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To investigate the meshing characteristics of involute spur gear pairs, a time-varying mesh stiffness (TVMS) model is developed in this study, which pays special attention to the nonlinearity of lubrication and friction in the meshing process. Here, to improve the modeling quality, four typical parameters are considered in the model, including the lubrication state, the non-Newtonian shear characteristics of the lubricant, the time-varying displacement of the asperity, and contact conditions along the meshing path. The proposed model provides an interdependence between tooth surface contact characteristics and gear comprehensive meshing stiffness, which can provide a guidance for enhancing the performance of involute spur gears. Furthermore, the effects of roughness, rotation speed, and load on TVMS are investigated, exhibiting distinct regional characteristics along the meshing path. Noticeable differences are observed in the intensity of disturbance in the meshing-in, meshing-out, single-tooth pair, and double-tooth pair contact areas. [ABSTRACT FROM AUTHOR]

Surface-projected piles, such as helical and under-reamed piles, are widely utilized in geotechnical engineering to enhance the load-carrying capacities of pile structures with surface projection part. Despite the use of a wide variety of surface-projected conditions, detailed investigations considering various dimensions and angles of surface-projected piles remain limited in the current literature. This study aims to assess the effects of surface-projected widths wp (10 mm, 20 mm, 40 mm) and angles θ (18°, 27°, 45°, 90°) on pile penetration resistance using a two-dimensional model and PIV analysis. Wider projections increased resistance, with a maximum of 1.84 kN—57% higher than conventional piles in the model ground. Penetration resistance was proportional to width at 90°; for wp = 20 mm, penetration resistance decreased with increasing θ, while for wp = 40 mm, it increased. Theoretical ultimate bearing capacity calculations emphasize differences from experimental results due to neglected shaft friction. Residual penetration resistance and particle displacement were observed for wp of 20 mm and 40 mm after failure. This study provides insights into optimizing surface-projected pile design and understanding ground failure mechanisms. [ABSTRACT FROM AUTHOR]

To improve the tribological performance of SS410 steel in seawater, TiCrN and CrSiN coatings were deposited using PVD sputtering and thoroughly analyzed. The CrSiN coating, which exhibits higher hardness and better corrosion resistance, achieved a protective efficiency of 83.70%, surpassing the TiCrN coating by 14% according to anodic polarization tests. Friction and wear properties were evaluated with a ball-on-disk tribometer in artificial seawater, following ASTM G77 standards. The CrSiN coating demonstrated lower friction coefficients and wear rates—1.362 × 10⁻⁶ mm3/N-m compared to 2.632 × 10⁻⁶ mm3/N-m for TiCrN at a 4N load—highlighting the positive impact of Si addition. These coatings markedly enhance the tribocorrosion resistance of AISI 410 steel, addressing issues in marine engine components, extending their service life, and ensuring reliable performance in severe marine conditions. SEM analysis of the uncoated SS410 surface revealed pits and deep grooves. [ABSTRACT FROM AUTHOR]

As an important turbocharging equipment, hydraulic pumps are prone to internal wear and corrosion problems. In order to improve its friction and wear performance, a ceramic coating strengthening scheme based on laser cladding technology was proposed. The roughness, thickness, width, hardness, and residual stress of the coating under different laser powers and scanning rates were measured, and the effect of process parameters on the coating structure was determined to ensure the optimal basic mechanical properties of the coating. Under the experimental conditions of 10–30 N pressure and 10–20 mm/s lubricated friction velocity, high cycle tribological tests were conducted, and the changes in average friction coefficient, wear amount, and surface wear mechanism were compared and analyzed. To verify the impact of reinforced coatings on corrosive environments, friction and wear tests were conducted in hydraulic oil environment with a pH of 6.4 and particle impurity content of approximately 5 %. Through electron microscopy, the friction morphology was observed and the wear mechanism was analyzed. In order to study the effects of different overloads (including temperature and pressure loads) on friction damage, overload friction damage analysis was conducted under low cycle fatigue loading conditions. The Rtec friction machine was applied, and the test temperature and pressure were set at 400 °C, 500 °C, 750 MPa, and 1000 MPa, respectively. The coating sample speed was set to 500 r/min and the slip rate is set to 5 %. Each sample was worn for 4 cycles under different pressures, with each cycle worn for 1 hour, then the surface roughness morphology and micro wear morphology were obtained. The research results indicate that the friction stability, wear resistance, and hardness of the coating have significantly improved, and it has stronger adaptability to hard or sharp materials, making it very suitable for the working environment of hydraulic pumps. [ABSTRACT FROM AUTHOR]

Rock pore structure coupled with fluid pressure plays an important role in controlling fault slip behavior. Observation of fluid-induced seismicity in geoenergy extraction has raised fundamental questions about the physics of fault rock structure and fault frictional stability in the presence of fluid. Here, we change the pore structure of faults by thermal treatment and report on the frictional stability of granite faults with pore evolution and pore fluid pressure in velocity stepping experiments under the rate-and-state framework, where the variation of pore fluid is monitored. The experiments under constant fluid pressure show that pore structure propagation leads to an increase in friction coefficient from 0.71 to 0.78. As the degree of pore propagation increases, the drained fault exhibits a transition from velocity strengthening to weakening behavior. The decrease in frictional stability could be caused by the coupling between the pore fluid and the well-connected pores, namely “fluid oscillation”. Pore pressure overpressurization could develop and cause non-uniform stress distribution along the fault surface due to pore fluid oscillation at velocity steps. The time required to equilibrate fluid pressure could be prolonged by fluid oscillation, leading to intrinsic velocity strengthening behavior appearing as velocity weakening. The decrease in rate-and-state parameter with elevating pore fluid pressure on high-porosity fault corroborates the fluid-induced fault destabilization. The fluid oscillation at the greater pore pressure could be responsible for fault reactivation. Therefore, the coupling effect of rock pore structure with pore fluid could be a potential mechanism governing fault frictional stability. [ABSTRACT FROM AUTHOR]

Based on the random distribution patterns of rock fragmentation (RF), a concrete–rock shear model (CRSM) considering RF was developed through the application of statistical theory. The significance and determination methods of the model parameters were elucidated. A comparison of the results based on the CRSM with and without consideration of RF with the experimental results from the concrete–rock shear test was performed, revealing a closer alignment for the model considering RF. This model effectively characterizes the yield deformation phase and the strain softening phase in the concrete–rock shear process. By utilizing load transfer theory and the CRSM considering RF, a differential equation of load transfer for rock-socketed piles (RSPs) considering RF was formulated by applying the Runge‒Kutta method. Considering RF, the pile top load versus settlement curves and the pile–rock relative displacement (sp‒r) versus pile side friction (τp‒r) curves exhibited a closer alignment with the results of full‒scale static load tests. The linear elastic deformation phase and the yield deformation phase of the sp‒r versus τp‒r curves were accurately characterized. In addition, a sensitivity study of the parameters was undertaken to analyse their effects on the concrete–rock shear mechanism and the load-bearing mechanism of RSPs. Highlights: Rock fragmentation is a crucial factor affecting the concrete–rock shear mechanism. The equation of the rock fragmentation variable was established to describe the fragmentation state of the rock during concrete–rock shearing. The bearing capacity of rock-socketed piles considering rock fragmentation closely aligns with the full-scale static load test results. [ABSTRACT FROM AUTHOR]

