Effect Of Normal Force Research Articles

Interparticle friction behaviors of kaolinite: Insights into macroscale friction from nanoscale

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

Nano friction behaviour between magnetic materials and copper considering the inter-diffusion effect

Copper, permalloy, cobalt, and silicon are the materials that have been widely utilised in magnetic devices. When the size of interest is down to the nanoscale, the inter-diffusion between certain materials becomes influential. This paper studies the nanoscale friction characteristics between frictional pairs with and without inter-diffusion properties through the atomic force microscope. The distinct evolution features of nanoscale friction force when inter-diffusion is involved are discovered experimentally, which is also confirmed through theoretical analysis. Firstly, through the thin film deposition method, four pairs of contact materials (Cu–Ni81Fe19, Si–Ni81Fe19, Cu–Co, Cu–Si) are designed for friction tests, in which diffusion occurs at the interface of Cu–Ni81Fe19 pair. Then, the effects of sliding velocity and loading force on the nano friction of each pair are measured. It is found that regardless of the diffusion phenomenon: (1) the adhesion force values exhibit a notable correlation to the values of the friction force; (2) the friction force in all four material pairs consistently increases with the growth of the normal loading force, although the growth rate may differ. In terms of the sliding velocity effect, the friction forces of immiscible materials (Si–Ni81Fe19, Cu–Co, and Cu–Si) are found to increase with the increasing sliding velocity. However, the friction force of Cu–Ni81Fe19, decreases with the increasing sliding velocity. Furthermore, a compositive friction model considering both the velocity and the normal force effect was proposed, which shows good agreement with the experimental results and explains the nano friction behaviour of both miscible and immiscible metals.

Effect of Normal Force Intensity on Tactile Motion Speed Perception Based on Spatiotemporal Cue.

While the relative motion between the skin and objects in contact with it is essential to everyday tactile experiences, our understanding of how tactile motion is perceived via human tactile function is limited. Previous studies have explored the effect of normal force on speed perception under conditions where multiple motion cues on the skin (spatiotemporal cue, tangential skin deformation cue, and slip-induced vibration cue) were integrated. However, the effect of the normal force on speed perception in terms of each motion cue remains unclear since the multiple motion cues have not been adequately separated in the previously reported experiments. In this study, we aim to elucidate the effect of normal force in situations where the speed perception of tactile motion is based solely on a spatiotemporal cue. We developed a pin-array display which allowed us to vary the intensity of the normal force without causing tangential forces or slip-induced vibrations. Using the display, we conducted two psychophysical experiments. In Experiment 1, we found that the speed of the object was perceived to be 1.12-1.14 times faster when the intensity of the normal force was doubled. In Experiment 2, we did not observe significant differences in the discriminability of tactile speed caused by differences in normal force intensity. Our experimental results are of scientific significance and offer insights for engineering applications when using haptic displays that can only provide spatiotemporal cues represented by normal forces.

The role of normal force on the fretting corrosion behaviour of alloy 690 TT tube against 410 stainless steel plate in high temperature high pressure water

The effect of normal force on fretting corrosion of Alloy 690 TT tube in high temperature high pressure water was investigated. Increasing the normal force accelerates the wear behaviour of the tube. The small normal force has a larger coefficient of friction. The wear mechanism changes from the dominant form of abrasive wear to delamination wear. The increase in normal force not only causes the wear debris layer (WDL) and the tribologically transformed structure to become thicker and more refined, but also affects the oxidation and corrosion behaviour of the tube and changes the composition of the WDL.

Effect of Normal Force on Fretting Wear Behavior of Zirconium Alloy Tube in Simulated Primary Water of PWR

Effect of Normal Force on Fretting Wear Behavior of Zirconium Alloy Tube in Simulated Primary Water of PWR

Distribution parameters of a plastic–elastic transition function for normal force effects on the abrasive wear of organic coatings

Distribution parameters of a plastic–elastic transition function for normal force effects on the abrasive wear of organic coatings

Влияние нормальной силы на сглаживание и упрочнение поверхностного слоя стали 03Х16Н15М3Т1 при сухом алмазном выглаживании сферическим индентором

