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In nitride films, an enhanced lubrication effect has been achieved through the incorporation of a soft metal element such as Ag. However, at medium and high temperatures, the favorable tribological properties cannot be sustained for an extended period due to the rapid depletion of Ag. To address this issue, a multilayer film design with W element doping is conceived to impede Ag depletion. MoN (Ag‐W)‐MoS2 (W) multilayer films with 4 different layers are prepared, and their tribological properties are systematically characterized across temperatures ranging from 25 to 800 °C. The results indicate that the tribological properties of four different multilayer films vary considerably at different temperatures. The 8‐layer multilayer film exhibits a relatively low friction coefficient that can be maintained at wide‐range temperatures. X‐ray diffractometer patterns are obtained before and after the friction test to elucidate the lubrication phases of different layers within the multilayer films at various temperatures. Additionally, 3D profiles of wear trajectory surfaces are generated, revealing enhanced wear resistance achieved by effectively inhibiting the migration of Ag. The low friction coefficient in multilayer films can be attributed to the oxidation of MoS2 and the generation of new lubrication phases, as confirmed by Raman spectra analysis. [ABSTRACT FROM AUTHOR]

High-speed gear reducers are highly sensitive to vibration and noise, especially in new-energy vehicles. Hence, the current nonlinear dynamics model of gears does not fully consider the influence of tooth microstructure on backlash and friction. This study establishes a nonlinear friction dynamics model for a high-speed helical gear system, which includes time-varying dynamic backlash and friction coefficient based on the fractal characterization of tooth roughness. Furthermore, it investigates the influence of tooth surface roughness on the dynamic performance by taking into account the interaction between friction and vibration under Elastohydrodynamic Lubrication (EHL). Theoretical simulation results show that an increase in tooth roughness leads to an overall deterioration in the dynamic performance of the helical gear system; however, local optimization can also be observed. In the case of a dynamic tooth backlash, the amplitude of displacement oscillations increases, and the number of frequencies increases; in terms of frictional coefficient, the amplitude of displacement oscillations increases, but the change is small compared with that of the dynamic tooth backlash, and the number of frequencies in the spectrum decreases. The results indicate that the proposed model can provide a reference for controlling the tooth roughness of high-speed gears. [ABSTRACT FROM AUTHOR]

Interparticle friction is an intrinsic property of particles, which plays an important role in the macroscopic and microscopic shear mechanical properties of granular materials. In this research, we investigate the shear behavior of granular materials with different friction coefficients using ring shear tests. The particle image velocimetry (PIV) technique was also used to analyze the shear flow characteristics. The results indicate that the peak shear strength of granular materials increases with the increase in shear rates, especially for granular materials with high friction coefficients. The shear stress fluctuation difference is smaller under low normal stress. Under high normal stress, the shear stress fluctuation of granular materials with high friction coefficient is higher than that of granular materials with low friction coefficient. In addition, the shear stress fluctuation shows a trend of increasing with the increase of shear rates. The range of the liquid phase flow region of granular materials decreases with the increase of friction coefficient and normal stress. This work reveals the shear flow characteristics of granular materials under different conditions, which can provide reference for the flow processes of geological disasters such as landslides and debris flows. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power 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.)

Membrane electrode assemblies (MEA) are composed of five principal layers: two gas diffusion layers on top of two catalyst layers surrounding the membrane. The understanding of the mechanical behavior at the different interfaces of the MEA is therefore essential and will be the subject of this study through the development of a new methodology to evaluate the friction coefficients between the different layers. The analysis of the MEA components and their assembly process impact will be considered. A morphological analysis based on confocal microscopy observations of the catalyst layer/microporous layer interface was conducted to evaluate the roughness of the different surfaces submitted to friction. Results show that the static friction increases with the addition of microporous layers and catalyst layers on their substates. The friction coefficients also increase after a low pressure hot pressing but they surprisingly decrease after an assembly performed at a high pressure. [Display omitted] • A new method is developed to measure the friction coefficient of MEA interfaces. • The influence of the MEA material and process on the friction coefficient is analyzed. • Morphological analysis of the surfaces of the MEA component were performed. • Hot-pressing step allows to tune the mechanical properties of MEA interfaces. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive exploration of an experimental device designed for determining friction coefficients between a circular bar and a set of wheels in a feed mechanism. In the realm of mechanical engineering, where efficiency is paramount, understanding and quantifying these coefficients play a crucial role in designing and optimizing mechanical systems. The research objectives encompass the development and testing of the experimental device, rigorous analysis of the results, and an assessment of its practicality and accuracy in discerning friction coefficients within advancing mechanisms. Originating from the practical necessity of designing a mechanism for advancing composite rods in manufacturing lines, this research delves into the importance of characterizing friction coefficients in bar element mechanisms. The methodology involves the implementation and testing of the experimental device under controlled conditions, data collection, and the application of analytical techniques to evaluate friction coefficients. The obtained results provide a nuanced understanding of friction coefficients in bar feed mechanisms, with implications for the design and optimization of mechanical systems. The conclusions emphasize the need for careful analysis of frictional forces to enhance the performance and durability of these mechanisms. [ABSTRACT FROM AUTHOR]

