Search Results (399)

Binder bonding strength (BBS) is critical to aggregate retention and friction performance in high-friction surface treatment (HFST). Although epoxy resin is traditionally used, asphalt-based binders offer a sustainable alternative; however, their bonding behavior and influence on polishing performance remain insufficiently understood. This study investigated the evolution and optimization of BBS in crumb rubber-modified (CRM) asphalt for rhyolite-based HFSTs. BBS was measured under dry and wet-conditioned states for two CR contents (10% and 15%), two CR types (cryogenic and ambient), two interaction temperatures (170 and 200 °C), and interaction times from 10 to 240 min. HFST performance was assessed using the British pendulum tester (BPT), dynamic friction tester (DFT), and circular track meter (CTM) under accelerated polishing. CR modification reduced dry BBS relative to the base binder but substantially improved moisture resistance: wet conditioning reduced base-binder BBS by 23.8%, versus 5.8–9.8% for CRM binders. BBS evolution was temperature-dependent. At 170 °C, BBS decreased and gradually recovered through 240 min, while binders prepared at 200 °C peaked at 120 min before declining. Type III factorial ANOVA identified CR content as the dominant factor affecting BBS, with interaction temperature, interaction time, and their combined effects also being significant. Despite lower BBS, 15% CRM binders generally retained higher HFST friction performance than 10% binders after accelerated polishing. The moderate relationship between dry BBS and coefficient of friction (COF) loss (R² = 0.68) confirmed that BBS alone could not predict HFST durability, while a stronger BPN-COF loss correlation (R² = 0.79) confirmed consistent rankings across friction test methods. Cryogenic CRM prepared at 200 °C for 120 min provided the best balance among bonding development, rheology, and friction retention. These findings demonstrate that while bonding strength alone does not govern HFST durability across interactions, its evolution with interaction time exerts a significant effect on friction retention within a given interaction condition, highlighting interaction-time optimization as a critical parameter for developing sustainable CRM-based HFSTs. Full article

The sturdy and stable unique polyhedral structure of FeOOH nanoparticles facilitates stress and load transfer, thereby forming a tighter mechanical interlock at the carbon fiber–matrix interface. In this work, the FeOOH nanocrystal layer in situ grown on flexible carbon fiber cloth was rationally designed and fabricated through hydrothermal synthesis. Then, the non-covalent cation–π bond was constructed at the interface between the iron ion-loaded FeOOH nanoparticles and indole-based poly(hexahydrotriazine) (In-PHT). Owing to the collaborative effects of physical anchoring and chemical bonding, the resultant composite exhibited an outstanding tensile strength of 322 MPa, and the friction coefficient significantly decreased by 63% compared with the composites without FeOOH nanoparticles. Moreover, the resultant worn composite showed an excellent self-healing property owing to the introduction of polyethylene wax (PEW) with a low melting point, and the healed friction coefficient remained almost unchanged. Extensive analyses verify that the phase-separated structure and Fe³⁺–π interactions across multiscale interfaces achieve the combined advantages of wear resistance and durability for recyclable carbon fiber-reinforced poly(hexahydrotriazine) composites (PHT-CFRPs). Full article

SBS-modified asphalt is widely used in high-grade pavements for its excellent rutting and fatigue resistance; however, how its friction behavior evolves under submerged conditions with surface distress remains poorly understood. To address this gap, we developed a rubber–asphalt friction tester to characterize quasi-static rubber–asphalt friction under submerged conditions with three typical distresses: pothole, crack, and surface void. Our results show that friction increases with roughness, load, and water temperature, but degrades progressively under cyclic loading. Among the three distresses, surface void offers the most stable friction performance, whereas pothole exhibits the largest friction loss under repeated loading, identifying them as high-priority repair targets. The positive temperature–friction correlation further implies that wet-skid risks are higher at lower temperatures, providing a basis for seasonal maintenance scheduling. Three-dimensional wear analysis reveals distinct mechanisms: pothole causes localized deep-pit wear, while surface void generates uniform roughening, explaining their contrasting durability. These findings directly support distress prioritization, friction-performance evaluation, and maintenance planning for SBS-modified pavements in rainy environments. Full article

