CuPb10Sn10/steel bimetals are effective sliding-bearing materials because they combine high load-bearing capacity with good friction-reducing and anti-adhesion properties. However, conventional melt casting often causes weak interfacial bonding, pore defects and Pb-phase segregation, restricting their use under severe service conditions. In this study, a CuPb10Sn10 alloy layer was deposited on a steel substrate by laser cladding (LC), with melt-cast (MC) bimetals used for comparison. The effects of the initial microstructure on mechanical properties and dry-sliding tribological behavior were examined. Additionally, molecular dynamics (MD) simulations based on experimentally characterized Pb-phase size, morphology and distribution were used to clarify Pb-rich lubricating-film formation and evolution. The results showed that LC refined the alloy-layer microstructure, homogenized the phase distribution, reduced porosity from 1.33% to 0.16%, and increased microhardness and interfacial shear strength by 62.55% and 71.32%, respectively. Under dry sliding, LC samples maintained lower and more stable friction coefficients over the load range and showed better anti-adhesion behavior and wear resistance during prolonged tests at 3 N. Wear-scar analysis demonstrated that heterogeneous microstructure and Pb segregation in MC samples hindered continuous lubricating-film formation, intensifying Fe transfer and adhesive tearing. In contrast, the refined microstructure and dispersed Pb phase in LC samples facilitated Pb extrusion and shear-induced spreading, forming a continuous Pb-rich lubricating film. MD simulations further indicated that dispersed Pb promoted dynamic film replenishment, reduced shear-force fluctuations and suppressed stick-slip motion. Overall, LC improves CuPb10Sn10/steel bimetals through microstructural refinement, defect suppression and Pb-rich film stabilization.

The motion stability of live working robots on power cables is a key factor influencing operational efficiency. Currently, most of these robots employ a suspended structure, which limits the accuracy of position localization and impairs the clarity of cable condition observation. Additionally, most stability analyses focus solely on the effects of external loads, while overlooking the impact of cable stiffness variations on the robot's motion stability along the cable. This study first proposes a straddle-type live working robot and develops its control system, enabling safer and more reliable live operations directly on power cables. Subsequently, the robot's tipping stability during cable traversal is analyzed, and dynamic models are established under three different cable stiffness conditions, leading to the identification of key factors influencing the robot's motion stability. Finally, a simulated utility pole test bench is constructed to conduct experiments on motion control performance, tipping performance, and motion stability. Experimental results show that the robot's control error remains below 6%, the minimum tipping angle ranges from 29 degrees to 32 degrees, and the average Jerk is less than 2 m/s3. These findings are expected to contribute to substantial advancements in the development of live working robots.

Over the recent years, aluminum-based alloys have garnered significant research interest owing to their lightweight nature, high mechanical strength, and good friction and wear resistance. In this study, Al-Bi-TiC alloys with varying Bi contents (5-25 wt%) are synthesized by leveraging the heterogeneous nucleation effect between Bi and TiC. The alloy microstructure as well as the synergistic friction and wear reduction mechanisms of Bi and TiC under dry sliding conditions are systematically investigated. The results demonstrate that Bi is transferred to the worn surface during reciprocating friction, contributing to friction reduction. Simultaneously, TiC particles promote Bi adhesion to the worn surface through a pinning effect. This cooperative interaction between Bi and TiC results in enhanced friction reduction and wear resistance. An optimal Bi content of 10 wt% yields the lowest friction coefficient (mu = 0.44) and minimal wear depth (138.11 mu m).

ObjectiveTo solve the problem of no direct mechanical or hydraulic connection between the brake actuator and the brake pedal in an electronic mechanical braking system, leading to no feedback of road feel, a brake pedal feeling simulator was proposed based on magnetorheological dampers.MethodsAnsys/Maxwell and Matlab/Simulink were used as the platform. The structural design of the sinking brake pedal feeling simulator, the structural design of magnetorheological damper, magnetic circuit analysis and electromagnetic simulation were carried out respectively, and the simulation analysis of traditional proportional-integral-derivative (PID) and fuzzy adaptive PID control under different working conditions of the whole system was compared.ResultsThe simulation results show that the brake pedal feeling simulator can track the characteristic curve of the traditional pedal well under different working conditions and has wide applicability. Compared with the traditional PID control effect, the fuzzy adaptive PID control has higher control precision and smaller control error, and has good application prospects.

