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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]

Anti-lock braking systems (ABS) enhance vehicle safety by preventing wheel lock-up, but their effectiveness depends on tire-road friction. Traditional braking systems struggle to maintain effective performance due to the risk of wheel lock-up on varying road surfaces, affecting vehicle stability and control. This study presents a novel method to improve ABS efficiency across varying friction conditions. The proposed approach employs a feedback control mechanism to dynamically adjust the braking force of each wheel based on the prevailing friction coefficient. Specifically, we incorporate a P-controller in the input signal and two additional P-controllers as output and input parameters for friction. By manipulating the proportional control values, key parameters such as wheel speed, stopping distance, and slip rate can be effectively managed. Notably, our investigation reveals intriguing interactions between the proportional controls, highlighting the complexity of ABS optimization. The method was evaluated through simulations across various friction conditions, comparing it to conventional ABS in terms of brake performance, stability, and stopping distances. The results indicate that the proposed method significantly enhances ABS performance across varying friction coefficients; however, additional research is warranted to address stopping distance and time issues, particularly in snowy and icy conditions. [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]

Currently, the task of increasing the reliability and wear resistance of mechanisms and machines is being solved on the basis of the use of new composite materials. The most effective method of obtaining composite materials is the use of geological activators, which are introduced into the friction zone of the components of mechanisms and machines through a lubrication system, which allows increasing the micro-moisture of the friction surfaces up to 2,3 times, as well as reducing friction in sliding and rolling bearings. According to the research results, it is found that the use of repair and restoration technologies in friction pairs leads to energy savings of 10–20 %, an increase in wear resistance by 2,5 times, an increase in the resource of lubricants by 2,5–5 times, a significant reduction in vibration noise, as well as an increase in the inter-repair resource by at least 2 times and a reduction in operating costs. However, for the widespread introduction of these technologies, additional studies are needed, which are given in this paper.

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]

Introduction. The power analysis of a chain transmission with a toothed chain and involute sprockets considers the centrifugal forces and the friction coefficients between the plate and the sprocket tooth. The work objectives are to determine all meshing forces, and to calculate the coupling coefficient of the gear chain with the involute sprocket in the drive gears.Materials and Methods. When evaluating the traction capacity of a chain transmission, such parameters as the power analysis and the coupling coefficient of the gear chain with the sprocket are important (it shows what fold the pressure on a given tooth is greater than the pressure perceived by the tooth in front). In the presented paper, the following diagrams are visualized: the arrangement of the plates in gearing with the involute sprocket teeth and the meshing forces. The factors that affect the involute profile of the sprocket tooth are considered. This includes the weight of the chain plate package and the force: centrifugal, friction, normal pressure and tension. At the same time, changes in the coupling coefficient for the subsequent teeth involved in traction are taken into account. The balance of the links i and i+ 1 of the gear chain is studied in the coordinate system XOY with the center on the axis of rotation of the involute sprocket. The method enables to determine all the desired forces through the geometric calculation of the values of the angular transmission parameters. Using the equations obtained, the following parameters are specified: the coupling coefficient Bi, the tension of the driving branch S1 and the slack branch S2.Results. A patented transmission stand with a gear chain and involute sprockets is presented. The tests carried out on itvalidated the study results of a chain transmission with a toothed gear and involute sprockets with the specified parameters. The correctness of the power analysis of the transmission with account for the centrifugal forces and the friction coefficients of the plates and the sprocket teeth was proved.Discussion and Conclusions. It is noted that the centrifugal forces and the friction coefficients during engagement affect significantly the traction capacity of a transmission with a toothed chain and involute sprockets. The data obtained can be used to accurately estimate the traction capacity of such gears.