Brush seals using compliant bristle packs can reduce turbomachinery leakage more effectively than conventional labyrinth seals, but their coupled structural and flow behavior makes design difficult. Under large pressure loading, bristles can deflect, lose contact with the rotor, and generate clearance, causing the sharp leakage increase known as blow-out. This study develops a model linking nonlinear bristle deflection, rotor–bristle contact loss, and leakage response. The bristle is treated as an inextensible nonlinear elastic member subjected to distributed pressure loading, backing-plate support, and frictional rotor contact. Contact and separated states are solved iteratively using boundary-value and initial-value solvers. Leakage through the bristle pack is calculated using a random bristle-bed formulation, and leakage through generated clearance is evaluated with an orifice-flow model. The model agrees well with published bristle-deflection predictions. Increasing pressure load reduces normal contact force until lift-off occurs, producing clearance and a sharp rise in leakage. Increasing front-plate free height shifted lift-off from pressure ratio ≈4 to ≈2, while clearance flow contributed up to 36.5% after lift-off. Brush-seal blowout is therefore governed by the transition from rotor–bristle contact to separation. Lower back-plate height can delay blow-out, but hysteresis and durability tradeoffs must be considered. Full article

Silver (Ag)-based conductive coatings are widely used in electrical contacts due to their excellent electrical conductivity, low contact resistance, good thermal stability and oxidation resistance, although their susceptibility to sulfidation and environmental corrosion is a concern under certain service conditions. In recent years, significant progress has been achieved in both the manufacture and performance optimization of Ag-based coatings to satisfy the demanding requirements of modern electrical and electronic systems. This review summarizes recent advances in fabrication techniques and processing parameters for Ag-based coatings, including electroplating, electroless deposition, magnetron sputtering, electrospark deposition, thermal spraying, and electrical explosion spraying on metallic substrates, particularly on copper and steel substrates. More attention is given to microstructural design strategies, such as the incorporation and homogeneous dispersion of reinforcement or solid lubricant phases within the Ag matrix, to enhance contact reliability and operational endurance. The performance of Ag-based coatings is analyzed in terms of their physical, chemical and mechanical properties, electrical contact resistance, friction and wear behavior, arc erosion resistance, and environmental durability under different service conditions. Key challenges, including coating degradation under high electrical loads, mechanical wear, and corrosive environments, are highlighted. Future research directions are outlined, focusing on multifunctional coating structures that enhance surface performance and ensure the long-term durability of electrical contacts. Full article

This study explores the development of low-friction, water-based coatings tailored for industrial applications in pharmaceutical glass packaging. The study focuses on scalable deposition strategies to obtain durable low-friction coatings suitable for industrial implementation. To balance mechanical performance and application efficiency, two different application approaches based on a two-component coating (aminosilane primer and lubricant) were investigated. In the first case, the coating is deposited in two steps, while in the second, a single deposition step is used. Characterization through contact-angle measurements and X-ray photoelectron spectroscopy confirmed successful deposition of the primer on the glass surface. Scratch resistance tests revealed an increase in the critical load for fracture initiation from 4.5 N for uncoated glass to 6.5 N for the best-performing coating, indicating improved resistance to surface damage. Friction performance was assessed via tribological tests, which demonstrated that the primer–lubricant coatings achieved the lowest coefficient of friction (approximately 0.2), compared with uncoated glass (stabilizing at approximately 0.3 after an initial value of 0.5) and lubricant-only coatings (approximately 0.4–0.5), confirming the beneficial role of the primer in the coating system. Representative profilometry measurements indicated sub-micrometric coating thicknesses, while UV–Vis measurements confirmed that the coatings preserved the high optical transparency of the glass substrate, with average visible transmittance values above 90%. Furthermore, the successful implementation of the coating using an automated spray system demonstrates its potential for scalable industrial production. These findings support the potential of environmentally sustainable water-based coatings for pharmaceutical glass packaging by combining improved mechanical performance with preserved optical transparency and compatibility with scalable spray deposition. Full article

