Search Results (123)

This study presents the development and experimental evaluation of an impregnation composition for cement concrete pavements aimed at improving ice-phobic performance while preserving tire–pavement adhesion characteristics. The formulation is based on a combination of keratin-containing raw materials and water-soluble polymer components. Optimization showed that a polymer concentration of 2.5% reduces concrete water absorption by 49–53% compared with untreated specimens. Freezing tests conducted at temperatures of 0 to −5 °C demonstrated an additional reduction in water absorption of treated specimens by 33–40% relative to uncoated concrete and improved resistance to ice formation. The influence of the impregnation on tire–pavement interaction was assessed using a direct shear method, revealing minor changes in friction coefficients of up to ~6% for polished and less than 1% for rough surfaces, remaining within acceptable safety limits. Wear resistance was evaluated through rolling tests with model vehicle wheels, where laboratory abrasion occurred after several thousand loading cycles, while probabilistic correction accounting for trajectory variability indicated an extension of service life to the order of tens of thousands of vehicle passes. The results confirm the potential of the keratin–polymer impregnation as an effective approach for enhancing the durability and operational safety of concrete pavements in cold climates. Full article

To solve the copper brittleness problem of copper-bearing steel, support the ferritic rolling process, and ensure the continuity of rolling across different phase regions, this study focused on copper-bearing steel with w(Cu) = 1.56%. Gleeble thermal simulation tests were conducted to investigate the deformation behavior of Cu-bearing steel, and a corresponding deformation resistance model was established; meanwhile, the precipitation characteristics of the second phase were characterized by high-resolution transmission electron microscopy (HRTEM). The results show that the deformation resistance of copper-bearing steel increases with decreasing temperature and increasing strain rate, and its deformation resistance–temperature curve shows a unique bimodal trend, where the inflection point at 840 °C is attributed to the austenite–ferrite phase transformation, and the inflection point at 920 °C is caused by the precipitation of B2-FeCu ordered nanoclusters. HRTEM observations confirm that these nanoclusters are metastable phases with a size of less than 5 nm, and their orientation relationship with the matrix is (011)_B2//(011)_α-Fe and [001]_B2//[001]_α-Fe. The area fraction of B2-FeCu ordered nano-precipitates is in the range of 4.27% to 5.32%, which can reduce the lattice distortion of the matrix and thus decrease dislocation slip resistance. The segmented modified Zhou-Guan model has a coefficient of determination (R²) greater than 0.96 between the predicted and experimental values, which can accurately guide the optimization of low-temperature rolling process parameters for copper-bearing steel. Full article

This paper investigates the influence of rolling resistance on fuel consumption in Class 8 heavy-duty vehicles, with a focus on a modeling approach through variations in the rolling resistance coefficient ($C_{rr}$) across different driving scenarios. Leveraging TruckSim’s multibody modeling approach for vehicle dynamics and MATLAB/Simulink co-simulation capability, the study provides insights into how tire rolling resistance affects energy efficiency under varying conditions while enabling controlled, repeatable comparisons across various scenarios. Results show that across the evaluated scenarios, increases in $C_{rr}$ impact the vehicle’s speed, fuel consumption, engine torque, and crankshaft spin. Specifically, increasing $C_{rr}$ from 0.004 to 0.013 was found to lead up to 68% higher fuel consumption in high demand scenarios. These findings aim to guide efforts to optimize tire design and vehicle performance that help achieve improved fuel efficiency. Full article

ZnMgAl layered double hydroxides (LDHs) were synthesised via coprecipitation, and oleic acid and stearic acid were grafted onto their surfaces via dehydration condensation to obtain two nano-lubricant additives, OA-ZnMgAl LDH and SA-ZnMgAl LDH. These surface modifications significantly improved the dispersion stability of ZnMgAl LDH in lubricating oil. Tribological tests showed that, at their respective optimal concentrations for friction reduction or wear resistance, ZnMgAl LDH, OA-ZnMgAl LDH, and SA-ZnMgAl LDH reduced the coefficient of friction by 3%, 20%, and 16%, and decreased the wear scar diameter by 7%, 9%, and 14%, respectively, compared with the base oil (XMP-Mobil 320). To clarify the lubrication mechanism, the wear morphology and chemical composition were analysed using 3D optical profilometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and FIB-SEM. The results indicate that LDHs react with the steel surface under load and shear to form a multilayer protective film consisting of an inner oxide layer and an outer graphite layer, preventing direct contact between friction pairs. In addition, the rolling and filling effects of partially unreacted LDHs further reduce friction and wear. Full article

