengthening of critical aerospace components, this study proposes a surface modification strategy for mandrels based on the anti-friction mechanism of micro-textures. Based on the Lame stress equation and the Mises yield criterion, a plastic strengthening stress distribution model of the hole wall was developed. Integrating Bowden’s adhesive friction theory, a parameterized numerical model was constructed to investigate the influence of micro-texture morphology on interfacial friction and wear behavior. An elastic–plastic contact model for micro-textured mandrels during hole extrusion strengthening was established using ANSYS. The effects of key parameters such as the micro-texture depth and area ratio on the contact pressure field, friction stress distribution, and strengthening performance were quantitatively analyzed. The results show that a circular micro-texture with a depth of 50 μm and an area ratio of 20% can reduce the fluctuation and peak value of the contact pressure by 41.0% and 29.7%, respectively, and decrease the average friction stress by 8.1%. The interfacial wear resistance and the uniformity of the residual compressive stress distribution on the hole wall are significantly enhanced, providing tribological insight and surface optimization guidance for improving the anti-wear performance and extending the service life of mandrels. Full article

Zirconia ceramics are promising materials for restoration and are widely used in the field of artificial teeth. However, wear resistance affects the longevity of artificial teeth. In this study, peacock tail feather micro-textures and groove micro-textures are prepared on the surfaces of zirconia ceramics via the laser ablation technique to improve their tribological properties. The effects of micro-textures on the surface wettability and tribological properties of zirconia ceramics are studied. The micro-textures improve the surface wettability and tribological properties of zirconia ceramics. The average coefficient of friction of peacock tail feather micro-textured samples decreases by 53% compared to that of the samples without micro-textures. Different operating conditions affect the friction properties of zirconia ceramics. The samples have the best friction performance when the rotational speed, load, and acid/alkaline environment are 200 r/min, 15 N, and weakly alkaline, respectively. Furthermore, the mechanism by which surface micro-textures reduce frictional wear is as follows: the textured grooves store debris, and the bottom edge of the textured groove acts as a cutting tool to cut debris, preventing debris from scratching the surface. The micro-textures store lubricant and form a liquid film on the ceramic surface to reduce wear. Full article

The low hardness and insufficient wear resistance of aluminum and its alloys restrict their broader application in various fields. The application of surface protective coatings can effectively enhance the hardness and wear resistance of aluminum and its alloys. This article provides a comprehensive review of the recent research progress of wear-resistant coatings fabricated on aluminum and its alloys. The relevant achievements in the recent research works of preparing wear-resistant coatings by one-step methods (such as anodic oxidation, micro-arc oxidation, cold spraying, plasma spraying, and electrodeposition) and two-step methods (anodic oxidation and physical vapor deposition, micro-arc oxidation and sealing, magnetron sputtering, and plasma nitriding) are mainly introduced. The working principles of each coating preparation method, along with their impacts on the microstructure and tribological performance of the coatings, were systematically examined. Additionally, a comparative analysis was conducted to evaluate the advantages and disadvantages of each coating preparation method. Full article

AlCoCrFeNi coatings were electrospark-deposited (ESD) on H13 steel substrates, and their nano-mechanical and tribological properties under a load of 2 N, 4 N, 6 N, 8 N, and 10 N were investigated by utilizing a nanoindentation instrument and a reciprocating friction and wear tester, respectively. The morphologies, composition, and phase structure of the as-deposited and worn AlCoCrFeNi coating were characterized using SEM (Scanning electron Microscope), EDS (Energy dispersive spectrometer), and XRD (X-Ray Diffraction). The results showed that the as-deposited AlCoCrFeNi coating with a nanocrystalline microstructure mainly consists of a BCC and B2 phase structure, and a gradient transition of elements between the coating and the substrate ensures an excellent bond between the coating and the substrate. The hardness of the AlCoCrFeNi coating exhibits an 8% increase, while its elastic modulus is reduced by 16% compared to the H13 steel. The AlCoCrFeNi coating remarkably increased the tribological property of the H13 steel under various loads, and its wear mechanism belongs to micro-cutting abrasive wear whilst that of the H13 steel can be characterized as severe adhesive wear. The friction coefficient and weight loss of the AlCoCrFeNi coating decrease with increasing load, both following a linear relationship with respect to the applied load. As the load intensifies, the work hardening sensitivity and oxidation degree on the worn surface of the coating are significantly enhanced, which collectively contributes to the improved tribological performance of the AlCoCrFeNi coating. Full article

