Search Results (107)

The development of sustainable and energy-efficient asphalt pavements is essential to address the growing demand for climate-neutral transportation infrastructure. This study investigates the structural design and functional performance of low rolling resistance asphalt mixtures utilizing reclaimed asphalt pavement (RAP) and warm mix asphalt (WMA) technologies. Ten mixtures with WMA additive—including asphalt concrete (AC) and stone mastic asphalt (SMA) with and without RAP—were evaluated for volumetric and mechanical performance. Laboratory results show that RAP addition did not compromise compaction nor indirect tensile strength ratio (ITSR), and in some cases improved these properties. SMA and SMA RAP-modified mixtures achieved the highest resistance to rutting (as low as 5.0% rut depth), while AC and SMA mixtures both demonstrated low rolling resistance (coefficients of energy loss 0.00604–0.00636). Resistance to low-temperature cracking was strong for all mixtures, with thermal stress restrained specimen test (TSRST) fracture temperatures ranging from −32.8 °C to −36.0 °C. SMA mixtures generally exhibited superior resistance to fatigue (up to 63 με at 1 million cycles). Overall, three asphalt mixtures with different particle size distribution containing 14% RAP and a WMA additive (SMA 8 S_1 R, SMA 8 S_3 R, and AC 11 VS_2 R) demonstrated the best balance of rolling resistance, durability, and circularity, and are recommended for field trials to support climate-neutral and sustainable road infrastructure. These results encourage broader adoption of circular practices in road infrastructure projects, contributing to lower emissions and life-cycle costs. Full article

To address the insufficient adaptability of imported peanut harvesting equipment’s soil-engaging components to the specific soil conditions in Xinjiang, this study conducted Discrete Element Method (DEM)-based calibration of soil mechanical parameters using field soil samples with 1–20% moisture content from typical peanut cultivation areas in southern Xinjiang. Through the EDEM simulation platform, a comprehensive approach integrating the Hertz–Mindlin with the JKR adhesion model and Hertz–Mindlin with the Bonding model was employed to systematically calibrate nine key parameters: coefficient of restitution, static friction coefficient, rolling friction coefficient, JKR surface energy, normal/tangential stiffness per unit area, critical normal/tangential force, and soil bonding disk radius. Adopting static angle of repose (SAOR) and unconfined compressive force (UCF) as dual-response indicators, a hybrid experimental design strategy combining Central Composite Design (CCD), Plackett–Burman (PB) screening, and Box–Behnken Design (BBD) optimization was implemented. Regression models for SAOR and UCS were established, yielding six sets of soil parameters optimized for different moisture conditions through parameter optimization. Field validation demonstrated the following: ≤3.27% error in SAOR, ≤1.46% error in UCF, and ≤5.05% error in drawbar resistance validation for field digging shanks. Experimental results confirm that the model demonstrates strong prediction accuracy for soils in typical peanut harvesting regions of southern Xinjiang, thereby providing key parameter references for the future self-developed, highly adaptive soil-engaging components with drag reduction optimization in peanut harvesters for the Xinjiang region. Full article

The traction behavior in cryogenic solid-lubricated ball bearings (CSLBBs) used in liquid rocket engines (LREs) affects not only the dynamic response of the bearing but also the lubricity and wear characteristics of the solid lubrication coating. The traction coefficient between the ball and raceway depends on factors such as contact material, relative sliding velocity, and contact pressure. However, existing traction curve models for CSLBBs typically consider only one or two of these factors, limiting the accuracy and applicability of theoretical predictions. In this study, a novel traction model for CSLBBs is proposed, which incorporates the combined effects of contact material, relative sliding velocity, and contact pressure. Based on this model, a tribo-dynamic framework is developed to investigate the tribological and dynamic behavior of CSLBBs. The model is validated through both theoretical analysis and experimental data. Results show that the inclusion of solid lubricant effects significantly alters the relative sliding and frictional forces between the rolling elements and the raceway. These changes in turn influence the impact dynamics between the rolling elements and the cage, leading to notable variations in the bearing’s vibrational response. The findings may offer valuable insights for the wear resistance and vibration reduction design of CSLBBs. Full article