Aluminum conductor cables are exposed to environmental conditions in service, where wind-induced vibrations generate multiaxial stresses and cause partial sliding between the stranded layers. Such dynamic loading can lead to fatigue or wear failure, particularly at the contact zones between wire layers. The influence of heat treatment and cold work on the wear of these aluminum wires remains unstudied. This work aims to evaluate the microabrasive wear of rolled and heat-treated 6201 aluminum alloy wires used in conductor cables. The wear tests were performed using free-ball microabrasive wear equipment and alumina (Al₂O₃) abrasive paste at a concentration of 0.40 g/mL of distilled water. The parameters used were as follows: 100 Cr6 steel balls with a diameter of 25.4 mm, sample inclination of 60°, normal force of 0.3 N, and shaft speed of 0.185 m/s or 280 rpm. The test time was set at 20 min, 30 min, 40 min, 50 min, and 60 min. The wear test data were processed using the Achard equation. The microabrasive wear test results indicate that the wear coefficient decreased by 19.1% after the artificial aging process, compared with the solution-treated alloy (95% CI: 15.5–22.3%), and this reduction was statistically significant (p < 0.001). After the combined treatment of rolling and artificial aging, the alloy had a drop in wear coefficient of 36.1% compared to the same solution-treated alloy (95% CI: 32.6–39.6%), representing the largest statistically significant improvement among the tested conditions (p < 0.001). Cold work (rolling) reduces the mobility of dislocations, requiring greater stress to deform the material, thereby increasing its stiffness and wear resistance. In this 6201 alloy, it is inferred that artificial aging led to the formation of Guinier-Preston zones, which evolved into the formation of metastable β” precipitates in needle-like form, coherent with the matrix. As the aging process progresses, the β’ particles evolve into larger β particles that are no longer coherent with the matrix. The combined processes of rolling and aging decrease the wear coefficient. Statistical analysis demonstrated that microstructural conditions explain approximately half of the total variability in the wear coefficient (η² = 0.495), indicating that the wear performance under the present experimental configuration is primarily governed by intrinsic strengthening mechanisms rather than experimental variability. Full article

This paper addresses global path planning for a wheeled mobile robot with two different kinematic structures, considering both shortest path and minimum energy consumption criteria. The main research question concerns how the robot’s kinematic structure and the selected planning algorithm influence the resulting path with respect to these criteria. Our review of the state of the art discusses selected path planning methods, including model-based approaches. To determine the energy optimal path, a simplified model of the PIAP GRANITE robot was developed. The robot can be configured as either differentially driven or skid-steered. In the differentially driven configuration, the robot has two driven wheels and two caster wheels, whereas in the skid-steered configuration all wheels are independently driven. The robot’s models are based on previous theoretical and experimental studies and include kinematics, dynamics, drive units, and wheel slip phenomena. For path planning, it was assumed that the robot can move straight or turn. A flat terrain representative of typical urban environments was modeled as a grid of square cells, each characterized by friction and rolling resistance coefficients. Path planning was performed using A*, Theta*, and RRT* algorithms. In order to quantitatively evaluate the results, quality indexes were defined, including path length, energy consumption, computation time, and the number of analyzed nodes. Simulation results are presented for selected terrain maps, both robot configurations, all algorithms, and both optimization criteria. The results show that the differentially driven configuration is consistently more energy-efficient. For the skid-steered robot, minimizing the number of turns is crucial due to high turning energy costs. The A* algorithm consistently finds optimal paths, whereas RRT* is faster but produces non-optimal and non-repeatable results. Theta* does not always achieve optimality due to limitations imposed by the line-of-sight function. Full article

Accurate modelling of agricultural vehicles is essential for optimizing drivetrain performance and energy efficiency, particularly as hybrid systems become more prevalent in sustainable farming. This study presents an experimental validation of a vehicle physical model using the Claas Xerion 3800 tractor. Coast-down tests were conducted to determine the rolling resistance coefficient, while GPS and diagnostic data were used to capture real-world vehicle dynamics and fuel consumption. The rolling resistance coefficient was calculated using two-stage aggregation method of multiple run data, yielding a statistically robust result. Simulation outputs showed close agreement with measured longitudinal responses, including vehicle acceleration, traction force, and fuel usage, with a 2.1% deviation in total fuel consumption. These findings demonstrate that the proposed modelling approach reliably replicates the vehicle’s macroscopic longitudinal dynamics and support its application in drivetrain optimization, hybrid system integration, and energy-efficient vehicle design studies. The validated framework contributes to the development of context-aware simulations capable of reflecting real-world off-road conditions and operational variability. Full article