Background: Wire ropes or cables are widely used solutions for force transmission in several industrial applications. Their hysteretic behavior may significantly influence control accuracy or the force transmission's efficiency. Cables traveling through sheaves can suffer a relatively high tension loss, which this article addresses. Objective: This paper aims to present a simple measurement method for the tension loss in cables traveling over sheaves on bearings. Methods: The presented measurement method uses a cable-pulley system with a spring installed at one cable end. The pulley is moved in a zig-zag pattern. The force is measured on both cable ends; this way, the tension loss can be determined as a function of the cable tension. The force was measured with S-type load cells, which are highly sensitive to off-axis loads; this problem can be overcome by proving that the force measurement has a proportional error, which can be eliminated from the frictional coefficient. The measurements are compared to two models from the literature; one approximates the power loss of a cable drive by calculating the work of the cable's inner friction, and the other is a cable bending model, which is used to determine the hysteretic energy of the cyclic bending. Results: The result of the measurement evaluation is a coefficient of tension loss that contains the loss coming from the cable bending and the bearing friction. Four cable types and a steel strip with negligible bending hysteresis were measured, the latter for control measurement. It is demonstrated that a significant part of the tension loss originates from the inner friction of the cable and that it is equal to the hysteretic energy of the cyclic bending. Conclusion: The presented method provides a robust measurement for the tension loss factor in cables traveling over pulleys. It is proven that the off-axis loads cause a proportional error in the force measured by S-type load cells, and this measurement error can be eliminated from the tension loss factor. The results demonstrated that the presented models can be used to predict the tension loss in cables traveling over sheaves. [ABSTRACT FROM AUTHOR]

For the purpose of improving the forming quality of cold extrusion internal thread and investigating the interactive effects of distinct process parameters on the forming quality of internal thread, this article established a regression response model between the influencing factors and optimization objectives by using the response surface experiment analysis method, and obtained the interactive effects of the bottom hole diameter, the extrusion speed and the coefficient of friction on the extrusion torque, extrusion temperature, and tooth height rate. The objective function was optimized using the regression model to obtain the optimal combination of parameters (bottom hole diameter 7.34 mm, extrusion speed 30 r/min, and friction coefficient 0.11). For the purpose of verifying the feasibility and validity of the theoretical model and the optimized design, internal thread extrusion experiments are carried out under the optimal combination parameters. The experiment results show that the extrusion torque is 3.17 N m, the extrusion temperature is 79.8 °C, and the tooth height rate is 77.23%, and the error with the predicted value is 8.56%, 2.57%, and 5.27%, respectively, which further demonstrates the accuracy of the model. [ABSTRACT FROM AUTHOR]

In this paper, we consider the frictional contact model between a piezoelectric body and an electrically conductive foundation. This contact is described by a reduced normal compliance law. To address this problem, we establish a mixed variational formulation and prove the existence of a unique solution. Moreover, we present an efficient algorithm for approximating the weak solution for the contact problem, taking into account both friction and electrical contact conditions. We conclude with numerical examples that demonstrate the practicality of the model. [ABSTRACT FROM AUTHOR]

Against conventional wisdom, corrugated grain boundaries in polycrystalline graphene, grown on Pt(111) surfaces, are shown to exhibit negative friction coefficients and non-monotonic velocity dependence. Using combined experimental, simulation, and modeling efforts, the underlying energy dissipation mechanism is found to be dominated by dynamic buckling of grain boundary dislocation protrusions. The revealed mechanism is expected to appear in a wide range of polycrystalline two-dimensional material interfaces, thus supporting the design of large-scale dry superlubric contacts. This work demonstrates non-Amontons frictional behavior and negative differential friction coefficients at graphene/Pt(111) surface grain boundaries due to dynamic buckling of dislocations, providing vital insights for the design of macroscopic dry superlubric contacts. [ABSTRACT FROM AUTHOR]

In this study, the tribological characteristics of TiN, AlTiN, and AlTiCrN coatings sliding against a SUS420J1 stainless steel pin were investigated in atmospheric and vacuum environments. The coatings were deposited on SUS440C substrates using the arc-physical vapor deposition technique. The friction and wear behavior of the coatings were evaluated based on the systematic analyses of the friction coefficient data as well as the physical and chemical state of the wear track. The results revealed that the friction coefficients of the SUS440C specimen and AlTiCrN coatings increased, whereas those of the TiN and AlTiN coatings decreased when the environment was changed from atmospheric to vacuum. It was confirmed that the formation of an oxide layer and adsorption of oxides on the surface were dominant factors that influenced the tribological behavior in the atmospheric environment. On the other hand, the compatibility, oxidation inhibition, and droplets of the surface mainly affected the frictional characteristics in the vacuum environment. The results of this work are expected to aid in the selection of proper coating materials for tribological systems operating in a vacuum. [ABSTRACT FROM AUTHOR]

Hydrogels have been the subject of significant research in the field of friction due to their exceptional lubricating properties. In this study, the G-quadruplex hydrogel with high selectivity for K+ ions was formed by introducing a mixture of G, 2-formylphenylboronic acid, and polyethylene glycol diamine into simulated artificial tears solution with high transparency, and an ultra-low coefficient of friction (COF) of about 0.004 was obtained based on the simulated ocular environment, thus achieving macroscopic superlubricity. In friction pairs simulating the ocular environment, to assess the frictional performance of the G-quadruplex hydrogel as both a lubricant and a friction pair based on the simulated ocular environment, we conducted experiments considering various factors such as concentration, sliding speed, and stress. Through these experiments, it was found that superlubricity was achieved when the G-quadruplex hydrogel was applied as lubricant or friction pair. This effect was attributed to the three-dimensional network structure and hydrophilicity of the hydrogel, which facilitated the formation of a highly bearing and flowing hydration layer, promoting macroscopic superlubricity. Compared to the G-quadruplex hydrogel with low concentration, the high concentration hydrogel (75 mM) exhibited increased mechanical strength and robustness in superlubricity. Combined with biocompatibility experiments, our synthesized G-quadruplex hydrogel has excellent biocompatibility and offers a novel approach to achieve superlubricity in ocular drug delivery. [ABSTRACT FROM AUTHOR]

