Search Results (5,134)

For projects such as tailings ponds, slopes, and foundations, loose materials such as rock, slag, and sand, which are composed of particles, often have low cohesion and rely mainly on friction to maintain stability. The shear strength parameters, namely, the internal friction angle and cohesion, are the core parameters that describe the mechanical properties of materials and are directly related to the engineering stability of the above projects. The shear strength properties of loose media are related to the geometric morphological characteristics of particles. Particles with high irregularity will increase the bite and friction of the contact interface between particles, thereby affecting the overall peak shear strength of the material. This study takes sand as the research object. Based on the Mask R-CNN algorithm in deep learning, a sand particle image dataset consisting of single, contact, and sand surface particles is established. An image segmentation model that can identify particles on the surface of the sand layer and obtain the corresponding particle mask is trained; a Python 3.11.4 program is written to automatically calculate seven characteristic parameters of particle morphological characteristics parameters, including the Feret major diameter, the particle Feret minor diameter, the particle aspect ratio, the particle roundness, the comprehensive shape coefficient, the roughness, and the convexity through the particle mask. This method can obtain the overall morphological characteristics of sand particles in real time and is a particle processing method that is a prerequisite for the subsequent rapid prediction of the strength properties of granular materials. Full article

Rocky shores are characterized by rough, multi-scale bathymetric variations that result in enhanced wave energy dissipation by bottom friction compared to sandy beaches. Realistic SWAN simulations of surface gravity waves across the rocky shores of Monterey (CA, USA) are conducted, and model results are compared to 20 inner-shelf observational sites spanning 34–5 m water depth. The wave field was highly variable during the study, including alternately low energy waves dominated by southern swell and higher energy local waves aligned with strong north-westerly winds. Including a modified bottom friction parameterization is required for the model to reproduce bulk wave statistics with high skill across the entire inner shelf. The SWAN simulation with the default bottom friction parameterization overestimates significant wave height relative to observations because the friction factor $f_e$ parameterization has a maximum value of 0.3. Additional simulations included two empirical formulations relating $f_e$ to the normalized wave excursion $A_b/k_N$ in the large roughness regime $A_b/k_N<1$. Both simulations incorporate a higher $f_e$ that is required to model strong bottom friction dissipation over rocky seabeds. The higher friction factors, with 80% falling within the range 0.43 to 5.38, are associated with variability in the normalized orbital excursion within $0.1<A_b/k_N<1$. This range corresponds to a large bottom roughness length scale, $k_N=0.5$ m, characteristic of rocky shore environments. Full article

This work focuses on the study of tribo-mechanical and microstructural properties of TiCN/ZrCN multilayer coatings with a modulation period of 12 nm, obtained by a conventional cathodic arc technique. The coatings were deposited at a temperature of 320 °C using nitrogen and methane reactive gases (N₂/CH₄) mixture in three different proportions. Surface morphology, composition, hardness, adhesion, friction and wear behavior were studied using atomic force microscopy, scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, nanoindentation, and scratch and wear tests. The analysis of the coating composition revealed a strict dependence of the carbon content on the CH₄ flow rate. It was found that the coatings with a carbon content of 14.6 at.% and 15.9 at.% consist of crystalline TiZr (C,N) with the presence of amorphous carbon. All the studied TiCN/ZrCN coatings showed improved tribo-mechanical properties compared to TiN/ZrN multilayers obtained under the same deposition conditions. The highest hardness of 40 GPa was obtained for the coating deposited at a N₂/CH₄ flow rate of 370/100 sccm. The lowest wear rate of 3.16 × 10⁻⁶ mm³/N·m under dry sliding conditions was observed in the multilayer coatings deposited at the N₂/CH₄ flow rates of 330/140 sccm. Full article

