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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. [ABSTRACT FROM AUTHOR]

Graphene on a stainless steel substrate will appear as localized bulges, and these bulges will lead to large fluctuations in friction force, which is the key to influencing the lubrication efficiency of graphene. Here, the effect of normal load on the nanofriction behavior of the bulged graphene on a stainless steel substrate is investigated. In the normal load study interval from 20 to 110 nN, an increment of 10 nN of normal load can increase friction force the more the normal load increases, and the two are not linearly correlated. The friction force in the graphene bulge region consists of two parts: the first part originates from the interaction of the graphene material itself in contact with the tip, and the second part originates from the resistance due to the pile-up of graphene deformation in front of the tip. The nonlinear correlation between the normal load and friction force is mainly related to the pile-up effect of bulged graphene. In addition, the friction force increase due to the graphene bulge region needs to go through a process, which is divided into two stages. The first stage is the increase in friction force due to the tip starting to contact the bulged graphene and the contact area increasing. The second stage is the increase in friction force due to the graphene regulating its configuration and repeatedly interacting with the tip. The normal load is linearly related to the first stage but not linearly related to the second stage. The nonlinear correlation between the normal load and friction force is mainly related to the second stage of friction force rise. Therefore, the change of normal load affects the stacking effect and the ability to regulate the configuration of bulged graphene, which leads to a nonlinear increase of friction force. This contributes to the application of graphene for nanolubrication of stainless-steel components in MEMS. [ABSTRACT FROM AUTHOR]

It is of great significance to deeply understand the stress damage mechanism of the pile–soil interface under cyclic loading for the safety control of engineering entities. Large-scale self-developed shear equipment was used to conduct cyclic shear tests of the interface between steel and siliceous sand, and the macroscopic shear characteristics and particle crushing characteristics were analyzed. Finally, the interface micro characteristics were analyzed through numerical simulation. The results indicate that the interface peak shear stress under constant stress conditions mainly exhibits strengthening characteristics, while under constant stiffness conditions it exhibits weakening characteristics. The position of the relationship curve between shear stress and normal stress gradually moves towards the direction of low normal stress as the experiment progresses, and the distance between the curves gradually decreases. The degree of particle breakage increases with the number of cycles but is mainly concentrated in the first few cycles. The principal stress is proportional to the normal stress, and its rotation degree gradually weakens with the normal stress. The contact number of particles at any angle increases with the normal stress. [ABSTRACT FROM AUTHOR]

Background: Worm gear sets are used in many applications of the transmission field. These mechanisms have interesting advantages. Despite this, its modelization is still challenging. This is due to its complex geometry. The goal behind this is to have an accurate model that allows improvement of the design of worm gear sets. Purpose: In this context, the paper presents a new mathematical model of a worm gear drive under rotational external excitations. Methods: Dynamic model is defined by fourteen degrees of freedom describing all rotations and translations of worm gear set, AQ1 bearings, a motor and a receiver connected together. First, equations of motion are developed to describe the dynamic behavior. Lagrange formula is, thus, employed. Elastic deformations of meshed teeth are considered. The normal load associated with the meshing is established as function of the model degrees of freedom through the elastic deflection. Second, a numerical simulation is carried out. Newmark Beta method is used to solve equations. Results: Numerical results are presented to discuss the model accuracy. The impact of the variation of friction coefficient and the stiffness of the worm gear is finally studied to discuss the consistency of the new formulation developed through this work. [ABSTRACT FROM AUTHOR]

