This study investigates the dry sliding tribological behavior of as-received Armox 500T steel using a pin-on-disc tribometer across three rotational speeds (350, 400, and 450 RPM) and four applied loads (20, 30, 90, and 120 N). Microstructural characterization confirmed a fine lath martensitic structure with retained austenite, yielding an average Vickers microhardness of 528.64 HV. Volume loss, specific wear rate, coefficient of friction, and surface roughness were evaluated as tribological responses. Rotational speed drove a mild-to-severe wear regime transition and dominated specific wear rate (similar to 88% ANOVA contribution), while applied load exclusively governed coefficient of friction (COF) (similar to 99.8%). An inverse relationship between surface roughness and specific wear rate at higher speeds was attributed to thermally induced surface flattening and mechanically mixed layer formation. The Time & times; Applied Load interaction was the largest contributor to volume loss, confirming the time-dependent nature of material removal. These findings provide practical guidance for avoiding critical speed-load combinations in sliding applications.
This study investigates the tribological performance of 65 Mn steel plow surfaces modified by combined ultrasonic shot peening and snake-inspired microtexturing under water lubrication. Ultrasonic shot peening was first applied to enhance surface hardness, followed by laser texturing to fabricate microstructures with different texture densities (18%, 27%, and 36%). Surface characteristics, including hardness, roughness, and morphology, were systematically characterized. Reciprocating friction and wear tests were conducted, and the lubrication mechanism was analyzed using numerical simulations in Ansys Fluent. Results show that shot peening significantly improves wear resistance despite increasing surface roughness, while microtexturing alone provides limited improvement. The combined treatment exhibits the best tribological performance at 27% texture density, reducing friction coefficient and wear rate by 25.58% and 69.14%, respectively. This improvement is attributed to enhanced hydrodynamic lubrication and load-carrying capacity induced by the microtextures, providing guidance for biomimetic wear-resistant surface design of agricultural tools under water lubrication.
This study systematically examines the wear performance and machining efficiency of vacuum-brazed diamond-coated milling tools under optimized processing conditions. Two widely used metamorphic-origin marbles, Mu & gbreve;la White (MW) and U & scedil;ak White (UW), were selected as workpieces. The experimental methodology involved milling operations on a CNC machining center, where spindle speed (6000-12000 rpm), feed rate (1500-3000 mm/min), and a constant depth of cut (1 mm) were selected as the key input process parameters. Machining performance was evaluated through surface roughness (Ra), cutting force (Fr), specific energy consumption (SE), and material removal rate (MRR), while wear mechanisms were characterized using Scanning Electron Microscopy (SEM) and digital microscopy on machined areas of 1 to 7 m2. Optimization analysis determined the ideal processing conditions to be 6000 rpm and 2281 mm/min for MW, and 12000 rpm and 3000 mm/min for UW, which were subsequently confirmed by validation experiments. Comparative findings indicated that the lower mechanical strength of MW marble resulted in greater material removal but increased tool wear (54%) compared to UW (47%). These results highlight the decisive influence of microstructural characteristics and operating parameters on tool wear, thereby contributing to the industry by offering guidelines for extending tool lifecycle and enhancing energy efficiency.
Ambient exposure to water vapour and oxygen undermines the long-term lubricity of magnetron-sputtered molybdenum disulphide (MoS2) coatings, yet the individual and synergistic contributions of the two species remain poorly quantified. Here we decouple their effects by ageing 1 & micro;m PVD-MoS2 films for 500 h in six precisely controlled gas/humidity atmospheres (dry, 25% RH and 50% RH; N-2 or air) followed by micro-tribological testing in dry N-2. Complementary "unaged" samples were slid directly in identical environments to probe instantaneous reactivity. Coefficient-of-friction data, Raman spectroscopy, SEM-EDS mapping and cross-sectional TEM reveal three key findings: (i) humidity alone raises steady-state friction by up to 2.5-fold, whereas dry oxygen has little effect; (ii) concurrent H2O and O-2 during storage triggers sub-surface penetration of O-species, formation of MoO2/MoO3 within wear scars and inhibition of basal-plane realignment, yielding a persistent friction penalty (& micro; approximate to 0.12) independent of run-in; (iii) ageing in dry or humid N-2 preserves lamellar re-orientation and maintains low friction (& micro; approximate to 0.05) after only 50 cycles. A mechanistic model is proposed in which adsorbed water lowers the activation barrier for oxygen insertion at defect and edge sites, corroborated by a 2-3 cm(-1) blue shift of the E-2(g)1 Raman band. By isolating the water-assisted oxidation pathway at ambient temperature, this study provides the first quantitative guideline for MoS2 component storage: moisture-free inert gas environments effectively arrest chemical degradation, whereas even moderate humidity in air accelerates tribo-oxidative damage. The insights inform design tools for precision-mechanical assemblies where pre-deployment shelf life is critical.