To address the technical challenge of high polymer gel viscosity reducers losing viscosity at elevated temperatures and difficulty in controlling fluid loss, a polymer-based nano calcium carbonate composite high-temperature tackifier named GW-VIS was prepared using acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N-vinylpyrrolidone (NVP), and nano calcium carbonate as raw materials through water suspension polymerization. This polymer gel can absorb water well at room temperature and has a small solubility. After a long period of high-temperature treatment, most of it can dissolve in water, increasing the viscosity of the suspension. The structure of the samples was characterized by infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy, and their performance was evaluated. Rheological tests indicated that the 0.5% water suspension had a consistency coefficient (k = 761) significantly higher than the requirement for clay-free drilling fluids (k > 200). In thermal resistance experiments, the material maintained stable viscosity at 180 °C (reduction rate of 0%), and only decreased by 14.8% at 200 °C. Salt tolerance tests found that the viscosity reduction after hot rolling at 200 °C was only 17.31% when the NaCl concentration reached saturation. Field trials in three wells in the Liaohe oilfield verified that the clay-free drilling fluid supported formation operations successfully. The study shows that the polymer gel has the potential to maintain rheological stability at high temperatures by forming a network structure through polymer chain adsorption and entanglement, with a maximum temperature resistance of up to 200 °C, providing an efficient drilling fluid for deep oil and gas well development. It is feasible to select nano calcium carbonate to participate in the research of high-temperature resistant polymer materials. Meanwhile, the combined effect of monomers with large steric hindrance and inorganic materials can enhance the product’s temperature resistance and resistance to NaCl pollution. Full article

Based on rolling contact fatigue life experiments, this study systematically investigates the effect of ultrasonic surface rolling processing (USRP) with a composite diamond-like carbon (DLC) coating on the rolling contact fatigue life of bearings through characterization and analysis. The results show that the USRP-composite DLC coating forms a synergistic mechanism between the coating and the substrate on the surface of specimens: the DLC coating resists surface wear with its high hardness and low friction coefficient, while USRP reduces substrate deformation and crack growth by decreasing surface roughness, increasing substrate hardness, and introducing residual compressive stress. Additionally, USRP enhances the adhesion between the coating and the substrate. The average wear volume of the USRP-composite DLC-coated specimens is 3.73 × 10¹¹ μm³, which is 30.95% lower than that of USRP-treated specimens and 85.38% lower than that of untreated specimens. The average fatigue life of the USRP-composite DLC-coated specimens is 6.55 × 10⁶ cycles, which is 94.94% higher than that of USRP-treated specimens and 208.24% higher than that of untreated specimens. Full article

Electron backscatter diffraction and scanning electron microscopy were performed herein to in situ investigate the influence of texture on the anisotropic deformation mechanism of TC11 forged components. The in situ tensile specimen was cut from the TC11 ring forging, and the tensile force–displacement curve was recorded while the slip lines in the specimen surface detected was traced during the in situ tensile test. The tensile results show that the yield and ultimate tensile strengths decreased in the order of transverse-direction (TD) > rolling-direction (RD) > normal-direction (ND) samples. The anisotropy of the tensile strength was related to the differences in the activated slip systems of the ND, TD, and RD samples. The slip lines results show that in the yielding stage, the ND, TD, and RD samples were dominated by Prismatic <a>, Pyramidal <c + a>, and Pyramidal <a> slips, respectively. In order to further analyze the relationship between the slip system and the yield strength, an anisotropy coefficient was determined to evaluate the differences in resistances for different activated slip systems, providing a good explanation of the variations in the tensile strength anisotropy. The ratios of the critical resolved shear stress (CRSS) of the basal, Prismatic <a>, primary Pyramidal <c + a>, and secondary Pyramidal <c + a> slip systems in the α phase were estimated to be 0.93:1:1.18:1.05 based on the type, number, orientation of slip activations, and Schmid factor. Moreover, the Prismatic <a> slips primarily occurred in the axial and radial (ND and RD) samples with [0001] and [$\stackrel{\mathrm{-}}{1}2\stackrel{\mathrm{-}}{1}2$] textures, whereas the Pyramidal <c + a> slip system was dominant in the TD samples with [11$\stackrel{\mathrm{-}}{2}2$] and [10$\stackrel{\mathrm{-}}{1}$2] textures. Overall, this research demonstrates that the activation of the α-phase slip depends on the grain orientation, SF, and the CRSS, promoting strong strength anisotropy. Full article

