Friction最新文献

As a common transport device, pipelines are permanently subjected to pressures generated by external loads and to the erosive effects of the substances transported inside. The addition of structures to the inner surface of the pipe has been demonstrated to enhance its strength and erosion resistance to a certain extent. In this paper, a novel bionic model is innovatively proposed using a leaf blade as a bionic prototype. It involves the leaf vein structure on the surface of the leaf blade and the growth arrangement law of the leaf blade (phyllotaxis-arrangement). A series of rigorous gas-solid erosion tests and compression tests were carried out on a 90° elbow pipe. The effects of the arrangement location (entrance, elbow), arrangement mode (uniform, interlaced, phyllotaxis), phyllotactic coefficient and vein fractal angle (30°, 45°, 60°) on the erosion resistance and compression capacity of the bionic model and pipe were also analysed. The test results demonstrate that, in comparison with standard bends, the dual bionic bends exhibit a maximum increase in erosion resistance of 41.1% and a maximum increase in compression resistance of 88.6%. The optimum erosion and compression resistance of the bionic model was obtained when the leaf vein fractal angle was 60°. In order to investigate the synergistic lifting principle of different bionic models, numerical simulation techniques were used to analyse the flow-solid coupling state inside the pipe, the resistance lifting inside the pipe, and the stress of the pipe when it is subjected to external loads. This study provides new ideas in the field of bionic erosion resistance and shows great potential for practical applications.

Reducing corrosion and wear has been a challenge to metal components in the marine environment for a long time. However, the problem of high cost and low efficiency hinder the discovery of new anti-tribocorrosion multi-principal element alloy (MPEA). This study reported a significant reduction in both wear and corrosion of single-phase CoCrNi MPEA through in-situ Laser-directed energy deposition (L-DED), that had only half tribocorrosion rate than pre-alloyed samples. Further, structure evolution mechanism of in-situ samples was revealed under different scales and interaction mechanism of tribocorrosion was clarified in detail. The results show that in-situ samples had finer cells and higher microhardness due to solid solution strengthening and nano-precipitation strengthening. The higher Cr₂O₃/Cr(OH)₃ ratio, higher R_ct, and a lower I_pass, indicated a denser and more protective passive film of in-situ samples. Further, in-situ sample demonstrated superior tribocorrosion resistance which was mainly due to lower corrosion-intensified wear loss (W_C) value. Moreover, load intensified the material loss of interactions between wear (W) and corrosion (S). This work will provide breakthrough in the wear-corrosion trade-off of MPEA design and promote the application of anti-tribocorrosion MPEAs in marine equipment.

As key supporting components in large-scale equipment, the lubrication performance of hydrodynamic thrust bearings directly determines the operational efficiency, stability and service life of the entire mechanical system. With the rapid development of modern industry, the demand for complex working conditions poses severe challenges to the lubrication systems of hydrodynamic thrust bearings, making the accurate evaluation and prediction of their friction and lubrication behaviors a critical technical issue in the field of mechanical engineering. This paper systematically summarizes the research progress of lubrication theories for hydrodynamic thrust bearings, covering the evolutionary process from early hydrodynamic (HD) lubrication theory to thermoelastic hydrodynamic (TEHD) lubrication theory that integrates thermal and elastic effects, and highlights the breakthroughs of computational fluid dynamics (CFD) technology in simulating complex flow fields. Concurrently, recent advances in thrust bearing performance testing technologies are summarized, which include fundamental tribological tests and bearing model test rigs, with detailed discussion on the progress in monitoring key parameters such as oil film pressure, thickness, and temperature. Performance enhancement strategies are systematically elaborated from two primary perspectives: the improvement of thrust bearing liner materials and the optimization of surface textures. Finally, by comprehensively analyzing existing research, future research directions are outlined, emphasizing the development of high-fidelity multi-physics coupling models, the integration of multi-sensor-integrated distributed dynamic measurement with algorithmic innovation, and the synergistic design and optimization of materials and surface textures. This paper aims to provide a systematic reference for the design, performance improvement, and cutting-edge research of hydrodynamic thrust bearings under complex working conditions.