Leaf low adhesion mechanisms are complex and the interplay between the influencing parameters is not well understood. In this paper new approaches have been utilised to assess the role of leaf layer moisture versus humidity on low adhesion. Using controlled testing in a climate chamber as well as laboratory and field testing, leaf layer moisture relationships were explored. Moisture was found to be the most important characteristic when compared with environmental changes (such as humidity) and the relationship between moisture and traction is qualified.
Slips and falls often result in non-fatal injuries due to reduced friction between footwear and flooring. A combined computational framework utilizing finite element analysis (FEA), computational fluid dynamics (CFD) and, alongside experimental tribological testing, to evaluate the performance of footwear outsoles was implemented. Twelve custom-designed outsoles were tested, where fluid pressure and mass flow rates were measured through CFD, and FEA was employed to analyze outsole deformation under normal loading conditions, incorporating the material properties of hyperelastic Neo-Hookean. A custom slip testing device assessed dry and wet friction. The results revealed that the square tread pattern exhibited the highest mass flow rates and decreased fluid pressures, followed by the vertical pattern. Increasing tread gaps correlated strongly (R2 = 0.92) with high wet friction. Horizontal patterns showed lower mass flow rates and higher fluid pressure. This model provides insights for improving outsole design and shoe performance to enhance safety.
Interfacial degradation during sliding electrical contact critically influences the signal integrity of brush-ring systems, yet its role in waveform distortion remains poorly understood. In this study, a synchronized tribological-electrical test platform was developed to directly correlate interfacial evolution with time-domain signal responses in copper-graphite brush-ring contacts. Progressive sliding over 80,000 cycles led to three distinct friction stages dominated sequentially by ploughing, adhesive, and abrasive-oxidative wear. Concurrently, the transmitted signal evolved from a near-sinusoidal waveform to a severely distorted triangular profile. Signal distortion was found to be weakly related to friction coefficient variations but strongly governed by the formation and evolution of friction-induced interfacial films. Graphite-rich and copper-oxide-containing films increased surface roughness and contact resistance from 0.23 to 0.68 m Omega, resulting in a rise in distortion ratio from 11% to 194% and an associated phase shift. These findings demonstrate that signal waveform integrity is primarily controlled by interfacial film evolution, providing mechanistic insight for tribological interface design in sliding electrical contacts.
Evaluating scuffing resistance of new materials for reciprocating engine components can be achieved using dynamic pressure sliding. Surface species responsible for low friction behaviour observed prior to scuffing initiation in a Grade 250 flake graphite cast iron under dynamic pressure (8-62 MPa) sliding conditions experienced by a heavy-duty diesel engine top compression ring were evaluated. Lubricated reciprocating tribometer tests were performed in a polyalphaolefin base oil with temperature incremented to 250 degrees C to induce scuffing. Friction and contact potential measurements revealed a transition from mixed to boundary lubrication, followed by a period of low friction preceding scuffing initiation. Post-test surface analysis was conducted using a range of advanced microscopy techniques (Raman, FIB, STEM, EDX and EELS) and suggested a complex series of tribochemical reactions are responsible for formation and removal of phases such as siloxanes and ferrous oxides that lead to the initiation of scuffing.