Aramid particles (AP) and polytetrafluoroethylene (PTFE) impart tribological application potential to AP/PTFE composites, but weak interfacial bonding and poor formation of high-quality transfer films hinder performance enhancement. In this study, AP was surface-functionalized using a simple, mild, eco-friendly polydopamine (PDA)-polyethylenimine (PEI) synergistic strategy to fabricate AP-PDA-PEI/PTFE composites. Systematic investigations were conducted on their microscopic mechanical properties, tensile strength, tribological performance, and underlying mechanisms. Results indicate that PDA-PEI modification enhances the interfacial microscopic mechanical properties between AP and PTFE. Compared to AP/PTFE, the modified composite's interfacial modulus is increased by 89.67 %. AP(10)-PDA-PEI/PTFE exhibits a tensile strength of 35 MPa, 59.1 % higher than AP(10)/PTFE. Characterizations of interfacial microtopography and elemental distribution confirm enhanced interfacial bonding. At 3 MPa, 6.5 MPa, and 10 MPa, AP(10)/PTFE has average friction coefficients of 0.185, 0.157, and 0.150, respectively, with wear rates of similar to 10(-6) mm(3)/(Nm). In contrast, AP(10)-PDA-PEI/PTFE shows optimal tribological performance: its average friction coefficients are reduced by 15.1 %, 12.0 %, and 30.2 %, with wear rate decreased to similar to 10(-7) mm(3)/(Nm) (one order of magnitude lower than unmodified AP(10)/PTFE). Wear scar and transfer film characterizations reveal that the composite's excellent performance stems from the synergy of optimized interfacial bonding and transfer film formation. Enhanced interfacial bonding inhibits AP debonding, while transfer film formation facilitates tribochemical reactions. This transforms the sliding contact mode to tribofilm-transfer film contact, achieving stable, low-wear lubrication.

Under high-speed and high-temperature current-carrying conditions, turbulence in the metal liquefaction layer significantly influences friction interface performance, especially in a magneto-thermal shock environment. The interplay between turbulence and interface roughness complicates the dynamic behavior of hybrid lubrication and electrical contact. To explore the underlying mechanisms, this study constructs a turbulent melt lubrication model by integrating magnetic, temperature, and tribological calculations using the finite difference method (FDM). The findings reveal that armature velocity variations notably affect interface heat distribution, causing melt waves to propagate along the contact interface. As working conditions change, the primary heat source at the interface shifts from Joule heat to a combination of viscous and Joule heat (63.81% and 36.19%, respectively), demonstrating the complexity of the energy conversion process. Notably, the formation of a metal liquefied layer reduces the coefficient of friction and alters the lubrication state, which is crucial for optimizing the performance of electromagnetic launching system (EMLs).

PurposeGears operating under starved lubrication and heavy loads often suffer from elevated friction and accelerated wear, leading to performance degradation or failure. This study aims to investigate the influence of micro-dimpled texture parameters on the tribological behavior of line contact sliding-rolling surfaces under such extreme conditions, aiming to optimize texture design.Design/methodology/approachSliding-rolling tests using cylindrical specimens were conducted to simulate gear meshing under starved lubrication and heavy loads. A quadratic rotation orthogonal combination test assessed the effects of dimple diameter, depth and spacing on the average friction coefficient and surface wear (quantified by roughness change, Delta Rz). Regression models were established using response surface methodology (RSM), followed by multi-objective optimization.FindingsThe experimental results show an optimal proportional relationship between the texture parameters, which made the tribological performance of the tested samples the best. Using the main objective function method, the texture parameters were optimized, yielding a preferred combination of 67 mu m in diameter, 54 mu m in depth and 654 mu m in spacing. Compared to non-textured surfaces, this optimized configuration reduced the average friction coefficient by 33.3% and the Delta Rz value by 42.3%.Originality/valueThis study experimentally evaluates and optimizes micro-dimpled textures for gear-like surfaces under extreme conditions, offering theoretical and practical guidance for enhancing tribological performance in oil-starved, high-load environments.Peer reviewThe peer review history for this article is available at: Link to the website.