The vast potential of deep-sea wind resources has driven substantial research focus on floating offshore wind turbines (FOWTs) in recent years. The wet-towing of the FOWT is critically challenged by the harsh conditions and remote locations of deep-sea sites. This paper proposes an innovative concept of FOWT based on the in-service FOWT “Sanxia Yinling”, establishing a numerical model of wet-towing for the FOWT in AQWA. The experiments of free-decay and wet-towing resistance in still water at the towing tank are carried out to validate reliability of the numerical model-integrated viscous damping and resistance coefficient of wind and current. Then, the method is applied to evaluate the effects of sea states and wet-towing speeds for the dynamic responses of the towing system. The results show that the natural periods of the FOWT in heave, roll and pitch DOFs all exceed 25 s, which is sufficiently longer than the typical wave spectral peak. In addition, the numerical model is verified against experimental data, showing close agreement. For the established towing configuration, safe operation requires sea states to be maintained at or below level 4 (significant wave height ≤ 2.5 m) and the towing speed at or below four knots. It is also found that a slack-taut cycle in towing lines at low speeds, which is attributed to wave excitation. Full article

Cr8 steel should be Steel containing ~8 wt.% of chromium is widely used in demanding die applications due to its excellent wear resistance; however, conventional shot peening, while enhancing strength, inevitably increases surface roughness, thereby compromising overall performance. To address this limitation, this study systematically investigates the influence of ultrasonic surface rolling (USR) step size—comparing 0.06 mm and 0.12 mm—on mitigating surface degradation and improving surface integrity. Friction wear and electrochemical corrosion tests demonstrate that USR effectively reduces surface roughness and enhances microhardness. The 0.06 mm step size achieves superior results, yielding the lowest surface roughness (0.8317 μm), highest microhardness (647.47 HV), lowest friction coefficient (0.655), and optimal corrosion resistance (minimum corrosion rate reduction: 3.472 µA·cm⁻², corresponding to an inhibition efficiency of 37.05%). These performance improvements are attributed to the synergistic effects of surface smoothing and work hardening, resulting from more uniform processing achieved under a smaller step size. Consequently, a 0.06 mm step size is determined to be optimal, establishing the integrated shot peening–USR process as a highly effective strategy for enhancing surface properties and extending the service life of critical Cr8 steel components in industrial applications. Full article

To enhance the abrasion resistance of TC4 titanium alloy and meet the demand for wear-resistant and corrosion-resistant friction pair materials for water-hydraulic components of marine equipment, the tribological properties of the material subsequent to ultrasonic rolling extrusion surface strengthening under seawater-lubricated conditions were investigated. The process of ultrasonic rolling machining was simulated and analyzed by the finite element method. The influence of process parameters on surface residual stress and surface roughness of TC4 was studied, and the appropriate range of process parameters was determined. The effects of key process parameters such as rolling times, static pressure, amplitude, and rotational speed on the surface properties of TC4 were investigated by the single-factor test method. Based on the response surface methodology, a prediction model of surface hardness and roughness of TC4 was constructed, and the process parameters were optimized and analyzed. The friction coefficient, wear amount, and wear rate of TC4 and CFRPEEK under seawater lubrication before and after strengthening were studied by wear tests. The wear morphologies of the specimens prior to and subsequent to strengthening were analyzed, and the friction and wear mechanisms were explored in depth. The results indicate that ultrasonic rolling extrusion surface strengthening process facilitates grain refinement in the surface layer of TC4, enhances surface hardness, and optimizes surface roughness, thereby improving its wear resistance. This is of guiding significance to the design and use of hydraulic components in seawater and has a promoting effect on the development of marine equipment. Full article

Oxidation is a critical factor contributing to material wear and the degradation of conductive performance during current-carrying tribological processes. The present study investigated the composite oxidation mechanisms that occurred during current-carrying rolling in mixed atmospheres containing O₂ and H₂O vapor. The results obtained in a dry N₂/O₂ mixture, humid N₂, and humid N₂/O₂ mixture indicated that the oxidation mechanisms on current-carrying rolling surfaces involved thermal oxidation, tribo-oxidation, and anodic oxidation. XPS analysis confirmed that the primary oxidation product was CuO. Conductive atomic force microscopy (C-AFM) revealed that surface oxidation caused a significant reduction in conductive α-spots, leading to an increase in contact resistance. Contact resistance exhibited a quasi-linear relationship with the surface CuO content. Contact angle measurements and adhesion tests showed that the enhanced hydrophilicity of the oxidized surface and the resulting high adhesion contributed to an increase in the macroscopic friction coefficient. In humid N₂/O₂ with 50% relative humidity (RH), the friction coefficient rapidly exceeded 0.8 when the O₂ content surpassed 25%. Wear morphology analysis demonstrated that this abrupt increase in the friction coefficient induced fatigue wear on the surface. Overall, the present study elucidated the composite oxidation mechanisms during current-carrying rolling and clarified the pathways through which oxidation affected current-carrying tribological performance. These findings may contribute to improved failure analysis and the safe, reliable operation of electrical contact pairs. Full article