Enhancing the durability of heavy-duty engines requires a deeper understanding of the wear failure mechanisms in critical big-end bearings. The complex interdependencies among tribology, dynamics, and wear behaviors pose challenges for accurate modeling, and the underlying failure mechanisms remain inadequately understood under demanding operating conditions. This study proposes a novel tribo-dynamic-wear coupling model for big-end bearings that integrates mixed lubrication, multi-body dynamics, and the transient evolution of wear morphology. A full-scale engine experiment is performed to validate the model’s accuracy, and a detailed surface failure analysis offers insights into the wear mechanisms under real-world conditions. The findings reveal a clear wear asymmetry between the upper and lower bearing surfaces, with the upper surface experiencing more severe wear. Additionally, an axial wear gradient is observed, with the test wear depth in the central region being approximately 9.10 μm greater than that at the edges. These distinct wear patterns are successfully predicted by the proposed model. The primary cause of exacerbated wear is identified as a significant reduction in hydrodynamic lubrication, driven by the combined effects of high load and low speed. This results in the highest transient solid contact force ratio (94.72%) among the three representative conditions (1,000, 1,400, and 1,800 r/min at 100% load). Another contributing factor is the concurrent occurrence of multiple wear mechanisms, including abrasive, oxidative, adhesive, and mild fatigue wear.

This study evaluated the friction, wear, and airborne brake wear particle (BWP) emissions of aluminum-based metal matrix composite brake discs fabricated from recycled aluminum alloy reinforced with silicon carbide particles (Al-SiCp MMC). The study further conducted a comparative analysis of the friction, wear, and BWP emissions of Al-SiCp MMCs against those of a commercial gray cast iron (GCI) brake disc, which served as a reference. The results show that the steady state coefficient of friction for all Al-SiCp MMC brake discs remained consistently between 0.4 and 0.45, within the typical range of brake materials. A clear transfer layer was observed on Al-SiCp MMC disc surfaces after testing, resulting in apparently milder wear due to material transfer and reduced BWP emissions. Al-SiCp MMC brake discs resulted in higher wear rates on the mating pins compared to GCI discs, with wear rates increasing as the fraction of secondary aluminum in the matrix increased. Within the measurement range of this study, both GCI and Al-SiCp MMC brake discs had mono-modal number-weighted particle size distributions in the steady state, with the mode size around 0.5 µm. Future research should employ advanced particle samplers capable of detecting nanosized particles and explore more severe testing conditions, including higher contact pressures, speeds, and temperatures.

Friction, as a nonlinear and complex phenomenon, significantly affects the performance of mechanical systems requiring high-precision motion control and force feedback. Accurate modeling of frictional behavior is essential for effective control and compensation. The LuGre friction model is widely used due to its computational efficiency; however, it retains only the first-order displacement term, resulting in limited accuracy and noticeable drift, which restricts its use in precision applications. To address these issues, this study proposes an improved friction model based on the LuGre framework. Discrete bristles are introduced to incorporate the influence of surface topography at the contact interface. Additionally, an iterative numerical scheme is employed to enhance computational accuracy. Simulation results demonstrate that the model captures key frictional phenomena, including stick-slip transitions, hysteresis, and friction lag. It also shows clear advantages over the LuGre model in representing non-local memory and non-drift characteristics. Experimental validation was conducted using a constant-velocity reciprocating test and a micro-amplitude sinusoidal excitation test, enabling stepwise parameter identification for slipping and sticking phases. A dual-frequency sinusoidal excitation test was further designed to evaluate model performance under complex dynamic loading. The simulated friction forces agree well with experimental measurements, verifying the model’s effectiveness and robustness. The proposed model enhances both accuracy and physical realism in friction modeling and can be applied in high-precision systems to solve the friction force output under the given input conditions.