Aluminium-based composites are quite interesting materials for automobile components design due to their promising characteristics, including strength-to-weight ratio, ease of fabrication and machinability, and cost effectiveness. In this present study, aluminium-based alloy composites filled with 0, 5, and 15 wt% ZrO2 particles were produced by a two-stage stir casting process. Microstructure, mechanical, tribological, and corrosion behaviour of the composites were evaluated using SEM, nanoindentation tests, wear tests, and Tafel polarization tests. Microstructural examination showed uniform distribution of ZrO2 particles into the alloy matrix. Based on the load against penetration depth curve, which was obtained from the nanoindentation test, reduction in depth of about 33% and 13% was noticed in 5 wt% and 15 wt% reinforced composites, respectively compared to unreinforced alloy (0 wt%). Utilization of ZrO2 as filler material was observed to be favourable for enhancement of hardness and elastic modulus compared with pure alloy. Incorporation of the ZrO2 particles in the alloy matrix, remarkably improved its wear resistance. Composite with 5 wt% depicted the lowest friction coefficient (0.4) and wear rate (2.3 x 10(-3) mm(3)/Nm). Additionally, the corrosion resistance performance of the alloy matrix composites was slightly improved with ZrO2 particles addition. The findings of the present experimental investigation provide a base in the design and manufacturing of aluminium-based alloy composites with desired mechanical, wear, and corrosion resistance properties for automobile applications.
The growing demands of high-speed rotary systems require journal bearings with enhanced tribological performance. Conventional lubricants consistently fall short, so nanolubricants-upgraded with nanoparticles are a viable alternative due to high thermal conductivity and load-carrying capacity. This article presents an extensive experimental investigation on elliptical journal bearing performance utilizing a journal bearing test rig with a variety of operating oils, speed and load parameters. Two base lubricants and nanolubricants synthesized by dispersing titanium dioxide (TiO2) and copper oxide (CuO) nanoparticles at three concentrations (0.5%, 1.0%, and 2.0% by weight) have been studied. Two important performance parameters, namely, hydrodynamic pressure distribution and oil film temperature have been evaluated under steady-state conditions. The results reveal that nanolubricants significantly enhance the static thermal bearing performance with all operating parameters. Specifically, nanolubricants prepared by blending TiO2 gave better results in comparison to CuO based nanolubricants with marked increase in hydrodynamic pressure (up to 15.67%) with insignificant rise (up to 3.83%) in oil temperature. Bearing performance has been further improved with increase in nanoparticles concentration. In addition, elliptical bearings also had preferred pressure contours compared with conventional circular bearings, which reveals their possible suitability under high-load bearing applications. The findings reveal the potential of nanolubricants and elliptical bearing geometries for increasing the reliability and performance of modern tribosystems.
The adoption of lubricants in metal forming processes at high temperatures holds particular significance. This practice facilitates reducing friction and wear, enhances metal formability, prevent seizure and galling, and extends tool life. However, elevated temperatures cause changes in lubricant properties, making it difficult to maintain effective lubrication. These changes may negatively affect the quality and efficiency of the forming process. Given the severity undergone at high temperatures, several solid inorganic salts are reported as an alternative to exhibit favourable lubrication performance. In this study, the lubrication performance of environmentally friendly albite (NaAlSi 3 O 8 ) was evaluated through ball-on-disc tests at elevated temperatures ranging from 550 to 950°C. The results demonstrate that albite can effectively decrease friction and wear loss across the tested temperature range, with a more pronounced effect at higher temperatures (890 and 950°C). The high-temperature lubrication mechanism of albite is attributed to the formation of a thick layer containing Na, Si, and O elements within the tribo-interface, which prevents direct contact between rubbing surfaces.
The environmental and health concerns associated with conventional brake pad materials containing heavy metals and toxic additives, hence necessitate the development of sustainable friction composites. This study presents an eco-friendly brake pad material reinforced with benzoylated Pseudoxytenanthera stocksii (bamboo) fibers, incorporating polydimethylsiloxane (PDMS) into a phenol-formaldehyde resin-based matrix as a sustainable alternative to graphene. The composite (C10S8) was fabricated via compression molding and subjected to comprehensive physical, mechanical, and tribological characterization. The incorporation of PDMS significantly enhanced friction stability, wear resistance, and mechanical properties, including hardness, density, and thermal stability, while reducing void content and increasing hydrophobicity. CHASE tribometer evaluations confirmed the composite's performance under realistic braking conditions, demonstrating reduced wear rates and particulate emissions. Scanning electron microscopy (SEM) of wear debris revealed minimal metallic content, suggesting a substantial reduction in carcinogenic particulates. These findings highlight the potential of PDMS-modified friction composites in mitigating brake wear pollution, offering a viable strategy for sustainable tribological applications.