In the field of aerospace, weapons and other complex assembly, there are more than 50 factors affecting the performance degradation of joint structures, among which the friction coefficient is the main factor. Nickel steel is widely used in large complex equipment due to its advantages of high strength. Therefore, this paper first establishes a theoretical model of friction coefficient based on fractal theory. Secondly, the friction coefficient experiment was carried out to measure the friction coefficient of nickel steel plates with different roughness under different normal loads. Finally, the experimental results are compared with the theoretical results, and the accuracy and error analysis of the model is carried out. The results show that the friction coefficient increases with the increase in roughness. When the normal load is greater than 50 kg, the friction coefficient gradually tends to be stable. The error of identification results of correction factor a was all within 5%. The error between theoretical model prediction and experimental data is 6%–15%, which indicates that the calculation of the friction coefficient has high accuracy. The results of this study can provide data and theoretical support for the friction coefficient evaluation of nickel steel plate joint structures, and contribute to the health detection and reliability evaluation of nickel steel plate joint structures. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A micro-arc oxidation (MAO) coating was in–situ grew on Ti6Al4V alloy to improve the friction-wear performance, and the morphologies, chemical compositions and phases of obtained coating were analyzed using a scanning electron microscope, energy dispersive spectroscopy, and X–ray diffraction, respectively. The effect of normal load on the tribological performance of MAO coating at 400 °C was investigated on a ball–on–disc wear tester. The results show that the MAO coating exhibits irregular–pore structure, which is mainly composed of TiO2 phase. The coefficient of friction (COF) and wear rate of MAO coating under the normal load of 2 N are 0.32 and of 0.84 × 10–5 mm3 N−1 m−1, respectively, showing the best friction reduction and wear resistance among the three kinds of loads. The wear mechanism of MAO coating under the normal load of 2 N is abrasive wear; while those under the normal loads of 4 and 6 N are adhesion wear fatigue wear, respectively, in which the MAO coating has the tendency of plastic deformation with the increase of normal load. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Functional Materials / Gongneng Cailiao is the property of Chongqing Functional Materials Periodical Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Erzincan University Journal of Science & Technology is the property of Erzincan Binali Yildirim Universitesi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The experiment was carried out in a reciprocating lubricated conformal sliding contact between steel discs of the same hardness. The effects of disc surface texturing on the friction coefficient at various operating conditions (temperature, normal load, and frequency of oscillations) were studied. Under various conditions, surface texturing caused friction reductions of sliding pairs. The largest reduction was 4.6 times at a lower temperature and 2.5 times at a higher temperature. The effect of the pit area ratio on the friction reduction was visible at a higher temperature. The highest dimple density of 25% corresponded to a lower coefficient of friction than the smallest density of 9%. The sliding pair with a dimple density of 17% led to large variation of the friction force. At lower temperatures, the coefficients of friction were lower compared to tests at higher temperatures. [ABSTRACT FROM AUTHOR]

Fretting wear phenomenon has a non-negligible impact on the reliability of the contact parts of mechanical power systems. The impact of temperature increases in actual working conditions is taken into consideration in order to increase the accuracy of fretting wear prediction. Temperature-dependent wear coefficients were added to the energy dissipation wear model, and the UMESHMOTION subroutine was created. A temperature-displacement-coupled finite element model of fretting wear is established based on a cylinder/plane fretting test of Ti-6Al-4V alloy materials. The model takes into account the interaction between temperature, stress, and wear. The effects of the plastic deformation of materials, temperature, number of cycles, fretting velocity, and variable normal load on wear and temperature rise are explored. The results show that the wear amount is small when the temperature rises, and the plastic deformation of materials is not considered. The wear profile is no longer a smooth Hertzian shape when the plastic deformation of materials is considered. The amount of wear increases with the fretting speed and the number of cycles. Meanwhile, the temperature of the contact area and the surface near the contact area increases with the increase in fretting speed. Peak temperature rise of the contact surface increases with the number of cycles, and its horizontal position moves with the cylinder specimen. Furthermore, the wear profile is less smooth under the variable normal load, but the two variable normal loads in the same phase have similar wear profiles and temperature rise distributions. The theoretical resources provided by the research work can be used to design control strategies and optimize mechanical power systems. [ABSTRACT FROM AUTHOR]

Copyright of Problems of Friction & Wear is the property of National Aviation University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Analysis of non-local, phase-lag, and temperature-dependent properties of modified couple stress thermoelastic diffusive medium is examined in conditions of exciting by thermomechanical sources. The governing equations are framed involving non-local, phase-lag, and temperature-dependent properties. These equations are simplified by using the potential functions and employing the Laplace and Fourier transforms for further study. The problem is solved by deploying suitable thermomechanical loads. A specific type of normal and thermal loading of the ramp-type is considered. The transformed components of the physical field like the displacements, stresses, temperature change, and chemical potential are derived. A numerical analysis is performed for these quantities using the numerical technique. The graphs of the resulting quantities are shown to analyze the impact of non-local, phase-lag, and temperature-dependent properties. The specific cases are also mentioned. [ABSTRACT FROM AUTHOR]

The friction behavior of high-purity titanium in microscale was experimentally investigated by using atomic force microscopy to scan two neighboring grains with different crystalline orientations across the grain boundary. The results indicated that there were obvious friction contrast (FG1/FG2) between the two neighboring grains. The friction contrast became more obvious when higher normal load was applied, and this trend could be well reproduced by using the DMT model. Based on this, the interfacial shear strength was identified as the main factor causing the friction contrast. Higher scan velocity reduced the friction, which was regarded as the result of the decreased ability to maintain a stable capillary bridge in ambient atmosphere. However, the scan velocity had no significant effect on the friction contrast. [ABSTRACT FROM AUTHOR]