Introduction. Sliding burnishing minimizes roughness and hardens of the steel surface. Quality of the formed surface and strength characteristics of the surface layer are determined by the burnishing speed, force and feed. Due to the danger of the surface micro-destruction during burnishing, the problem of selecting the favorable value of the normal force at a given feed arises. The current investigation aims to study the effect of normal force during dry diamond burnishing with a spherical indenter on smoothing the surface microprofile and strain hardening of the 03Cr16Ni15Mo3Ti1 austenitic steel surface layer. Research methods. Profilometry, scanning electron microscopy (SEM), microdurometry are used. Results and discussion. As the result of dry burnishing of deformation-stable austenitic steel 03Cr16Ni15Mo3Ti1 with a spherical indenter with a 2 mm radius made of natural diamond at a sliding speed of 10 m/min and feed rate of 0.025 mm/rev, it is found that in the investigated variation range of the burnishing normal force (100...200 N) the value of the smoothing coefficient of the initial steel surface microprofile after finish turning is 79...90 %, the greatest smoothing with a decrease in the average roughness parameter Ra from 1.0 to 0.1 µm is achieved at a force of 150 N; during diamond burnishing the initial (after finish turning) surface is hardened by 15...43 % (up to 382...444 HV), as the burnishing force raises from 100 to 175 N, a non-monotonic increase of the average microhardness from 409 to 444 HV 0.05 takes place; burnishing with a load of 175 N forms a gradient-hardened layer with a thickness of 300...350 μm with the appearance of individual microfractures in the form of beadings and micro-cracks on the surface, the maximum hardening is caused by the formation of a highly dispersed surface layer of 30...40 μm thick with a structure of highly dispersed austenite and the corresponding activation of grain-boundary and dislocation strengthening mechanisms. The results can be used when selecting the diamond burnishing parameters of parts made of corrosion-resistant austenitic steels according to the criteria for obtaining low surface roughness without significant microfractures and effective strain hardening of the surface layer.

Micromechanical tangential force measurements between tetrahydrofuran hydrate particles

To reveal the mechanism of shear failure between gas hydrate particles can provide an important theoretical basis for controlling hydrate aggregation in oil and gas pipelines and for controlling sand production during gas production from natural gas hydrate reservoirs. Here we used a self-built micromechanical force test device to investigate the effects of normal forces, contact time, and temperature on tangential forces exerted between hydrate particles. The main controlling factors were analyzed according to the Mohr-Coulomb strength criterion. The test results show that the tangential force is proportional to the normal force and contact time, and that the temperature has a significant impact on the friction angle. Also, at a given temperature and for a short contact time (<30 s), the friction angle at the particle scale is very close to the friction angle measured by geotechnical tests at the macroscopic scale. Due to hydrate dissociation, the friction angle and cohesive force display the greatest variations around the phase-equilibrium temperature. In addition, possible tangential failure modes under various conditions are proposed to deeply reveal the mechanism of micro force between hydrate particles.

Understanding the damage mechanism of asphalt binder under controlled-stress fatigue loads in dynamic shear rheometer

Fatigue damage is one of the major distresses of asphalt binder. Most of the previous studies have focused on the crack growth in asphalt binder while cracking is not the only type of damage that occurs during fatigue process, which means that the damage mechanism of asphalt binder under fatigue loads is not well understood. This study characterized and compared the fatigue damage features of asphalt binder under controlled-stress time sweep tests with different amplitudes of fatigue loads. Cohesive failure appearances of all the involved asphalt binder were collected and employed to analyze the failure process. These failure appearances showed that there were primarily two types of pattern in the failure appearance: factory roof morphology and the wave-shaped pattern. Factory roof morphology was related to the cracking of asphalt binder, and the wave-shaped pattern was linked to the plastic flow of asphalt binder. Combining the failure appearance and the collected rheological properties proved that two types of damage occurred in asphalt binder in the time sweep test: elastic damage and plastic flow damage. The former and the latter one respectively dominated the failure process of asphalt binder under small- and large-amplitude fatigue loads. During the elastic damage process, phase angle of asphalt binder held constant while the complex shear modulus kept decreasing. During the plastic flow damage process, obvious variations on both complex shear modulus and phase angle can be observed. It addition, it was found that the profile of the failure surface was concave rather than horizontal, which proved the non-negligible effect of normal force on the cracking behavior of asphalt binder.