Background/Objectives: Staphylococcus epidermidis (RP62A) and Staphylococcus aureus (UAMS-1) are clinically relevant pathogens frequently implicated in implant-associated infections due to their ability to form biofilms. RP62A is typically linked to persistent, chronic, low-grade infections, whereas UAMS-1 is associated with acute, invasive disease. Both strains serve as representative models for chronic and acute periprosthetic joint infections (PJIs). The objective of this study was to examine and compare in vitro biofilm formation by RP62A and UAMS-1 on orthopaedic materials/disc surfaces of defined composition. Methods: In vitro biofilm formation assays were performed using orthopaedic disc surfaces composed of cobalt–chromium alloy (CoCr), titanium alloy (Ti), and polyethylene (PE) after 72 h of incubation. Biofilm biomass was quantified using crystal violet staining, with absorbance measured at OD₅₇₀. A polystyrene (PS) surface served as a control. Additionally, retrieved orthopaedic explant components were used as substrates for in vitro biofilm assays, in which RP62A was incubated for 72 h on the explanted surfaces. Supporting assays on glass slides were conducted to examine strain-specific biofilm-related architecture. Results: In vitro biofilm mass quantification assays showed strong biofilm formation by RP62A across all tested surfaces, with the highest absorbance on CoCr (OD₅₇₀ = 5.80 ± 0.19). Notably, biofilm formation on CoCr was 76% higher compared to PS (p < 0.0001). No significant differences were observed among all three surface discs (p > 0.1). Biofilm formation was highest on PE for UAMS-1 (OD₅₇₀ = 1.29 ± 0.09) and was significantly greater than on Ti (178%, p < 0.001) and CoCr (196%, p < 0.0001). In the in vitro assays performed on retrieved explant components, RP62A showed pronounced biofilm accumulation on polyethylene tibial inserts, particularly in regions of mechanical wear and friction. Supporting assays on glass slides were performed to examine strain-specific surface microstructural, revealing dense network-like structures for RP62A and thinner, discontinuous layers for UAMS-1. Conclusions: RP62A formed dense biofilms in vitro on multiple orthopaedic implant materials and retrieved explant components, consistent with its association with chronic periprosthetic joint infections. Increased biofilm accumulation was observed on mechanically worn polyethylene surfaces. In contrast, UAMS-1 showed lower biofilm formation on metallic disc surfaces, indicating strain- and material-dependent differences. These findings highlight the relevance of implant material selection and surface integrity for strategies targeting biofilm-associated implant infections. Full article

Compression textiles have been widely applied in medical, sportswear, and daily usage, with single-jersey structures produced by circular knitting dominating the market due to their thinness and light weight. However, the presence of seams may compromise compression performance and wearer comfort. This study investigates the effects of yarn type, number of yarns, and loop length on pressure, stretchability, and thermal comfort of seamless punch-lace knitted fabrics and explores their potential application in compression textiles. The results show that yarn number is the dominant factor influencing fabric stiffness, stretchability, and pressure. Fabrics with increased yarn content demonstrate higher maximum load and compression pressure. Smaller loop lengths and additional reinforcing yarns improve dimensional stability and resistance to extension. Air permeability decreases with increasing yarn number due to increased fabric thickness and reduced porosity, while thermal conductivity increases and is positively associated with ventilation resistance, indicating a trade-off between heat transfer and breathability. Surface friction and roughness are significantly affected by yarn number, yarn type, and loop length, whereas water vapour permeability shows no significant relationship with the investigated variables. Overall, seamless punch-lace knitted fabrics demonstrate strong potential for compression applications, although careful design is required to balance breathability and thermal comfort. Full article

