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The Chilean copper mining industry generates large amounts of waste rock materials. These structures must be designed, operated, and closed considering their physical stability. Although these structures generally do not present physical stability problems, superficial failures may occur, where waste rock material is subjected to low confining pressures. The identification of the internal friction angle, necessary for stability calculations, is based on the characterisation of these materials under high confining pressures. This assumption is not representative of the loading conditions in the superficial layers. To address this issue, numerical large-scale triaxial tests, using the contact dynamics method, are performed to identify the internal friction angle of these materials under low confining pressures. To model these material, irregular polyhedrons were generated using statistical data of crushed aggregates, considering the morphology and the particle size distribution from experimental waste rock materials. The proposed numerical approach was validated by comparing it to literature data for confining pressures over 0.5 MPa. Our results indicate that the internal friction angle stabilises at 39° for confining pressures below 0.1 MPa. This study provides important insights into the physical stability of waste rock dumps and contributes to the development of more accurate stability calculations for these structures. [ABSTRACT FROM AUTHOR]

The shape change of the thruster can reflect its motion state, and motion control of the thruster can be carried out more effectively by monitoring its motion state. The unique structure of the origami thruster increases the difficulty of sensor configuration, which significantly limits the application of origami structures (ORSs) in the thruster field. To solve the above problems, we propose a triboelectric sensor (TES) based on a triboelectric nanogenerator, which can be perfectly matched with an ORS and used to monitor the shape of an underwater thruster. The TES proposed can sense the folding angle of the structural unit of the origami thruster and then monitor its shape. The effects of different friction layer materials, different friction layer thicknesses, and multiple pairs of friction subs in series/parallel were analyzed on TES output characteristics. A scheme with thin copper sheets as electrodes, the polyethylene terephthalate resin as dielectric layers, and four pairs of friction pairs connected in parallel were selected for sensor performance testing. Finally, the origami thruster and TES are assembled for underwater testing. The shape of the origami thruster was monitored using the TES. The dihedral angle that TES can detect ranges from 22.5° to 63.5°, corresponding to the radius variation of the thruster ranging to 44.4%. The maximum error between the output result and the measured value was 4.19%, which proves that TES has a good detection effect on the shape change of the thruster and has a broad application prospect in robot motion monitoring. [ABSTRACT FROM AUTHOR]

This paper investigates the tribological behavior of B 4 C-hBN multiphase ceramics with varying the hBN mass fraction when paired with TC4 (Ti6Al4V) titanium alloy under synthetic seawater environment. The study reveals that, an increase in hBN mass fraction of B 4 C-hBN multiphase ceramics leads to a notable reduction in the material's friction coefficient, while simultaneously contributing to a decrease in TC4 disc's wear rate. At a mass fraction of 30 wt% for hBN, the friction coefficient drops to its lowest value (0.250). Additionally, at a mass fraction of 30 wt% hBN, the wear rate of the ceramic pin is 1.47 × 10⁻⁴ mm³·N⁻1·m⁻1, which is lower than the wear rate observed at a mass fraction of 20 wt% hBN (1.70 × 10⁻⁴ mm³·N⁻1·m⁻1). This suggests that the enhancement of tribological behavior is not mutually exclusive with the refinement of the material's machinability, and the two can synergistically coexist. In synthetic seawater, the high concentration of chlorine (Cl) ions accelerates the oxidation reaction on the TC4 disc interface, resulting in the formation of compounds including H 3 BO 3 , TiO 2 , CaCO 3 , Mg(OH) 2 and Al(OH) 3. These substances form a lubricating tribo-chemical film that provides lubrication and protection. This study demonstrates that hBN as a secondary phase additive can effectively improve the frictional performance of B 4 C multiphase ceramics in synthetic seawater, by forming a tribo-chemical film that notably improved the friction and wear behavior. Additionally, the tribo-chemical film can reduce the shear rate of the fluid on the tribo-pair. For these reasons, the tribo-chemical film markedly lowers the friction coefficient and wear rate. This provides important theoretical and experimental support for the development of high-performance wear-resistant materials. [ABSTRACT FROM AUTHOR]

Lubricant friction modifier additives are used on lower viscosity engine oils to mitigate boundary friction. This work presents the development of a graphene-based material as an oil friction modifier additive, from formulation to actual vehicle tests. The graphene material was initially characterized using scanning electron microscopy (SEM) and Raman spectroscopy, which revealed the predominance of graphene nanoplatelets (GNPs) with an average of nine layers. After functionalization, two GNP additive variants were initially mixed with a fully formulated SAE 0W-20 engine oil and tribologically evaluated using reciprocating sliding tests at 40 and 120 °C and Hertzian pressure up to 1.2 GPa when both variants presented friction reduction. Then, the GNP additive variant with better performance was evaluated in a vehicle emission test using a fully formulated 5W-20 SAE oil as a reference. The addition of 0.1% of GNPs reduced fuel consumption by 2.6% in urban conditions and 0.8% in highway ones. The urban test cycle was FTP75 and higher benefits of the GNP additive occurred especially on the test start, when the engine and oil were still cold and on test portions where the vehicle speed was lower. [ABSTRACT FROM AUTHOR]

The preparation of biological phenolic resin (PF) with green recyclable biomaterials instead of phenol is a research hotspot for solving current resource and environmental problems. In this study, on the basis of introducing lignin into the phenolic system, daidzein of a renewable resource with a rigid structure was selected to modify lignin-based phenolic resin (LPF), and the improvement of the mechanical and thermal properties of the modified phenolic resin under different substitution ratios was studied. The friction materials were prepared with a daidzein-modified lignin-based phenolic resin (D-LPF) as the matrix binder, and their effects on the mechanics and friction and wear properties of friction materials were investigated. The results show that when the proportion of daidzein replacing phenol is 12%, the highest Tp can reach 152.4 °C, and the Tg of the modified D-LPF resins is significantly higher than those of PF and LPF. The highest Ts of D-LPF is 203.3 °C, which is also significantly higher than those of PF and LPF (184.7 °C and 174.6 °C, respectively). The maximum carbon residue rate at 800 °C is 64.2% and is greatly improved compared with the 55.1% and 56.7% of PF and LPF. The bending strength and impact strength of D-LPF-matrix friction materials are obviously higher than those of PF- and LPF-matrix friction materials. The specific wear rate of D-LPF-matrix friction materials is 0.70 × 10−4 mm3/Nm, which is obviously lower than those of PF- and LPF-matrix friction materials and shows good applicational prospect as a matrix resin in friction materials. [ABSTRACT FROM AUTHOR]