The development of sustainable, high-performance friction composites is critical for the automotive industry, given the environmental and health concerns associated with conventional brake pad materials such as asbestos and copper. This study investigates the effect of incorporating micro- and nano-sized Al₂O₃, SiC, and carbon nanotubes (CNTs) into a novel, eco-friendly, asbestos-free, and copper-free brake pad formulation. Six composite samples were fabricated via a cold-pressing and hot-molding process: five formulations containing a single, size-controlled micro-/nano-sized reinforcement (Al₂O₃, SiC, and CNTs), and one reference formulation (CBP# Reference) containing an unrefined, commercial-grade combination of Al₂O₃ and SiC in place of the size-controlled additive. All formulations were rigorously characterized for their physical, mechanical, and tribological properties. The nano-Al₂O₃ formulation exhibited the highest density (2.197 g/cm³) and compressive strength (249.7 MPa), while the micro-SiC formulation achieved superior wear resistance, recording the lowest weight loss (0.0053 g) and the highest hardness (90 HV). The nano-SiC formulation offered the most balanced overall performance, combining high hardness (86.2 HV) with the highest average friction force (33.65 N) and the most stable friction-time response among all samples. The CNT-reinforced formulation produced the highest maximum friction force (42.07 N) but showed only moderate improvement in density, hardness, and compressive strength relative to the ceramic-reinforced samples. Compared with the CBP# reference, all five developed formulations exhibited higher hardness and coefficient of friction alongside lower weight loss, confirming their potential as durable, sustainable alternatives for automotive brake friction applications. Full article

Aluminium remains relatively uncommon in civil structures; however, its durability and light-weight nature make it an attractive alternative for vehicular bridges. Recent applications use aluminium bridge decks supported by steel girders. However, galvanic corrosion and thermal incompatibility limit full and optimised behaviour. This research explores the use of Bobbin Tool Friction Stir Welding (BTFSW), which improves the welded aluminium behaviour while significantly improving fatigue detail classification, as it is critical for bridges. This configuration optimises material use, reduces structural weight, and supports Accelerated Bridge Construction (ABC) practices by enabling modular prefabrication and rapid installation. The findings highlight aluminium’s potential as a primary bridge material. Full article

Polyurethane (PU) foams are widely used in footwear midsoles because their cellular structure, density, impact-attenuation capability, and mechanical durability can be tailored through formulation design. In this study, polyester-based PU foams were prepared at different isocyanate indices while keeping the main formulation components constant, and their structure-property relationships were evaluated under midsole-relevant conditions. The samples were characterized by density, tensile and compression testing, standard abrasion wear testing, water absorption, temperature-dependent flexural resistance, Fourier transform infrared (FTIR), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis/derivative thermogravimetry (TGA/DTG), and dry/wet tribometry. FTIR results confirmed the formation of urethane/urea-related linkages and the absence of detectable residual isocyanate groups, whereas DSC indicated broad heat-flow events typical of segmented PU systems, including high-temperature events that should be interpreted together with TGA. TGA/DTG analysis showed similar initial degradation behavior for all formulations; however, the 138-index sample exhibited the highest t_90% value, indicating improved high-temperature mass retention. Tribometric tests revealed an environment-dependent coefficient of friction (COF) response: the 138-index sample exhibited the lowest steady-state COF under dry sliding (μ_ss = 0.211), whereas the 113-index sample showed the lowest COF value under wet sliding conditions (μ_ss = 0.176). Overall, among the three stable formulations investigated, the 113-index formulation exhibited the most balanced multi-property performance. These results suggest that, within the tested formulation range, midsole-relevant PU foam performance is associated with a balance of formulation characteristics rather than simply with increasing the isocyanate index. Full article

Fixed orthodontic appliances promote biofilm-mediated enamel demineralization and release metallic ions, motivating surface strategies that are intrinsic to the device rather than dependent on patient compliance. Chitosan, a biodegradable polycationic biopolymer, has been proposed as a multifunctional coating. This narrative review critically appraises the evidence for chitosan-based coatings on orthodontic appliances across three pillars—antimicrobial performance, ion-release/corrosion mitigation, and clinical translation—with explicit calibration of evidentiary strength. The evidence base is heterogeneous and of markedly uneven quality across the three pillars, and the conclusions below are weighted accordingly. Consistent with its narrative design, the literature was surveyed for critical synthesis rather than exhaustively, without formal eligibility screening, risk-of-bias appraisal, or quantitative pooling. Antimicrobial efficacy is the best-supported pillar, consistent in vitro and now extended by two short in vivo randomized trials, although all endpoints are microbiological surrogates rather than white spot lesion outcomes. Ion-release mitigation remains a plausible but insufficiently demonstrated effect: it is supported only indirectly, through electrochemical corrosion proxies on predominantly implant substrates, and no study quantifies ion-release reduction from a coated appliance. Coating durability under combined enzymatic and mechanical load—and its effect on friction—remains largely uncharacterized. Chitosan coatings are promising but translationally immature; durability, not antimicrobial potency, is the rate-limiting barrier. Defined clinical-endpoint and appliance-level ion-release studies are required. Full article