Computational investigation of the effect of microstructure on the scratch resistance of tungsten-carbide nickel composite coatings

Sliding wear was simulated for tungsten carbide-nickel (WC-Ni) composites with different WC particle sizes and volume fractions under various normal forces. Johnson-Cook and Johnson-Holmquist models were employed to simulate the mechanical behaviour of the Ni and WC phases, respectively. Using high-powered parallel computing, a detailed parametric study was conducted to understand the effects of normal force, WC particle size, WC particle volume fraction, and their interaction on the worn volume and the material removal mechanisms in WC-Ni metal matrix composite coating materials. This allowed for investigation of the competition and transition between microploughing, microcutting, and microfatigue. The results revealed that the stress was distributed better in the composite coating with higher particle volume fraction and smaller particle size, which increased the ability of the composite coating to resist deformation and wear. It was also found that the material removal mechanism changed from microploughing to microcutting with an increase in particle volume fraction. The worn volume was calculated for different combinations of intrinsic (e.g., WC particle size and volume fraction) and external (e.g., normal force) parameters considered in this study. The data obtained was used to train a machine learning-based model using artificial neural networks. The trained model was further employed to predict the worn volume, and the results revealed that a mechanistic modelling approach can predict worn volume reasonably well.

Study on the tensile behavior of helical auxetic yarns by modeling and mechanical analysis

Two-component auxetic yarns with helical wrapping structure showed negative Poisson’s ratio under axial tension. It was the interaction force, especially the normal force, between the two filaments that led to the outer contour diameter of the complex yarn being expanded. Both the deformation behavior of structure and cross section presented greater effect on Poisson’s ratio and auxetic effect. However, the previous geometrical model that has been reported was without considering the interaction force between the two components. Mechanical model with axial tension and the normal force was carried out to theoretically calculate Poisson’s ratio of the complex yarn. The results showed that the cross section of the filament was from circular shape to elliptical shape under the normal force. Theoretical value from the mechanical model with considering the effect of normal force on the radial strain was in good accordance with the experimental results of Poisson’s ratio.

Effects of Normal Force on the Tribocorrosion Behavior of a Nickel-Based Superalloy in Alkaline Solution: An Electrochemical Study.

The tribocorrosion behavior of Inconel 690TT in NaOH (pH = 9.8) solution at different normal forces was investigated by an electrochemical method. The results indicated that normal force had a great effect on the tribocorrosion behavior and mechanism. When normal force increased from 15 to 30 N, fretting regime was in gross slip regime (GSR), and wear volume gradually increased. When normal force further increased to 45 N, wear volume significantly decreased due to the fretting regime changing from GSR to partial slip regime (PSR). When fretting ran in GSR, the corrosion resistance decreased with the negative shift of open circuit potential (OCP). However, when the fretting regime changed to PSR, the corrosion reaction significantly decreased due to the adhesive wear. Fretting wear broke the passive film at the contacting surface, which caused the worn surface to be more active and prone to corrosion. However, the broken passive film was quickly repaired in subsequent oxidation. The break and repair of passive film strongly depended on normal force. In GSR, the increase in normal force aggravated the break of passive film. In PSR, the passive film was not easy to break with a further increase of normal force.

Analytical Calculation of the Tooth Surface Contact Stress of Cylindrical Gear with Variable Hyperbolic Circular-Arc-Tooth-Trace

In order to theoretically research the tooth surface maximum contact stress of a Cylindrical Gear with Variable Hyperbolic Circular-Arc-Tooth-Trace (VH-CATT), the computing formula of maximum contact stress of VH-CATT cylindrical gear is investigated according to Hertz formula in this paper. Insufficient contact fatigue strength will lead to pitting corrosion, plastic deformation of tooth surface and other damages. Therefore, the maximum contact stress of tooth surface must be carried out. The contact stress calculation formula is particularly considering the effect of normal force, total carrying length, synthetical curvature radius, and position angle. The present work establishes analytical solutions to research the effect of different parameters for the contact stress of VH-CATT cylindrical gear incorporating elastic deformation on the tooth surface, and which have shown that the different module, transmission ratio, pressure angle, tooth width, and the cutter head radius have a crucial effect on the contact stress and contact ellipse of VH-CATT cylindrical gear along the tooth width direction. Moreover, a finite element analysis is carried out to verify the correctness of the theoretical computing formula of contact stress of VH-CATT cylindrical gear. By contrast with the theoretical calculated value and the stress value of finite element analysis, its error is very small. It is indicated that the derived formula of contact fatigue strength of VH-CATT cylindrical gear has high accuracy and can accurately reflect the real contact stress value of tooth surface, which is beneficial for research on tooth break reduction, pitting, wear resistance and fatigue life improvement of the VH-CATT cylindrical gear. The study results also have a certain reference value for the design and check calculation of the VH-CATT cylindrical gear.

