Surface Friction Coefficient Research Articles

Load‐deformation behavior of injection bolts for maintenance of steel structures under dynamic loads

AbstractConnections of steel‐structures under dynamic loads need to be slip‐resistant according to EN 1993‐2. Bolted connections without slip can be realized with fitted bolts, preloaded high strength friction grip (HSFG) bolts or injection bolts. Injection bolts are particularly advantageous because the increased effort required for reaming the holes for fitted bolts or for special surface preparation for HSFG bolts can be avoided. The paper focuses on the experimental analysis of connections with non‐preloaded and preloaded injection bolts according to EN 1090‐2. Different resins and curing conditions are considered, as well as different surface treatments or friction coefficients. Thus, the interaction between the slip resistance and the bearing resistance of preloaded injection bolts is investigated more detailed.

Atomistic analysis of the phase transformation and wear regimes of textured Wurtzite-SiC hexagonality using molecular dynamics simulation

The surface nano-polishing features and wear regime of textured Silicon carbide (SiC) substrates are studied using molecular dynamics modelling. Surface groove-shaped textures improve nano-polishing performance. This method also reduces subsurface wear damage. Switching from cutting to adhering regime can enhance surface roughness, frictional coefficient, and wear regime by decreasing depth. Specifically, reducing polishing depths improved surface roughness from 1.77% to 9.33%. Increasing polishing speed or crystal direction indicates an adherent wear regime and improves surface roughness from 2.6% to 9.61%. Nano-polishing the (0001) plane produced more heat than other planes. Thus, the (0001) plane has more graphene-like structure atoms and is closer to completion than other planes. This discovery helps texture SiC-based materials increase their anti-friction and wear properties.

Hydrothermal analysis of Ag and CuO hybrid NPs suspended in mixture of water 20%+EG 80% between two concentric cylinders

This paper investigates the mixture of hybrid nanofluid (NF) flow between two concentric cylinders numerically. Ethylene glycol (80%) and water (20%) comprise the base fluid. Additionally, copper oxide (CuO) and silver (Ag) NPs are added. The hybrid NF flows between the two coaxial cylinders is studied. The inner cylinder is fixed and the outer cylinder is rotating. A radial magnetic field also affects fluid flow, and joule heating joule heating is also considered. The transformed system of nonlinear ordinary differential equations is solved numerically using the fifth-order Runge-Kutta method. Numerical solutions are obtained for fluid velocity and velocity gradient, fluid temperature and temperature gradient, pressure, surface friction coefficient and Nusselt number under the influence of different variables. The computer code is validated by comparing the variation of temperature of hybrid nanofluid with the numerical published data, a good agreement was observed. As the magnetic field parameter is increased, the fluid's velocity reduces. The fluid temperature increases as the magnetic field parameter and Brinkman number were increased. The skin friction coefficient increases with the enhancement of volume percentage and the magnetic field parameter. The Nusselt number rises with increasing of the magnetic field and Brinkman number.

Modified polyamide fibers with low surface friction coefficient to reduce microplastics emission during domestic laundry

The widespread presence of microplastics has become a serious threat to humans and ecological environments because they carry many pollutants and can be easily ingested by aquatic organisms. Fibrous microplastics (FMPs) released from synthetic fiber garments during domestic laundry are a major source of contamination. Herein, we report a facile FMPs mitigation strategy for polyamide 6 (PA6) fibers by incorporating environmentally friendly polydimethylsiloxane (PDMS) during melt spinning. The obtained PA6/PDMS fibers showed a lower friction coefficient than the pure PA6 fibers. Surface morphology, tribology, and washing characterizations verified that a 60% reduction in FMPs shedding was achieved by reducing the friction. In addition, the low-surface-friction PA6/PDMS fabrics with high hydrophobicity exhibited improved waterproof and anti-stain behaviors. It is important to note that none of the essential properties, such as surface structure, dyeing and printing of the fabrics were compromised after PDMS blending. This study provides a green and scalable route for mitigating laundry microfibers using a fiber domain design.