Surface-dominated failures such as micropitting, scuffing, and rolling contact fatigue remain critical challenges for 20CrMnTi gear steel under high-stress and poor lubrication conditions. Inspired by the composite bionic “checkerboard + dot-matrix dimple” architecture found in natural surfaces, this study aims to develop an optimized biomimetic texture combined with a graphene solid lubricant coating to enhance the tribological performance of 20CrMnTi alloy. Laser surface texturing was employed to fabricate the bionic pattern on 20CrMnTi substrates, followed by deposition of an oxysilane-graphene coating. Reciprocating ball-on-disc tribological tests were conducted under both dry friction and oil-lubricated conditions. The results showed that under dry friction, the optimized textured and coated specimen achieved an average friction coefficient of ~0.18, representing a ~62% reduction compared to the untextured surface (~0.47). Under oil lubrication, the friction coefficient was further reduced to ~0.10–0.11, demonstrating a synergistic effect among the texture, graphene coating, and lubricant. Wear volume decreased by over 70% under dry conditions. The dominant wear mechanism shifted from severe adhesive–abrasive–oxidative wear to mild adhesive and abrasive wear. These findings suggest that the proposed composite bionic texture combined with a graphene coating offers an effective strategy for improving the tribological durability of 20CrMnTi gear. Full article

Microbially Induced Carbonate Precipitation (MICP) and Enzyme-Induced Carbonate Precipitation (EICP) have emerged as promising sustainable alternatives to conventional ground improvement techniques. This paper presents a focused review of Cone Penetration Test (CPT)-based assessment of bio-cemented soils, synthesizing findings from studies spanning laboratory column tests, centrifuge models, and field trials. The review examines how CPT measurements, including tip resistance (q_c), sleeve friction (f_s), and pore pressure response (u), reflect the cementation mechanisms, treatment heterogeneity, soil-type effects, and scale dependency characteristic of MICP and EICP treatments. Key findings indicate that MICP and EICP produce distinct CPT responses: MICP-treated sands generally show stronger cementation-related stiffness signatures and more persistent improvement, whereas EICP-treated soils more commonly exhibit sharper near-surface q_c gains that may be more susceptible to reduction with time. However, long-term field CPT evidence for EICP durability remains limited. CPT interpretation is more uncertain in fine-grained and heterogeneous soils, where low permeability, preferential flow, localized cementation, and penetration-induced disturbance can produce irregular profiles that are difficult to interpret from q_c alone. Fundamental limitations of conventional q_c-based CPT interpretation in bio-cemented ground are identified, including its inability to decouple cementation effects from density, stress state, and environmental variability. Multi-sensor CPT platforms integrating shear-wave velocity probes, acoustic emission monitoring, and geochemical sensors are identified as the most promising pathway toward reliable characterization. Three priority developments are outlined: standardized CPT interpretation protocols with calibrated conversion functions for major soil types, validated multi-sensor platforms deployable under field conditions, and machine-learning tools for spatial treatment quality assessment. This review provides a structured CPT-based synthesis of bio-cemented ground and establishes an interpretive basis for future standardized assessment protocols in geotechnical practice. Full article