Pile foundation structures are widely used in the construction of high-piled wharves in coastal soft soil areas due to their excellent adaptability to such environments. However, the extensive, deep backfilling involved in constructing these wharves can easily induce negative skin friction (NSF) on the piles, resulting in safety issues such as excessive settlement during the service life of the structures. This paper presents an indoor model experiment to examine the distribution of the THE NSF under varying pile-top loads and surcharge effects on single pile and double-sleeve pile foundations. The potential of double-sleeve pile foundations to mitigate the NSF was also explored. The results show that the axial force within the double-sleeve pile's protected section remains essentially stable, though it is affected by the surface surcharge in the unprotected section. Time effect is exhibited both for the axial force and the NSF, gradually increasing over time. Compared to single piles, double-casing pile foundations can effectively isolate the down drag load caused by surrounding soil settlement, thereby reducing or eliminating the NSF on the pile sides. [ABSTRACT FROM AUTHOR]

Mandrel is an indispensable tool for manufacturing hollow curved components with large diameter by rotary draw bending. In this paper, an analytical model of mandrel parameters in numerical control (NC) rotary bending of a large diameter tube using a spherical hinge mandrel was proposed, and then the mandrel extension length and core number were preliminarily determined. A nonlinear 3D elastoplastic finite element (FE) model for simulating the NC rotary bending was established. The influences of mandrel-cores on the tangential stress, strain, and bending deformation characteristics were systematically studied. The results show that the maximum prediction errors of wall thicknesses and cross-section distortion are all less than 10%, and the simulated wrinkling position and number also showed good agreements with experimental ones, which indicate that the established FE model is accurate and reliable. Compared with the tube bending without mandrel-cores, the difference between maximum tangential tensile and compressive stresses, as well as the shift of stress and strain neutral layers, was smaller for tube bending with mandrel-cores, which had a good inhibitory effect on cross-section distortion and wrinkling. During tube bending with mandrel-cores, the compressive deformation zone was only located within the zone from the bending tangent point to the section position of 30°, and the tangential compressive strain reached peak value at the section position of 30°. Among the mandrel parameters, core number has a significant influence on cross-section distortion, while mandrel extension length is more sensitive to the wall thickness thinning. The cross-section distortion decreased while the wall thinning rate increased with increasing mandrel extension length, core number, and decreasing the clearance between mandrel and tube. A low friction between the mandrel and tube can decrease cross-section distortion and wall thinning rate. The appropriate mandrel extension length, core number, and clearance between mandrel and tube in NC rotary bending of ⌀ 76 × 1.2 × R150 mm tube were 9 mm, 3, and 0.2 mm, respectively. [ABSTRACT FROM AUTHOR]

Various machine learning (ML) and deep learning (DL) techniques have been recently applied to the forecasting of laboratory earthquakes from friction experiments. The magnitude and timing of shear failures in stick-slip cycles are predicted using features extracted from the recorded ultrasonic or acoustic emission (AE) signals. In addition, the Rate and State Friction (RSF) constitutive laws are extensively used to model the frictional behavior of faults. In this work, we use data from shear experiments coupled with passive acoustic (variance, kurtosis, and AE rate) interleaved with active source ultrasonic monitoring (transmitted wave amplitude) to develop physics-informed neural network (PINN) models incorporating the RSF law and AE rate generation equation with wave amplitude serving as a proxy for friction state variable. This PINN framework allows learning RSF parameters from stick-slip experiments rather than measuring them through a series of velocity step experiments. We observe that when the stick-slip cycles are irregular, the PINN models outperform the data-driven DL models. Transfer learning (TL) PINN models are also developed by pre-training on data collected at one normal stress level followed by forecasting shear failures and retrieving RSF parameters at other stress levels (i.e., with different recurrence intervals) after retraining on a limited amount of new data. Our findings suggest that TL models perform better compared to standalone models. Both standalone and TL PINN-estimated RSF parameters and their ground truth values show excellent agreements thus demonstrating that RSF parameters can be retrieved from laboratory stick-slip experiments using the corresponding acoustic data and that the transmitted wave amplitude provides a good representation of the evolving frictional state during stick-slips. [ABSTRACT FROM AUTHOR]

This article presents wheel wear in light rail traffic and the friction behavior of wheel material under both dry and lubricated conditions. The main purpose of this research is to study the wheel-rail tribology for the Addis Ababa Light Rail Transit and to evaluate the friction and wear behavior of the wheel material under both dry and lubricated conditions. Composition, hardness, and ring compression tests were conducted to characterize the existing and the developed material. The percentage composition of carbon, manganese, and silicon gained 0.5%, 0.7%, and 0.25%, respectively, for existing and 0.8%, 1.15%, and 0.38% for alloyed wheel steel. It is also shown that the hardness value of the wheel material increased from 98.88 to 99.7 HRC when the existing material is compared with the developed material. The samples with dimensions outer diameter of 42 mm, inner diameter of 21 mm, and height of 14 mm were used for this study, and the dimensional change occurring under ring compression is different depending on the dry and lubricant conditions. Based on experimental analysis, 0.15, 0.13, and 0.09 were the evaluated coefficients of friction for dry, grease, and oil conditions, respectively. It is concluded that 0.09 is a coefficient of friction and oil is a suitable lubricant. To minimize wheel wear in the wheel-rail, proper lubrication and better application, improved wheel material, and revised track alignment for easier cornering and improvement are required. [ABSTRACT FROM AUTHOR]

The friction and initial setting position of preform have an important influence on the metal flow and cavity filling during die forging process of large-scale component, especially for closed-die forging with flash of large-scale titanium alloy strut. This paper studies the influence of processing parameters on the die forging process of large-scale strut by targeting the filling difference (f) between right and left cavities, and some relational models such as relationship between friction and preform position were established. The results indicated that the friction amplitude (m) and initial setting position (x) of preform have notable influence on the filling states of right and left cavities, but the loading speed (v) of upper die and initial temperature ( T d ) of dies have little influence on the filling state; with the initial position of preform moving to right cavity (head of strut), the fluence of m on f reduces, but the fluence of x increases; the established relationship between m and x can obtain the feasible region with an optimal point for initial setting position of preform, and the feasible region with a linear range for the initial setting position of preform can be obtained by considering the expected accuracy of filling difference f, and then the feasible region with an areal range for the initial setting position of preform can be obtained by considering the fluctuation of frictional condition in further. [ABSTRACT FROM AUTHOR]