Passenger cars, sports utility vehicles (SUVs), and light trucks/vans, constituting the overwhelming majority of all road vehicles globally, burn about 25% of all fossil fuels, emit significant amounts of greenhouse gas emissions (CO₂), and deteriorate the environment. Nearly three-quarters of the engine power generated by burning fossil fuels is required to overcome aerodynamic resistance (drag) at highway driving speeds. Streamlining the body shape, especially the projected frontal area, can lead to a decrease in aerodynamic drag. Even though drag coefficients have plateaued since the late 1990s, further altering body shape might worsen vehicle cooling. Thus, the primary objective of this study is to explore the potential for aerodynamic drag reduction and improved cooling performance through careful component design unaffected by stylistic restraints. A variety of strategies for protecting the cooling intakes to reduce the drag coefficient are considered. The potential cooling drag reduction was found to be around 7% without compromising the cooling performance, which is in line with predictions for roughly 2.9% and 1.7% fuel consumption reductions for highway and city driving conditions, respectively. The study also reveals that passenger electric cars designed for city driving conditions possess a battery-to-kerb weight ratio of around one-quarter of the kerb weight, and vehicles designed for higher ranges have significantly higher ratios (nearly one-third), resulting in higher rolling resistance and energy consumption. The reduction of battery weight for EVs, streamlining vehicle shapes, and applying active and passive airflow management can help reduce aerodynamic drag and rolling resistance further, enhance driving range, and reduce energy consumption and greenhouse gas emissions. Full article

This study develops a Bayesian optimization framework to calibrate two discrete element method (DEM) parameters—the cohesion-related surface energy coefficient (k) and the rolling resistance coefficient (μ_r)—based on experimental void ratio data obtained from powder consolidation tests. The optimized parameter set reproduces the void ratio obtained from the consolidation experiment, demonstrating efficient and physically plausible calibration under confined loading. However, when these parameters are applied to powder spreading simulations, the resulting powder beds become excessively cohesive, leading to poor layer uniformity. This discrepancy is attributed to (i) the mismatch in mechanical scaling (σ/E) between the experimental and simulated conditions and (ii) the shift in dominant particle-scale mechanics from normal-force-controlled consolidation to shear-dominated spreading. The results indicate that DEM parameter calibration for powder bed-based additive manufacturing should incorporate shear-related experimental metrics and scaling considerations rather than rely solely on consolidation-based fitting. Full article

Tire–road friction is a fundamental factor in vehicle safety, energy efficiency, and environmental sustainability. This narrative review synthesizes current knowledge on the tire–road friction coefficient (TRFC), emphasizing its dynamic nature and the interplay of factors such as tire composition, tread design, road surface texture, temperature, load, and inflation pressure. Friction mechanisms, adhesion, and hysteresis are analyzed alongside their dependence on environmental and operational conditions. The study highlights the challenges posed by emerging mobility paradigms, including electric and autonomous vehicles, which demand specialized tires to manage higher loads, torque, and dynamic behaviors. The review identifies persistent research gaps, such as real-time TRFC estimation methods and the modeling of combined environmental effects. It explores tire–road interaction models and finite element approaches, while proposing future directions integrating artificial intelligence and machine learning for enhanced accuracy. The implications of the Euro 7 regulations, which limit tire wear particle emissions, are discussed, highlighting the need for sustainable tire materials and green manufacturing processes. By linking bibliometric trends, experimental findings, and technological innovations, this review underscores the importance of balancing grip, durability, and rolling resistance to meet safety, efficiency, and environmental goals. It concludes that optimizing friction coefficients is essential for advancing intelligent, sustainable, and regulation-compliant mobility systems, paving the way for safer and greener transportation solutions. Full article

As the operating conditions of rolling bearings become increasingly demanding, traditional steel bearings can no longer fully meet the performance requirements of critical equipment. Silicon nitride full ceramic ball bearings, with intrinsic properties such as a low thermal expansion coefficient, low density, corrosion resistance, and wear resistance, offer significant advantages in extreme temperatures, high-speed operation, and harsh corrosive environments. As a result, they have become a key technical solution for the core transmission systems of high-end equipment. However, the dynamic evolution of their service performance under varying operating conditions—such as load and speed—remains insufficiently understood. This study systematically investigates the service performance evolution mechanism of silicon nitride full ceramic ball bearings under self-lubrication conditions. The key findings will provide a theoretical foundation for optimizing and regulating performance under extreme operating conditions. Full article