Corn stalk fibers extracted from cattle manure (CSFCM) represent a unique class of natural fibers that undergo biological pre-treatment during ruminant digestion. This study systematically investigates the optimization of CSFCM-reinforced friction materials through controlled silane treatment (2–10 wt.%). The biological pre-treatment through ruminant digestion creates distinctive fiber properties that influence subsequent chemical modification. Physical characterization revealed that optimized interface modification at 6 wt.% silane treatment (CSFCM-3) effectively enhanced the fiber–matrix compatibility while achieving a 34.2% reduction in water absorption and decreased apparent porosity from 9.03% to 7.85%. Tribological evaluation demonstrated superior performance stability, with CSFCM-3 maintaining friction coefficients of 0.35–0.45 across 100–350 °C and exhibiting enhanced thermal stability through a fade ratio of 14.48% and recovery ratio of 95%. The total wear rate showed significant improvement, reducing by 26.26% to 3.433 × 10−7 cm3 (N·m)−1 compared to untreated specimens. Microscopic analysis confirmed that the optimized silane modification promoted the formation of stable secondary plateaus and uniform wear patterns, contributing to enhanced tribological performance. This investigation establishes an effective approach for developing high-performance friction materials through precise control of silane treatment parameters. The findings demonstrate the potential for developing sustainable friction materials with enhanced performance characteristics, offering new pathways for eco-friendly material design that effectively utilizes agricultural waste resources. [ABSTRACT FROM AUTHOR]

This study investigates the combustion characteristics and critical thermodynamic conditions for the ignition of TC4 and TC17 alloys under high-speed friction conditions. The results indicate that, under identical rubbing conditions, both the critical pressure and the ignition temperature of the TC17 alloy are higher than those of the TC4 alloy. The critical ignition conditions for both alloys increase with thickness, while they decrease with increasing rotational speed, oxygen concentration, and oxygen pressure. The primary characteristics in the initial stage of friction ignition are abrasive and adhesive wear. As the duration of friction increases, material from the friction surface begins to peel away, creating favorable conditions for ignition. At the moment of ignition, significant peeling occurs, along with visible cracks and molten structures, resulting in the production of a substantial amount of titanium oxide on the friction surface. Based on the ignition theory proposed by Frank-Kamenetskii, the reaction order, adsorption coefficient, pre-exponential factor, and activation energy of the ignition criterion under high-speed friction conditions were determined by fitting and analyzing the experimental results. The ignition temperatures of the TC4 and TC17 alloys at different speeds were predicted with a relative error of less than 2.06%. This demonstrates that the Frank-Kamenetskii model can be utilized to explain the critical ignition conditions of titanium alloys under high-speed rubbing conditions. [ABSTRACT FROM AUTHOR]

To avoid wear and tear of the slip ring due to electrical corrosion, the slip ring needs to undergo the running-in process under atmospheric conditions without current after assembly. To address the urgent demand for long-service capability space conductive slip rings in the aerospace field, the running-in behavior and failure mechanism between the AgCuNi alloy and Au-electroplated layer are investigated using a ball-on-disc tribometer in this paper. The results show that the transfer film composed of Au plays an important role in modifying the friction during the sliding process. With the accumulation of wear debris composed of Ag on the disc, the contact material of the friction pair changed from Au and Au to Au, Ag and Au, so the surface roughness of wear tracks increased. Finally, the transfer film broke, which made the layer fail. This paper reveals the key element failure mechanism that causes transfer film failure in the running-in contact area, which is used to reveal the friction behavior and failure mechanism of slip ring friction pair materials, and provides a basis for the selection of running-in parameters during the running-in process of slip rings before power-on operation. [ABSTRACT FROM AUTHOR]

Pressureless sintered silicon carbide (PS-SiC) ceramics are widely used as friction materials in the aerospace industry, and enhancing the self-lubricating properties of PS-SiC ceramics under dry friction is highly significant. In this study, an infrared femtosecond laser was used to treat the surface of PS-SiC ceramics, and the effects of various processing parameters on surface microstructure, chemical composition, and graphitization degree were investigated. More importantly, SiC decomposes into amorphous carbon and stays on the surface of PS-SiC ceramics under the photothermal effect, and the amorphous carbon realizes the transition to the ordered graphite structure by controlling the laser energy. The highly graphitized, carbon-containing micro/nanostructures on the surface of laser-treated PS-SiC ceramics promote the formation of stable carbon-based tribofilms during sliding, which significantly enhances the tribological properties of PS-SiC ceramics under dry friction. This study proposes a method for inducing graphitization on the surface of PS-SiC ceramics using an infrared femtosecond laser, providing a manufacturing approach and theoretical support for the development of high-performance PS-SiC ceramic friction materials. [ABSTRACT FROM AUTHOR]

Purpose: Industrial drivetrains use wet disk clutches for safe and reliable shifting. Advances over the past decades regarding the formulation of lubricants and the composition of friction materials have led to reliable clutch systems. In this context, the friction behavior is crucial for the correct operation of the clutch. Nevertheless, the friction behavior and its influencing factors are still the object of modern research. The purpose of this study is to investigate how the choice of the steel disk influences the noise vibration and harshness (NVH) behavior of wet industrial clutches. Design/methodology/approach: To investigate the influence of the steel disk on the friction and NVH behavior of industrial wet disk clutches, experimental investigations with relevant friction systems are conducted. These tests are performed at two optimized test rigs, guaranteeing transferable insights. The surface topography of the steel disk and the friction lining are measured for one friction system to identify possible relations between the surface topography and the friction behavior. Findings: The steel disk can influence the friction behavior of wet disk clutches. Using a different steel disk surface finish, corresponding results can show differences in the shudder tendency, leading to a nonfavorable NVH behavior – different gradients of the coefficient of friction over sliding velocity cause this phenomenon. Originality/value: This work gives novel insights into the friction and NVH behavior of industrial wet disk clutches. It supports engineers in the optimization of modern friction systems. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2024-0054/ [ABSTRACT FROM AUTHOR]