In this work, silicon oxide based coatings with embedded graphene nanoplatelets (content ranging from 1.8 wt.% to 7.2 wt.%) have been developed following the sol-gel route, using AISI430 stainless steel as substrate and dip and roll-to-roll as coating techniques. The tribological and corrosion behaviour of these coatings have been evaluated and compared to bare steel. Concerning tribological behaviour, the coefficient of friction and wear print were significantly reduced with increasing the graphene nanoplatelets content. Regarding corrosion, all coatings showed improved corrosion behaviour compared to bare steel. However, higher concentration of nanoplatelets revealed a negative effect on the corrosion resistance, probably due to aggregation. Taking into account these two counteracting effects, as final part of this work, a bilayer coating with different graphene content has been proposed and fabricated. A top layer, with high graphene nanoplatelets concentration has allowed enhanced tribological properties whereas bottom layer, with no graphene nanoplatelets assures corrosion inhibition under harsh environments. Full article

This study introduces a novel gradient dual-phase structure design in brass, achieved through ultrasonic severe surface rolling (USSR) processing, which enables an unconventional asymmetric bilayer structure—comprising a hardened surface layer (>1 mm thick) and a ductile substrate—distinct from conventional hard-soft-hard sandwich configurations in gradient nanostructured materials. Microstructural characterization reveals a gradient dual-phase (α + β′) structure in the hardened layer, progressively transitioning into a homogenized dual-phase structure in the substrate. This unique architecture endows the USSR brass with exceptional mechanical properties, including a yield strength of 582.4 ± 31.0 MPa, ultimate tensile strength of 775.3 ± 33.9 MPa, and retained ductility (9.3 ± 1.0%), demonstrating an outstanding strength-ductility synergy. The USSR brass also demonstrates superior wear resistance with a 42.32% reduction in wear volume and 40.82% decrease in coefficient of friction compared to its as-received counterpart under oil lubrication. This architectural paradigm establishes a robust framework for engineering high-performance brass that simultaneously achieve an exceptional strength-ductility balance and enhanced wear resistance. Full article

This study investigates the impact of a conductive Electric Road System (ERS) rail on vehicle dynamics and stability through numerical simulations. The ERS rail, designed for dynamic charging of electric vehicles, was modeled and tested under various operational conditions, including different vehicle types (SUV and city car) and skid resistance levels (Side-friction coefficient (SFC) ranging from 0.20 to 0.60). Simulations were implemented at multiple speeds (50 to 130 km/h) to assess longitudinal, lateral, vertical accelerations, roll, yaw, pitch angles, and braking performance during lane changes and emergency braking maneuvers. Experimental tests using instrumented vehicles (Peugeot E-2008, Renault Clio 3) were conducted to calibrate the numerical model and validate the simulation results. Key findings reveal that, while the ERS rail slightly increases vertical acceleration and braking distance, it does not compromise overall vehicle stability. Lane-change tests showed minimal trajectory deviations (below 0.20 m) and acceleration levels remained within safety limits. However, discomfort was noted at higher speeds (90–110 km/h) with low skid resistance (SFC = 0.20). This comprehensive evaluation provides valuable insights into the safety and operational performance of ERS rails, emphasizing the importance of optimizing rail skid resistance to ensure practical large-scale deployment and enhanced road safety. Full article