Surface texturing plays an increasingly important role as it can directly influence the tribological behaviors of contact surfaces in many ways. In texturing, tribological performance depends upon the types of design texture used and methods of fabricating texture on the surface. In this research work, friction and wear behaviors of surface textured EN-31 alloy steel have been investigated under wet condition by using DUCOM linear reciprocating tribometer. The textured dimples are fabricated by micro-EDM and micro-drilling CNC machining processes. Initially un-textured surfaces of EN-31 alloy steel with EN-8 steel pin are experimented for friction and wear under ISO-68 and ISO-220 lubricant oil. Under the different normal load conditions, it has been observed that the ISO 68 oil gives better friction-wear characteristics with respect to ISO-220 oil. Then after textured surfaces were investigated by using optimized ISO-68 lubricant. Experimental results on micro-EDM provide better friction and wear properties with respect to micro-drilling CNC. Surface texturing may act as wear debris trapper, lubricant reservoirs, hydrodynamic lift, and retarding the lubricant molecules flow in a particular path where potential exists. In this work, it has observed that texturing by micro-EDM enhanced mixed lubrication and minimum friction in mixed lubrication leads to decrement of wear loss. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to compare the influence of the normal load on the friction and wear behaviour of nickel-based alloys, which is use communally in the industry. We chose two samples of nickel-based alloys (NI-Cr-B-Si-C-W) elaborated by isostatic compression with a difference in their microstructure composition and quantity of micro constituent. The friction coefficient, the wear loss and the wear rate are evaluated using a tribometer (pin on disc) and a test bench created to reproduce the same industrial environment. Experiments showed that the applied normal load affects differently on the behaviour of the samples. The results conclude that the friction and wear resistance of the alloy do not just depend on the increase of the normal load but also on the distribution, the location and the morphology of the hard compounds formed in the alloys. [ABSTRACT FROM AUTHOR]

Purpose: Random point-contact between the space bearing retainer and the rolling elements may cause wear of the space bearing retainer. The paper aims to clarify the friction and wear behaviors of polyimide bearing retainer under point-contact condition. Design/methodology/approach: Space bearing retainers were cut into flat specimens and the tribological behaviors of the specimens were studied under point-contact condition using a friction and wear testing machine. Different sliding velocities and normal loads were used to simulate the running state of space bearing retainer. The wear behaviors of the space bearing retainer were analyzed by SEM and white light interferometer. Findings: The friction coefficient of the polyimide composites decreased with increase in sliding velocity from 1 to 5 mm/s. Moreover, with increase in sliding velocity and normal load, the wear rate of the polyimide composites decreased and increased, respectively. Moreover, the wear behaviors of the polyimide composites were mainly determined by the combined actions of ploughing friction and adhesive friction. The lubricating properties of transfer film and wear debris were limited under point-contact condition. Practical implications: The paper includes implications for the understanding of the wear mechanism of the polyimide composites space bearing retainer under point-contact condition and then to optimize space bearing retainer materials further. Originality/value: Under point-contact condition, wear debris can hardly participate in the friction process because of limited contact area. Consequently, the wear debris has limited impact on the wear process to decrease the friction and wear. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0017/ [ABSTRACT FROM AUTHOR]

The pin-on-disc test model system was used to simulate contact wear between wheel flange and rail gauge corner. Pins were extracted from a class C cast steel wheel and discs were extracted from premium and intermediate steel grades rail, both hypereutectoid and with hardness between 321 and 392 HB. Rails are pearlitic and the bainitic wheel is in its first life. Dry and lubricated tests were performed with normal load variation (40, 80 and 120 N). Under dry condition, there was no influence of the pair hardness to mass loss of the tribosystem studied, contrary to what is stated by literature. For the lubricated tests, mass loss was significantly lower and regardless of both, hardness ratio and normal load, than in the other tests. This shows the technological importance of: (i) implementing wheel flange lubrication (locomotive embedded process); (ii) improving rail lubrication techniques (mobile or way side process) and/or friction coefficient measurement techniques and (iii) need for revision of wheel standards and/or specifications. [ABSTRACT FROM AUTHOR]