Designing the roller and determining the required passes to manufacture the bar depend on the estimation of the pressure value during the bar rolling operation. Numerous researchers have proposed a mean unit pressure formula based on the flat rolling process formula. However, it is challenging to predict the pressure accurately using these formulas. Hence, the principle of sticking and slipping friction as well as weak plane strain is applied to derive the analytical formula based on slab analysis. To apply the proposed formula for different types of passes, the given pass shape is converted into an equivalent rectangular bar and assumed that it is pressed between two flat plates. Prediction of metal flow stress value is calculated by using Shida's formula with the proposed equation for the correction in input temperature of the hot metal. The constitutive formula of the roll separating force (RSF) is proposed based on these parameters. A comparison is made between the suggested formula and the experimental values which is available in the literature. The findings reveal that the RSF values obtained by applying the suggested method offer a reliable approximation for different kinds of passes. [ABSTRACT FROM AUTHOR]

Due to its simple design and cost-effectiveness, Bromhead ring shear apparatus is widely used to assess the drained residual strength through various testing procedures such as single stage, preshearing, and multistage. However, when compared to back-calculated case histories, values obtained through these testing procedures were found to be higher due to wall friction. To address this, Stark and Vettel (Geotech Test J 15:24–32, 1992) have introduced the "Flush testing procedure" which involves adding remolded soil to the specimen and reconsolidate it, in order to minimize the wall friction. Although the procedure yielded satisfactory results, it is more time-consuming. This paper presents a comparison between a proposed preconsolidated presheared flush (P.P.F) and flush testing procedures. The test results showed that this procedure has successfully minimized the effect of wall friction, providing values lower than those obtained using the flush procedure in shorter time. [ABSTRACT FROM AUTHOR]

Based on the characteristics of octopus arm suction cup shape and distribution, a laser cylindrical texture with dimensions of R = 500 μm, W = 200 μm, and H = 50 μm was designed on the surface of G20CrMo substrate material using laser surface processing technology. The grooves of texture were filled with SnAgCu and comparative tests were respectively conducted under dry friction and grease lubrication conditions with a loading force of 10 N, reciprocating frequency of 1 Hz, and stroke of 8 mm. A comprehensive characterization and parameter analysis of wear scars were performed using various material surface analysis instruments. The experimental results showed that the cylindrical textured surface filled with SnAgCu reduced the friction coefficient by 22.9% compared to G20CrMo substrate surface under the dry friction condition. In addition, under the grease lubrication condition, although the cylindrical textured unfilled surface resulted in a higher friction coefficient, the friction coefficient and wear loss of cylindrical textured surface filled with SnAgCu were respectively reduced by 18.6% and 60% compared to those of G20CrMo substrate surface. [ABSTRACT FROM AUTHOR]

In this research work, Al matrix is reinforced with graphene, synthesized by the powder metallurgy method, and further processed by the hot extrusion process. The microstructure of aluminum and Al-graphene composite samples was investigated using FESEM and optical microscopy. The grain structure is investigated to analyze the grain size of pure aluminum and aluminum-graphene composites. Pin on Disk wear test setup is used to investigate the tribological behavior of the developed composites. Developed samples were tested experimentally to evaluate the influence of graphene addition, applied load, and sliding velocity on wear behavior. From the results, the wear rate of Al-Graphene composites is observed to be lower compared to monolithic aluminum samples. However, wear rate increases with the increase in velocity of sliding and the applied load. The Coefficient of Friction (COF) of composite samples was less than that of pure aluminum samples. Results reveal that the graphene-Al composites exhibit superior tribological properties during tribological tests and exhibit a 38.1% reduction in wear rate at a 60 N load. [ABSTRACT FROM AUTHOR]

This paper reports an algorithm for measuring the time-averaged skin friction vector field τ ¯ (X) starting from time-resolved temperature maps, acquired by a functional coating of temperature-sensitive paint. The algorithm is applied to a large area around a wall-mounted cube, immersed in the turbulent boundary layer over a flat plate. The method adopts a relaxed version of the Taylor Hypothesis operating on time-resolved maps of temperature fluctuations T ′ measured on the slightly warmer bounding surface. The procedure extracts U ¯ T (X) , the celerity of displacement of T ′ , as the best approximation of the forecasting provided by the frozen turbulence assumption near the wall, where its rigorous application is inappropriate. The τ ¯ (X) estimation is based on the hypothesis of a linear relationship between U ¯ T (X) and U ¯ U (X) , chained to the one between U ¯ U (X) and U ¯ τ (X) . We assess the outcomes of the proposed algorithm against those derived by the 2D and 3D Lagrangian particle tracking (LPT) methodology 'Shake-The-Box', whose advent has made available high-quality near-wall flow field information. Furthermore, data from high-density 2D time-resolved LPT allows exploring the suitability of the linear relationships chain between U ¯ T (X) and U ¯ τ (X) in the proposed context. [ABSTRACT FROM AUTHOR]

A dry frictional interface loaded in shear often displays stick–slip. The amplitude of this cycle depends on the probability that a microscopic event nucleates a rupture and on the rate at which microscopic events are triggered. The latter is determined by the distribution of soft spots, P(x), which is the density of microscopic regions that yield if the shear load is increased by some amount x. In minimal models of a frictional interface—that include disorder, inertia and long-range elasticity—we discovered an ‘armouring’ mechanism by which the interface is greatly stabilised after a large slip event: P(x) then vanishes at small argument as P (x) ∼ x θ (de Geus et al., Proc Natl Acad Sci USA 116(48):23977-23983, 2019. ). The exponent θ is non-zero only in the presence of inertia (otherwise θ = 0 ). It was found to depend on the statistics of the disorder in the model, a phenomenon that was not explained. Here, we show that a single-particle toy model with inertia and disorder captures the existence of a non-trivial exponent θ > 0 , which we can analytically relate to the statistics of the disorder. [ABSTRACT FROM AUTHOR]

This paper presents an analytical methodology that provides the vibration characteristics of monopile–wheel composite foundation embedded in homogeneous saturated soil, when the top of the foundation is subjected to a harmonic horizontal load. In the proposed frame, the horizontal resistances along the pipe pile due to the vibrations of the outer and inner elastic soil and compressible seawater are considered by using the Biot porous medium theory, plane strain model and radiation wave theory. The closed-form expression of the frictional force caused by the wheel vibration is calculated through the three-dimensional continuum mechanics theory. Based on the Euler beam model, the dynamic governing equations of different pile segments in the composite foundation are simulated as a one-dimensional linear elastic rod. Analytical solutions of dynamic impedances of composite pile in the frequency domain can be derived by virtue of the boundary and continuity conditions. Following the validation of the proposed methodology, the sensitivity of the dynamic response and natural vibration frequency of this innovative foundation to the main geometrical problem parameters is studied. The results show that increasing the wheel radius, wheel thickness and embedded length can improve the dynamic stiffness of the composite foundation, and increase the natural frequency of foundation–soil system simultaneously. Finally, the differences of the dynamic responses between the composite foundation and single pile with the same fabricating cost are discussed in detail, and the corresponding analysis proves the superiority of the composite pile under offshore loading conditions. Meanwhile, the contribution of the friction wheel to the dynamic behavior of composite foundation under different parameters is also investigated. [ABSTRACT FROM AUTHOR]