The paper includes a theoretical approach to the frontal mechanical seals with rubber bellows, used in the conveyance of fluids in centrifugal pumps, in terms of friction coefficients, balancing and possible fluid losses. The study also presents an experimental study for a mechanical seal with rubber bellows and a shaft diameter of 35 mm, operating at different speeds at the pump shaft and different pressures of the transported fluid. At higher pressure the seal is balanced and at lower pressures is discharged. [ABSTRACT FROM AUTHOR]

Mechanical properties provide information to design and develop suitable machines (equipment) for processing, transporting, and conveying chestnuts. Four chestnut cultivars that have not been studied before were investigated in the study carried out for this purpose. Some engineering properties of Macit 55, Akyüz, Ali Nihat, and Bouche de Betizac chestnut cultivars were determined and compared. The mechanical properties were determined by rupture force, rupture energy, deformation, and firmness values. The friction coefficients of chestnut varieties on a galvanized sheet, stainless steel, and rubber surfaces were investigated. Mechanical properties were determined using a Universal Testing Machine. The values obtained from the samples were obtained by compression between the parallel plate along the X, Y, and Z axes. For the static friction coefficient, while the galvanized sheet surface had the lowest value (0.145), the rubber surface had the highest value (0.212). For rupture forces, the force required to break the chestnut at the Z loading axis position (714.09 N) was higher than the required force at the Y loading axis position (396.35 N) of the fruit.

Copyright of EMERG: Energy. Environment. Efficiency. Resources. Globalization is the property of Romanian National Committee of World Energy Council 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.)

The friction behavior of widespread clay minerals is a major concern in many geo-engineering problems, such as the stability of soft soil foundations and the induction of seismic fault zones. The present work aimed to study the friction behaviors of kaolinite at the particle level using the molecular dynamics method. The effects of normal force (F n), shear velocity (v), and interfacial water film on nanofriction were discussed. The "stick-slip" phenomenon and periodic evolution of friction forces (F f) were observed in dry friction and became less pronounced with water lubrication. The dry F f of kaolinite was found to be insensitive to F n. However, wet F f exhibited a linear increase with F n and then transitioned to a non-linear relationship as slip displacement increases due to the continuous loss of water molecules from the interface during friction. Notably, at high loads (F n ≥ 30 nN), the peak friction of wet kaolinite showed characteristics similar to dry friction. A velocity-strengthening behavior of kaolinite at high velocities was observed in both dry and wet conditions. The macroscale friction coefficients of kaolinite were predicted from nanofriction data and results showed good agreement with experimental values. This study lays the foundation for bridging micro- and macro-mechanical behaviors, suggesting a new pathway for acquiring precise macroscopic friction of minerals through cross-scale studies. • Interparticle friction behavior of kaolinite is investigated using MD simulations. • The effects of normal force, shear velocity, and water lubrication on friction behavior are discussed. • Kaolinite exhibits both velocity-strengthening and weakening friction. • Nanofriction coefficient of hydrated kaolinite is estimated at high speed. • Macroscopic friction coefficients are predicted from microscale friction. [ABSTRACT FROM AUTHOR]