Damage to seeds by screw working bodies

Seed damage caused by screw working bodies of agricultural machines reduces the seed quality and increases the total cost of crop production. This paper describes the impact interaction of a particle with screw flights when seeds are fed into the transportation zone. There are velocity dependences during the impact and reflection of seeds on the screw surface at the maximum distance of the radius from the screw rotation axis. The potential energy lost by seeds when interacting with screw flights is determined. The paper considers the way transporting the seed material by screw working bodies impacts seed damage. The potential energy accumulated after impact by the reflecting surface and the particle depends on the magnitude and direction of the falling velocity to the screw belt, the auger geometric and kinematic parameters (the screw diameter; the inclination angle of the helix to the screw axis and the angular velocity), as well as the physical and mechanical properties of the particle and the reflecting surface (recovery and friction coefficients). Previous studies have shown that the critical angular velocity of the screw flight depends on the screw casing and the reduction factor of the circumferential velocity. In turn, the reduction factor depends on the transported seed material and the geometric parameters of the screw. It is possible to diminish the destruction of the seed material due to impact interaction with the working surface of the screw by reducing the inclination angle of the screw flight α, the angular speed of the screw rotation ω and its radius R. It also requires direct the seed flow closer to the rotation center. Reducing injury to seeds during transportation in a screw device requires a higher critical angular velocity of the screw. To increase the working angular velocity of the screw without exceeding its threshold of critical angular velocity, it is advisable to use screws with a large pitch and polymer screws with a wider pitch.

Ceramic–Titanium Alloy Artificial Hip Joint Wear Simulation and Experimental Study

The wear of artificial joints can lead to joint noise and tissue pathology within the human body, which is a primary factor affecting their service life. In response to the issue of wear in ceramic–titanium alloy artificial hip joints, this study employed hip joint wear simulations and experimental wear testing on hip joint specimens to investigate the impact of different contact surface parameters on the wear of ceramic–titanium alloy articulating surfaces. The objective was to provide guidance for joint surface treatment to minimize wear. The simulation results demonstrated that the contacting surfaces of the articulating components exhibited a crescent-shaped surface composition before and after wear. The initial variation in the surface friction coefficient had minimal influence on the wear rate after stabilization, whereas excessively high friction coefficients led to erratic changes in wear depth. Based on the simulation results, experimental research was conducted to compare the wear results of different surface roughness values ranging from 60 to 550 nm. The findings revealed that a surface roughness of 150 nm exhibited the least amount of wear and the best anti-wear performance. Furthermore, an exploration of the mechanism behind the influence of different surface friction coefficients on the wear of the articulating surfaces provided valuable insights for surface processing and wear analysis of artificial joints.

Impact of Beam Deflection Geometry on the Surface Architecture and Mechanical Properties of Electron-Beam-Modified TC4 Titanium Alloy.

This paper aims to investigate the impact of beam deflection geometry on the structure, surface architecture, and friction coefficient of electron-beam-modified TC4 titanium alloys. During the experiments, the electron beam was deflected in the form of different scanning geometries, namely linear, circular, and matrix. The structure of the treated specimens was investigated in terms of their phase composition by employing X-ray diffraction experiments. The microstructure was studied by scanning electron microscopy (SEM). The surface architecture was examined by atomic force microscopy (AFM). The friction coefficient was studied by a mechanical wear test. It was found that the linear and circular deflection geometries lead to a transformation of the phase composition, from double-phase α + β to α' martensitic structure. The application of a linear manner of scanning leads to a residual amount of beta phase. The use of a matrix does not tend to structural changes on the surface of the TC4 alloy. In the case of linear geometry, the thickness of the modified zone is more than 800 μm while, in the case of EBSM using circular scanning, the thickness is about 160 μm. The electron-beam surface modification leads to a decrease in the surface roughness to about 27 nm in EBSM with linear deflection geometry and 31 nm in circular deflection geometry, compared to that of the pure TC4 substrate (about 160 nm). The electron-beam surface modification of the TC4 alloy leads to a decrease in the coefficient of friction (COF), with the lowest COF values obtained in the case of linear deflection geometry (0.32). The results obtained in this study show that beam deflection geometry has a significant effect on the surface roughness and friction coefficient of the treated surfaces. It was found that the application of a linear manner of scanning leads to the formation of a surface with the lowest roughness and friction coefficient.