We discuss a model describing the spin orbit resonance cascade. We assume that the body has a two-layer (core–shell) structure; it is composed of a thin external shell and an inner and heavier solid core that are interacting due to the presence of a viscous friction. We assume two sources of dissipation: a viscous one, depending on the relative angular velocity between core and shell and a tidal one, smaller than the first, due to the viscoelastic structure of the core. We show how these two sources of dissipation are needed for the capture in spin–orbit resonance. The shell and the core fall in resonance with different time scales if the viscous coupling between them is big enough. Finally, the tidal dissipation of the viscoelastic core, decreasing the eccentricity, brings the system out of the resonance in a third very long time scale. This mechanism of entry and exit from resonance ends in the 1 : 1 stable state. [ABSTRACT FROM AUTHOR]

Risks associated with large landslides pose a severe threat to human life and property. Hence, the creep phase, the signal before the occurrence of large landslides, plays a significant role in the safety of mountainous areas. However, the mechanism of movement in the creep phase remains unclear. In this study, landslide events were divided into six blocks based on a thermo-poro-mechanical model. Blocks represent different landslide areas, which cannot be viewed collectively because of their varying external environments or intrinsic properties. We found that the phases of movement (stationary, creep, and rapid) of different blocks differed. Dividing the landslide into blocks may compensate for the disadvantage that a single sliding body model cannot reflect local creep. Additionally, friction strengthening and weakening were considered in this model. Friction strengthening refers to the phenomenon in which the friction coefficient increases with velocity, whereas friction weakening refers to the phenomenon in which the friction coefficient decreases with velocity. In this study, friction strengthening and weakening occurred before and after the critical velocity, respectively. Our findings suggest that the rapid movement of a landslide is mainly affected by the friction-weakening stage and the thermal-pressure generation stage. Furthermore, the former has a more profound influence than the latter. Notably, this model shows that the creep phase is controlled by friction strengthening. This study is expected to stimulate new ideas for landslide prediction. Highlights: The creep phase is controlled by frictional strengthening. Rapid movement of landslides is affected by friction weakening and thermopressure. Multi-block models are better suited to studying local creep. Different instincts for landslide areas should be considered comprehensively. [ABSTRACT FROM AUTHOR]

Pins and jacks play an important role in the transmission capability and reliability of electrical connectors. Their surface coating is especially vulnerable under mechanical friction or varying temperature condition. In this work, the repetitive mechanical insertion and withdrawal experiments are conducted with the use of self-designed test rig. The wear and corrosion behaviors of circular electrical connectors are experimentally investigated under mechanical operations at temperature ranging from 25 to 120 °C. The variations in contact resistance and force observed in the mechanical wear tests are recorded and interpreted explicitly. The effect of temperature on the insertion characteristic curve is compared and analyzed. Based on the variation in contact resistance and force, surface morphology and element analysis, the degradation mechanisms of connectors under different temperatures are illustrated explicitly. The mechanical lifetime of connectors is approximately 12,500, 15,000 and 8500 at 25, 60 and 120 °C, respectively. The results show the temperature stress has a substantial influence on the wear and corrosion behavior of electrical contact interface. [ABSTRACT FROM AUTHOR]

In this paper, an extension of the Timoshenko model for plane beams is outlined, with the aim of describing, under the assumption of small displacements and strains, a class of dissipative mechanisms observed in cementitious materials. In the spirit of micromorphic continua, the modified beam model includes a novel kinematic descriptor, conceived as an average sliding relevant to a density of micro-cracks not varying along time. For the pairs of rough surfaces, in which such a distribution of micro-cracks is articulated, both an elastic deformation and a frictional dissipation are considered, similarly to what occurs for the fingers of the joints having a tooth saw profile. The system of governing differential equations, of the second order, is provided by a variational approach, endowed by standard boundary conditions. To this purpose, a generalized version of the principle of virtual work is used, in the spirit of Hamilton–Rayleigh approach, including as contributions: (i) the variation of the inner elastic energy, generated by the linear elasticity of the sound material and, in a nonlinear way, by the mutual, reversible deformation of the asperities inside the micro-cracks; (ii) the virtual work of the external actions consistent with the beam model, i.e., the distributed transversal forces and the moments per unit lengths; besides these two contributions, constituting the conservative part of the system, (iii) the dissipation due to friction specified through a smooth Rayleigh potential, entering a nonlinear dependence of viscous and Coulomb type on the sliding rate. Through a COMSOL Multiphysics implementation, 1D finite element analyses are carried out to simulate structural elements subjected to three- and four-point bending tests with alternating loading cycles. The dissipation of energy is investigated at varying the model parameters, and the predictions turn out to be in agreement with preliminary data from an experimental campaign. The present approach is expected to provide a valuable tool for the quantitative and comparative assessment of the hysteresis cycles, favoring the robust design of cementitious materials. [ABSTRACT FROM AUTHOR]

While the tool-chip contact behavior plays a dominant role in determining tool-chip friction, the intermittent cutting condition applied by ultrasonic vibration assistance significantly alters the thermomechanical properties of the tool-chip interface, which subsequently affects the microstructure evolution in the chip formation process. In the present work, we elucidate the mechanisms of grain refinement, as well as their dependence on vibration amplitude, in ultrasonic elliptical vibration-assisted cutting (UEVC) of polycrystalline copper by multi-scale numerical simulations. Specifically, two simulation approaches of finite element simulation and cellular automaton are bridged based on the thermomechanical condition of the tool-chip interface, which is subsequently utilized to reveal the tool-chip friction-induced microstructural evolution in the formed chip. Finite element simulation results indicate that the temperature and strain in the tool-chip interface during UEVC are both significantly higher than that during ordinary cutting, due to the high frequent impact of tool on chip, as well as the dominant shear frictional force between tool and chip. Consequently, corresponding cellular automaton simulations demonstrate the promoted grain refinement through dynamic recrystallization in chip during UEVC from ordinary cutting, due to the intensified thermomechanical condition in the tool-chip interface. Subsequent evaluation on the influence of vibration amplitude on grain refinement in chip during UEVC is further conducted, which shows the more pronounced grain refinement for higher amplitude, accompanied with lowered tool-chip contact length and cutting force. At the highest amplitude of 4 µm, the proportion of DRX reaches the highest value of 89.5% accompanied with the lowest average grain size of 81 nm. [ABSTRACT FROM AUTHOR]