Featured Application: Ceramic bridge bearings are designed for long-term durability, extreme low- and high-temperature environments, and applications where the use of metallic components is restricted. This study evaluates the potential of ceramic materials as friction components in bridge bearings, focusing on durability and frictional behavior under high-load conditions. Bridge bearings traditionally use materials such as PTFE and UHMWPE, which suffer from wear, oxidation, and deformation over time, leading to costly maintenance and frequent replacements. To address these limitations, zirconia-based ceramics were selected for their high hardness, wear resistance, and low friction coefficient. Frictional tests on ceramic samples, including surface roughness adjustments and stress conditions, indicated a stable frictional performance with minimal wear over extended cycles. The results suggest that ceramic materials can maintain consistent frictional properties without lubricant use, potentially reducing bearing maintenance costs and extending their service life. These findings suggest that ceramics could serve as a promising alternative to conventional friction materials in bridge bearings by offering enhanced durability, reduced maintenance requirements, and improved operational reliability. [ABSTRACT FROM AUTHOR]

In this article, the authors present the results obtained within a complex experimental program that focuses on determining the tribological characteristics of the friction materials used in transmission belts, which are critical active components in manipulators within the pharmaceutical industry. The elements of transmission belts, having the role of ensuring the movement of cardboard packaging—used when packing the foils with medicine capsules—and stopping them during the insertion of the foils, were studied. This repetitive cycle—travel-braking—leads to the wearing of the friction material on the active surface of the belt. The experiments were carried out in a dry environment (air) by testing different types of friction materials (original belt, 3D printed TPU 60A, and TPU 95A). While the study is limited to these three materials, the results highlight the significant influence of material type and infill percentage on the coefficient of friction (COF) and wear resistance. TPU 60A achieved the highest COF at 100% infill, indicating a superior grip but experienced substantial wear, under the same conditions. Conversely, TPU 95A demonstrated a lower COF, suggesting reduced grip, but exhibited exceptional wear resistance. The aim of the research is to provide a preliminary investigation into the materials' wear resistance and braking effectiveness. The experiments utilized appropriate samples to replicate real operational conditions, particularly focusing on the nature of contact between the moving belt and the packaging. [ABSTRACT FROM AUTHOR]

This study investigates the high-temperature wear behavior of laser-cladded (LC) cobalt-based Stellite 6 alloy coatings and compares the wear resistance of the cladding layer to the grey cast iron (GCI) substrate material at three different elevated temperatures: 150 °C, 250 °C, and 350 °C. Wear mechanisms at elevated temperatures were analyzed using SEM-EDS and Raman Spectroscopy to understand the material removal processes and degradation for the discs and counterpart composite friction material pins, respectively. The results indicated a significant improvement in wear resistance for cobalt-based alloy cladding at high temperatures. Wear rates were reduced by 5.0 %, 43.0 %, and 16.0 % at 150 °C, 250 °C, and 350 °C, respectively. The LC - brake pin tribo-pair exhibited a continuous increase in friction coefficients (CoF) with an increase in testing temperatures. The wear mechanism for laser-cladded discs exhibited a combination of abrasive and adhesive wear, with abrasive wear prevailing at 150 °C and increased adhesive wear at 250 °C and 350 °C. However, at 350 °C, decomposition of phenolic resin and the adhesive wear mechanism, led to brake pin failure. For GCI discs oxidative wear was identified as the predominant wear mechanism. The improved knowledge of wear mechanisms on LC Stellite 6 against composite brake pins, is set to enhance surface modification of GCI for brake disc applications. [Display omitted] • Wear testing at elevated temperatures of the laser-cladded Stellite 6. • The CoF for the laser cladded surface was less than that of GCI at 150 °C and 250 °C. • The wear rate of the laser cladded surface increased steadily, while GCI displayed an unpredictable nature. • Wear rate of counterpart pins increased drastically at 350 °C and the wear debris were large in dimensions. [ABSTRACT FROM AUTHOR]

This article presents a laboratory device by which the course of two signals can be detected using two types of sensors—strain gauges and the DEWESoft DS-NET measuring apparatus. The values of the coefficient of friction of the brake lining when moving against the rotating shell of the brake drum were determined from the physical quantities sensed by tensometric sensors and transformed into electrical quantities. The friction coefficient of the brake lining on the circumference of the rotating brake disc shell can be calculated from the known values measured by the sensors, the design dimensions of the brake, and the revolutions of the rotating parts system. The values of the friction coefficient were measured during brake lining movement. A woven asbestos-free material, Beral 1126, which contained brass fibers and resin additives, showed slightly higher values when rotating at previously tested speeds compared to the friction coefficient values obtained when the brake drum rotation was uniformly delayed. The methodology for determining the friction coefficient of the brake lining allowed the laboratory device to verify its magnitude for different friction materials under various operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of four clutch disc friction materials (from different manufacturers) used in manual transmissions. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were employed for the microstructural and chemical characterisation of the friction materials. To reveal the tribological properties of the selected clutch discs, three measurements of the friction coefficient between the material and the cast iron disc were conducted. The findings were employed to construct an artificial neural network using Easy NN software (V 14), with the objective of optimising the friction material. The chemical composition of the friction materials was employed as the input data, whereas the minimum, maximum, and average values of the friction coefficient, as well as the temperature generated during friction, were utilised as the output data. To assess the efficacy of the neural network, the correlation between the importance of input data and their sensitivity to output data was examined. It was determined that the model with three hidden layers exhibited a notable correlation between the six most influential chemical elements and their sensitivity. Based on this neural model, the chemical composition of the friction disc materials was optimised using the "Query" mode, aiming to minimise discrepancies in friction coefficients and temperature development. [ABSTRACT FROM AUTHOR]