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]

Deep drawing is characterized by extremely complex deformation that is influenced by process characteristics such as die and punch shapes, blank shape, blank holding force, material properties, and lubrication. The optimization of the deep drawing process is a challenging issue due to the complicated functions that define and relate the process parameters. However, the optimization is essential to enhance the productivity and the product cost in the deep drawing process. In this paper, a MATLAB toolbox (Pattern Search) was employed to minimize the maximum deep drawing force (Fd-min) at different values of the operating and the geometrical parameters. As a result, a minimum deep drawing force chart (carpet plot) was generated to show the best combination of friction coefficients at the blank contact interfaces. The extracted friction coefficients guided the selection of proper lubricants while minimizing the deep drawing force. A finite element analysis (FEA) was applied through 3D model to simulate the deep drawing process. The material modeling was implemented utilizing the ABAQUS/EXPLICIT program with plastic anisotropy. The optimization results showed that the deep drawing force and the wrinkling decrease when compared with experimental and numerical results from the literature. [ABSTRACT FROM AUTHOR]

The double-disc straight-groove (DDSG) grinding method is a new precision machining approach employed for the rolling surface of bearing rollers. The friction coefficient and wear resistance of grinding disc materials affect the grinding performance due to the operation on the workpiece. However, relevant research on DDSG is rather limited currently. Therefore, we analyzed the friction principles of the DDSG method and conducted friction and wear experiments to facilitate appropriate material selection for grinding discs. The optimal friction conditions for grinding disc materials were determined to ensure steady rotation of cylindrical rollers. In addition, the friction coefficients, wear resistance, and clogging resistance of various materials such as PTFE, PMMA, cast iron, brass, and fixed abrasives were measured by friction and wear experiments under grinding conditions. The friction pairs of PMMA-AISI 52100 and PTFE-AISI 52100 exhibited sliding friction coefficients of 0.14 and 0.03, respectively, along with a high grinding efficiency and excellent wear resistance. The friction pairs of both bearing steel-fixed abrasive and bearing steel-brass were easily clogged, leading to dramatic changes in the sliding friction coefficients, and neither fixed abrasive nor brass was found to be a suitable material for grinding discs. Thus, PMMA and PTFE were selected as the materials for upper and lower grinding discs. Moreover, a verification platform was built to implement the DDSG grinding method where a continuous rotation of ground roller was observed. Overall, this study provides a basis for feasible material selection and an appropriate material combination for designing a grinding machine based on DDSG. [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.

A method for predicting and calculating friction coefficients and kinetic characteristics for electrodialysis separation of industrial solutions containing nickel ions was developed. Approximations for predicting friction coefficients that could then be used to calculate kinetic characteristics for electrodialysis separation of industrial solutions were obtained using the developed method. The discrepancy between experimental and theoretically calculated data was estimated in most instances at ≤ 5%, indicating that the developed method was acceptable for use. [ABSTRACT FROM AUTHOR]

The general stages of application of modeling of mass transfer of substances through a membrane in solution separation process for designing industrial apparatuses are presented. Numerical values of empirical coefficients are obtained to calculate friction coefficients of solvent–membrane, solute–membrane, and solute–solvent systems for anode-adjacent and cathode-adjacent membranes for separation of model aqueous CuSO4, Fe(NO3)3, and Ni(NO3)2 solutions of engineering industries. [ABSTRACT FROM AUTHOR]

Describing the effects of surface roughness on flow resistance remains a first‐order challenge for modeling shallow overland flow using the Saint Venant equations (SVE). This challenge has resulted in a proliferation of roughness schemes relating the properties of a uniform rough surface to bulk velocity and resistance, making selection of an appropriate roughness scheme daunting—especially on heterogeneous surfaces. For hydrological predictions, a roughness scheme is appropriate if the resulting SVE solutions predict outcomes such as water balance partitioning between runoff and infiltration, the hillslope hydrograph, and the discharge velocity with uncertainties that are less than or comparable to uncertainty in measurements. To assess the sensitivity of hydrological predictions to the choice of a roughness scheme, multiple schemes are first calibrated to each other under equilibrium flow conditions while imposing the kinematic wave approximation at the outlet. This approach yields analytical relations between the parameters of different roughness schemes when applied to the same hillslope and discharge. The approach is used to provide a parameterization of five commonly used roughness schemes for a common surface, and the predictions of the schemes for multiple patchily vegetated hillslopes are compared. The results suggest that, once calibrated, there is minimal prediction sensitivity to the choice of roughness scheme across a wide range of rainfall conditions. Operationally, the results demonstrate that parameterizing a roughness schemes is of higher significance for predicting hydrological patterns than the precise formulation employed. Key Points: Roughness effects in nonkinematic overland flow can be approximated using a kinematic wave approximationThe sensitivity of hydrological predictions to the depth‐velocity scaling exponents closing the friction slope is smallParameterizing the "scale" of roughness remains a key source of uncertainty [ABSTRACT FROM AUTHOR]

