Search Results (872)

As global energy demand rises, developing unconventional oil and gas resources has become a strategic priority, with horizontal well technology playing a key role. However, wellbore instability during drilling often leads to irregular geometries, such as enlargement or elliptical deformation, causing issues like increased friction and stuck-pipe incidents. Most studies rely on idealized, regular wellbore models, leaving a gap in understanding cuttings transport in irregular wellbore conditions. To address this limitation, this study employs a coupled CFD-DEM approach to investigate cuttings transport in enlarged wellbores by modeling the two-way interactions between drilling fluid and cuttings. The study analyzes the impact of various factors, including drilling-fluid flow rate, drill pipe rotational speed, rheological parameters, wellbore enlargement ratio, and ellipticity, on wellbore cleaning efficiency. The result indicates that increasing the flow rate in conventional wellbores reduces cuttings volume by 75%, while in wellbores with a 0.7 enlargement ratio, the same flow rate only reduces it by 37.8%, highlighting the limitations of geometric complexity. In conventional wellbores, increasing drill pipe rotation reduces cuttings volume by 42.6%, but in enlarged wellbores, only a 13% reduction is observed, indicating that rotation alone is insufficient in large wellbores. Optimizing drilling fluid rheology, such as by increasing the consistency coefficient from 0.3 to 1.2, reduces cuttings volume by 58.78%, while increasing the flow behavior index from 0.4 to 0.7 results in a 38.17% reduction. Although higher enlargement ratios worsen cuttings deposition, a moderate increase in ellipticity improves annular velocity and enhances transport efficiency. This study offers valuable insights for optimizing drilling parameters in irregular wellbores. Full article

Fiber laser surface texturing was applied to AA1050 aluminum to improve friction and wear performance of PTFE coatings. A Taguchi L16 design varied texture geometry (square, diamond, hexagon, circle), scanned area ratio (20% to 80%), and laser power (40 to 100 W) prior to primer plus PTFE topcoat deposition (25 to 35 µm). Dry reciprocating sliding against a 6 mm 100Cr6 ball was conducted at 20 N, 1 Hz, and 50 m, and wear track geometry was measured by non-contact profilometry. The non-textured reference exhibited an average COF of 0.143, whereas the lowest mean COF was achieved with diamond 60% and 40 W (0.095) and the highest with hexagon 60% and 100 W (0.156); hexagon 20% and 60 W matched the reference. ANOVA indicated scanned area ratio as the dominant contributor to COF (39.72%), followed by geometry (35.07%) and power (25.21%). Profilometry confirmed reduced coating penetration for optimized textures: the reference wear track was approximately 1240 µm wide and 82 µm deep, compared with 930 µm and 34 µm for square 80% and 40 W, 997 µm and 39 µm for diamond 60% and 40 W, and 965 µm and 36 µm for hexagon 40% and 40 W. Full article

The operating conditions of engines in motor vehicles used in conditions of high air dustiness resulting from sandy ground and helicopters using temporary landing sites were analyzed. The impact of mineral dust on accelerated abrasive and erosive wear of components and assemblies of piston and turbine engines was presented. Attention was drawn to the formation of dust deposits on turbine engine components. Possibilities for minimizing abrasive wear through the use of two-stage intake air filtration systems in motor vehicle engines were presented. Three forms of protection for helicopter engines against the intake of dust-laden air and for extending their service life are presented: intake barrier filters (IBF), tube separators (VTS), and particulate separators (IPS) called Engine Air Particle Separation (EAPS). It has been shown that pleating the filter bed significantly increases the filtration area. It has been shown that increasing the suction flow from inertial filters increases separation efficiency and flow resistance. IPS are characterized by a compact design, low external resistance, and no need for periodic maintenance, but it has a lower separation efficiency (86–91%) than VTS and IBF systems (up to 99.3–99.9%). The tested “cyclone-partition filter” filtration system achieves a filtration efficiency of 99.9%, reaching the acceptable pressure drop value four times slower than if it were operating without a cyclone. Two-stage filtration systems ensure high friction durability at the lowest possible energy costs. Full article