h-BN spherical nanoparticles, known as white graphene, have good anti-wear properties, long service life, chemical inertness, and stability, which provide superior lubricating performance as a solid additive item to nanofluids. However, the poor dispersion stability of h-BN nanoparticles in nanofluids is a bottleneck that restricts their application. Currently, to prepare h-BN nanofluids with good dispersion stability, a cold plasma (CP) modification of h-BN nanoparticles is proposed in this study. In this research, h-BN nanofluid with added surfactant (SNL), CP-modified h-BN nanofluid with N₂ as the working gas (CP(N₂)NL), and CP-modified h-BN nanofluid with O₂ as the working gas (CP(O₂)NL) were prepared, separately. The mechanism of the dispersion stability of CP-modified h-BN nanofluid was analyzed using X-ray photoelectron spectroscopy (XPS), and the performance of CP-modified nanofluid was analyzed based on static observation of nanofluid, kinematic viscosity, and heat transfer properties. Finally, friction and wear experiments were conducted to further analyze the tribological performance of h-BN nanofluids based on the coefficient of friction, 3D surface morphology, surface roughness (Sa), scratches, and micro-morphology. The results show that CP-modified h-BN nanofluid has excellent dispersed suspension stability and can be statically placed for more than 336 h. The CP-modified h-BN nanofluid showed stable friction-reducing, anti-wear, and heat transfer performance, in which the coefficient of friction of h-BN nanofluid was about 0.66 before and after 24 h of settling. The Sa value of the sample was reduced by 31.6–49.2% in comparison with pure cottonseed oil (CO). Full article

Tribology is the branch of science and engineering that focuses on understanding friction, wear, and lubrication, which is essential for saving energy, improving performance, reducing vibration, and creating eco-friendly lubricants and wear resistance. Over the past decade, nanomaterials have captured the immense interest of tribology science. This review aimed to analyze how graphene and its derivatives can be incorporated into lubricants to enhance their properties, particularly in mitigating friction and wear. This is due to graphene’s excellent specific properties, such as a low friction coefficient, mechanical strength, high thermal and electrical conductivity, biocompatibility, high load-carrying capacity, wear resistance, and chemical stability. This study briefly introduces graphite, graphene, and graphene oxide, as well as presents graphene as a material for tribological applications. Among other things, the environmentally friendly possibilities of chemical reduction of reduced graphene oxide are analyzed here, as well as the macro-, micro-, and nano-tribological examination of graphene and its derivatives. Despite what is already known about graphene in tribology, further research is needed to gain a deeper understanding of development regarding integration with different materials, long-term performance, eco-friendly synthesis using green reducing agents, and comprehending how these approaches may affect systems at various scales. Full article

With rapid advancements in agricultural mechanization, enhancing the wear resistance and lifespan of rotary tiller blades is crucial for boosting productivity. This study examines how surface textures affect the friction and wear of 65Mn steel in quartz sand slurry. The results show that laser processing treatment significantly improves the wear resistance of 65Mn steel blades through the lubrication effect due to the wear debris capturing ability of the laser-processed micro-pits. Samples with surface textures processed using a laser scanning speed of 200 mm/s exhibit the best anti-wear property under loads of both 70 N and 100 N, reducing the wear loss by approximately 44.19% and 36.22%, respectively, compared to the non-textured samples. With the applied load increase to 100 N, laser-processed textures can still reduce wear damage but with an impaired anti-wear effect due to the gradually flattening of some textures due to long-term friction and crush damage by high load conditions. These findings help to augment wear resistance and prolong the operational lifespan of 65Mn steel rotary tiller blades, thereby contributing to a more robust understanding of the tribological enhancements achievable through the laser surface texturing process. Full article

Solid-lubricated rolling bearings are widely used in the aerospace field and are key components to support spacecraft rotors. During the start-up of the engine, the sharp acceleration may cause bearing skidding, resulting in damage of the solid lubricating film and a reduction in the remaining useful life of the bearing. However, the existing research on the tribo-dynamic responses of solid-lubricated ball bearings mostly relies on semi-empirical tribological models, which are limited in their ability to reveal the micro–macro sliding mechanisms of the ball–raceway contact interface. In this paper, a novel tribo-dynamic model for solid-lubricated angular contact ball bearings is developed by applying Kalker’s rolling contact theory to the Gupta dynamic model. The interpolation method is adopted to calculate contact parameters to improve the model’s efficiency. Using the proposed model, the dynamic response of the bearing in the acceleration process is studied, and the mechanism and influence characteristics of skidding, over-skidding, and creepage of the rolling element are analyzed. The results show that the main reason for skidding is that the traction force is not enough to overcome the resistance, and the gyroscopic effect is the main cause of over-skidding, which follows the principle of conservation of the angular momentum of the ball. Full article

Surface microtexture, as a branch of surface engineering, has always been an active research object due to its ability to significantly improve matrix properties. Especially by combining surface microtextures with biomimetics, the concept of surface microtextures has been greatly expanded. The emergence of biomimetic microtextures has also endowed mechanical components with better tribological properties and longer service life. This article reviews the preparation techniques of surface microtextures and summarizes the advantages and limitations of various microtexture preparation techniques. We discuss the morphologies of different biomimetic microtextures and the unique properties they impart to the substrate surface, explore the influence of biomimetic microtexture morphology and size parameters on their tribological properties, and reveal the mechanism of biomimetic microtextures applied to cutting tool surfaces. Finally, the application of biomimetic microtextures in cutting tools is prospected. Full article