This study presents an advanced method for modeling energy consumption in electric trucks by incorporating regenerative braking probability into conventional modeling equations. Traditional models typically assume uniform regenerative energy recovery, ignoring the variability introduced by differing driving behaviors and braking scenarios. To address this gap, the proposed method explicitly integrates regenerative probability, capturing the dynamic interactions between driving conditions and regenerative braking events. The research involves systematic data preprocessing techniques, including outlier detection and correction, to ensure high data integrity. Moreover, a genetic algorithm is employed to optimize critical features such as aerodynamic drag coefficient, rolling resistance, and regenerative braking efficiency and probability, aiming to minimize discrepancies between predicted and actual energy consumption. The validation results demonstrate that the enhanced model provides a significantly improved accuracy in predicting energy recovery and state-of-charge estimations, supporting more effective and sustainable energy management practices for electric truck operations. Full article

The valve stem made of 20CrMo1V1A has low surface resistance and high susceptibility to corrosion, significantly curtailing its service life. To address these issues, a high-quality ultrasonic rolling (USR) technology was applied to the 20CrMo1V1A stainless steel valve stem to enhance its corrosion resistance and mechanical properties. Subsequently, fatigue and corrosion tests were conducted on the valve stem. The results indicate that USR produces surfaces with a roughness average (Ra) of 0.3 μm and a gradient nanostructure on the valve stem surface. This unique microstructural modification resulted in a 27% improvement in surface hardness and nearly a three-fold grain size reduction. Additionally, the friction coefficient and electrochemical corrosion rate dropped by 47% and 32%, respectively. Therefore, USR was applicable for enhancing multiple properties of valve components as an additional final processing step for achieving high-performance valve stems. Full article

This study aims to develop a theoretical formula to help bus operators easily predict electricity consumption while introducing a certain type of electric bus on a predetermined route. The formula requires vehicle-side information (such as air resistance coefficient, rolling resistance coefficient, vehicle weight, powertrain efficiency, kinetic energy recovery rate, auxiliary equipment electricity consumption, and other vehicle-related data) for construction and road-/operation-side information (such as average driving speed, number of starts and stops, road gradients, and other road-/operation-related data) for prediction. First, herein, as a basic study to construct the theoretical formula, a developed electric bus and its vehicle electricity consumption simulator are employed. We then perform a comparative analysis considering the comparison of loss between the actual operation on public roads and the assumed constant velocity when running on flat roads. Next, we develop theoretical equations for the generalization of velocity and gradient changes and simplified modeling of electricity consumption prediction. Considering the burden of information collection on operators, we categorize it into three stages. In this paper, we first organize the minimum necessary road-/operation-side information (route/operational indicators). Next, we propose a theoretical formula for electricity consumption prediction constructed based on vehicle-side information. Finally, we validate the validity and accuracy of the constructed formula using electric buses and their on-road operational data that we developed earlier. The verification results showed that, after obtaining vehicle-side and road-/operation-side information, the theoretical formula constructed in this study achieved an electricity consumption prediction with an average error of 6% (high-accuracy method). This result demonstrates the practicality of using the theoretical formula to predict the electricity consumption/range of electric buses operating on specific routes. Full article