In this study, a novel reverse friction stir processing (FSP) was adopted to investigate the effects of multi-pass reverse FSP on the microstructure, microhardness, bonding strength, and tribological properties of NiCrBSi coatings deposited on 6061-T6 aluminum alloy via atmospheric plasma spraying (APS). The results demonstrate that reverse FSP effectively eliminates pores, unmelted particles, and interlamellar defects in the as-sprayed coating without causing mechanical damage to the coating surface inside the processed zone. With an increase in processing passes, a micron-scale diffusion zone forms at the coating/substrate interface, transforming the bonding mechanism from mechanical interlocking to metallurgical bonding. Mechanical property tests reveal that compared with the as-sprayed state, the microhardness and tensile bonding strength of the three-pass FSPed coating are increased by 26.0% and 171.1%, respectively, indicating significantly improved mechanical properties. Tribological tests demonstrate that the main wear mechanism of the as-sprayed coating is severe abrasive wear. After multi-pass FSP, the wear mechanism of the coating transforms into a mixed wear mechanism. Among them, the FSP3 coating exhibits mild abrasive wear accompanied by local adhesive wear. Full article

During high-speed flight, intense friction on the aircraft surface always occurs due to atmospheric fluid medium. The resultant high frictional drag will trigger a significant aerothermal effect, and thus raise the surface temperature sharply to 1000–3000 °C. This extreme heat not only remarkably reduces the aerodynamic efficiency but probably also causes thermal failure of the structural integrity and damage of internal components. Therefore, robust heat-resistant materials are the preferred choice for designing high-speed aircraft due to their benign tolerance to high temperature, oxidation and ablation as well as large strength and durability. This work systematically unveils the generation mechanism of frictional drag in high-speed flight and introduces the characteristics and applications of typical thermal insulation materials (TIMs). After that, the recent progress in a thermally protected material system including metal-based alloys and metal-doped compound materials, ultra-high-temperature ceramics (UHTCs), carbon (C)/carbon (C) and C/SiC composites, ceramic matrix composites (CMCs), UHTCs-modified C/C and C/SiC composites is conducted. Finally, the current technical bottlenecks are discussed, simultaneously proposing the development direction of novel TIMs for the potential applications for high-speed aircrafts. Full article

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

This study evaluates the tribological properties of lean medium manganese advanced high-strength steel (AHSS) subjected to five different heat treatment processes. The tests were conducted under dry reciprocating conditions using the ball-on-flat method, with a G40 steel ball, a 10 N load, and 1000 cycles at room temperature. Friction behavior, wear resistance, nanoindentation hardness, surface roughness, and microstructural changes were examined. The results showed that heat treatment significantly influenced the microstructure and hardness of the samples. The Mn-Q sample, with fresh martensite, achieved the highest hardness (483 HV5), while the Mn-Q&P 500 °C sample had the lowest (336 HV5), with a 30% reduction due to tempering. The Mn-HR 500 °C sample showed the highest surface roughness (Sa = 1.876 μm) due to microstructural heterogeneity. Despite similar coefficients of friction across all samples (0.55–0.57), the Mn-Q&P 500 °C sample exhibited the best wear resistance, 18% higher than the Mn-HR 500 °C variant. Wear mechanisms were identified as a combination of abrasion and oxidation, where the latter slightly reduced the coefficient of friction (COF) but increased surface degradation. These findings highlight the potential of lean medium Mn AHSS for tribological applications, offering a favorable balance of wear resistance and frictional stability. Full article

Cr-based composite coatings with superior wear resistance are in growing demand for high-performance applications in the automotive, aerospace, and general manufacturing sectors. In this study, an Al10Cu alloy produced via powder metallurgy was coated with a chromium/nanodiamond (Cr/ND) composite layer using an electrodeposition process to enhance its tribological performance. The coatings were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The resulting Cr/ND layer exhibited a uniform thickness of 73.5–76.2 μm and markedly improved surface hardness (809.4 HV), representing a 15-fold increase over the uncoated alloy (53.6 HV). Pin-on-disk tribological testing under dry sliding conditions showed complete elimination of detectable mass loss (0.00 mg vs. 0.55 mg for uncoated) within the measurement system resolution, indicating excellent resistance to both abrasive and adhesive wear. XRD analysis revealed the formation of a hexagonal close-packed Cr₂H phase with incorporated nanodiamond particles. To capture and predict the temporal evolution of the friction coefficient, a customized dual-layer long short-term memory neural network—optimized with a look-back window of 3 timesteps and ReLU-activated dense layers—was implemented. The model achieved superior predictive performance on the coated system, with validation and test R² values of 0.9973 and 0.9965, respectively, demonstrating enhanced modeling accuracy for surface-engineered materials. These findings demonstrate a significant advancement in wear protection for aluminum alloys and introduce a robust data-driven approach for real-time friction prediction in engineered surfaces. Full article