A detailed numerical analysis has been accomplished to explore the influence of geometrical parameters of geocell reinforcement on the load carrying behavior of footing using three-dimensional finite element techniques. The influencing parameters considered such as shape, height, pocket size, stiffness of geocell reinforcement, and friction angle of infill materials. Results indicate that the inclusion of the geocell reinforcement irrespective of the shape of geocells significantly enhances the strength and stiffness of the foundation system. However, the pressure-settlement behavior is noticeably influenced by the shape of the geocells. The load carrying capacity is found to be minimum for square shaped (i.e., 400 kPa) followed by circular, diamond, and honeycomb shapes (i.e., 1000 kPa) of geocells. With increase in height of geocell mattress, the performance of the foundation system increases noticeably. The findings indicate that the load bearing capacity increases significantly up to a height ratio (H/B) of 1.5, beyond which further increment found to be marginal. Additionally, the efficacy of the system improves with increase in stiffness of reinforcement and reduces with increase in geocell pocket size. Furthermore, it is evident that the higher frictional angle of the soil mobilizes enhanced resistance on the interface, improving the overall performance. [ABSTRACT FROM AUTHOR]

Helmet-testing headforms replicate the human head impact response, allowing the assessment of helmet protection and injury risk. However, the industry uses three different headforms with varying inertial and friction properties making study comparisons difficult because these headforms have different inertial and friction properties that may affect their impact response. This study aimed to quantify the influence of headform coefficient of friction (COF) and inertial properties on oblique impact response. The static COF of each headform condition (EN960, Hybrid III, NOCSAE, Hybrid III with a skull cap, NOCSAE with a skull cap) was measured against the helmet lining material used in a KASK prototype helmet. Each headform condition was tested with the same helmet model at two speeds (4.8 & 7.3 m/s) and two primary orientations (y-axis and x-axis rotation) with 5 repetitions, totaling 100 tests. The influence of impact location, inertial properties, and friction on linear and rotational impact kinematics was investigated using a MANOVA, and type II sums of squares were used to determine how much variance in dependent variables friction and inertia accounted for. Our results show significant differences in impact response between headforms, with rotational head kinematics being more sensitive to differences in inertial rather than frictional properties. However, at high-speed impacts, linear head kinematics are more affected by changes in frictional properties rather than inertial properties. Helmet testing protocols should consider differences between headforms' inertial and frictional properties during interpretation. These results provide a framework for cross-comparative analysis between studies that use different headforms and headform modifiers. [ABSTRACT FROM AUTHOR]

Dummy headforms used for impact testing have changed little over the years, and frictional characteristics are thought not to represent the human head accurately. The frictional interface between the helmet and head is an essential factor affecting impact response. However, few studies have evaluated the coefficient of friction (COF) between the human head and helmet surface. This study's objectives were to quantify the human head's static and dynamic COF and evaluate the effect of biological sex and hair properties. Seventy-four participants slid their heads along a piece of helmet foam backed by a fixed load cell at varying normal force levels. As normal force increased, static and dynamic human head COF decreased following power–law curves. At 80 N, the static COF is 0.32 (95% CI 0.30–0.34), and the dynamic friction coefficient is 0.27 (95% CI 0.26–0.28). Biological sex and hair properties were determined not to affect human head COF. The COFs between the head and helmet surface should be used to develop more biofidelic head impact testing methods, define boundary conditions for computer simulations, and aid decision-making for helmet designs. [ABSTRACT FROM AUTHOR]

Tensile strength characterization of brittle materials by means of uniaxial tensile tests is often unfeasible, as most samples form chips during specimen preparation, leading to unacceptable geometric deviations. For this reason, the disc specimens used in Brazilian tests to determine indirect tensile strength are preferred. Despite its influence on the induced stress field and the location of the failure initiation point, the actual stress distribution along the contact is still under debate. In the present work, the complex variable method is used to develop a new analytical formulation based on the simplest possible shear stress distribution along the disc boundary that fulfils elastic equilibrium. Based on this formulation, an integration method is used to obtain the stress field generated inside specimens—elastic discs—that are subjected to distributed shear forces on their contact rims. An application of this method to the Brazilian test case is performed, proving that shear and frictional forces can be considered simultaneously. Furthermore, a mathematical procedure to simultaneously consider radial and shear stress distributions along the loaded boundary is developed to determine any possible stress field for relevant practical applications. The results confirm that shearing significantly increases stress in the vicinity of the contact area, which may explain the wedge failure pattern sometimes observed in real test specimens. Additionally, the proposed formulation guarantees that if failure is initiated in the centre of the specimen, the applied shear stress distribution no longer influences the indirect tensile strength of the material, although it influences the final test output if failure is initiated at any other point along the vertical diameter. [ABSTRACT FROM AUTHOR]

The reduction of frictional power losses in power transmitting gears takes a crucial role in the design of energy- and resource-efficient drivetrains. Water-containing lubricants like glycerol and polyalkylene glycols have shown great potential in achieving friction within the superlubricity regime with coefficients of friction lower than 0.01 under elastohydrodynamic lubrication. Additionally, a bio-based production of the base stocks can lead to the development of green lubricants. However, one challenge associated with the application of water-containing lubricants to gearboxes is the evaporation of water and its impact on the lubricant properties. In this study, the influence of water evaporation on elastohydrodynamic friction and film thickness was investigated for three water-containing polyalkylene glycols. Two nominal water contents of 20 wt% and 40 wt% and two viscosities were considered. The results show that the friction increases continuously with higher evaporated water content, while the overall friction level remains low in nearly water-free states. A similar trend is observed for film thickness, where the strong increase in viscosity results in a notable increase in film thickness. Nevertheless, the sensitivity of friction and film thickness to water evaporation is low for small amounts of evaporated water. This allows generous thresholds for permissible variations in water content. [ABSTRACT FROM AUTHOR]

The most important role of footwear is to ensure safe, functional walking, and foot protection. For the proper functionality of not only the work shoes, the anti-slip behavior of the shoe under various conditions and environments plays an important role in the prevention of slips, trips, falls, and consequent injuries. This article is intended to review the current understanding of the frictional mechanisms between shoe outsoles and various counterfaces that impact the evaluation of outsole slipperiness. Current research focuses on the mechanisms driving outsole friction on different ground surfaces or the definition and description of parameters that influence outsole friction. Subsequently, the review discusses the effect of various surface contaminants on footwear friction. Lastly, challenges and outlooks in the field of footwear outsoles are briefly mentioned. [ABSTRACT FROM AUTHOR]

Friction has been considered to mediate physiological activities of cells, however, the biological friction between a single cell and its ligand-bound surface has not been thoroughly explored. Herein, we established a friction model for single cells based on an atomic force microscopy (AFM) combined with an inverted fluorescence microscopy (IFM) to study the friction between a highly sensitive platelet and fibrinogen-coated surface. The study revealed that the friction between the platelet and fibrinogen-coated tip is mainly influenced by specific ligand–receptor interaction. Further, we modeled the biological friction, which consists of specific interaction, non-specific interaction, and mechanical effect. Besides, the results suggested that the velocity can also affect specific ligand–receptor interactions, resulting in the friction change and platelet adhesion to fibrinogen surfaces. The study built a friction model between a single cell and its ligand-bound surface and provided a potential method to study the biological friction by the combination of AFM and IFM. [ABSTRACT FROM AUTHOR]