This study investigates the influence of dimple-type microtextures on the dynamic performance of gear systems, with spur gears selected as the research object. The effects of such microtextures on time-varying mesh stiffness (TVMS) and vibration response are systematically explored. An analytical TVMS model that accounts for the influence of texture diameter, depth, and spacing was developed and validated using the finite element method. Based on this model, a dynamic model of microtextured gears was constructed to analyze the impact of different texture parameters on vibration behavior. The results show that the introduction of microtextures significantly affects both mesh stiffness and vibration response. Specifically, increasing the texture diameter and depth reduces TVMS and amplifies vibration, while decreasing texture spacing also lowers TVMS and intensifies vibration. Among the three parameters, texture diameter and spacing exhibit a more pronounced influence on vibration than texture depth. Finally, a vibration testing platform for microtextured gears was established. Experimental tests were performed on gear pairs with no textures, optimized microtextures, and deteriorated microtextures. The experimental results closely matched the simulation outcomes, validating the accuracy of the proposed model. These findings provide a theoretical basis for the parameter optimization and practical application of microtextured gears.

The effects of the conversion rate of Si to SiC (Rs) on braking behavior was investigated. The results indicate that a moderate Rs (38.360) combined with a uniform distribution of pyrolytic carbon facilitates the formation of a homogeneous metal tribo-layer, maintaining a stable coefficient of friction (COF) and superior wear resistance. High Rs (92.518) and lower pyrolytic carbon concentration are more susceptible to abrasive and fatigue wear, leading to surface delamination. Fewer Rs (9.475) and abundant pyrolytic carbon contribute to the hightemperature oxidation of pyrolytic carbon accelerates adhesive wear, resulting in an increased COF and inferior wear resistance.

While the mechanical reinforcement of filler particles has been extensively recognized as a critical factor in enhancing the wear resistance of polytetrafluoroethylene (PTFE) composites, the tribological mechanisms beyond mere mechanical effects remain poorly understood for fillers within the same elemental group. This study systematically investigates the tribological enhancement of PTFE composites through a comparative analysis of micron-sized (50 mu m) and nano-sized (20 nm) alumina (Al2O3) particles with distinct mechanical properties. The results of nanoindentation experiments showed that 50 mu m Al2O3 enhanced the mechanical strength of PTFE more significantly than 20 nm Al2O3. Conversely, infrared spectroscopy and microscopic characterization unveiled a contrasting phenomenon. Nano-Al2O3 particles facilitated the formation of tribochemical products, particularly aluminum-organic complexes, which promoted the development of coherent transfer films during frictional sliding. Wear tests demonstrated that the nano-Al2O3/PTFE composite exhibited a lower wear rate than the micron-Al2O3/PTFE composite, despite the lower mechanical strength of the nano-fillers. These findings collectively underscore that tribochemical reactions, rather than mechanical reinforcement alone, dominate the wear performance of polymer composites. The high surface area and chemical reactivity of nano-fillers synergistically enhance interfacial interactions, establishing a paradigm shift in the design of high-performance tribological materials.

The rapidly solidified Al100-xNix ribbons with x = 0, 3.1, 10 and 25 (labeled as Ni0, Ni3.1, Ni10 and Ni25) were melt spun with the microstructures of monophasic alpha-Al, alpha-Al + Al3Ni eutectic mixture, alpha-Al + Al3Ni hypereutectic mixture, and sole peritectic Al3Ni phase, respectively. As shown in the electrochemical and XPS tests, these ribbons have a monotonic increase in the passive current density, wetting angle, the charge density and Al 2p binding energy of outer layer with increasing Ni content, indicating the electrical properties of their passive films changed continually. In addition, their pitting potential, later corrosion resistance, oxygen diffusion parameter decrease first and then increase with the addition of Ni, showing a minimum in Ni3.1 ribbon with the eutectic microstructure, which is ascribed to the numerous alpha-Al/Al3Ni interfaces. These results can help us to deeply understand the passivation of Al-Ni alloys and explore their application in the anti-corrosion environment.