Depending on humidity, some technical properties of T. chebula (black halile) dried fruit were investigated. It was observed that various properties, such as dimension, geometric mean diameter, and arithmetic mean diameter, increased linearly with increasing moisture content. With the increase in moisture content, sphericity increased from 57.2% to 67.7%, surface area increased from 487.65 mm² to 805.03 mm², porosity increased from 0.49 to 0.59, and the angle of repose increased from 22.77° to 27.86°. However, moisture content, true density, and bulk density decreased from 1.85% to 3.27%, 1469.54 kg/m³ to 1740.22 kg/m³, and 735.64 kg/m³ to 705.99 kg/m³, respectively. When the moisture content increased from 1.85% to 3.27%, the static and dynamic friction coefficient increased from 0.231 to 0.495 and 0.311 to 0.637, respectively. The lowest static and dynamic friction force values were obtained for stainless steel and the highest for rubber surface. When moisture content increased from 1.85% to 3.27%, tensile strength decreased from 446.46 N to 257.59 N. Rupture energy and deformation increased with an increase in the moisture content of the fruit. When the moisture content increased from 1.85% to 3.27%, the rupture energy and deformation increased from 0.09 J to 0.27 J and 0.83 mm to 1.76 mm, respectively. [ABSTRACT FROM AUTHOR]

Diffusive behavior of human serum albumin (HSA) in the presence of Mg2+ and Cu2+ ions was studied by pulsed field gradient nuclear magnetic resonance (PFG NMR) and dynamic light scattering (DLS). According to NMR data yielding measurements of HSA self-diffusion coefficient, a weighted average of the protein monomers and oligomers diffusion mobility in the presence of metal ions was observed. While the short-time collective diffusion measured by DLS showed one type of diffusing species in ion-free HSA solution and two molecular forms of HSA in the presence of metal ions. The light intensity correlation function analysis showed that HSA oligomers have a limited lifetime (lower limit is about 0.4 ms) intermediate between characteristic time scales of PFG NMR and DLS experiments. For a theoretical description of concentration dependence of HSA self- and collective diffusion coefficients, the phenomenological approach based on the frictional formalism of non-equilibrium thermodynamics was used (Vink theory), allowing analysis of the solvent–solute and solute–solute interactions in protein solutions. In the presence of metal ions, a significant increase of HSA protein–protein friction coefficient was shown. Based on theoretical analysis of collective diffusion data, the positive values of second virial coefficients A2 for HSA monomers were obtained. The A2 values were found to be higher for the HSA with metal ions compared with the ion-free HSA solution. This is due to the more pronounced contribution of repulsion in protein–protein interactions of HSA monomers in the presence of Mg2+ and Cu2+ ions. [ABSTRACT FROM AUTHOR]

Frequency dispersion of dielectric permittivity ε1(ν) and dielectric loss ε2(ν) dynamic coefficients is studied; temperature T, density ρ, and concentration C dependences of these coefficients are calculated; and Cole–Cole diagrams are constructed using analytic expressions derived previously for these coefficients from kinetic equations of electrolyte solutions for potassium iodide solutions while considering the contributions of the generalized potential of the interaction of ion-molecular systems. The calculation results agree well with the experimental data for KI solutions. [ABSTRACT FROM AUTHOR]

This paper tests the use of various barrier and corridor effects in cost distance calculation, which often serves as a proxy for accessibility in Land-Use and Land-Cover Change (LUCC) models. The most suitable friction coefficients for barrier effects of slope and water, and corridor effect of roads, are identified by empirical sensitivity analysis. The influence of accessibility on urbanisation, agricultural intensification, and extensification, afforestation, and deforestation in Slovakia is modelled in the present study. The most significant improvement was achieved using the corridor effect of roads for accessibility to the nearest district town, while the barrier of slope significantly improved the effect of accessibility to the nearest commune. Different optimal friction coefficients were identified for different land cover changes; however, only some of them were sensitive to the change of coefficients. [ABSTRACT FROM AUTHOR]

Friction is one of the important factors in sheet metal forming. It greatly affects dynamic behaviors of metal sheets and stress and strain distributions in the metal sheets. In this study, deformation characteristics, stress–strain distribution, and change law of symmetrical parts in the process of deep drawing are analyzed using a new theoretical model based on the plastic flow law and partitioning the forming area. In the model, the least-square method is used to linearize the friction coefficient in nonlinear problems and reverse the calculation of friction coefficients to interpret the friction coefficient. To evaluate the model, the friction coefficient in sheet metal drawing of axis-symmetric deep drawing parts under various friction conditions was measured using a self-developed measuring system. The comparison between the experimental results and the calculation using the model shows a good agreement. The results show that the drawing force increases with the increase in punch depth; the friction coefficient decreases with the rise in punch depth. The friction coefficient obtained by fitting is relatively stable, and the average error is less than 3%. Using the friction coefficient model in finite element simulation analysis, it shows that the thickness and blank shape errors are less than 5%. The novel method studied in this paper shows great significance in support for theoretical research, numerical simulation research, and sheet metal stamping performance evaluation.