This study introduces a machine learning (ML) framework to predict the Coefficient of Friction (CoF) and Specific Wear Rate (SWR) in aluminum-based composites reinforced with SiC and MoS 2 . Utilizing a robust dataset of 948 records, eight ML models were developed and optimized via GridSearchCV. Hyperparameter tuning was transformative, with the optimized Ridge model achieving exceptional test R² values of 0.96 for CoF and 0.90 for SWR. Feature importance analysis identified Material, Sliding Load, and MoS 2 % as critical factors. The models infer a key synergistic mechanism: SiC enhances wear resistance, while MoS 2 reduces friction. This work validates a finely-tuned ML approach as a highly accurate and efficient computational alternative to traditional experimental methods for tribological performance modeling and MMC design.
Composites of Ti6Al4V reinforced with 1, 3, and 5 wt. % of three distinct refractory nitrides: h -BN, TiN, and AlN nanoparticles, were fabricated using spark plasma sintering (SPS). The sintered composites were characterized and investigated comparatively in terms of their microstructure, phase composition, densification, mechanical, and wear characteristics, achieved through the use of field-emission gun scanning electron microscopy, X-ray diffraction, Archimedes’ method, nanoindentation technique, and ball-on-disk wear tests. The unreinforced alloy presented a two-phase microstructure comprising α and β phases. Reinforcement with refractory nitrides resulted in significant microstructural alterations and the development of nitride-rich secondary phases. The composites’ relative densities declined with increasing reinforcement content, falling from 98.4 to 97.4% for h -BN, 98.62 to 97.63% for TiN, and 98.64 to 95.14% for AlN. Compared to the unreinforced alloy, the nanoindentation results established that the sintered composites exhibit a continuous appreciation in hardness and elastic modulus with the highest values (70.782 ± 0.794 GPa and 356.76 ± 4.05 GPa, respectively) shown by Ti6A4V-5 wt. % h -BN. In addition, the unreinforced alloy exhibits a higher specific wear rate at each applied load than the composites, which is attributed to the improved hardness features of the refractory nitride-reinforced Ti6Al4V-based composites.
This study investigates the effect of SiO 2 nanoparticles on the tribological performance of 10W-30 engine oil under different operating conditions using a simulation-based approach in MATLAB/COMSOL multiphysics. Four nanoparticle weight concentrations (0.01%, 0.02%, 0.05% and 0.1%) were analysed at rotational speeds of 100, 250 and 400 RPM under a constant load of 10N. A mathematical model combining the Reynolds equation and asperity contact mechanics was developed to evaluate the hydrodynamic and asperity load contributions. Results demonstrate that increasing SiO 2 concentration significantly enhanced the lubricant's performance: the coefficient of friction decreased by up to 32% at 0.1% SiO 2 , film thickness increased from 0.45 µm to 0.68 µm up to 51%, and load-carrying capacity improved by 35%, with more pronounced effects at higher rotational speeds (RPMs). Limitations of the model include assumptions of idealized asperity contact and uniform nanoparticle dispersion, which were addressed via mesh convergence tests and validation against experimental trends. Mesh validation confirmed good agreement between simulated film and hydrodynamic pressures, supporting the model's reliability.
Titanium alloys are used in the automotive and aerospace industries, but perform poorly at high temperatures due to inadequate wear and friction properties. This study investigates Cr 3 C 2 -25%CoNiCrAlY and WC-CoCr coatings applied via High-velocity oxygen Fuel on a titanium-31 substrate. Coatings were evaluated from 200–800 °C under 20 N and 30 N using a ball-on-disc tribometer. Characterization techniques included scanning electron microscope, X-ray diffraction, microhardness, porosity, and bond strength. WC-CoCr coating showed higher hardness and bond strength than Cr 3 C 2 -25%CoNiCrAlY. Both coatings exhibited reduced wear rates until 600 °C, after which the wear rates increased at 800 °C due to enhanced oxidation. The coefficient of Friction decreased with increasing temperature. At 600 °C, oxide phases helped reduce wear and friction. WC-CoCr coating shows better wear resistance than Cr 3 C 2 -25%CoNiCrAlY coating and the substrate. Wear mechanisms changed from abrasive and fatigue at 200 °C to oxidative and adhesive at 800 °C. Volumetric ball loss was higher for WC-CoCr due to its greater hardness.