This paper established an accurate discrete element for ultrasonic vibration-cutter-soil interaction model to study the interaction mechanism between the soil-engaging component and the soil. In order to reduce the interaction between calibration parameters and improve the calibration accuracy, it is proposed that the soil constitutive, contact parameters, and bonding parameters be calibrated by combining the soil repose angle experiment and the soil resistance experiment of ultrasonic vibration cutting. The study adopts the Hertz-Mindlin (no slip) contact model used in EDEM, to explore soil particle interactions. The central composite design is used to achieve systematic investigation. 3-factor 3-level orthogonal design experiment was employed using the coefficient of restitution, the coefficient of static friction, and the coefficient of rolling friction as key test factors and soil’s repose angle as the response index. Based on the Hertz-Mindlin with bonding contact model, Design-Expert 13.0 software was used to design the Plackett-Burman experiment, the steepest ascent, and the Box-Behnken experiment. With the maximum soil cutting resistance in ultrasonic vibration cutting experiment used as the response value, the adhesion parameters were optimized, and the optimal solution combination was obtained as: Normal Stiffness = 4.635 × 10⁶ N/m, Shear Stiffness = 3.401 × 10⁶ N/m, and Bonded Disk Radius = 2.57 mm. The optimal parameter combinations obtained from the calibration experiments were verified in two ways: ultrasonic vibration cutting and non-ultrasonic vibration cutting. The results showed that the errors between the simulation values and the actual values of the two comparative experiments were less than 5%, and the model calibrated for the three parameters can be used to study the drag reduction mechanism of ultrasonic vibration cutting in soil. Full article

Nowadays, Thin Dense Chromium (TDC) coatings are being industrially used in rolling bearings applications due to their claimed advantages such as high hardness, low wear, and good corrosion resistance. However, despite their broad commercial use, very little has been published in the open scientific literature regarding their microstructure, nanomechanical, and tribological properties. In this paper, TDC coatings with a thickness of about 5 µm were deposited by a customized electrochemical process on ASTM 52100 bearing steel substrates. Surface microstructure and chemical composition analysis of the TDC coatings was carried out by scanning electron microscopy and atomic force microscopy. The results revealed a coating with a dense, nodular, and polycrystalline microstructure. Unlike standard electrodeposited “Hard Chromium” coatings, TDC coatings show no presence of micro/nano-cracks, likely contributing to their superior corrosion resistance. The nanomechanical behavior, studied by nanoindentation as a function of penetration depths, exhibits a pronounced size effect near the coating surface that can be linked to the nodular microstructure. A hard surface with hardness H_IT 14.9 ± 0.5 GPa and reduced elastic modulus E_r = 216.8 ± 3.9 GPa was observed. Tribological characterization under the presence of lubricants was performed by two single-contact tribometers using coated and uncoated steel balls against flat steel substrates. An in-house fretting wear rig was used to measure the lubricated friction coefficient in pure sliding conditions, whilst the friction performance in rolling/sliding lubricated conditions was evaluated using a WAM test rig. In pure sliding, TDC/TDC contacts show ~13% lower friction than for steel. Under rolling/sliding conditions with 5% sliding, the traction coefficient of TDC/TDC coating contact was at least 20% lower than that for steel/steel contact. The tribological results obtained in various contact conditions demonstrate the benefits of applying TDC coatings to reduce bearing friction. Full article

Today, reducing vehicle energy consumption is a crucial topic. For electric vehicles, reducing energy consumption is essential to address some of the most critical issues associated with this type of vehicle, such as the limited range of electric powertrains and the long battery recharging times. To lower the environmental impact during the vehicle’s use phase and reduce energy consumption, vehicle mass reduction (lightweighting) is an effective strategy. The objective of this work is to analyze the vehicle parameters that influence lightweighting outcomes on a real driving cycle, representative of the home-to-work travel in northern Italy. In particular, a previous work carried out on standard driving cycles is repeated in order to observe whether it is possible to draw the same conclusions regarding the variability in the lightweighting outcome. This study was conducted using two opposite vehicle models, a compact car and an N1 vehicle, simulated through a well-established vehicle simulation tool for energy consumption estimation. To conduct this analysis, several simulations with variable vehicle mass, and with different vehicle parameters, such as aerodynamics and rolling resistance, were performed to estimate energy consumption across a real-world driving cycle, acquired via GPS on board the vehicle during a home-to-work journey in northern Italy. This study reveals that even for the real driving cycle, as for the WLTC and US06 standards, the parameters that most influence the outcome of the lightening are the rolling resistance, the characteristics of the battery pack, the aerodynamic coefficients, and the efficiency of the transmission. Finally, the standard cycle that best fits with the real one considered in this study is the Artemis Urban Cycle. Full article