To reduce the loss of skid resistance of pavement in wet weather, pavement grooving is used to improve aircraft operation safety on runways. This study presents an analytical solution to analyze mechanical interactions between tire tread rubber and pavement surface grooves for calculating friction coefficients of aircraft tires on runway pavements. The energy dissipation theory is utilized to calculate the contribution of rubber-groove interlock and the friction on plane part of pavement surface due to surface texture is accounted using Brush model. The comparison of model results and field measurements proves the capability of the proposed method to predict friction coefficients of aircraft tire on runway pavements with various groove configurations. The evaluation of trapezoidal grooved pavement shows similar friction coefficients compared to the standard square grooved pavement regulated by the Federal Aviation Administration (FAA). The friction coefficients of grooved pavement vary depending on the inclined angles of groove and edge-to-edge spacing that are two important geometry parameters. The findings demonstrate the pronounced influences of rubber deposits and groove deterioration on skid resistance of runway pavements. The analysis results can be further used to design optimized groove configuration and determine maintenance threshold for safe operation of aircraft on runways. [ABSTRACT FROM AUTHOR]

Foil-type gas journal bearing has low load-carrying capacity and poor operational stability. Metal rubber-bump foil gas journal bearing with three structure pads (MR-BFGJBTSPs) are proposed to achieve satisfactory bearing characteristics. The equivalent stiffness model of metal rubber damping element is developed, considering the contact states of metal wires: separation state, sliding contact state, viscous contact state. The stiffness prediction model is presented based on the modified LuGre model, integrating the friction coefficients. The static and dynamic bearing performances of MR-BFGJBTSPs are analyzed, integrating the stiffness and damping of hybrid elastic support structure. Results show that the predicted structure stiffness K c compares best to limited test data. The load-carrying capacity of MR-BFGJBTSPs increases when the friction coefficients μ tb , μ bh increase. • Metal rubber-bump foil gas journal bearing with three structure pads (MR-BFGJBTSPs) are proposed. • The stiffness prediction model of the hybrid elastic support structure is presented based on the modified LuGre model. • The static and dynamic bearing performances of MR-BFGJBTSPs are analyzed, integrating the structure stiffness and damping. [ABSTRACT FROM AUTHOR]

An experimental investigation into the structural response and slip resistance of aluminium alloy–stainless steel connections fastened by means of high-strength stainless steel swage-locking pins is presented herein. Thirty-seven friction tests on aluminium alloy–stainless steel shear connections featuring different surface treatments and material grades were carried out. Complementary material tests were also performed, while the roughness and hardness of the connected surfaces were measured. The failure modes, load–slip responses, friction coefficients and preloading behaviour of all specimens are fully reported, while the test setup, specimen dimensions, configurations of fasteners, and positions of displacement measurements, are explained. The slip factors corresponding to the different surface treatments are presented, while the key parameters affecting the preload losses of the swage-locking pins and the friction coefficients are described. Finally, the suitability of various surface treatments for aluminium alloy–stainless steel connections is evaluated, while design slip factors, as well as correction coefficients accounting for the influence of different material grades and preload levels on the response of the examined connections, are set out. • Friction tests on aluminium alloy–stainless steel shear connections fastened by swage-locking pins conducted. • Key parameters affecting the preload losses of the swage-locking pins and the friction coefficients described. • Suitability of various surface treatments for aluminium alloy–stainless steel connections evaluated. • Design slip factors, as well as correction coefficients, set out. [ABSTRACT FROM AUTHOR]