Accurate understanding of the frictional behavior at the tool-chip interface is critical for the cutting process. To quantitatively analyze the ratio of the sticking contact length to tool-chip contact interface length, a concise calculation model was proposed. Orthogonal cutting experiments and friction experiments were conducted to acquire the friction coefficients for use as input parameters to the model. Calculations found that the ratio, the sliding contact length, and the tool-chip contact interface length showed downward tendencies with increasing cutting speed. The maximum value of the ratio was 63.2 %, achieved at 1000 m/min, whereas the minimum was 58.6 %, achieved at 800 m/min. Furthermore, as the cutting speed rises, the sliding and apparent friction coefficients decrease, while the sticking friction coefficient remains nearly constant. The findings are helpful to improve people's cognition of sticking-sliding contact, the quality of machining, and determine the thickness and length of the tool coating. [ABSTRACT FROM AUTHOR]

In this report, the with-in wafer non-uniformity (WIWNU) of material removal rate and its optimization are discussed from both the machine side and consumable side. At the machine side, the pressure and velocity distribution are the major reasons for the non-uniform material removal rate across the wafer. The velocity distributions for the rotational type and linear type of machines are analyzed systematically. The rotational part of the velocity is the contributor of the velocity non-uniformity. The pressure non-uniformity in both cases of the solid-solid contact and the solid-fluid-solid contact are discussed. Adding the retaining ring is an effective way to reduce the pressure non-uniformity at the edge of the wafer in the solid-solid contact mode. In the solid-fluid-solid contact mode, the friction coefficient is identified as the major contributor to the non-uniformity. A process window of pressure and velocity in terms of small non-uniformity can be obtained by combining the model proposed in this report and the Stribeck curve of the friction coefficients. At the consumable side, a systematic method is proposed to optimize the WIWNU in solid-solid contact mode, based on the material removal model developed in previous works [5, 6, 7]. The basic idea is to reduce the sensitivity of the material removal on pressure and velocity distribution.

Deep drawing is characterized by extremely complex deformation that is influenced by process characteristics such as die and punch shapes, blank shape, blank holding force, material properties, and lubrication. The optimization of the deep drawing process is a challenging issue due to the complicated functions that define and relate the process parameters. However, the optimization is essential to enhance the productivity and the product cost in the deep drawing process. In this paper, a MATLAB toolbox (Pattern Search) was employed to minimize the maximum deep drawing force (Fd-min) at different values of the operating and the geometrical parameters. As a result, a minimum deep drawing force chart (carpet plot) was generated to show the best combination of friction coefficients at the blank contact interfaces. The extracted friction coefficients guided the selection of proper lubricants while minimizing the deep drawing force. A finite element analysis (FEA) was applied through 3D model to simulate the deep drawing process. The material modeling was implemented utilizing the ABAQUS/EXPLICIT program with plastic anisotropy. The optimization results showed that the deep drawing force and the wrinkling decrease when compared with experimental and numerical results from the literature.

The present work investigates the lubricant capabilities at room and hot-forging temperatures (>1400 K) of three types of lubricants with two different graphite concentrations (8% and 12%). These lubricants are distinguished by measuring the percentage of chemical elements and average size of graphite particles. Later, two standardized methods, i.e., pin-on disc and ring test, are utilized to assess the main friction differences under laboratory and real industry conditions, respectively. The results exhibit that the friction values at room temperature are lower for lubricant B, no matter which type of graphite concentration is used, whereas at hot-forging temperatures, greater percentage of graphite enhances lower frictional values when higher deformations are assessed. Additionally, the ring tests performed at hot-forging temperatures show significant tribology differences when the degree of deformation reaches 50%. Particularly, the lubricant B shows the lowest values of friction coefficients of 0.22 and 0.21 for 8% and 12% of graphite concentration, respectively. Therefore, it can be concluded that the selection of a proper type of lubricant (regarding chemical composition and size of solid suspension) and the graphite concentration are sensitive parameters, when it comes to achieve different bulk deformations combined with extreme temperatures like in hot-forging process. [ABSTRACT FROM AUTHOR]