The present study investigates the effect of low-temperature ion plasma nitriding on the phase composition, microstructure, tribological behavior, and corrosion resistance of 30Cr13 martensitic stainless steel. Plasma nitriding was carried out at temperatures of 400, 450, and 480 °C in a dissociated ammonia atmosphere using a pulsed DC glow discharge. The phase composition and structural evolution of the surface layer were analyzed by X-ray diffraction, while the morphology and thickness of the modified zone were examined using scanning electron microscopy. The tribological properties were evaluated under dry sliding conditions using a ball-on-disk configuration, and corrosion resistance was assessed by potentiodynamic polarization in a 3.5 wt.% NaCl solution. It was established that low-temperature ion plasma nitriding leads to the formation of nitrogen supersaturated martensite (α′N) and the nitride phase ε-(Fe_2–3)N, with their relative fraction governed by the treatment temperature. An increase in the nitriding temperature resulted in a rise in the surface’s microhardness up to 1100–1150 HV and a change in the thickness of the modified layer, reflecting nitrogen redistribution between the solid solution and nitride constituents. The predominance of the α′N phase at 400–450 °C ensured the most stable tribological behavior and reduced corrosion rate, whereas an increased fraction of ε-(Fe_2–3)N at 480 °C led to a higher microhardness and a greater abrasive wear component while maintaining satisfactory corrosion resistance. The obtained results confirm the decisive role of phase composition in the nitrided layer in determining the tribological and corrosion performance of 30Cr13 steel, and may be used for optimizing the surface hardening parameters of components operating under combined friction and corrosive environments. Full article

Friction braking is the most spread braking system in vehicles, where the morphologies of the disc and the braking pads are essential to ensure that friction reduces rotation speed efficiently. However, modern braking systems are submitted to a complex balance between functionalities: braking ability, resistance to wear, and limited noise emission, i.e., squealing. This article studies the evolution of the morphology of a braking pad in a pin-on-disc configuration to further understand its influence over surface functionalities. Data collected from a pin-on-disc tribometer, and topographies are coupled to perform a multiscale and multiphysics analysis of the braking pad surface. Relevancy of roughness parameters regarding braking ability, surface wear, pad temperature and noise emission is evaluated with a bootstrap-based relevancy analysis. Relevant scales of the pad morphological structures are identified for surface wear (446 µm), braking ability (19.5 µm), pad temperature (2717 and 446 µm) and squealing frequency (1720 and 15.7 µm). Correlations between test bench data and roughness parameters highlighted the role of wear plateaus on the braking pad surface. These plateaus are formed by the damaged surface peaks during braking or by compaction of the third body trapped across the braking pad surface. Full article

Future contributions to sea level rise from the Antarctic Ice Sheet due to climate change remain one of the largest uncertainties for future sea level. Improving predictions of ice mass loss is a major goal of numerical ice sheet models, but a major difficulty is that ice sheet models assume an empirical fit to modern-day observed speeds to infer sliding parameters. While this results in accurate modern-day comparisons, predictions for future or past climates that have substantially different conditions will be inaccurate if the empirical sliding law used is not appropriate. To help constrain which basal physics is most appropriate and therefore which basal parameterizations should be used in ice sheet models, here, we pursue an understanding of which physical mechanisms are most likely to explain the spatial variability in flowline speeds throughout the Antarctic Ice Sheet. Specifically, we compare observed flowline surface speeds with predictions of speeds from internal ice deformation and Weertman sliding using a conservative range of physical parameters. Despite large uncertainties, we find a number of flowlines where the predictions can be distinguished from each other and one can infer that one of the two mechanisms, or a third mechanism, Coulomb frictional failure, may likely be principally responsible. Geographic patterns in the dominant mechanism are observed. Weertman sliding appears dominant in several flowline clusters in East Antarctica, and there are regional consistencies in the estimated nearness to flotation at locations of inferred initiation of Coulomb failure. Weertman sliding at faster rates is also observed within regions of inferred Coulomb failure, consistent with theoretical expectations. The key finding that the dominant deformation mechanism varies along and between Antarctic flowlines may complicate how ice sheet models need to be parameterized if accurate predictions of future ice loss and sea level rise are to be accurate. Full article