Study on Friction Characteristics of ADC12-POM Gear Pair

In a transmission system, the cooperative utilization of metal small gears and plastic large gears not only significantly reduced the system weight and noise levels, but also harmonized strength and longevity between the gears of varying sizes. Nevertheless, the existing research on metal-plastic friction remains insufficient. This study focused on the ADC12-POM gear pair, conducted sliding friction tests between polyoxymethylene (POM) plastic balls of different diameters and ADC12 metal plates using a self-made reciprocating friction and wear testing machine. The friction coefficients between the ADC12-POM sliding pairs were evaluated under different load and velocity conditions, and subsequent nonlinear regression analysis using the IBM SPSS software yielded an initial calculation model for the friction coefficients at the contact surfaces of the ADC12-POM gear pair. By analyzing the Engagement characteristics of gears, we calculated the variations in curvature radius, relative sliding velocity, and load distribution coefficient during the Engagement process. This enabled us to establish a computational model for determining the tooth surface friction coefficient of the ADC12-POM gear pair. Furthermore, we derived the relationship between Engagement efficiency and the friction coefficient and conducted experimental investigations to assess the efficiency of gear Engagement. The deviation between the theoretically calculated Engagement efficiency and the experimental results was approximately 2%, thereby confirming the feasibility of the friction coefficient calculation model.

Measurement of road friction coefficient using strain on tire sidewall

If road friction coefficients can be measured in real time, the performance of advanced driver-assistance systems (ADASs), such as anti-lock braking systems (ABS) and automatic braking systems, can be improved. Generally, ADASs use information obtained from wheel speed sensors and acceleration sensors. However, it is difficult to accurately measure the road friction coefficients using these sensors. Therefore, many studies have been conducted to measure road friction coefficients using strains at the inside surface of a tire tread, which are the only places that ground road surfaces. However, sensors installed on the inside surface of a tire tread, where significant deformation occurs locally because of protrusions on road surfaces, can easily be peeled off or damaged. Therefore, this study investigated a method for measuring road friction coefficients using strains on the sidewalls of the tires. If the sidewalls of tires are used instead, stable measurements can be expected because the sidewalls of tires are harder to deform locally compared with the inside surface of a tire tread. First, using an experimental device that simulates the complete slip state of a tire, we measured the relationship between the triaxial direction loads acting on the ground surface of the tire and the strain induced on the sidewall of the tire. Subsequently, we established experimental formulas that express the relationship and devised methods for measuring the road friction coefficient. It was confirmed that the friction coefficients of multiple friction surfaces, even under triaxial direction loads, could be accurately measured using the proposed method. In conclusion, the proposed method was confirmed to be able to measure the load acting on a tire and friction coefficient of the tire grounding surface at low speeds and under full-slip conditions.

A new TiAlSiN coated tool and its machining performance evaluation for milling difficult-to-machining materials under MQL conditions

In this study, the Si and Al contents in a coating composition were improved, and a new TiAlSiN-coated tool was fabricated using high-power pulsed magnetron sputtering (HiPIMS). For comparison purposes, four types of coated tools, typically used in the market, were selected to mill 304 stainless steel in a minimum quantity lubrication environment. To evaluate the machining performance of the tools, the criteria of tool wear, workpiece surface roughness, and milling force were considered. The machining performance of the TiAlSiN-coated tools remained stable for all four working conditions, and it had the smallest compound milling force and tool wear in the experiment. The primary wear forms of the tools were coating peeling, oxidation wear, and adhesive wear. Under working conditions 1 and 2, due to the lower initial surface friction coefficient and thermal barrier effect, the workpiece surface roughness of the TiN-coated tools was the smallest, followed by that of the TiAlSiN. However, under inadequate working conditions, because of the good wear resistance of the TiAlSiN coating, it was not rapidly worn. This resulted in a lower average friction coefficient during processing and the workpiece surface exhibited the minimum surface roughness. A comparative analysis of the processing state of the five coatings under four groups of parameters indicated that the TiAlSiN coating had good processing stability, wear resistance, and a low surface friction value. The TiAlSiN-coated tools had better machining performance than the other four commercial-coated tools for 304 stainless steel machining, especially under working conditions 3 and 4.