In this paper, a semi-analytical calculation model for the coefficient of friction (COF) of single spherical protrusions is presented. It allows the prediction of the deformative friction part (μdef) and adhesive friction part (μadh) of the friction pairings steel ∣ polyethylene with ultra-high molecular weight (PE-UHMW) and polyoxymethylene (POM) ∣ PE-UHMW. The experimental studies included unlubricated friction tests, which served to determine the total COF (μtot), as well as tests being lubricated with silicone oil, from which μdef is obtained. Based on the verification tests, it could be shown that both states of lubrication result in the same deformation and that the relationship between the rear angle (ω) and μdef postulated in the calculation model is valid. Therefore, friction tests with segmented spheres were carried out, which allow a specific variation of the ω. It can be concluded that for both pairings the μdef is generally of minor significance (approx. 1/3 μtot) and the influence of the μadh predominates (approx. 2/3 μtot) the friction process. Furthermore the μtot decreases with increasing contact pressure especially in the low pressure range and depends on the form of motion (continuous and discontinuous). [ABSTRACT FROM AUTHOR]

Ultra-low friction is crucial for the anti-friction, anti-wear, and long-life operation of nanodevices. However, very few two-dimensional materials can achieve ultra-low friction, and they have some limitations in their applications. Therefore, exploring novel materials with ultra-low friction properties is greatly significant. The emergence of ternary two-dimensional materials has opened new opportunities for nanoscale ultra-low friction. This study introduced nickel phosphorous trisulfide (NiPS3, referred to as NPS), a novel two-dimensional ternary material capable of achieving ultralow friction in a vacuum, into the large nanotribology family. Large-size and high-quality NPS crystals with up to 14 mm × 6 mm × 0.3 mm dimensions were grown using the chemical vapor transport method. The NPS nanosheets were obtained using mechanical exfoliation. The dependence of the NPS nanotribology on layer, velocity, and angle was systematically investigated using lateral force microscopy. Interestingly, the coefficient of friction (COF) of NPS with multilayers was decreased to about 0.0045 under 0.005 Pa vacuum condition (with load up to 767.8 nN), achieving the ultra-low friction state. The analysis of the frictional dissipation energy and adhesive forces showed that NPS with multilayers had minimum frictional dissipation energy and adhesive forces since the interlayer interactions were weak and the meniscus force was excluded under vacuum conditions. This study on the nanoscale friction of a ternary two-dimensional material lays a foundation for exploring the nanoscale friction and friction origin of other two-dimensional materials in the future. [ABSTRACT FROM AUTHOR]

Three triangular friction block configurations are commonly employed in high-speed train brake systems, namely, unperforated, perforated configuration with one circular hole, and perforated with three circular holes. In this study, we adopted these friction block types to investigate the effect of perforated friction block configurations on the brake performance of high-speed trains based on a self-developed brake test rig. The results indicate the significant impact of the number of the holes on the wear behavior, temperature distribution, and vibration characteristics of the brake interface. The friction surface of the unperforated block is covered by wear debris, while the perforated blocks produce less wear debris. Furthermore, the one-hole block exhibits a more uniform temperature distribution and better vibration behavior than that with three holes. The friction brake is a dynamic process, during which separation and attachment between the pad and disc alternatively occur, and the perforated structure on the friction block can both trap and expel the wear debris. [ABSTRACT FROM AUTHOR]

In numerical models that adopt a no-slip boundary condition, a jet initially separates from the shore and flows eastward south of the inter-gyre boundary. This premature separation is caused by positive vorticity created by friction on the western boundary, which is paired with negative vorticity created by the conservation of the potential vorticity advected from the south. In this study, we propose a new model that includes vortex pair forcing in the western boundary region, where a vorticity structure causes separation and extension of the western boundary current (WBC) jet. Our model can separately treat flow that is locally driven by large-scale wind and the WBC extension jet driven by a vortex pair. We confirmed that our model could successfully replicate an extension jet prematurely separated from the western boundary for a wind-driven, two-layer quasi-geostrophic model. The dominant physical structure of the jet in our vortex pair forcing model differed in the upstream and downstream regions. In the upstream region, the intrusion of vortex pairs due to forcing is the dominant factor, while in the downstream region, the effect of eddies begins to manifest. We also examined the effects of a large-scale wind-driven background flow on the jet. When the background flow only contains an eastward component, the jet extends eastward. When the background flow contains a meridional component, this strongly affects the extended jet and can terminate the eastward jet structure. [ABSTRACT FROM AUTHOR]

The influence of electric current pulses passing between parts during fretting wear of titanium alloys is examined. A description of the test bench and a description of the test methodology are given. [ABSTRACT FROM AUTHOR]

Fluoroelastomer (FKM), a thermosetting elastomer, stands out with its excellent friction characteristics and exceptional attributes of chemical, vacuum, and heat resistance, setting it apart from typical rubber materials. Leveraging these qualities, FKM emerges as the optimal material for friction pads used in extreme environments requiring high temperatures and vacuum, such as space and semiconductor processes. In this study, we introduce micropatterned bolt-inserted FKM pads (BIFP) designed to enhance friction, productivity, and usability. To produce BIFPs with improved friction characteristics, various microstructures were designed and tested for their friction performance. Additionally, to meet the demand for extended durability, we conducted 500,000-cycle repetitive tests. In terms of performance, durability, and usability, the developed BIFPs will be utilized widely, especially in industrial settings requiring harsh operating conditions. [ABSTRACT FROM AUTHOR]

Polymer-based self-lubricating materials are designed to improve the efficiency and reliability of mechanical systems, reducing energy consumption and material loss. Herein, inspired by the texture of the smooth leaf surface, the polyether ether ketone was first subjected to a sulfonation treatment before the plant texture was introduced to the surface of the sulfonated polyether ether ketone (SPEEK) films. The optical microscopy results indicate the successful construction of different bionic textures on SPEEK film surface. Based on the reduction in the contact area between the friction pairs, and the accommodation of abrasive debris by the uneven bionic textures, the tribological performance of SPEEK films under dry friction conditions shows unique advantages. Additionally, the wear morphology and self-lubrication mechanism of bionic textured films were investigated by 3D profilometry, SEM, and XPS. The results show that under the effect of frictional heat and frictional force, the bionic texture morphology changes to fish scale, which reduces the resistance to friction, resulting in a lower friction coefficient and wear rate. This strategy of constructing bionic textures on functional polymer surfaces using a facile process provides a reference for exploring novel self-lubricating materials. [ABSTRACT FROM AUTHOR]