Applying accurate normal load to a specimen in direct shear tests under constant normal stiffness (CNS) is of importance for the quality of the resulting data, which in turn influences the conclusions. However, deficiencies in the test system give rise to a normal stiffness, here designated as system normal stiffness, which results in deviations between the intended and actual applied normal loads. Aiming to reduce these deviations, this paper presents the effective normal stiffness approach applicable to closed-loop control systems. Validation through direct shear tests indicates a clear influence of the system normal stiffness on the applied normal load (13% for the test system used in this work). The ability of the approach to compensate for this influence is confirmed herein. Moreover, it is demonstrated that the differences between the measured and the nominal normal displacements are established by the normal load increment divided by the system normal stiffness. This further demonstrates the existence of the system normal stiffness. To employ the effective normal stiffness approach, the intended normal stiffness (user defined) and the system normal stiffness must be known. The latter is determined from a calibration curve based on normal loading tests using a stiff test dummy. Finally, a procedure is presented to estimate errors originating from the application of an approximate representation of the system normal stiffness. The approach is shown to effectively reduce the deviations between intended normal loads and the actual applied normal loads. [ABSTRACT FROM AUTHOR]

The paper deals with the plane problem of normal and tangential load for microperiodic composite with slant lamination. The boundary condition was considered as a normal and tangential load given on the surface of the composite half-plane. Microperiodic composite consisted of two components, differing in their Young's modules. The homogenized model with microlocal parameters, which is presented by Woźniak (Int J Eng Sci 25:483–498, 1987. 10.1016/0020-7225(87)90102-9), Jędrysiak (Compos Struct 202:1253–1262, 2018. 10.1016/J.COMPSTRUCT.2018.05.155) was used to solve the considered problem. The problem was formulated and solved using the averaged boundary condition given by Perkowski et al. (Compos Sci Technol 67:2683–2690, 2007. 10.1016/J.COMPSCITECH.2007.02.013). The considered boundary value problem will be solved using the Fourier transform method. An analytical solution was obtained in a general form for any form of the function describing normal and tangential loads on the surface of a half-plane. An analytical solution was determined for the special cases of an elliptical, normal and tangential loads and for the special case of the concentrated force. The results are shown in the form of figures. [ABSTRACT FROM AUTHOR]

Purpose The purposes of this paper include studying the friction coefficient of polyoxymethylene (POM) under a broad range of normal load and sliding velocity; developing a mathematical model of friction coefficient of POM under a broad range of normal loads and sliding velocities; and applying the model to dynamic finite element (FE) analysis of mechanical devices containing POM components.Design/methodology/approach Through pin-on-disc experiment, the friction coefficient of POM in different normal loads and sliding velocities is investigated; the average contact pressure is between 5 and 15 Mpa and the sliding velocity is from 0.05 to 0.9 m/s. A friction algorithm is developed and embedded in the FE model to simulate the friction of POM in different normal loads and sliding velocities.Findings The friction coefficient of POM against steel declines with the increase of normal loads when the contact pressure is between 5 and 15 Mpa. The friction coefficient of POM against steel increases markedly when the sliding velocity is between 0.05 and 0.15 m/s, it decreases sharply between 0.15-0.45 m/s and then it stabilizes at high sliding velocity between 0.45 and 0.9 m/s. The friction coefficient of POM in different working operations has a significant effect on contact stress and shear stress. The simulation data and experiment data of POM friction force fit very well; therefore, it can be concluded that the friction algorithm and FE model are accurate.Originality/value The friction coefficient of POM under a broad range of normal loads and sliding velocities is investigated. The friction coefficient model of POM is established as a function of normal loads and sliding velocities in the dry sliding condition. A friction algorithm is developed and embedded in the FE model of the friction of POM. The mathematical model of the friction coefficient accurately agrees with the experiment data, and simulation data and experiment data of the POM friction force fit very well. [ABSTRACT FROM AUTHOR]

The interface bonding condition between asphalt concrete layers is unquestioned as one of the significant factors influencing pavement performance. In order to research the interface characteristics of asphalt pavement under traffic loading, this paper presents a procedure to estimate shear strength between the asphalt layers via a direct shear test where both normal and shear stresses are applied to the interface. To do this, first, laboratory testing was conducted under varying conditions of temperature, vertical pressure, and tack coat application rate to analyze the influence of each parameter on interface shear strength. Second, the results from the tests were statistically analyzed for the significance level of each factor on interface shear strength. Finally, prediction models describing interface shear strength under the combined effect of shear and normal stresses at three different temperature levels are proposed and their feasibility is validated. All things considered, findings of this study hope to lead to a greater understanding of the monotonic behavior of interface performance in asphalt pavements. [ABSTRACT FROM AUTHOR]