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]

Comparative investigation on friction and wear properties of SiC, Si(3)N(4), Al(2)O(3), and ZrO(2) lubricated with seawater was carried out on a ring-on-ring contacted tribological test apparatus, and their worn surfaces were observed by an ultra-depth optical microscope. The results reveal that the friction coefficients of Si(3)N(4) and SiC are obviously lower than those of Al(2)O(3) and ZrO(2) when they slide against the polyetheretherketone (PEEK) composite in seawater, and the friction stability of ZrO(2) is so poor that it is not suitable for seawater hydraulic piston pumps. When the contacted load increases from 400 to 1000 N, the wear rate of Al(2)O(3) is still the highest, while the wear rates of SiC and Si(3)N(4) change from positive to negative, which indicates that plastic transfer is occurred under a heavier load. When they slide against the PEEK in seawater, the main tribological mechanism of SiC, Si(3)N(4), and Al(2)O(3) is slightly abrasive wear, while both abrasive wear and adhesive wear occur for ZrO(2). Generally, both SiC and Si(3)N(4) have wide prospect applied in seawater hydraulic piston pumps, and particularly Si(3)N(4) exhibits excellent friction and wear properties in seawater.

Abstract The non-Markovian dynamics of a charged particle linearly coupled to a neutral bosonic heat bath is investigated in an external uniform magnetic field. The analytical expressions for the time-dependent and asymptotic friction and diffusion coefficients, cyclotron frequencies, variances of the coordinate and momentum, and orbital magnetic moments are derived. The role of magnetic field in the dissipation and diffusion processes is illustrated by several examples in the low- and high-temperature regimes. The localization phenomenon for a charged particle is observed. The orbital diamagnetism of quantum system in a dissipative environment is studied. The quantization conditions are found for the angular momentum. [ABSTRACT FROM AUTHOR]

Copyright of Wood Industry / Drvna Industrija is the property of Drvna Industrija 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 work investigates some tribological parameters of the surfaces of friction pairs made of steel, with mineral layers. A comparative study of the friction coefficient of 18CrNiMo7-6 steel specimens with and without a mineral coating is performed. The lowest friction coefficient value was achieved for samples with mineral coating, without HFC hard surfacing before creating a mineral layer, and it was approximately 15% lower in comparison with the samples with HFC hard surfacing, but without mineral coating. The friction coefficient in the temperature range of 30..140 °C, with constant displacement speed of samples with mineral coatings is practically unchanged for every sample type, the variation range does not exceed 0.02, as contrasted with the friction coefficient of the samples with hard surfacing, but without mineral coating. The value of the coefficient of volumetric wear of an aluminum oxide toroid during rotation with disks with some types of mineral coatings was at the level of detection limit (less than 1.2x10-9 mm3/Nm), which is significantly less than the coefficient of volume wear of a toroid during rotation with disks without coating (4-7)X10-8 mm3/Nm. [ABSTRACT FROM AUTHOR]

The quantum Langevin formalism is used to study the charge carrier transport in a two-dimensional sample. The center of mass of charge carriers is visualized as a quantum particle, while an environment acts as a heat bath coupled to it through the particle–phonon interaction. The dynamics of the charge carriers is limited by the average collision time which takes effectively into account the two-body effects. The functional dependencies of particle–phonon interaction and average collision time on the temperature and magnetic field are phenomenologically treated. The galvano-magnetic and thermo-magnetic effects in the quantum system appear as the results of the transitional processes at low temperatures. [ABSTRACT FROM AUTHOR]