This paper introduces a novel non-linear friction model for ice that incorporates melting effects. By coupling frictional heating with a dynamic melting process, the model effectively captures the reduction in friction resulting from the formation of a lubricating melt film and shear-thinning behaviour at the contact interface. Validation against established literature models and experimental data demonstrates that the formulation accurately characterises the transition from static to dynamic friction over a broad range of sliding velocities (emphasising high sliding velocities) and temperatures. Sensitivity analyses further reveal that the power-law index and shear-thinning coefficient are critical parameters in tuning the model response, ensuring its applicability from low- to high-velocity regimes. This versatile analytical tool has significant implications for predicting ice friction in applications spanning winter sports, transportation safety, and the design of advanced friction-modulating surfaces.
Slips and falls occur due to inadequate slip resistance from running shoes on track surfaces, leading to injuries. To address this, the current study evaluated the slip resistance of eighteen commonly used running shoes on two different track surfaces under controlled slipping conditions. Shoe outsoles were replicated using thermoplastic polyurethane to assess the slip resistance performance on common surfaces such as ethylene propylene diene monomer (EPDM) and synthetic material-based track surfaces. Slip resistance was quantified using a robotic biofidelic slip testing device, which measured the available coefficient of friction (ACOF). The results showed that the synthetic surface provided better resistance. Furthermore, a correlation between ACOF and apparent contact area was also analysed. Shoes with modified hexagonal or block-based tread designs and radial tread grooves demonstrated the highest ACOF. It is expected that this research will assist runners in selecting shoes that enhance their performance and reduce slip-related injuries.
Triboelectric nanogenerators (TENGs) have gained significant attention as a promising technology for efficiently capturing ambient mechanical energy, particularly for powering the vast network of devices in emerging smart cities. It can also be used in IoT-based sensors in remote and inaccessible locations, which require ultralow power to operate. This research focuses on the design and fabrication of a simple, spring-assisted, contact-separation mode TENG for energy harvesting applications. The device is fabricated by spin-coating multiple layers of PEDOT:PSS and silver nanosheet (AgNS) dispersion onto a 2.5 x 2.5 cm2 ITO-coated glass substrate, which serves as the tribopositive layer, while PTFE is used as the tribonegative material. Comprehensive characterizations, including UV-Vis spectroscopy (confirming AgNS SPR at 469 nm), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) (showing crystalline AgNS), and scanning electron microscope (SEM, indicating good AgNS dispersion within the PEDOT:PSS matrix), were performed. Electrical performance was evaluated under manual finger tapping, yielding a peak open-circuit voltage (Voc) of 232 mV, a peak short-circuit current (Isc) of 782 nA, and a corresponding short-circuit current density (Jsc) of 125 nA/cm(2). These results demonstrate the successful fabrication of the PEDOT:PSS/AgNS-based TENG and highlight its potential as a sustainable energy harvesting solution for low-power smart devices, IoT nodes, and vibration sensing applications.
The tribological characteristics of graphene oxide (GO) coatings deposited by the electrophoretic deposition method on a novel honeycomb laser-engraved pattern on AISI 52100 alloy steel surface are evaluated and compared with that of commonly engraved patterns like Sierpinski, Gosper, Hilbert, and Peano. The electrophoretic deposition parameters were optimised using the Taguchi method with ethanol as electrolyte. The most critical parameter was identified to be post-deposition heat treatment temperature and the impact of the same on crack density for GO coating is found to be proportional to the coefficient of friction (COF). Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDX) were used to analyse the coated samples and tribological tests were carried out using pin-on-disc equipment. The results reveal that the GO-coated honeycomb structure achieved superior tribological performance compared to other engraved patterns, with the lowest mean COF (0.18) and wear loss (0.29 x 10-3g), indicating a 58.6% decrease in COF and a 90% reduction in wear loss relative to the pure substrate. The results show that GO-coated honeycomb-engraved surfaces exhibit enhanced tribological behaviour, making them suitable for low-friction components in automotive, aerospace, and bearing applications.