The motion state of the friction plate in a wet friction clutch is investigated by analyzing the causes of friction coefficient formation. This study establishes static and dynamic friction coefficient models for the friction plate based on a fractal model. The fractal dimension and scaling coefficient are studied to understand the fractal characteristics and variation patterns of the surface morphology of friction pairs during engagement. The MM6000 friction and wear testing machine is utilized for experiments, measuring surface morphology changes due to wear and changes in the engagement motion state of the friction plate. The theoretical content is compared and analyzed to verify the accuracy of the friction coefficient prediction model for the friction pair. Experiments are conducted on paper-based friction materials under different bonding pressures, and the relationship between bonding times and surface morphology changes is established. A comparative experiment between the joint motion state and dynamic simulation is performed, concluding that the micro convex contact model has certain accuracy in predicting the contact state of friction plates under various working conditions. [ABSTRACT FROM AUTHOR]

There has been growing interest in using sustainable and eco‐friendly products to produce engineering materials. For this purpose, composite material applications obtained from agricultural wastes are gaining popularity. This study examines the synergistic effect of rice husk and rice stalk wastes on the fade and recovery performance of brake friction composites. Brake friction materials were developed using rice husk and rice stalk separately and in two different weight percentages as a 5–10 ratio in the formulation. For comparison purposes, a reference brake pad using copper as a substitute and a commercially available brake pad were used. Various physical, mechanical and thermal properties were analyzed. The tribological behavior of friction composites was evaluated on the Krauss test device in line with the ECE R90 procedure. The worn surface properties were analyzed using scanning electron microscopy. Tribo test results of friction composites were taken as criteria for performance optimization. While the importance weight of the criteria was determined by AHP, the VIKOR method was used in the sorting of alternatives. The experimental results have revealed that rice husk‐added friction composites had a good coefficient of friction value with better fade and recovery performance compared to rice stalk‐added ones. Increasing the amount of rice husk and rice stalk in the formulation tended to decrease the fade performance; however, it has increased the wear rate and recovery properties. Optimization results have shown that the brake friction composite containing 5 wt % rice husk ranks first in meeting the desired tribological criteria. Highlights: Cu‐free rice husk and rice stalk‐added friction composites were developed.Fibrous structure in the matrix developed the contact plateaus.Rice husk‐based tribo‐layer protected the composite from further wear damage.The addition of agro‐waste to friction composites exhibited good potential. [ABSTRACT FROM AUTHOR]

Highlights To investigate the influence of waste tire rubber (WTR) and fly ash (FA) on mechanical and tribological properties of composite brake linings, 8 different formulations of 8–40 wt% FA and 10–12 wt% WTR were selected. The mechanical tests showed that high amounts of resin and FA result in the highest hardness. The inclusion of WTR, decreased hardness and internal shear strength; however, increased the acetone extraction and resistance to coefficient of friction (COF) fluctuations. With the use of WTR, steady COF fluctuations with the temperature changes are achieved. The tribological properties were evaluated with both a drum‐type and disc‐type dynamometer by the SAE‐J661 standard. Reduced COF fluctuations were observed in <15 wt% FA and 10 wt% WTR containing samples. The highest COF was obtained for the 14 wt% FA and the lowest wear rate for the samples containing 8 wt% FA. The brake composites exhibited consistent COF in the range of 0.34–0.52, and wear rates lower than 7 wt%. Two compositions containing 40 and 25 wt% FA (no WTR), and one containing 10 wt% WTR and 8 wt% FA provided the best results. Finally, four best compositions were selected and worn surfaces were analyzed with SEM after full‐scale dynamometer tests. Three composites with high waste percentage were successfully manufactured Fly ash and waste rubber are used without any post‐processing to cut costs Waste rubber increased resistance to COF fluctuations with temperature change Full‐scale dynamometer tests are performed for friction and wear properties Worn surfaces were analyzed with SEM method [ABSTRACT FROM AUTHOR]

The tribological behavior of graphite (glass fiber) and silicon carbide (SiC) (glass fiber) composites is the main topic of this paper's examination of recent and significant research trends in composite materials. The study analyzes wear characteristics with different applied loads in both dry sliding and oil lubrication conditions using a pin-on-disc the layout. The investigation shows that the load and velocity of the samples have an impact on wear rates and friction coefficients. According to experimental findings, oil-lubricated sliding has a lower wear rate and coefficient of friction than dry sliding. The study also reveals that, as compared to fiberglass without fillers, the use of graphite fillers in fiberglass composites dramatically reduces wear. The purpose of this study is to offer useful data for subsequent research on hybrid composite material wear analysis. [ABSTRACT FROM AUTHOR]

This study investigates how lithological changes can affect the strike-slip fault propagation patterns using analogue models. Strike-slip fault zones are long structures that may cut across pre-existing tectonic or lithological steep boundaries. How strike-slip faulting is affected by a laterally heterogeneous upper crust is crucial for understanding the evolution of regional and local fault patterns, stress reorientations, and seismic hazard. Our models undergo sinistral distributed strike-slip shear (simple shear) and have been analysed by particle image velocimetry (PIV). We use quartz sand and microbeads as brittle analogue materials over a viscous mixture to distribute the deformation through the model. The first models investigate strike-slip faulting in a homogeneous upper crust using quartz sand or microbeads only. Three further models examine how the presence of a central section which laterally differs in its properties influences strike-slip faulting. The main observations are the following: The homogeneous upper crust shows typical Mohr–Coulomb strike-slip faults, with synthetic fault strikes related to the angle of internal friction of the material used. The heterogeneous upper crust has a profound effect on synthetic fault propagation, interaction, and linkage, as well as the kinematic evolution of antithetic faults that rotate around a vertical axis. The orientation of the central section determines whether antithetic fault activity concentrates along the entire length of the central contact or not. In the first case, fault activity is segmented or the number of different faults formed is increased in distinct domains. In the second case, the properties of the central material determine fault propagation, interaction, and/or linkage across the central domain. These findings have potential implications for nature that have been seen in the NW Iberian Peninsula. In this area, the change in direction of the sinistral faults and the position of the antithetic faults can be explained due to lithological change. [ABSTRACT FROM AUTHOR]