In nanoscratch experiments, the frictional shear force vector applying on each element of the contact surface between the nanoindenter and material is in the direction of material flow lines or relative displacement vectors. In this paper, the material flow lines in the nanoscratch test around the Berkovich nanoindenter in the face-forward orientation are investigated. The finite element simulation of nanoscratch test is conducted to calculate and track the trajectory of the material points located on the material surface. The material flow lines around the nanoindenter are qualitatively and quantitatively explained and a new method entitled focal point method is proposed to describe the material flow lines in the contact surface. The evolution of the material flow lines in terms of the material properties and local friction coefficient is studied. The adhesive friction coefficient is calculated using the pattern of flow lines obtained by the focal point method. There is a close agreement between the predicted friction coefficients and those obtained from the finite element simulation and experiment, so that the error percent is about 5.7%. [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]

The mean free path, the electronic stopping power and the straggling parameter of a heavy charged particle moving through a homogeneous free-electron gas are addressed in the low-velocity regime and within the dielectric formalism using the Lindhard dielectric function. Simple analytical formulas are developed for these macroscopic cross sections, which are more accurate in the whole electron density range than those proposed to date by some authors. [ABSTRACT FROM AUTHOR]

The addition of graphene nanosheets (GNSs) in lubricating grease could significantly reduce the interfacial friction and improve the load-bearing capacity of the parts. Therefore, it has been considered as having great potential as lubricant additives. In this study, we synthesized GNSs that are prepared by a modified Hummer method, and investigated the effect of GNS with different concentration (0.5%, 1%, 2%, 3%, and 4 wt%) on the tribological properties of the calcium grease. The friction and wear experiments were performed using a four-ball tribometer. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to examine the GNS and the friction mechanisms. Results indicate that the friction reduction ability and anti-wear property of the base grease can be improved with the addition of GNS. It was also found that the friction reduction decreases by 61%, and the wear scar diameter (WSD) decreases by 45%, and the extreme-pressure (EP) properties increased 60% at 3 wt% GNS. It is clear that the GNS in grease easily forms protective deposited films to prevent the rubbing surfaces from coming into direct contact, thereby improving the entire tribological behavior of the grease. [ABSTRACT FROM PUBLISHER]

In this study, some physical properties (three axial dimensions, geometric mean diameter, sphericity, volume, surface area, unit mass, true and bulk density) and frictional characteristics (angles of repose and static and dynamic coefficients of friction against four structural surfaces namely aluminium, plywood, galvanized iron and rubber) as a function of maturity indices for Ashraf variety of pomegranate arils were investigated. All physical properties of pomegranate arils were significantly (P<0.05) affected by changing maturity in the studied stages. The obtained results showed that studied physical properties (except sphericity and true density) and frictional characteristics increased with an increase in maturity. The highest static coefficient of friction for pomegranate arils was against the rubber surface, followed by plywood, galvanized iron, and finally aluminium surfaces. In addition, static coefficient of friction values were higher than the dynamic coefficient of friction at similar maturity stages of the samples and on the same surfaces. The emptying angle of repose found to be higher than the filling angle of repose for pomegranate arils at all maturity stages. Static and dynamic coefficient of friction as well as empting angle of repose increased linearly with advancement of maturity. [ABSTRACT FROM AUTHOR]

THE EXACT ANALYTICAL EXPRESSIONS FOR the time-dependent cross-correlations of the translational and rotational Brownian displacements of a particle with arbitrary shape were derived by us in [3, 4]. They are in this work applied to construct a method to analyze the Brownian motion of a particle of an arbitrary shape, and to extract accurately the self-diffusion matrix from the measurements of the crosscorrelations, which in turn allows to gain some information on the particle structure. As an example, we apply our new method to analyze the experimental results of D. J. Kraft et al. for the micrometer-sized aggregates of the beads [8]. We explicitly demonstrate that our procedure, based on the measurements of the time-dependent cross-correlations in the whole range of times, allows to determine the self-diffusion (or alternatively the friction matrix) with a much higher precision than the method based only on their initial slopes. Therefore, the analytical time-dependence of the cross-correlations serves as a useful tool to extract information about particle structure from trajectory measurements. [ABSTRACT FROM AUTHOR]