This study explores the tribological performance and meshing stiffness of microcavity spur gear pairs operating under starved lubrication and heavy load conditions. Sliding-rolling tests and analytical modeling were performed on three gear surface types: Type A (nontextured), Type B (microcavities with 67 mu m diameter, 54 mu m depth, and 654 mu m spacing), and Type C (microcavities with 128 mu m diameter, 13 mu m depth, and 599 mu m spacing). Compared to the nontextured Type A, Type B reduced the friction coefficient by 16.8% (initial value: 25.9%) and decreased wear depth, as indicated by a 23.5% reduction in surface roughness (Rz). The time-varying meshing stiffness (TVMS) model further showed that Type B mitigated stiffness degradation (<= 0.25%) by lowering friction, whereas Type C increased both friction and contact area, leading to greater stiffness loss (up to 0.5%). These results suggest that an appropriately designed microcavity texture can enhance tribological behavior while maintaining meshing stiffness, providing valuable insights for improving gear performance under extreme operating conditions.

BackgroundEnhanced marrow adiposity is frequently linked with a decline in bone density. The underlying mechanisms responsible for bone loss in diabetes are not well understood. In this investigation, we employed an alloxan-induced diabetes rabbit model to unravel the association between marrow fat content and bone resorption, utilizing magnetic resonance spectroscopy.MethodsForty 4-month-old male New Zealand rabbits were randomly allocated into two groups: a control group and an alloxan-induced diabetic group, each consisting of 20 rabbits. Biochemical analyses covered plasma glucose, enzyme levels, lipid profiles, blood urea nitrogen, creatinine levels, and markers of bone turnover. Quantification of bone marrow adipose tissue utilized both MR spectroscopy and histological examinations. Dual-energy X-ray absorptiometry and microcomputed tomography were employed to determine bone density and trabecular bone microarchitectures. The expression levels of marrow adipocyte markers (peroxisome proliferator-activated receptor-gamma2, CCAAT/enhancer-binding protein-α, and fatty acid binding protein 4) and markers of bone resorption [tartrate-resistant acid phosphatase (TRACP) and cathepsin K] were assessed using RT-PCR.ResultsDiabetic rabbits exhibited significant increases in marrow fat fraction (MFF) over time (MFF increased by 13.2% at 1.5 months and 24.9% at 3 months relative to baseline conditions, respectively). These changes were accompanied by the deterioration of trabecular microarchitectures. Marrow adipogenesis was evident through a 31.0% increase in adipocyte size, a 60.0% rise in adipocyte number, a 103.3% increase in the percentage of adipocyte area, and elevated mRNA expressions of marrow adipocyte markers. Osteoclast markers (TRACP and cathepsin K RNA and serum TRACP5b levels) were elevated in diabetic rabbits. MFF exhibited a robust correlation with trabecular bone microarchitectures. A significant positive correlation was identified between ΔMFF and serum ΔTRACP5b levels. Moreover, MFF at 3 months showed a strong positive correlation with serum TRACP5b levels (r = 0.763), as well as with the mRNA expression of osteoclast markers, including TRACP (r = 0.784) and cathepsin K (r = 0.659), all with p <0.001.ConclusionsRabbits with type 1 diabetes experience an expansion of marrow adiposity, and this enhanced marrow adiposity is associated with increased osteoclast activity.

Power connectors are crucial components for transferring current from the main conductor to the branch lines. The failure of cylindrical clamps may seriously affect the operational safety of grid power systems. In this paper, the dynamic response and fatigue life of cylindrical clamps under vortex-induced vibration are systematically investigated. First, the aerodynamic parameter model of the conductor and the finite element model of the power line were established based on the actual distribution line. The effects of vibration load on the dynamic response of cylindrical clamps under various wind speeds were investigated independently. Secondly, the stress distribution and fluctuation time course curves of each part of the cylindrical clamp were analyzed. Finally, based on the Weibull distribution, a wind field with an annual average wind speed of 5 m/s was established to evaluate the fatigue life of the cylindrical clamp. The stress results reveal the vulnerable areas of the cylindrical clamps and their failure modes. The fatigue life results indicate that the weakest location is the contact interface between the conductor and the clamp, with a fatigue life of 12.43 years. This study fills a research gap in stress distribution and fatigue life of power connectors in breeze vibration environments and could offer valuable insights for optimizing and assessing the safety of power connectors.