Friction hysteresis, a common event in ultrathin two-dimensional materials, is significantly influenced by their deformation. This study explores the friction hysteresis of suspended graphene with varying thicknesses using atomic force microscopy (AFM) conducted under controlled humidity conditions. Compared with that in the supported case, the friction in the suspended graphene cases demonstrates significant hysteresis. The degree of friction hysteresis on suspended graphene increased with decreasing thickness and increasing relative humidity and cut-off load. Both deformation hysteresis and adhesion hysteresis contribute to the friction hysteresis of suspended graphene, with deformation hysteresis playing a dominant role. The finite element simulation revealed that the sliding process enhanced deformation and increased the contact area for the major friction hysteresis. The deformation hysteresis of suspended graphene expands the contact area and increases energy dissipation during unloading, resulting in significant friction hysteresis. These findings advance our understanding of friction hysteresis on graphene in terms of deformation hysteresis.

The rapid evolution of advanced equipment that utilizes gears, including aviation engines, helicopters, and wind turbines, imposes escalating demands for enhanced reliability, prolonged lifespan, increased power density, and sustained durability of gears. Gear contact fatigue issues, associated with materials, geometries, and operating conditions, are crucial to modern gear design. To date, enormous theoretical and experimental studies have been conducted to understand gear contact fatigue mechanisms. To compile and categorize key investigations within a broad and active research field, this work reviews recent studies of gear contact fatigue. Emphasizing theories, tests, and anti-fatigue design approaches, this work aims to provide a comprehensive overview of recent developments in this significant area of research.

Material failure caused by load impacts frequently results in significant economic losses and negative effects. The application expansion of shear thickening fluid (STF) under special impact conditions is expected to lead to the design of a prospective impact-resistant structure because of its shear thickening effect, with an instantaneous response and reversible viscosity change. Herein, core–shell nanospheres (PS@ZIF-8) were synthesized using polystyrene (PS) nanoparticles as the base template. PS@ZIF-8 was used as the unique dispersed phase and was introduced uniformly into hydroxyl-functionalized ionic liquids (ILs) via simple ball mill dispersion to obtain novel STF systems. The performance of novel STF systems, such as the critical shear viscosity and peak viscosity, could be enhanced with increasing PS@ZIF-8 content. Importantly, the STF systems retained a significant shear thickening effect even after several shear scanning cycles because of the interaction between the dispersed phase (PS@ZIF-8) and the dispersion medium (ILs). The structural stability of PS@ZIF-8 in ionic liquids was also investigated, and the STF suspensions exhibited excellent stability in quantitative comparison experiments after centrifugal disruption at 8,000 r/min and standing for 60 days. In addition, a loading impact experimental method was developed to better investigate the anti-impact-wear performance of STF systems filled with limited space. The results of the tests revealed that the novel STF systems had outstanding flexibility in terms of energy absorption capacity and impact wear resistance. This study provides a strategy to prevent material failure under load impact and highlights the potential of these novel STF systems for designing efficient and stable impact-resistant structures.

Ultra-low wear technology provides an effective solution to prolong the service life of mechanical equipment. However, there are still significant challenges in achieving ultra-low wear at the steel/steel interface over long periods. In this work, a PAO10-SPAN65 composite semisolid lubricant (PAO10/SP65) was designed with sorbitan tristearate (SPAN65) and base oil poly α-olefin 10 (PAO10). The wear rate of the steel lubricated with PAO10/SP65 (1.31×10⁻⁸ mm³·N⁻¹·m⁻¹) was 96% lower than that of PAO10 (3.52×10⁻⁷ mm³·N⁻¹·m⁻¹). In addition, after 10 h of friction testing at a contact pressure of 0.82 GPa, the wear of the steel surface is still close to zero, with a wear rate of 4.13×10⁻⁹ mm³·N⁻¹·m⁻¹. This study provides a new design idea for realizing ultra-low wear of engineering steel.