Niobium nitride (δ-NbN) coatings were deposited on AISI 316L austenitic steel using reactive DC magnetron sputtering. This study investigates the effects of air oxidation on the surface morphology, topography, roughness, nanohardness, adhesion, and wear resistance of NbN coatings. Their microstructure and thickness were analyzed by scanning electron microscopy (SEM), while surface morphology and roughness were assessed using atomic force microscopy (AFM), and surface topography was assessed by an optical profilometer. Nanohardness was measured using a Berkovich indenter. Adhesion was evaluated via progressive-load scratch testing and Rockwell indentation (VDI 3198 standard). Wear resistance was assessed using the “ball-on-disk” method. Both as-deposited and oxidized NbN coatings improved the mechanical performance of the substrate surface. Air oxidation led to the formation of an orthorhombic Nb₂O₅ surface layer, which increased surface roughness and reduced hardness. However, the brittle oxide also contributed to a lower coefficient of friction. Despite reduced adhesion and increased surface development, the oxidized coating exhibited a significantly lower wear rate than the uncoated steel, though several times higher than that of the non-oxidized NbN. Considering its good wear and corrosion performance, along with the bioactivity confirmed in earlier research, the oxidized NbN coating can be considered a promising candidate for biomedical applications. Full article

AISI 1045 steel often undergoes premature failure under combined corrosive-wear conditions due to its insufficient surface durability. To address this, a hot-dip aluminum (HDA) coating was deposited on the steel substrate. The microstructure, corrosion behavior, and tribological properties of the coating were systematically characterized using scanning electron microscopy (SEM), electrochemical techniques, and tribometry. The results reveal that the coating exhibits a continuous triple-layer structure, consisting of the steel substrate, an intermediate Fe-Al intermetallic compound layer, and an outer aluminum-rich layer. In a 3.5 wt.% NaCl solution, the coating formed a protective Al₂O₃ film, demonstrating clear passivation behavior. It significantly enhanced the substrate’s performance, achieving an approximately 90% reduction in wear rate and a substantial increase in charge transfer resistance. The coated sample showed a lower friction coefficient (0.24) compared to the bare substrate (0.34). Herein, this work demonstrates that a straightforward and industrially viable hot-dip aluminizing process can effectively improve the corrosion and wear resistance of medium-carbon steel. The findings provide a practical surface-hardening strategy for such steels operating in aggressive environments. Full article

This study aimed to examine the influence of sputtering temperature on the bonding structure and properties of non-hydrogenated chromium/nickel co-doped diamond-like carbon (DLC) films synthesized via direct current magnetron sputtering. The Cr/Ni doping levels in the coatings were regulated by varying the shield opening above a chromium-nickel (20/80 at.%) target, resulting in a total metal co-doping concentration ranging from 6.1 to 8.9 at.%. The thickness of the Cr/Ni-DLC films ranged from 160 to 180 nm. Meanwhile, the deposition temperatures of 185 °C and 235 °C were achieved by adjusting the substrate-to-target distance. The XPS and Raman spectroscopy results indicated enhanced graphitization of the Cr/Ni-DLC films with a decrease in the synthesis temperature. XPS results indicated the formation of carbon-oxide and metal-oxide bonds, with no evidence of metal carbide formation in the doped DLC films. Furthermore, both the nanohardness and Young’s modulus demonstrated significant improvement, while the friction coefficient was reduced more than twice as the deposition temperature increased. These findings provide valuable insights into the influence of deposition temperature on Cr/Ni co-doped DLC films, highlighting their potential as advanced functional coatings. Full article

Desert photovoltaic (PV) plants suffer significant efficiency loss due to dust deposition, which is closely linked to near-surface aerodynamic conditions. This study investigates how PV array row spacing influences key aerodynamic parameters. Numerical simulations using the Realizable k-ε turbulence model were performed for multi-row arrays with varying normalized spacings (D/L = 0, 0.5, 1, 1.5, 2). Results show that the friction velocity and aerodynamic roughness length initially increase, then decrease with row number before stabilizing. Their stabilized values exhibit a positive linear correlation with D/L. Empirical formulas were fitted. These findings provide a theoretical basis for optimizing the layout of desert PV plants to mitigate dust-related efficiency losses. Full article

This article presents an in-depth analysis of the application of thermal deposition techniques, in particular thermal spraying, to improve the properties of materials used in agricultural components that work the soil, such as agricultural plows (mainshare and foreshare). Due to the difficult operating conditions, characterized by abrasive wear, mechanical shocks, and chemical exposure from various soils, these surface coatings aim to increase the durability and corrosion resistance of the materials of components intended for working with the soil. The study investigates thermal deposition methods and their effects on the microstructure, hardness, and friction resistance of the obtained layers. The study highlights experiments that reveal significant improvements in mechanical properties, highlighting superior behavior in real conditions of agricultural use. Nevertheless, soil types significantly influence the abrasive wear rate of the components and also their corrosion, which depends on the soil pH. The results confirm that the use of thermal deposition represents a sustainable and effective solution for extending the life of plows, thus reducing maintenance costs and increasing the efficiency of agricultural processes. This research contributes to the optimization of agricultural equipment, providing an innovative approach for adapting plows to the increasing demands of agricultural exploitation. Full article