The meshing contact performance of spiral bevel gears is critical for transmission accuracy and service life but is inevitably influenced by manufacturing deviations. Existing tooth contact analysis (TCA) and lubrication-related studies for spiral bevel gears are mostly based on ideal theoretical tooth surfaces, failing to reflect the actual meshing state of as-machined gears with inherent machining deviations, and have poor robustness for complex deviated spatial surfaces. To accurately assess the actual meshing state, this paper proposes a novel contact performance analysis method based on a high-precision digital tooth surface reconstructed from one-dimensional probe measurement data. Unlike traditional TCA methods that rely on complex principal curvature calculations, this approach eliminates the mounting distance parameter by simplifying the meshing coordinate system, and employs a variable-radius cylindrical cutting method combined with a binary search algorithm to determine the instantaneous contact ellipse, effectively reducing computational complexity and improving solution robustness for deviated tooth surfaces. Experimental validation demonstrates that the digital tooth surface achieves a reconstruction accuracy of 2.6 × 10⁻⁵ mm. Furthermore, the method accurately predicts the contact pattern location and transmission error, with a discrepancy of only 4.7% compared to theoretical design values, which is highly consistent with the no-load rolling test results. This study confirms that the proposed method effectively reflects the actual meshing condition of machined gears, providing a practical theoretical foundation for the high-quality manufacturing and control of spiral bevel gears. Meanwhile, the high-fidelity contact characteristics of as-machined tooth surfaces output by this method can provide reliable input boundaries for thermoelastohydrodynamic lubrication (TEHL) simulation, friction loss prediction and anti-scuffing design of spiral bevel gears considering machining deviations. Full article

Friction stir welding (FSW) is a key technology for manufacturing T-shaped thin-walled structures and avoiding fusion welding defects. However, the quantitative relationship between its process parameters and the microstructure properties of the joint remains unclear. To address this, this study established regression models via response surface methodology (RSM) relating rotational speed (w), welding speed (v), and plunge depth (h) to the mechanical properties of T-joints. The optimal process parameters (400 rpm, 60 mm/min, 0.21 mm) were determined, under which the ultimate tensile strength (UTS) and weld nugget hardness (WNH) of the joint reached 74.1% (377 MPa) and 94.4% (153 Hv) of the base materials (BM) respectively, with v showing the most significant influence on joint mechanical properties. Microstructural observations revealed that from the BM to the stirring zone (SZ), the grains underwent a continuous evolution from coarsening, partial recrystallization to complete dynamic recrystallization (DRX). In the SZ, due to severe plastic deformation and high heat input, the continuous dynamic recrystallization (CDRX) was the dominant mechanism, and the grain was significantly refined. The heat input in the thermomechanical affected zone (TMAZ) is relatively low, mainly geometric dynamic recrystallization (GDRX). DRX-driven grain refinement was the primary strengthening factor in the joint, with hardness closely related to grain size. However, thermal cycling induced softening in the heat-affected zone (HAZ) and promoted the precipitation of brittle compounds such as Al₃Mg₂ and MgZn₂, which caused crack initiation exhibiting intergranular brittle fracture. Subsequently, under stress drive, it extends to SZ, mainly characterized by ductile fracture. Full article