Effect of Normal Forces on the Electrical Endurance of Tin-Plated Contacts Under Elevated Temperature Fretting Conditions

In this article, an attempt is made to explore the effects of normal force and temperature on the threshold displacement amplitudes of tin-plated electrical contacts at elevated temperatures. Fretting tests were conducted at 323, 348, and 373 K at normal forces of 1, 1.25, 1.5, and 2 N. Riders and flats made from a 0.3-mm-thick brass sheet were coated with $10~\mu \text{m}$ of tin. Dimples were commonly found at the center of the contact area of the test specimens corresponding to an unlimited lifetime. In the testing temperature range, the threshold displacement amplitude decreases with an increase in the temperature and with a decrease in the normal force. In this range, the threshold displacement amplitude was found to be controlled by the oxidation of a tin-plated surface. The activation energy was found to be 7.5 kJ/mole, which is close to the value of the activation energy for the growth of tin oxide film. The threshold displacement amplitude can be represented in the form of an Arrhenius equation and is proportional to the normal force.

Normal force and displacement amplitude influences on silver-plated electrical contacts subjected to fretting wear: A basic friction energy – contact compliance formulation

During the last decades, the use of connectors in electrical devices for automotive has significantly increased. This raise in the number of electrical and electronic devices on board has led to a growing number of breakdowns. Indeed, this connectors need to keep a low and stable electrical contact resistance (ECR) but due to engine vibrations, fretting wear damage occur. Characterized by small oscillatory motions, fretting induces wear and oxide debris layer (third body) decaying the electrical contact resistance. The aim of this work is to study the effects of two main factors, which are the normal contact force and the displacement amplitude. In this study, a silver-plated contact (2 µm of thickness) was investigated applying various loading parameters: 2 N < P < 6 N and ±3 µm < δ* < ±20 µm. Results show that the ECR endurance decreases when the displacement amplitude increases regardless of the normal force. However, a non-monotonic evolution is found regarding normal force effect. Indeed, for a given displacement amplitude, a rise of the normal force tends to increase the contact pressure but at the same time induces a reduction of the effective sliding amplitude due a larger tangential accommodation. Hence, by coupling a friction energy density approach with a basic compliance description, the synergic effect of the normal force and the displacement amplitude is described and the ECR endurance predicted.

Experimental research on frictional resistance of smart isolation tool during maintenance operation in offshore pipeline

PurposePipeline maintenance technology using smart isolation tool is becoming more widely used in the global scope. This paper aims to investigate the effects of parameters on the frictional resistance between the slip and pipeline and the frictional characteristics under different lubrication films.Design/methodology/approachAn experimental platform consisting of slip, pipeline and data acquisition system was developed, wherein the slip slips on the pipeline under different normal forces and velocities. In addition, three lubrication conditions, namely, dry wall, oil liquid and black powder on the wall, were investigated to study the effects of lubrications on the frictional coefficient and characteristics.FindingsResearch results indicate that the frictional force and coefficient were sensitive to normal force. The crude oil affected the frictional coefficient within a certain range of normal force, and the black powder enhanced the surface roughness in the natural gas pipeline. However, velocity had no effect on them. In addition, different contact behaviors could be observed from the frictional coefficient curves.Originality/valueIn this paper, the effects of normal force and velocity on frictional resistance of sliding slip during decelerating process in pipeline were investigated, and the effects of lubrication films on frictional characteristics were also revealed. The research results are of great value to improve the prediction accuracy of smart isolation tool, and also provide a guiding significance for the development of maintenance operation in pipelines.

Effect of normal force on the fretting wear behavior of Inconel 690 TT against 304 stainless steel in simulated secondary water of pressurized water reactor

Abstract For understanding the long term fretting mechanism, the effect of normal force on the fretting wear behavior of 690 TT heat transfer tube against 304 stainless steel (SS) ball in simulated secondary water with 106 total fretting cycles was studied. The changes of the friction coefficients can be divided into five stages: small and slowly increase stage, sharply increase to a peak point, dramatically decrease to a steady value, steady stage, and continuously increase stage. And the friction coefficient decreases with the increase of the normal force. The morphologies of the worn scars under different normal forces are quite different. A stratified layer structure is formed on the 690 TT surface during the fretting wear process when the normal force is 60N.