Shear spinning is a bulk forming technique used to produce hollow, rotationally symmetric parts. Although the shear spinning process has been used for the last six decades in numerous industries, in the literature, the understanding of the mechanics of the process is limited. This study provides insight into process mechanics using physical trials and numerical models. Modelling the process is challenging because of the incremental nature of the process; existing numerical models in the literature suffer from lengthy computational times and simplifications. In this study, two numerical models with different approaches to the kinematics of the spinning process are modelled with input from tests to determine friction coefficient and material properties. Then they are validated against physical trials by comparing both part geometry and strain distribution. Validated numerical models are then employed to investigate the fundamental aspects of shear spinning mechanics; evolution of strains, roller forces and part geometry in a broad range of process conditions. [ABSTRACT FROM AUTHOR]

The brake disk and friction material parameters were taken as design variables, with the negative damping ratio of the unstable mode as the optimization target. The central composite design method was employed to obtain suitable data sample points. A neural network response surface model was constructed to predict the real part values of the unstable mode. Structural optimization design was then conducted using a screening method to derive optimized parameters for the brake disk structure and physical parameters such as density, elastic modulus, and Poisson's ratio of the friction material. The optimized coefficient of the negative damping ratio of the brake system's unstable mode was enhanced, thereby reducing the likelihood of brake squeal. Harmonic response analysis showed a significant optimization effect on the curve of brake disk amplitude fluctuations with frequency. These findings offer valuable insights for improving the stability of disk brake systems. [ABSTRACT FROM AUTHOR]

The current paper focuses on developing and designing a not actively driven module for material handling operations in the field of intra-logistic. This device, belonging to the class of systems known as smart surfaces, is planned to be assembled with others to create manipulative arrays. As a novel feature, the reported concept aims to generate the frictional forces required for surface operation avoiding motors and with a simplified design. The article not only presents the design of the concept, but also the analytic models used to describe its operation and handling forces. In addition, a characterization of the fundamental parameters and the validation of the mentioned analytic descriptions together with the functioning itself are reported. As result, the analysis and the measurements presented show a real solution for a not actively driven concept, along with a methodology to characterize it and predict its handling capabilities. Specifically, the validation test proved that the model is able to represent the behavior of the friction forces with relative errors mainly in the range of 10% or lower. [ABSTRACT FROM AUTHOR]

In geotechnical construction, floating granular piles (FGPs) are employed to increase the bearing capacity and decrease the settlement of soft and highly compressive silt materials. FGPs have been installed more quickly and cost effectively than full depth piles, thereby shortening the construction period and saving on materials. Therefore, the present paper investigates the behavior of FGPs under short-term, displacement-controlled conditions through laboratory testing and numerical simulations using Plaxis 3D. Granular piles (GPs) with diameters of 60, 75, and 90 mm corresponding to the respective spacing (s) of 3.1d, 2.5d, and 2d were installed in soft clay employing the unit cell concept. The piles with lengths of 4d, 5d, and 6d were chosen as multiples of the pile diameter (d), alongside end-bearing piles with a length of 7d for comparative analysis. Lengths (4d–7d) and diameters (60–90 mm) of the GPs, area replacement ratios (9.43%–22.67%), angles of internal friction of the granular material (35°–45°), undrained shear strength of the surrounding clay (10–30 kPa), and pile spacings (2d–3.1d) were investigated. The outcomes of laboratory experiments were analyzed against the results obtained from the numerical simulations performed using Plaxis 3D. Results suggest that the load carrying capacity (LCC) of GPs considerably increased, by a factor of 2.6 to 3.1 in comparison with the untreated ground, as the length of the piles increased from 4d to 7d. Larger diameters and higher friction angles also significantly improved the LCC. Failures observed were mainly due to the bulging of the FGPs. The findings support a more cost-effective and friendly alternative to traditional foundation approaches, helping to promote more sustainable and resilient construction practices in geotechnically demanding regions. [ABSTRACT FROM AUTHOR]

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The interplay of conductivity and friction in layered materials such as graphite is an open area of investigation. Here, we measure local conductivity and friction on terraces of freshly cleaved highly oriented pyrolytic graphite via atomic force microscopy under ambient conditions. The graphite surface is found to exhibit a rich electrical landscape, with different terraces exhibiting different levels of conductivity. A peculiar dependency of conductivity on scan direction is observed on some terraces. The terraces that exhibit this dependency are also found to show enhanced friction values. A hypothesis based on tip asymmetry and the puckering effect is proposed to explain the findings. Our results highlight the non-triviality of the electrical and tribological properties of graphite on the nanoscale, as well as their interplay. [ABSTRACT FROM AUTHOR]

We examined the impact of 3D-printing parameters, such as the deposition pattern, deposition speed, and layer height, on the tribological performance measured through the coefficient of friction and cumulative linear wear. Optimizing these factors can significantly influence material wear and friction, which is critical for ensuring durability and functionality in practical applications like a cylindrical gear assembly for a vertical-articulated robot. The purpose of the study was to investigate these relationships by employing the Box–Behnken design (BBD) method to systematically analyze the effects of these parameters, while also using scanning electron microscopy (SEM) for detailed microstructural characterization. The findings aim to provide insights that can guide the development of more efficient and wear-resistant 3D-printed materials. The strong impact of layer height on CLW was noted, showing that lower layer heights can either improve or worsen wear depending on the combination of speed and pattern, with layer height playing a dominant role in determining wear performance. Lower speeds and specific patterns, particularly lines and concentric patterns, tend to result in higher COF values. The validation test results, with a COF of 0.2215 and CLW of 29.2075, closely align with the predicted values of 0.2064 and 27.3, showing small percentage errors of 7.3% for COF and 6.5% for CLW. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials are potential candidates for electronic devices due to their unique structures and exceptional physical properties, making them a focal point in nanotechnology research. Accurate assessment of the mechanical and tribological properties of 2D materials is imperative to fully exploit their potential across diverse applications. However, their nanoscale thickness and planar nature pose significant challenges in testing and characterizing their mechanical properties. Among the in situ characterization techniques, atomic force microscopy (AFM) has gained widespread applications in exploring the mechanical behaviour of nanomaterials, because of the easy measurement capability of nano force and displacement from the AFM tips. Specifically, AFM-based force spectroscopy is a common approach for studying the mechanical and tribological properties of 2D materials. This review comprehensively details the methods based on normal force spectroscopy, which are utilized to test and characterize the elastic and fracture properties, adhesion, and fatigue of 2D materials. Additionally, the methods using lateral force spectroscopy can characterize the interfacial properties of 2D materials, including surface friction of 2D materials, shear behaviour of interlayers as well as nanoflake-substrate interfaces. The influence of various factors, such as testing methods, external environments, and the properties of test samples, on the measured mechanical properties is also addressed. In the end, the current challenges and issues in AFM-based measurements of mechanical and tribological properties of 2D materials are discussed, which identifies the trend in the combination of multiple methods concerning the future development of the in situ testing techniques. [ABSTRACT FROM AUTHOR]