Anchor Behavior of One-Side Bolt with Flip-Top Collapsible Washer

With the development of blind bolts that can be installed from the outer side of a section, the application of steel pipe hollow sections in prefabricated structures has become possible. The novel one-side bolt with a flip-top collapsible washer (FTW-OSB) is proposed, which can fold the washer at the end of the bolt to achieve a simple and efficient installation. Firstly, the components and installation process of the FTW-OSB are introduced. Additionally, axial tensile tests were carried out on three types of new bolts, and the failure mode, load–displacement curve, and ultimate capacity were analyzed. Based on this, the finite element model was verified, and through a series of finite element parameter analyses, the influence of washer size and construction, the friction coefficient, and the contact surface size on the new bolt were analyzed and optimized. The results show that the L-shaped washer can prevent washer rotation and has better anchoring performance than the I-shaped washer. The washer thickness, height, and upper contact surface size are the key factors affecting the anchoring performance of the FTW-OSB bolt. Among these factors, when the washer thickness increases from 0.1 d0 to 0.3 d0, the ultimate capacity and initial stiffness of the FTW-OSB bolt increase by 136.5% and 100.3%, respectively. The lower contact surface size and friction coefficient can be ignored. The failure model of the FTW-OSB is mainly washer shear failure and bolt tension failure. By effectively adjusting the washer thickness, side wall height, and upper contact surface size, shear failure of the washer can be avoided and an anchoring performance can be achieved that is the same as that of the same type of 10.9-grade ordinary high-strength bolt.

Dynamic force modeling and mechanics analysis of precision grinding with microstructured wheels

The application of structured surfaces on advanced tools is an effective method for enhancing the machining performance. The modeling of dynamic grinding force is of great significance for improving tool surface structure design and improving grinding accuracy. In this paper, a novel dynamic force modeling and mechanics analysis of precision grinding with microstructured wheels was put forward. A grinding wheel topography model was established by considering the non-simplified position-posture-shape-size multiple random grains morphological characteristics. On this basis, the material removal pattern of the microstructured multiple random abrasive grains was identified based on grinding kinematics and undeformed chip thickness. The grain diameter, average bearing width, flat surface area, friction coefficient and total number of active abrasive grains in the grinding area were considered. Their effects on the amplitude and frequency of grinding force were discussed in detail, and the precision grinding experiment was carried out. The results show that the dynamic force model proposed could accurately evaluate the influence of microstructure tools on forces with an error rate of 6.7% or less. Compared with the original grinding wheel, the addition of microstructure reduces the grinding force by 49.6%− 94.3%. By controlling the force components, the force frequency is more concentrated, and the disorder of the grinding force signal is suppressed. Furthermore, the carbon emission model was calculated, and it can be seen that microstructured wheels can obviously reduce carbon emission, which is a novel processing technology to realize low-carbon manufacturing.

An Exploration of the Influence of Abrasive Water Jet Pressure on the Friction Signal Characteristics of Fixed Abrasive Lapping Quartz Glass Based on HHT

Abrasive water jetting is an effective dressing method for a fixed abrasive pad (FAP) and can improve FAP machining efficiency and the impact of abrasive water jet (AWJ) pressure on the dressing effect; moreover, the machining state of FAP after dressing has not been thoroughly studied. Therefore, in this study, the FAP was dressed by using AWJ under four pressures, and the dressed FAP was subjected to lapping experiments and tribological experiments. Through an analysis of the material removal rate, FAP surface topography, friction coefficient, and friction characteristic signal, the influence of AWJ pressure on the friction characteristic signal in FAP processing was studied. The outcomes show that the impact of the dressing on FAP rises and then falls as the AWJ pressure increases. The best dressing effect was observed when the AWJ pressure was 4 MPa. In addition, the maximum value of the marginal spectrum initially rises and then falls as the AWJ pressure increases. When the AWJ pressure was 4 MPa, the peak value of the marginal spectrum of the FAP that was dressed during processing was the largest.