A method of calculating and analyzing wear rate of materials under fretting condition

Fretting phenomena exist widely in structural engineering. In recent years, it has attracted more attention from scientists and technicians. In order to study the fretting wear in depth, we establish a new method of calculating the wear rate of material in vibratory environment. Firstly, according to the characteristics of friction pair and fretting wear process in fretting friction system, the asymmetric double potential well model is proposed and the potential energy function of the model is given. The transfer of particles between the two kinds of materials during the fretting is regarded as the motion of the particles in the two potential wells which are asymmetrical, and the particle motion equation in the potential well is established. Furthermore, considering the characteristics of the randomness, time-varying and irreversibility of particle motion in fretting friction system, a theoretical model is established by using the non-equilibrium statistical theory, which is based on the particle equation motion, combined with the Langevin equation in random theory and the Foker-Planck equation in the non-equilibrium statistical theory. The probability density distribution function of particles moving from the interior of the material to the material surface at any time is obtained. A method of calculating the wear rate is proposed by integrating the probability density distribution function. Secondly, by calculating the wear rate of the friction pair which consists of metal materials Mg and Fe, we obtain the potential energy function of the asymmetric double potential well model as the different surface energies of both materials. Furthermore, the probability density distribution function of particles moving in this friction pair is calculated. Then, the change of wear rate with wear time and width of potential well is derived, and the effect of normal force on wear rate is further analyzed. The results of calculation and analysis show that the wear rate of material decreases with the decrease of the width of the potential well in the friction pair system, decreases with the increase of wear time and increases with the increase of the normal force of the load, and the surface of the relatively soft material in the friction pair system is more likely to wear off. Finally, the conclusions of the theoretical model accord with the experimental results, illustrating the applicability of the theoretical model.

The Effect of Normal Force on Tribocorrosion Behaviour of Ti-10Zr Alloy and Porous TiO2-ZrO2 Thin Film Electrochemical Formed

The tribocorrosion behaviour of Ti-10Zr alloy and porous TiO2–ZrO2 thin film electrochemical formed on Ti-10Zr alloy was evaluated in Fusayama-Mayer artificial saliva solution. Tribocorrosion experiments were performed using a unidirectional pin-on-disc experimental set-up which was mechanically and electrochemically instrumented, under various solicitation conditions. The effect of applied normal force on tribocorrosion performance of the tested materials was determined. Open circuit potential (OCP) measurements performed before, during and after sliding tests were applied in order to determine the tribocorrosion degradation. The applied normal force was found to greatly affect the potential during tribocorrosion experiments, an increase in the normal force inducing a decrease in potential accelerating the depassivation of the materials studied. The results show a decrease in friction coefficient with gradually increasing the normal load. It was proved that the porous TiO2–ZrO2 thin film electrochemical formed on Ti-10Zr alloy lead to an improvement of tribocorrosion resistance compared to non-anodized Ti-10Zr alloy intended for biomedical applications.

Shape accuracy analysis of multi-point forming process for sheet metal under normal full constrained conditions

In order to study the shape accuracy of multi-point forming (MPF) process for sheet metal under normal full constrained conditions, the in-depth analysis of shape accuracy of workpieces in multi-point forming with individually controlled force-displacement (MPF-ICFD) process is conducted in this paper by combining experiment, theoretical analysis and numerical simulation. The influences of normal force, material thickness and material properties on the shape accuracy of the feature surface are studied, and the shape accuracy characteristics of the sheet under different parameters are obtained. Afterwards, the stress and strain characteristics of sheets are obtained by numerical simulation. Finally, the effect of normal force on shape accuracy was revealed by establishing a mechanical model of the sheet metal under normal full constrained conditions. Moreover, the amount of springback reduction in MPF-ICFD is defined quantitatively. Compared with the normal unconstrained conditions, the shape accuracy of sheet metal is improved significantly under normal full constrained conditions. The stress and plastic deformation are more uniform and the amount of springback is smaller. For Q 295 steel plate with thickness of 2.0 mm, the difference between the maximum value and the minimum value of the reaction force of punch decreases from 4515.9 N to 1475 N when the forming force is 2500 N. Besides, the bending moment of the sheet on the unit width decreases from 357.9 N • mm to 328.1 N • mm. The average shape error E rr and the amount of springback Δk decreases by 60.05% and 16.03%, respectively.