The research focused on the effect of graphite proportion and the incorporation of fly ash in Fe-Cu-based friction materials produced via powder metallurgy technique. Microstructural investigation of the specimens demonstrated the homogenous distribution of the secondary element (Cu), lubricant (graphite), and reinforcements (fly ash) in the matrix (Fe). A maximum density of 5.7 g/cm3 was attained for the specimens, with an overall density of 70 pct of theoretical density. FM03 specimens showed a better wear resistance of 4.7 × 10−8 g/Nm with an optimum coefficient of friction of 0.4. The specific wear rate of the conventional friction material was 97.7 pct higher than the FM03 specimens. [ABSTRACT FROM AUTHOR]

This study shows that the progressive adhesion of weld material to the tool in friction stir welding AA 2024-T3, up to tool saturation, brings about a decrease in power consumption until a plateau is reached. The cause of this behavior is the hindering of the stirring action of the tool due to the material accumulated on it. The built-up material changes the nature of the tool/material interaction and then the friction condition at their interface. The direct consequence is a decrease in the shearing strain and therefore in the heat generated by friction. Bits of this adhering material break off from the tool at intervals. Macro and micro detachments are identified. Micro-detachments happen continuously at small periodic intervals and produce vibrations. The amplitude of these vibrations increases in all their characteristic spectral components up to tool saturation. Macro-detachments generate oscillations in power consumption and leave galling on the weld bead. [ABSTRACT FROM AUTHOR]

Design and testing of real materials is a costly process and usually requires some specific equipment. To alleviate this task numerical methods can be leveraged. In this work we show possible modelling technique for closed-cell material structure using Weaire–Phelan unit cells. As an example existing aluminum structures were used and modelled parametrically, allowing to establish different geometrical models for different applications. Numerical simulations for compression was also done on the developed models to reveal the material response. The influence on the cell wall thickness and the friction between the material and the compression plate was investigated. It was found that the friction coefficient has no significant effect on the material response, except in the case where bonded connection was assumed. It was also demonstrated that material response and the porosity controlled by cell wall thickness have an approximately linear relationship with each other. This method proved to be a flexible and alternative solution of real laboratory tests and targeted to reduce costs of material design. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Different proportions of rare earth oxides, specifically cerium oxide and yttrium oxide, were incorporated into phenolic resin-based friction materials to mitigate the thermal degradation of resin-based friction materials. The effects of these additives on the mechanical properties and tribological performance of resin-based friction materials were thoroughly investigated, and the microstructure and phase composition were characterized via field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The addition of rare earth oxides favorably improved the density, hardness, compression strength, and shear strength of the composites, with rare earth yttrium oxide dominating the hardness of the composites and cerium oxide dominating the compression strength of the composites, but changes in the ratio of the two had a small effect on their density, shear strength, and impact strength. Among them, the highest density, hardness, compressive strength, and shear strength of the modified sample could reach 2.310 g/cm3, 118 HRL, 187.5 MPa, and 43.5 MPa, respectively, and their properties were improved by 7.7%, 14.6%, 19%, and 51%, respectively, compared with the unmodified sample Y0. The incorporation of rare earth oxides was not conducive to the improvement of the fade friction coefficient and recovery friction coefficient of the composites, but was beneficial to the stabilization of the recovery friction coefficient of the composites and the reduction in their average wear rate, with the yttrium oxide-dominated matched samples focusing on high-temperature stability, and cerium oxide-dominated matched samples focusing on the antioxidant reduction property. The homogeneous dispersion and synergistic enhancement effect of the rare earth oxides in the matrix materials enhanced the structural integrity and densification of the matrix materials and improved the interfacial strength and surface wear resistance of the composites. The worn surface of the unmodified sample Y0 was mainly abrasive and thermal fatigue wear, the worn surface of the yttrium oxide-dominated matched samples Y1 and Y2 was mainly abrasive wear, and the worn surface of the cerium oxide-dominated matched samples Y3 and Y4 was mainly adhesive and thermal fatigue wear. [ABSTRACT FROM AUTHOR]

[Display omitted] Biological lubricating materials play a crucial role in normal human activities due to their extremely low coefficients of friction (COFs). However, synthetic friction materials typically exhibit higher friction coefficients and wear rates compared to natural lubricating materials. To address this issue, we propose a novel lubrication strategy: reducing the friction coefficient of synthetic lubricating materials through supramolecular dynamic exchange. The incorporation of B-N supramolecular dynamic bonds enhances the stability of the polymer network structure, resulting in superior mechanical properties and resilience. The dynamic behavior of B-N bonds during friction reduces the frictional resistance of mechanical interlocking networks in motion, thereby significantly improving the frictional performance of supramolecular coatings. We anticipate that elucidating the dynamic structure-performance relationship in supramolecular coatings will advance the development of supramolecular lubricating materials and inspire innovative approaches to constructing new lubricating materials. [ABSTRACT FROM AUTHOR]