Precisely estimating and controlling the friction of a stone on ice is one of the abilities that is essential for good curling players. We propose here a new, simple, and player-friendly method for measuring friction using only stopwatches. As for friction control, it is known that friction must be modified by sweeping using brushes. It is widely performed not only to extend the stopping range of the stone but also to control the curls, although there is little scientific evidence to support the curl-controlling effects. We conducted a measurement to examine the effects, and we propose a potential method for assisting players to try similar kinds of quantitative studies themselves. The results we obtained suggest positive effects of the left–right asymmetric sweeping with 95% reliability for sweeping on the opposite half-side to assist curling. [ABSTRACT FROM AUTHOR]

The tightness and stability of the pipe connections are particularly important for pressurized environments. Pipe fittings are one of the most important subgroups of fittings. These fittings are not only used for connection purposes, but these fasteners may also have additional purposes such as sealing. In this study, a simulation model of the pipe fitting was created to evaluate the sealing performance. The obtained forces in the simulations were then used in the modified version of the classical bolt-tightening moment equation. In this equation, the additional parameter, R, is embedded. This parameter depends on the distance from the center (torque arm, x), slope parameter (k), and friction constant (S) between the body or nut and the ring parts. The consistency and applicability of the new equation were discussed by comparing the obtained results with the experimental results. It has been observed that there is a good agreement between the comparative results. [ABSTRACT FROM AUTHOR]

Heavy loads and fatigue wear of the contact areas between the hydraulic cylinder block and the sealing ring seriously affect the sealing performance. In order to prolong the service life of the hydraulic system, the bionic self-lubricating samples were prepared by filling SnAgCu and Ti3C2Tx (SACT) into surface biomimetic textures, and the effect of wear frequency on the tribological properties of the samples was tested. Tribological properties were tested using a multifunction tribometer, the counter pairs were 42CrMo steel and polyurethane, respectively. Compared with smooth 42CrMo, bionic self-lubricating samples were easier to form smooth continuous worn surface at the appropriate frequency (5 Hz). Meanwhile, the average friction coefficient, wear loss, equivalent noise pressure level and noise intensity are minimum. [ABSTRACT FROM AUTHOR]

In this study, the seismic performance of an ancient pagoda with significant historical and cultural values in China is upgraded by using overall friction pendulum bearing (OFPB) seismic isolation technology, This technique can be used to isolate the pagoda without damaging it. By implementing the OFPB seismic isolation retrofit on the pagoda and comparing and analyzing it with the unretrofitted seismic model, the response of the pagoda under the action of nine seismic waves of three types, namely, near-field earthquakes, far-field earthquakes, and common earthquakes, is investigated. The results show that the OFPB seismic isolation technique significantly reduces the seismic response of the ghats, in which the acceleration amplification factor is reduced by a maximum of 82.46%, the inter-story displacement is reduced by a maximum of 85.15%, and the base shear force is reduced by a maximum of 96.76%. In addition, the tensile damage of the ghats with OFPB seismic isolation was significantly controlled. While the model without seismic isolation has serious damage under the same seismic action and even faces the risk of collapse. The results of the study confirm that the OFPB seismic isolation technology plays a key role in improving the seismic performance of the tower, which is of great theoretical and practical significance to the protection of the tower, and provides an effective technical way for the protection of the tower in the seismic-prone areas. [ABSTRACT FROM AUTHOR]

In this work, we consider intermediate inflation in the context of the generalized non-minimal derivative coupling (GNMDC) model. In the GNMDC model, inflation is driven by a canonical scalar field that is coupled not only to gravity but also to the derivative of the scalar field. The model introduces new dynamics and features during the inflationary epoch. We find inflationary solutions with a power law scalar field for the power law coupling function. Additionally, we determine the inflaton potential that generates intermediate expansion of the scale factor. We also discuss the background equations in the high friction limit and derive constraints on the parameters of our model. Furthermore, we investigate the cosmological perturbations in the slow roll approximation within the GNMDC model, and we calculate the scalar and tensor spectral index and the tensor-to-scalar ratio during intermediate inflation. We compare the results of this model with observational data that can be used to test the model using cosmic microwave background radiation data. Overall, we establish conditions for the inflaton potential that ensure the continuation of accelerated expansion during slow roll inflation. We numerically analyze the power spectrum and spectral index for scalar and tensor modes in intermediate inflation in the high friction limit, and we use Planck 2018 data to obtain constraints on the parameters of the model. We demonstrate that intermediate inflation in the GNMDC model is successful in evaluation and explanation of background and perturbation quantities using observational data. [ABSTRACT FROM AUTHOR]

Forging of sintered Al–Fe–Sn samples was carried out in a closed die at different temperatures. The flow of the material under the influence of frictional forces was non-uniform, and the sample was fractured. It has been established that in order to maintain the integrity of the two-phase material, forging must be carried out with the application of back pressure. It is recommended to forge the composites at elevated temperatures. [ABSTRACT FROM AUTHOR]

The efficiency of mixed convection peristaltic flow can be investigated through pressure rise per wavelength (Δ P λ) and frictional forces ( F λ ). The main aim of the present study is to discover the sensitivity analysis of non-Newtonian fluids using the Bingham plastic fluid model. In order to achieve this objective, we have empirically modeled the pressure rise per wavelength (Δ P λ) and frictional forces ( F λ ) as a function varying with leading parameters of problem. The flow problem is governed by three coupled nonlinear partial differential equations. They are reduced to nonlinear coupled ordinary differential equations by using the long wavelength and low Reynolds number approximations. They are solved numerically using MATLAB built-in routine bvp4c to analyze the sensitivity of pressure rise per wavelength ( Δ P λ ) and frictional forces ( F λ ). We first derive the empirical model among each of responses Δ P λ and F λ and physical parameters which govern the flow using response surface methodology. The goodness of fit of empirical model is decided on the basis of coefficient of determination ( R 2 ) obtained from the analysis of variance (ANOVA). The coefficients of determination ( R 2 ) are 99.78% both for Δ P λ and F λ . The higher values of R 2 determine the goodness of fit of empirical model. No correlation has been developed to optimize Δ P λ and F λ in peristaltic flow for Bingham plastic fluids using RSM. The results of sensitivity analysis revealed that Δ P λ and F λ are most sensitive to flow rate (q) at all levels such as low (− 1), medium (0) and high (+ 1). The sensitivity of Δ P λ to Bingham number (Bn) shows a distinct behavior with varying levels of flow rate (q). At low level (− 1) of flow rate (q), the sensitivity is positive, and at high level (+ 1) of flow rate (q), the sensitivity becomes negative. Conversely, the sensitivity of F λ to Bingham number (Bn) at low to high level of flow rate (q). [ABSTRACT FROM AUTHOR]