The development of high-strength cast irons with multiphase metal matrix structures is one of the new areas of modern materials science and mechanical engineering. This is so because of the high dissipative properties of such materials, which, in turn, ensure an improvement in their functional characteristics. It is known that one of the effective methods for obtaining alloys with a heterogeneous structure is a multi-stage heat treatment. Therefore, this study aimed to enhance the corrosion and friction properties of high-strength cast irons by combining different processing methods to create a bainite-martensitic matrix. High-strength cast irons with high ductility micro-alloyed with boron were chosen as the object for research. The experiments studied the effect of various types of multi-stage heat treatment on the structural features, tribological properties, hardness and corrosion resistance. The cast irons were quenched in water or liquid nitrogen after a controlled duration of isothermal exposure at different temperatures. It was established that cooling of isothermally hardened samples in liquid nitrogen makes it possible to effectively engineer the morphology and amount of the formed martensitic phase. It was observed that the high-strength cast irons with 10–15% lower bainite, residual austenite and martensite have the best frictional characteristics. This innovative method allowed the quenching of cast iron directly into liquid nitrogen without violent cracking. Full article

The novel forced wave generator (NFWG) is a critical component of the harmonic drive (HD) without a flexible bearing. Tribological design is required to increase the load-carrying capacity and reduce the frictional resistance in the elliptical sliding pairs (ESPs) between the flex spline (FS) and the NFWG. As the thin-walled FS operates under cyclic deformation with large displacement in the HD, this paper investigates the effects of the distribution region, depth, shape, and density of micro-dimple textures on the outer contour surface of the NFWG on the load-carrying capacity and the frictional resistance of the ESPs using the CFD method. The analysis reveals that the load capacity and lubrication performances of the ESPs are significantly enhanced when the micro-dimple textures are fully distributed on the outer contour surface of the NFWG, with a depth of 0.1 mm, a radius of 6 mm, and a distribution density of 3.9%. The results provide a reference for the practical design of ESPs in the HD under extreme mechanical transmission conditions. Full article

To enhance the operational stability and service life of tapered roller bearings (TRBs), this study investigates the application of surface texturing technology using laser marking to fabricate micro-dimples with controlled diameters and distributions on the TRB outer ring. An orthogonal experimental design was implemented to systematically evaluate the effects of three key dimple parameters—diameter, depth, and angular distribution—on the tribological performance under starved lubrication. The results demonstrate that the textured surfaces significantly improve friction-reducing performance and wear resistance. Optimal dimple parameters (diameter: 200 μm, depth: 10 μm, angular interval: 0.9°) were identified, achieving a 43.6% reduction in the average coefficient of friction (COF) and a 75.7% decrease in wear loss compared to smooth bearings. These findings would offer a practical approach to enhancing the durability and operational reliability of TRBs in industrial applications. Full article

Motivated by the potential of surface texturing to enhance the tribological performance of micro- and nano-electromechanical systems (MEMS/NEMS), this study proposes a novel non-linear optimization approach for designing textured surfaces. This model minimizes the contact area between interacting surfaces and deformation during sliding under dry conditions by controlling key design parameters, such as the size and shape of the designed surface. We test the performance of the proposed model using the lotus leaf surface with dimensions of 248 × 136 micrometers. Due to the large size of the model, we propose a solution approach which consists of a data aggregation step, an optimization step, and a data disaggregation step. The optimization step decomposes the model into smaller models that are easier to solve. Via the sensitivity analysis, we highlight the trade-offs between data aggregation and model decomposition and their effect on the quality of the solutions found. In conclusion, our approach bridges the gap between fabrication capabilities and design requirements, paving the way for significant advances in tribological performance and surface engineering. Full article

Natural fiber-reinforced composites have become an important field of research due to their environment-friendly nature, low cost, lightweight, and excellent mechanical properties. In the current study, natural composites were fabricated by the hand layup technique to investigate the influence of pineapple leaf fiber (PALF) orientation on the mechanical properties and water absorption behaviors of epoxy composites. Pineapple leaf fibers, known for their natural fiber reinforcement capabilities, were incorporated into polymer matrices at various orientations (45°, 60°, 75°, and 90°) to evaluate their impact on the composite’s performance. Mechanical properties (tensile strength, flexural strength, impact energy, and micro-hardness) were assessed to understand how fiber alignment influences the overall structural integrity of the composite. Additionally, the water absorption characteristics of the fabricated composites were assessed by immersing specimens in water and measuring water uptake over time. Results revealed that fiber orientation plays a crucial role in enhancing mechanical strength and tribological properties, with composites reinforced with fibers aligned at 90° demonstrating efficient load transfer and reduced water absorption. Conversely, composites with fibers oriented at 45° showed relatively lower mechanical strength, higher water absorption, and lower tribological performance. These findings suggest that the optimization of fiber orientation in polymer composites can lead to enhanced performance and durability, making them suitable for an extensive range of eco-friendly and sustainable applications. Full article