Knowledge of shear friction material properties is central to the design of reinforced concrete elements. These shear friction properties are impacted by components of concrete mix design that impact the roughness of a cracked plane, including the strength of the mortar and aggregates. In this paper, 72 shear friction tests are undertaken on multigeneration recycled aggregate concrete that successively crushes and reuses concrete to make three generations of aggregate. The results of these tests are brought together with 314 existing shear friction test results on virgin and recycled aggregate concrete to develop a new unified model to predict the shear capacity of initially uncracked concrete. The results of the modeling show that even after multiple generations of recycling aggregate, no significant decline occurs in the shear strength of concrete and that the shear strength is most strongly influenced by the confining stress. The analysis of the test results across multiple studies identifies critical areas for future research, including the need for better reporting of actual confining stresses and the reporting of crack widths to allow for a more complete understanding of behavior. [ABSTRACT FROM AUTHOR]

Friction-induced vibration in the wiper system of passenger cars not only causes impaired visibility as a result of uneven water film distribution on the windscreen surface, but also leads to noise problems by transmitting vibrations as sound to the passengers. In this study, a novel experimental apparatus was developed to simulate the wiper system, enabling the change in normal support stiffness and the precise adjustment of the yaw angles of a shortened rubber blade and its flexible base relative to the drive direction of a glass plate. The use of fluorescence observation provided a significant advantage, enabling precise measurements of the position of the rubber blade tip and the water film thickness in the contact area of the rubber blade and the glass plate during operation. In conjunction with this, an accelerometer and a gap sensor were employed to measure the normal and tangential motions of the support structures, respectively. This comprehensive setup allows for precise control of blade support conditions, and provides accurate measurement for motions of rubber blade and support structures, making it a powerful tool for investigating friction-induced vibration in the wiper system. The experimental results clearly demonstrated the effectiveness of applying large yaw angles to both the rubber blade and the flexible base in suppressing friction-induced vibration, resulting in smooth motion at any drive speed. These findings have the potential to improve wiper performances under actual operating conditions. [ABSTRACT FROM AUTHOR]

A numerical experiment is performed to evaluate the behaviour of externally pre-stressed steel–concrete composite beams (EPSCCBs) up to their ultimate stages, considering second-order effects, tendon material and friction at tendon–deviator locations. The tendon force evolution with loading and slip at the steel–concrete interface is explored. A three-dimensional finite-element model is used to include all these aspects. The idea is to deconstruct the project of eight experimental EPSCCBs with different tendon profiles, considering the above-mentioned issues. The main findings indicate that the inclusion of second-order effects is essential for predicting the stress paths near the collapse loads and slip demands at the steel–concrete interface, while external tendons made of carbon fibre-reinforced polymer (CFRP) can be used as a substitute for classical steel ones, as they presented similar behaviours. The largest tendon force increments occurred for the CFRP tendons compared to other tendons made of glass, aramid and basalt fibre-reinforced polymers. Furthermore, it was found that a friction coefficient between 0.2 and 0.4 at the tendon–deviator interface better matches the available experimental tendon force evolution with loading. This finding seems to counteract the common assumption of using a null friction coefficient as suggested in other works. [ABSTRACT FROM AUTHOR]

This study aims to investigate the outcomes of carbonaceous products, derived from the decomposition of the components of vehicular brake materials, under high-temperature wear tests. Pin-on-disc (PoD) wear tests were conducted by using cast iron discs against pins made of commercially available low-steel friction material. Tests were carried out at different temperatures: 155 °C, 200 °C, 250 °C, and 300 °C. The characterization of the sliding plateaus on worn pin surfaces was based on X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. It was noted that at temperatures above 200 °C, the thermal degradation of the inorganic resin, used as a material binder, occurs. An interesting observation was recorded at 300 °C; the brake pin material's friction curve showed higher stability despite having an excessive wear rate. However, the brake pin's specific wear coefficient was higher at this temperature than was observed in the other friction tests. A detailed study of the friction plateaus on the worn-out pins at 300 °C revealed that the decomposed carbon resin product, i.e., the distorted graphite, was widespread over the surface of the pin. Lubricant stabilization can be expected, as established by the observed values of the coefficient of friction (CoF), retaining values within the 0.4–0.6 range, even at high temperatures. Other friction material components may have contributed to the formation of this ubiquitous carbonaceous interface film. [ABSTRACT FROM AUTHOR]

Impregnated graphite is a common material for friction pairs in aeroengine seals, especially at high temperatures. For the convenience of the application of graphite materials in aeroengines, an SRV-4 tribometer and a synchronous thermal analyzer are employed to study the tribological properties and thermal stability of pure, resin-impregnated, metal-impregnated, and phosphate-impregnated graphite against stainless steel from room temperature to 500 °C. The results indicate that impregnations can improve the wear resistance and thermal stability of graphite at high temperatures. Compared with other impregnated graphite materials, the resin-impregnated graphite shows a good friction coefficient and poor wear rate and thermal stability over 300 °C, due to the degradation and oxidation of the resin-and-graphite matrix. The metal- and phosphate-impregnated graphite materials exhibit excellent wear resistance and thermal stability under 500 °C as a result of the protection of the impregnations, while the average friction coefficient of the metal-impregnated graphite is much greater than the phosphate-impregnated graphite, and even reaches 2.14-fold at 300 °C. The wear rates for the graphite impregnated with resin, metal, and phosphate are 235 × 10−7, 7 × 10−7, and 16 × 10−7 mm3N−1m−1 at 500 °C, respectively. Considering all aspects, the phosphate-impregnated graphite exhibits excellent tribological properties and thermal stability. [ABSTRACT FROM AUTHOR]

We investigated the effect of lepidocrocite-type layered titanate, which is compounded in brake pads, to reduce brake particle emissions. The dust reduction effect of titanate was evaluated using a small-scale inertial brake material friction test dynamometer. The results suggested that brake particle emissions are related to the microphysical structure of the pad surface, such as the uniformity of the friction film and secondary plateau formation, and that friction materials containing titanate contribute significantly to reducing both particle mass (PM) and particle number (PN) emissions of brake particles in both non-asbestos organic (NAO) and low-steel (LS) pads. In particular, LS pads generally have a problem of having more brake particles than NAO pads, but this study found that brake particles can be significantly reduced by compounding titanate instead of tin sulfide. [ABSTRACT FROM AUTHOR]