Aluminium alloy-stainless steel structures combine the benefits of high strength-to-weight ratios of aluminium alloys with the excellent ductility of stainless steels. In order to explore the slip resistant aluminium alloy-stainless steel connections, this paper emphasized the surface characteristics and slip resistance of various surface treatments on aluminium alloy and stainless steel plates. Six applicable treatment methods for aluminium alloy-stainless steel slip resistant faying surfaces were experimentally investigated with specifications for the key parameters explored for the treatment procedures. The feasibility of two novel surface treatment methods on aluminium alloy and stainless steel surfaces was evaluated by material tests and the inspection for coatings. The key characteristics of the treated surfaces were comprehensively tested, including the 3D scanned surface topography, measured hardness and roughness. The relationships between the material type, hardness and roughness values under various surface treatments were discussed, which suggested the specific provisions for slip resistant connections in aluminium alloy-stainless steel structures were required. Friction tests of 18 shear connections were conducted to study the friction coefficients of different materials and surface treatments. The impactions of the surface characteristics on slip resistant behaviours of the treated surfaces were analysed. The roughness of the stainless steel surfaces and the hardness of the aluminium alloy surfaces influence the friction coefficients of the examined connections. Through comparative studies, the arc spraying and supersonic cold spraying, as two novel surface treatments, are suggested for the faying surfaces of aluminium alloy-stainless steel shear connections relying on their remarkably high friction coefficients. While the grit blasting and wire brushing also presented pronounced slip resistant capacities among the four examined mechanical surface treatments. • Friction tests of aluminium alloy and stainless steel connections conducted • Treatment methods on the aluminium alloy-stainless steel frictional faying surfaces suggested • Surface treatments of aluminium alloy and stainless steel shear connections tested • Results of tests on aluminium alloy and stainless steel surface characteristics presented • Applicable slip resistant surface treatment methods specified • Material properties, hardness and roughness of the treated surfaces experimentally analysed [ABSTRACT FROM AUTHOR]

Friction is one of the important factors in sheet metal forming. It greatly affects dynamic behaviors of metal sheets and stress and strain distributions in the metal sheets. In this study, deformation characteristics, stress–strain distribution, and change law of symmetrical parts in the process of deep drawing are analyzed using a new theoretical model based on the plastic flow law and partitioning the forming area. In the model, the least-square method is used to linearize the friction coefficient in nonlinear problems and reverse the calculation of friction coefficients to interpret the friction coefficient. To evaluate the model, the friction coefficient in sheet metal drawing of axis-symmetric deep drawing parts under various friction conditions was measured using a self-developed measuring system. The comparison between the experimental results and the calculation using the model shows a good agreement. The results show that the drawing force increases with the increase in punch depth; the friction coefficient decreases with the rise in punch depth. The friction coefficient obtained by fitting is relatively stable, and the average error is less than 3%. Using the friction coefficient model in finite element simulation analysis, it shows that the thickness and blank shape errors are less than 5%. The novel method studied in this paper shows great significance in support for theoretical research, numerical simulation research, and sheet metal stamping performance evaluation. [ABSTRACT FROM AUTHOR]

Evolution of static and kinetic friction coefficients across the depth of a horizontal wellbore and field validation against the downhole parameters is presented in this paper. It has been observed in the literature that stick–slip oscillations exist in drill strings even with bit off-bottom and persist with the bit on bottom. In the past, various lumped mass models have failed to explain this phenomenon, as they have only considered bit–rock interaction to be the main reason for the stick–slip oscillations. The model considered in this study was used previously to estimate the friction factors at particular connections with bit off-bottom. For effective estimation of the downhole parameters, the model employs an adaptive soft sensor, robust to capture the disturbances occurring at the downhole. Using only the topside measurements (i.e., surface measurements), downhole RPM is estimated along with the evolution of friction coefficients (static (μ s) and kinetic (μ k)) using the soft sensor. For obtaining the friction factors profile, those values of μ s and μ k that converge and remain stable for a specified time are considered. The model is first validated against the downhole RPM data obtained for a well in North America. It was observed that the estimates of the downhole RPM obtained using the model are in close agreement with that of the actual data. Next, the model was employed to obtain reasonable downhole RPM estimates for another well in North America where the downhole data is unavailable. • Drillstring dynamics are modeled using a distributed drillstring model. • Include the effects of tension in the drillstring in calculating the normal force with torsional motion is the dominant dynamic. • Obtain the friction factors profile across the entire run of the well bore. • Validation of the model against the field data for the entire run of the well bore for a couple of horizontal wells across North America. • The model provides estimates for downhole RPM, surface RPM and surface Torque that match closely with the field data. [ABSTRACT FROM AUTHOR]