Flexible graphite packing rings are widely employed in high-temperature and high-pressure valve sealing systems owing to their intrinsic lubricity and thermal stability, yet their service reliability is often compromised by low mechanical strength, pronounced creep, and unstable tribological behavior under extreme conditions. Here, we present an interface-engineered strategy to enhance the service performance of graphite packing rings via reinforcement with surface-functionalized PAN-based carbon fibers (PAN-CFs; carbonized fibers derived from polyacrylonitrile precursors). Through controlled oxidative modification of carbon fibers combined with high-temperature graphite expansion, a three-dimensional reinforced graphite network with uniform fiber dispersion was constructed. The influence of PAN-based carbon fiber (PAN-CF) content (0–7 wt%) on compressive strength, thermal stability, friction behavior, and long-term durability was systematically evaluated. An optimal performance was achieved at 5 wt% PAN-CF, featuring a ~58% increase in compressive strength, a stable friction coefficient of 0.15–0.18, and enhanced creep resistance, while retaining over 78% of the initial strength after 1000 h of sustained loading. Microstructural and complementary structural analyses suggest that these improvements are associated with interfacial mechanical anchoring, fiber embedding, and load-transfer reinforcement enabled by fiber surface functionalization and the expanded graphite architecture. This work offers a practical material-level approach to improving the long-term reliability of graphite-based sealing components in demanding industrial environments. Full article

Poly(methyl methacrylate) (PMMA) remains a clinically important denture base polymer because of its favorable processability, aesthetics, repairability and long-term prosthodontic use; however, its limited surface hardness and susceptibility to sliding-induced degradation constrain surface durability. This study establishes the structure–chemistry–microstructure–tribology relationships and composition-window predictive behavior of heat-polymerized PMMA reinforced with titanium diboride (TiB₂). PMMA/TiB₂ composites containing 1, 3 and 5 wt.% TiB₂ were prepared and compared with unreinforced PMMA. X-ray diffraction confirmed preservation of the broad amorphous/semi-amorphous PMMA response, while TiB₂-related crystalline features became increasingly detectable with reinforcement content. ATR-FTIR showed retention of the characteristic C–H, ester C=O and C–O/C–O–C vibrations. SEM/EDS demonstrated progressively greater particle-related surface contrast and local Ti/B-associated elemental signatures. Vickers microhardness increased from 20.0 ± 0.7 to 35.0 ± 1.39 HV0.03, corresponding to a 75.0% improvement at 5 wt.% TiB₂. After 1000 m of dry sliding, total mass loss decreased from 32.4 ± 0.5 to 14.9 ± 0.4 mg (54.0% reduction), overall coefficient of friction decreased from 0.58 to 0.35, and representative wear-track width decreased from 481.4 to 101.8 µm. A parsimonious distance–composition interaction model retained strong grouped leave-one-composition-out performance for cumulative wear (R² = 0.9622; RMSE = 1.53 mg), while a linear composition model provided the most robust hardness prediction (R² = 0.9317; RMSE = 1.50 HV0.03). More complex nonlinear models did not improve prediction for held-out compositions. Within the investigated 0–5 wt.% window, 5 wt.% TiB₂ provided the most effective combination of matrix preservation, surface hardening, wear suppression and frictional stabilization. Full article

Forgings currently have long lead times, motivating technology developments that produce parts with forge-like properties and have shorter timelines. Solid-state processes such as additive friction stir deposition (AFSD) offer this potential; however, large-scale deposition of high-temperature materials remains limited by tool durability, thermal management, and process stability. In this study, new polycrystalline cubic boron nitride (PCBN) AFSD tools, integrated with a liquid-cooled tool holder, are developed and evaluated for bulk deposition of 316 L stainless steel. Tool geometry modifications, including increased puck diameter and a drafted feed exit orifice, enabled graphite-free deposition by mitigating feedstock swaging. A minimum deposition rate is identified that maintains stable material flow and avoids excessive actuator forces. Comparing the use of PCBN tools with different shank materials shows that tungsten carbide shanked tools have improved thermal management relative to tools with a nickel-based shank. This improved thermal regulation resulted in more stable deposition, reduced tool wear, and successful multi-layer builds. Additionally, the use of a fully enclosed inert gas environment reduces surface oxidation and interlayer oxide formation. Electron microscopy was used to reveal limited tool-related contamination in the deposition. The contamination observed was dispersed boron nitride particles rather than continuous interfacial layers of tool material as observed in other literature. These results demonstrate that PCBN tooling combined with active cooling can enable stable, bulk AFSD of high-temperature alloys. Full article