The crucial significance of brake friction materials lies in ensuring automobile safety and performance. This drives the ongoing development of these materials to meet rigorous criteria. Recent developments in friction materials have improved the effectiveness of braking systems, resulting in increased safety and comfort. Modern society has increasingly adopted environmentally friendly friction materials, replacing conventional alternatives. The advancements in brake friction material development primarily focus on improving braking performance while simultaneously reducing environmental pollution caused by dangerous substances in brake pads. Understanding the different formulations of brake pads and the impact of the materials used is essential due to the complex and expert‐dependent nature of the brake pad manufacturing process. This review aims to fill knowledge gaps surrounding the basic formulations of brake pads and provide insights to researchers on the impact of different ingredients in creating friction brake pads. This research not only highlights the influence of various components on the friction and wear characteristics of brake pads but also addresses the importance of a comprehensive understanding of their fundamentals. The novelty of this review is justified by the lack of up‐to‐date, thorough reviews on brake friction materials, particularly in light of the recent advancements in the field. This review focuses on the developments and innovations in brake friction materials over the last 15 years. It aims to bridge the knowledge gaps regarding the basic formulations of brake pads and provide valuable insights into the influence of various components on their friction and wear characteristics. By addressing both the performance improvements and environmental considerations, this review offers a timely and essential resource for researchers and practitioners in the automotive industry. Highlights: Exploration of various ingredients used in the brake friction composites.Ingredients influence on the various characteristics of brake friction composites.Different formulations and its usage in the brake friction composites.Recycled materials usage in the friction composites‐waste to wealth approach. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs), as novel electronic devices for converting mechanical energy into electrical energy, are better suited as signal-testing sensors or as components within larger wearable Internet of Things (IoT) or Artificial Intelligence (AI) systems, where they handle small-device power supply and signal acquisition. Consequently, TENGs hold promising applications in self-powered sensor technology. As global energy supplies become increasingly tight, research into self-powered sensors has become critical. This study presents a self-powered sport sensor system utilizing a triboelectric nanogenerator (TENG), which incorporates a thermoplastic polyurethane (TPU) film doped with graphene and polytetrafluoroethylene (PTFE) as friction materials. The graphene-doped TPU nanocomposite film-based TENG (GT-TENG) demonstrates excellent working durability. Furthermore, the GT-TENG not only consistently powers an LED but also supplies energy to a sports timer and an electronic watch. It serves additionally as a self-powered sensor for monitoring human movement. The design of this self-powered motion sensor system effectively harnesses human kinetic energy, integrating it seamlessly with sport sensing capabilities. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the effect of mullite on the mechanical properties and friction of carbon fiber (CF)-reinforced friction material. Design/methodology/approach: CF-reinforced friction materials with varying content of mullite were fabricated by hot press molding, and then the tribological properties were tested on the MRH-3-type tribometer under ambient conditions with the ring-on-block configuration. Findings: The experimental results indicated that the addition of mullite increased the density and compressive strength of friction material. However, the flexural strength of friction material decreased by 16% with the addition of 15 Wt.% mullite. The friction coefficient was proportional to the mullite content. Friction material with 12.5 Wt.% mullite showed the highest friction stability under different loads, whereas friction material with 10 Wt.% mullite exhibited the highest friction stability under different sliding speeds. Originality/value: By boosting the resistance to deformation under load and increasing the specific heat capacity, mullite contributed significantly to the friction stability of the friction material. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to prepare an oil-impregnated porous polytetrafluoroethylene (PTFE) composite with advanced tribological properties using citric acid as a novel pore-forming agent. Design/methodology/approach: Citric acid (CA) was used to form pores in PTFE, and then oil-impregnated PTFE composites were prepared. The pore-forming efficiency of CA was evaluated. The possible mechanism of lubrication was proposed according to the tribological properties. Findings: The results show CA is an efficient pore-forming agent and completely removed, and the porosity of the PTFE increases with the increase of the CA content. The oil-impregnated porous PTFE exhibits an excellent tribological performance, an increased wear resistance of 77.29% was realized in comparison with neat PTFE. Originality/value: This study enhances understanding of the lubrication mechanism of oil-impregnated porous polymers and guides for their tribological applications. [ABSTRACT FROM AUTHOR]

This article presents a contact 3D thermomechanical finite element model of a railway vehicle disk brake. The distinctive feature of the model is the interdependence of the sliding velocity, coefficient of friction, temperature, contact pressure, and friction material wear, derived from a unified system of equations of heat dynamics of friction and wear. Another important aspect is high geometrical compatibility of the model with physical object. The radial location of the rotation point of the brake pad holder, axis of the mounting plate, and middle of the lining agree with the guidelines of UIC 541-3. All these features allow for a detail study of wear distribution and its further optimization. Based on the recorded experimental data, an analytical form of the coefficient of friction dependent on the sliding velocity and temperature was created. The single braking simulation from initial velocity of 140 km h − 1 to a stop, took into account friction material wear based on the generalized Archard's law. The analysis of the results is focused on wear, temperature, contact pressure components of the stress tensor, velocity, and coefficient of friction. The highest average temperature of the six thermocouples was equal to 130.7 °C, while the corresponding calculated value was 128.4 °C. [ABSTRACT FROM AUTHOR]

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, the frictional traction forces developing in the annular space between two concentric vertical cylinders consisting of the outer surface of a cylindrical rod and the inner sidewall of a wider circular cylinder will be analyzed. The experiments carried out for this study allowed us to measure the traction on the rod for several filling heights, H. For the rod, it is possible to find a linear relation between the theoretically computed traction T r o d and the traction measured experimentally, T r o d M . Based on these results, it is possible to understand the fascinating phenomenon of the lifting, by the rod, of the weights of the mass of grains and of the outer cylinder. Finally, a physical analogy between this problem and the upward movement of trees in tornadoes can be identified. [ABSTRACT FROM AUTHOR]