Time‐dependent mixed convection of Prandtl–Eyring hybrid nanofluid flow over a vertical cone: Entropy analysis

AbstractThe current work is motivated by the rising applications of non‐Newtonian hybrid nanofluids and entropy optimization in large‐scale industries. The Prandtl–Eyring nanofluid model, one of the numerous non‐Newtonian fluid models, is developed using molecular theory rather than empirical formulas. This study investigates the mixed convection flow of Prandtl–Eyring nanofluids from a vertical conical surface. This problem's governing equations are highly nonlinear and linked. Mangler's nonsimilar transformations were used to obtain a nondimensional representation of the governing equations. The obtained equations were linearized and discretized using Quasilinearization and the implicit finite difference method. This study concludes that, compared to Newtonian fluids, Prandtl–Eyring fluids have reduced surface friction and fluid velocity. When comparing the Prandtl–Eyring hybrid nanofluid to the Newtonian hybrid nanofluid, we find that the latter improves energy transmission by about 11%. With the Prandtl–Eyring hybrid nanofluid model instead of the standard Newtonian model, entropy generation (EG) can be reduced. Energy transport efficiency is improved by changing the nanoparticles shape from spherical to lamina. Concisely at , the and boosted approximately by 29% and 17%, respectively, when shapes of the nanoparticles are changed from spherical to the lamina. The findings of heat transfer strength and surface friction coefficient are in excellent agreement with previously reported data.

Heat variation on MHD Williamson hybrid nanofluid flow with convective boundary condition and Ohmic heating in a porous material

The aim of the present study is to explore the variation of heat on MHD Williamson hybrid nanofluid (Ag-TiO2/H2O) model for steady two-dimensional and incompressible flow with a convective boundary condition in a curved coordinate porous system with Ohmic heating. Nusselt number is distinguished by the process of thermal radiation. The partial differential equations are controlled by the curved coordinate’s porous system, which depicts the flow paradigm. Employing similarity transformations, the acquired equations were turned into coupled non-linear ordinary differential equations. The governing equations were disbanded by RKF45 via shooting methodology. The focus is on examining physical characteristics such as heat flux at the wall, temperature distribution, velocity of flow, and surface friction coefficient for a variety of related factors. The analysis explained that increasing permeability, Biot and Eckert numbers enhance temperature profile and slowdown heat transfer. Moreover, convective boundary condition and thermal radiation enhance the friction of the surface. The model is prepared as an implementation for solar energy in processes of thermal engineering. Morever, this research has enormous applications in the industries of polymer and glass, also in the field of heat exchangers styling, cooling operations of metallic plates, etc.

Achieving near-infrared-light-mediated switchable friction regulation on MXene-based double network hydrogels

AbstractMXene possesses great potential in enriching the functionalities of hydrogels due to its unique metallic conductivity, high aspect ratio, near-infrared light (NIR light) responsiveness, and wide tunability, however, the poor compatibility of MXene with hydrogels limits further applications. In this work, we report a uniformly dispersed MXene-functionalized poly-N-isopropylacrylamide (PNIPAM)/poly-2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS) double network hydrogel (M—DN hydrogel) that can achieve switchable friction regulation by using the NIR light. The dispersity of MXene in hydrogels was significantly improved by incorporating the chitosan (CS) polymer. This M—DN hydrogel showed much low coefficient of friction (COF) at 25 °C due to the presence of hydration layer on hydrogel surface. After illuminating with the NIR light, M—DN hydrogel with good photothermal effect rapidly raised the temperature to above the lower critical solution temperature (LCST), which led to an obvious increase of surface COF owing to the destruction of the hydration layer. In addition, M—DN friction control hydrogel showed good recyclability and controllability by tuning “on-off” of the NIR light. This work highlights the construction of functional MXene hydrogels for intelligent lubrication, which provides insight for interface sensing, controlled transmission, and flexible robotic arms.