Mechanical forces, chemical and electrochemical reactions, and environmental variables can all lead to surface degradation of parts. Composite coatings can be applied to these materials to enhance their surface characteristics. Recently, nickel-based composite coatings have gained greater attention because of their remarkable wear resistance. The efficiency, precision, and affordability of this process make it a popular method. In addition, electroplating nickel-based composites offers a more environmentally friendly alternative to traditional dangerous coatings such as hard chrome. Tribological and wear characteristics are highly dependent on several variables, such as particle parameters, deposition energy, fluid dynamics, and bath composition. Mass loss, coefficient of friction, hardness, and roughness are quantitative properties that provide useful information for coating optimization and selection. Under optimized electrodeposition conditions, the Ni-SiC-graphite coatings achieved a 57% reduction in surface roughness (Ra), a 38% increase in microhardness (HV), and a 25% reduction in wear rate (Ws) compared to pure Ni coatings, demonstrating significant improvements in tribological performance. Overall, the incorporation of SiC nanoparticles was found to consistently improve microhardness while graphite or MoS₂ reduces friction. Differences in wear rate among studies appear to result from variations in current density, particle size, or test conditions. Furthermore, researchers run tribology studies and calculate the volume percentage using a variety of techniques, but they fall short in providing a sufficient description of the interface. This work primarily contributes to identifying gaps in tribological research. With this knowledge and a better understanding of electrodeposition parameters, researchers and engineers can improve the lifespan and performance of coatings by tailoring them to specific applications. Full article

This article presents the results of research on a composite filament made of a thermoplastic polymer with the addition of steel powder, used to produce samples using Fused Deposition Modeling (FDM) 3D printing technology. Samples were printed with different print orientations (0° and 90°) to assess the effect of print direction on mechanical and tribological properties. Sample hardness was tested using the Shore D method. Wettability was determined by measuring the contact angle using an optical tensiometer. Tribological wear tests were conducted using the ball-on-disk method. During the tests, the friction coefficient was recorded, and the wear traces were analyzed using an optical microscope. Friction-wear tests were conducted under dry friction conditions and with a physiological saline solution. The obtained results allowed for determining the relationship between print orientation and the mechanical properties and wear resistance of the analyzed composite material. Full article

Carbon nanotubes/2Al2 composites, due to their low density, high specific strength, and high elastic modulus, are representative lightweight structural materials for next-generation aerospace applications. Traditional processing methods are inefficient and have long production cycles, making them unsuitable for the demands of efficient, rapid, and intelligent manufacturing of complex structures. This article proposes the use of metal additive manufacturing technology to solve this problem. For the first time, a 22 mm high carbon nanotube/2Al2 composite was fabricated using additive friction stir deposition, and the changes in surface morphology, microstructure, mechanical properties, and corrosion resistance of the as-deposited composite were systematically studied. After additive manufacturing, the composite exhibited a continuous and defect-free, typical onion-like structure. The as-deposited microstructure consists of uniformly equiaxed grains with an average grain size of 1.23 μm to 1.62 μm and uniformly distributed Al₂Cu particles. The tensile strength and elongation of the as-deposited composite in both the transverse and processing directions are no less than 450 MPa and 15%, respectively, superior to those of the base material. After additive manufacturing, the as-deposited composite exhibited a corrosion current density of 0.19 μA cm⁻² in the transverse direction—only 4% of that of the base material. This enhanced corrosion resistance is attributed to the uniform distribution of precipitated phases achieved through additive manufacturing, which suppresses micro-galvanic corrosion, resulting in minimal, uniform corrosion. This study provides a research foundation and technical support for the additive manufacturing of aluminum-based composites. Full article