Refractory high-entropy alloys (RHEAs) are categorized as difficult-to-machine materials due to their excellent mechanical properties. Electrical discharge machining (EDM) is a special processing method for RHEAs, which faces challenges such as low machining efficiency. In this work, electrochemical discharge machining (ECDM) was proposed for (TiVZrTaW)99.5N0.5 and (TiVZrTa)W5 (at. %, denoted as W20N0.5 and W5, respectively) RHEAs, and their machining performances were investigated and compared with EDM. At a peak current of 25 A, the material removal rate (MRR) using ECDM is more than twice that of EDM for W20N0.5 (reaching to 1.24 mm3/min) and 1.5 times higher than that for W5. Both W20N0.5 and W5 RHEAs exhibited higher MRR in ECDM based on the analyses of the influence of top diameter, bottom diameter, machining depth, and surface roughness (Ra). The process and mechanisms of material removal were examined through the microstructural morphology and elemental distribution analyses. This work proposed a more effective route for machining RHEAs by ECDM compared to the conventional EDM.

This paper introduces the basic structure of the gear transmission system in multiple-unit trains and established the corresponding kinetic equation model. Subsequently, the corresponding finite element model was constructed using the kinetic equations of the system. After verifying its validity, the paper tested the intrinsic frequency, critical axle speed, and transmission error of the transmission system under varying mesh stiffness. The first- order intrinsic frequency and axle critical speed showed significant increases when the mesh stiffness exceeded 104 N/m, but they remained essentially unchanged after reaching 109 N/m. The transmission error decreased as the mesh stiffness increased. In conclusion, the design of the gearing system in multiple-unit trains should focus on achieving a sufficiently large gear meshing stiffness. However, considering the cost of improving the meshing stiffness, an excessively high meshing stiffness may not necessarily yield better results. Based on the findings, this paper suggests that a meshing stiffness of 109 N/m exhibits the most favourable effect.

By substituting 10 wt% of conventional graphite particles, pitch coke particles with fine mosaics demonstrate superior performance in enhancing the braking properties of copper metal matrix composites (CMMCs) operating at various conditions. When mated with C/C-SiC, the coefficient of friction increases by 18.6 % at low speeds and 38.8 % at high braking speeds, along with a significant enhancement in wear resistance across various counterparts. This improvement is attributed to the incorporation of pitch coke with fine mosaics and superior mechanical properties, which not only imparts high thermal capacity and mechanical strength to the CMMCs but also fosters a synergistic interaction between pitch coke and the iron oxide layer, stabilizing the friction layer.

Different ternary system Fe-based metallic glass catalysts were constructed to boost photocatalytic reactive black 5 dye degradation with persulfate assistance. Compared with FePC and FeBSi catalysts, Fe atoms in the FeBC catalyst exhibited a high energy level and a unique atomic coordination structure causing its efficient photocatalytic activity like a high k value, a strong total organic carbon removal rate, and a low activation energy value. Meanwhile, the green and environmental friendliness of the metallic glass catalyst/persulfate/ultraviolet system for dye degradation was determined. Density Functional Theory simulations confirmed that the FeBC catalyst had an excellent catalytic performance due to its unique atomic coordination environment, which induced the reduction in the energy barrier (only 1.36 eV) during the conversion of S2O82- to SO4 -center dot. Moreover, the Relaxation and Rejuvenation catalysts were prepared by treating the as spun FeBC ribbon with high temperature annealing and cryogenic thermal cycling, showing a higher crystallinity and a higher energy state than the as spun counterpart, respectively; and both treated catalysts exhibited a higher catalytic degradation activity. Especially, the Rejuvenation catalyst offered a high catalytic degradation ability of kSA center dot C0 = 13114 mg m-2 min-1, a large k value of 0.981 min-1, and a strong reusability of 44 cycles without decolorization efficiency decay. This study may inspire the design of high activity metallic glass catalysts and expand their potential applications in environmental remediation. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Fibrous copper powder (FC) featuring fibrous topography is fabricated by water -atomization, cyclic oxidation, and grinding. Prominent hardness and deformation resistance of FC are identified compared to electrolytic copper powders (EC). Copper/graphite metallic composites with FC (CCF) are endowed with higher hardness (increased by 22.65 %) and tensile modulus (increased by 135.4 %). The CCF shows stable friction coefficient, and the wear resistance is improved by 52.1 %, ascribed to the ideal mechanically -bonded Cu/ graphite interfaces and higher strength of the matrix. The integral grains on the matrix and approximately 5 mu m stress layer around the Cu/graphite interfaces of CCF contribute to excellent mechanically -bonded, where the nano -hardness and elastic modulus of CCF are increased by around 300 % compared to CCE, exerting superiority of the mechanically -bonded Cu/ graphite interfaces.