АСИМПТОТИЧЕСКИЙ ПОДХОД К РЕШЕНИЮ КОНТАКТНОЙ ЗАДАЧИ ДЛЯ ТЕЛА КАЧЕНИЯ С ТОНКИМ ДЕФОРМИРУЕМЫМ ОБОДОМ

On the basis of an asymptotic approach to solving the elasticity theory boundary value problem for a thin strip rigidly linked to a non-deformable base, the differential equations are derived for determining the normal and shear loads distributed on the strip face free from fastening. These equations are used to solve the contact problem for a rigid cylinder with a thin elastic rim with a non-deformable horizontal rough support surface. The cylinder loading by a vertical force is considered for a given cylinder center settling. The calculated diagrams of contact pressure and shear contact stresses are obtained. In contrast to the previously used methods, the developed technique makes it possible to take into account the presence of adhesion and slip zones in the contact area, as well as to use a mathematically strict solution of the constitutive equations for contact pressure and shear contact stress. The value of the vertical force acting on the rigid cylinder for a given cylinder center displacement is determined. The stress tensor intensity distribution in the rim is established. The results of the developed technique application are compared with the calculated estimates obtained on the basis of the exact solution of the boundary value problem for a strip of arbitrary thickness and within the method, involving the use of the Winkler base simplified model. The dependences of the results error for the developed method on the thickness and Poisson's ratio of the rim material are obtained. The paper describes the effect of the rim-support surface friction coefficient on the contact pressure, shear contact pressure, and the maximum intensity of the stress tensor in the rim. It is concluded that it is reasonable to use the developed technique at solving contact problems for rolling elements with a relatively thin elastic rim.

The Characterization of Soft Antifriction Coating on the Tin Bronze by Electro-spark Alloying

Soft materials such as silver, copper and Babbitt SnSb11Cu6 were deposited on the surface of tin bronze by electro spark alloying (ESA) to form the antifriction coating. The data of the antifriction coating were tested by electronic balance, three-dimensional optical profilometer, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), Vickers microhardness tester and tribometer. The mass gain, roughness, thickness, surface morphology and phase composition, cross-section and element distribution, microhardness and tribological properties of the antifriction coating were analyzed. The results show that the grain size of the antifriction coating is fine and the metallurgical bonding between the coating and the substrate is good. The surface of each substrate is composed of three layers of coating. The optimal parameters of electro spark alloying are as follows: the discharge voltages of Ag, Cu and Babbitt alloy coatings are 60 V, 60 V and 30 V respectively, the energy storage capacitance is 150 μF, 150 μF and 90 μF respectively, and the working efficiency is 3 min/cm2, 3 min/cm2 and 4 min/cm2 respectively. Under the optimized parameters, the average mass transfer efficiency is 54.4 mg/cm2, the average surface roughness is 32.3 μm, and the maximum thickness is about 160 μm. The surface friction coefficient of the soft antifriction coating is 55.6 % of that of the tin bronze substrate. The main wear mechanisms of the soft antifriction coating prepared by electro spark alloying technique are plastic deformation accompanied by slight polishing.

FriC-PM: Machine Learning-based road surface friction coefficient predictive model using intelligent sensor data

Providing a robust traffic management system is a given for road authorities today, for safer mobility and reliable day-to-day operations. Therefore, to improve traffic management procedures in order to provide an open road for road users at all times, understanding road surface friction measurement is crucial. Currently, the automatic prediction model of road surface friction measurement (FriC-PM) is highly demanded by road transport owners and operators. The prediction accuracy of road surface friction is linked to several external variables related to the weather conditions, road surface micro- and macro-texture, tire properties, driving speed and behaviour of road users. This paper presents a trained novel predictive model developed for the measurement of road surface friction considering a big dataset of 18 months with daily records through novel intelligent road-based passive sensor measurement, on a Spanish highway section. The trained predictive model is developed on the machine learning (ML) approaches, namely support vector machine (SVM), and validated with the K-Fold cross-validation (CV) algorithm taking into account various kernels. In addition, error evaluation strategies are applied to the trained model in order to identify the efficiency, accuracy, and reliability of the predictive model. The main purpose of the proposed prediction model is to provide comprehensive knowledge about predictive road surface friction coefficient, and to support decision-making elements to road owners or operators for reliable predictive maintenance process.

Quasilinear Hyperbolic Systems Applied to Describe the Magnetohydrodynamic Nanofluid Flow

This study examines the flow of hyperbolic nanofluid over a stretching sheet in three dimensions. The influence of velocity slip on the flow and heat transfer properties of a hyperbolic nanofluid has been investigated. The partial differential equations for nanoparticle solid concentration, energy, and motion were turned into ordinary differential equations. Nanoparticle mass fluxes at boundaries are assumed to be zero, unlike surface concentrations. The influence of the main parameters on flow characteristics, surface friction coefficients, and the Nusselt number has been visualized. The results suggest that Brownian motion has a negligible impact on the heat transfer rate. The ratio of the elastic force to the viscosity force was found to decrease the fluid velocity. The resulting thermophysical properties of nanofluids are in agreement with previous research. The present findings can be used to expand the potential for using nanofluids as a coolant in critical thermophysical and industrial installations.