This study systematically investigates the composition–structure–property relationships in electrospark-deposited Cr-Ta coatings (10, 25, and 40 at.%) on CrNi₃MoVA steel for wear resistance applications. Microstructural characterization reveals that the Cr-10Ta coating exhibits a dense microstructure with excellent metallurgical bonding to the substrate, consisting of a reinforcing Cr₂Ta Laves phase and Fe-Cr solid solution. In contrast, higher Ta content (25–40 at.%) results in the formation of brittle Ta oxides and the development of cracks. Mechanical testing indicates that the Cr-10Ta coating exhibits superior hardness (6.35 GPa) and elastic–plastic deformation resistance (H/E = 0.041, H³/E² = 0.0109), outperforming both higher-Ta coatings and the substrate material. Corresponding tribological assessments reveal that the Cr-10Ta coating achieves the lowest friction coefficient (~0.4) along with a minimal wear rate, which can be attributed to its synergistic combination of fine-grained structure, high dislocation density, and Laves phase reinforcement. The findings underscore that precise control over Ta content serves as an effective strategy for optimizing the wear resistance of Cr-Ta coatings through microstructural engineering. Full article

The aim of the study was to develop and evaluate the properties of MED610 material coated with a thin titanium (Ti) layer deposited by physical vapour deposition (PVD) for medical applications. The coating was designed to improve biocompatibility and selected functional characteristics, such as the material’s tribological resistance. Two groups of samples—unpolished and polished—were prepared to enable an assessment of the influence of surface topography on functional performance. A titanium layer was applied to both groups, followed by an analysis of the surface geometric structure, contact angle, and tribological properties in an artificial saliva environment with neutral pH, simulating oral cavity conditions. The results of these investigations allowed for a comprehensive assessment of the influence of surface topography and the presence of a Ti coating on the functional properties of MED610, a material approved for contact with soft tissues. The findings confirmed that the application of a titanium coating favourably affected the structure and durability of the material—the coating reduced surface roughness by 20–45% and exhibited good adhesion to the substrate. The polishing and coating processes significantly altered the tribological properties: they increased the coefficient of friction by approximately 31% while simultaneously reducing volumetric wear by up to 75% for uncoated samples and by 44% for samples with a Ti coating. Full article

Bamboo rhizomes, the belowground stems of bamboo, play a crucial role in ecosystem functioning and material cycling; however, they have long been regarded as forest residues, receiving limited research attention. This review systematically summarizes current knowledge on the anatomical structure, chemical composition, physical and mechanical properties, and applications of bamboo rhizomes, thereby highlighting their potential for high–value utilization. Based on existing studies, a three-tier framework of rhizome characteristics is proposed: (1) age–driven changes, including lignin deposition, cellulose distribution, and cell wall development; (2) interspecific differences in chemical and anatomical traits, which modulate mechanical performance and durability; and (3) functional differentiation between rhizomes and culms, reflecting adaptation to belowground environments. Within this framework, the structural, chemical, and physicomechanical properties of bamboo rhizomes exhibit tight coupling, thus providing theoretical guidance for species selection, harvesting strategies, and processing. Moreover, bamboo rhizomes have been applied in handicrafts, agricultural organic fertilizers, and composite materials, and they show emerging potential in high-friction functional materials and bio–based composites. Nevertheless, systematic investigations remain limited, particularly regarding structure–property relationships, interspecific performance variability, and optimized processing technologies. Therefore, future research should focus on multidimensional characterization, elucidation of structure–property coupling mechanisms, and development of high–value processing techniques, in order to promote the transformation of bamboo rhizomes into value–added products, thereby supporting green bamboo industry development and the “Bamboo Instead of Plastic” initiative. Full article

When an orthokeratology (ortho-k) lens contacts the ocular surface, tear film components such as lipids and proteins rapidly adsorb onto the lens, which may increase friction and contribute to discomfort if not properly removed. Polysaccharides have been reported to reduce protein deposition and improve lubrication, prompting the investigation of alginate acid and lambda-carrageenan in modulating the tribological properties of ortho-k lenses. An in vitro tribological property analysis of ortho-k lenses and protein adsorption and desorption analyses were carried out to investigate the lubricating ability of alginate acid and carrageenan. Zeta potential and turbidity analyses were further conducted to examine potential interactions between polysaccharides and tear film proteins. Tear film proteins significantly increased the friction coefficient of the ortho-k lens, whereas the addition of alginate acid and carrageenan markedly reduced friction. Electrostatic interaction and polysaccharide–protein complex formation were identified as possible mechanisms underlying these effects. These results demonstrate that alginate acid and carrageenan can modify the tribological and interfacial behavior of ortho-k lenses in protein-rich environments, suggesting their potential application in reducing friction-related complications in ortho-k lens wearers. Full article