In the present work, A356/SiC Metal Matrix Composite (MMC) with different weight percent of SiC particles were fabricated by two different techniques, such as Mechanical stir-casting and Electromagnetic stir casting. The wear and frictional properties of the metal matrix composites were studied by performing dry sliding wear test using a pin-on-disc wear tester for both electromagnetic stir casting samples and mechanical stir casting samples. The wear rate increases with the addition of normal force, while decreases when the percentage of reinforcement is increased. Frictional coefficient increases by increasing the normal force and percentage of reinforcement. By increasing percentage of reinforcement and using electromagnetic stir casting process, the higher frictional coefficient and lower wear rate are obtained. [ABSTRACT FROM AUTHOR]

In this paper, the effect of rock bridge surface on the shear behavior of planar non-persistent joints under low and high normal loads has been investigated using particle flow code in 2 Dimensions. PFC2d was calibrated with respect to the data obtained from experimental laboratory tests to ensure the conformity of the simulated numerical models response. The models consisting non-persistent joint were simulated and tested by shear loading under low and high normal loads. The discrete element simulations demonstrated that the failure pattern was mostly influenced by normal load, while the shear strength was linked to the failure pattern and failure mechanism. The failure patterns were found reasonably similar to the experimentally observed trends. [ABSTRACT FROM AUTHOR]

Shear failure of rockmass along a weak plane occurs frequently in rock slopes and in underground tunnels. To study the shear behaviour and acoustic emission (AE) characteristics of joints under different experimental conditions (asperity height, shear rate, and normal load), irregular artificial saw-tooth joints with different asperity heights were sheared in the laboratory, and the AE signals were detected and analysed. The results demonstrated that the strength of the joints increased with increases in normal load and asperity height, while the strength of the joints first increased and then decreased when the shear rate was elevated. The ideal curve of the cumulative hits could be divided into a quiet period, a slow rise period, and a sharp growth period, which could be used to monitor and predict the potential shear failure of the joints. The higher the asperity was, the higher the peak energy rate and the lower the peak hit rate, and cumulative hits at failure were because of differences in asperity size and number. The peak hit rate and cumulative energy tended to increase gradually with the decrease in shear rate, and the minimum peak hit rate and energy rate at failure were both attained at the maximum shear rate. In addition, curves of the energy rate and hit rate showed large fluctuations at higher shear rates. The peak energy rate and cumulative energy under low normal stress could be greater than the peak energy rate and cumulative energy under high normal stress, and the peak hit rate and cumulative hit number under high normal stress could be larger than that of under low normal stress. [ABSTRACT FROM AUTHOR]

This paper investigates the dry sliding wear behaviour of AA6061/ZrB2/SiC hybrid composite prepared by the stir casting. A pin-on-disc wear apparatus was used for this study. The effect of ZrB2 and SiC particulate content and normal load on wear rate was analyzed. The insitu fabricated ZrB2 and the reinforced SiC particles enhance the wear resistance of the AA6061 composite. The worn surface analysis of the composite as a function of ZrB2 and SiC particulate content and normal load are also presented. [ABSTRACT FROM AUTHOR]

Cu and Cu-MoS coatings were fabricated by cold spray, and the fretting wear performance of the two coatings was compared. A mixture (95 wt.% Cu + 5 wt.% MoS) was used as feedstock for the composite coating. Coatings were sprayed with identical gas flow conditions on the substrates pre-heated to approximately 170 °C. The morphology of coating top surface and polished cross sections was analyzed by scanning electron microscopy (SEM) and light optical microscopy (LOM). The influence of MoS on Cu deposition was examined. The local MoS concentration within the coating was found to affect the hardness. Fretting tests were carried out at two different normal loads, and the influence of MoS on friction and wear was studied. The morphology and elemental compositions of the wear scars and wear debris were observed by SEM and energy dispersive x-ray spectroscopy (EDS), respectively. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The high strength, low weight, and outstanding corrosion resistance properties possessed by titanium alloys have led to a wide range of successful applications in aerospace, automotive, and chemical industries and in power generation. Titanium alloys are characterized by poor wear resistance properties and their utilization has been excessive in nontribological applications. Surface texturing is a well-known and effective means of surface modification to improve the tribological properties of sliding surfaces. In the present work, modification of titanium alloy surfaces (Ti6Al4V) was done by lapping and laser surface texturing. The wear-resistant coating, AlCrN, was applied over the modified titanium alloy surfaces, with and without a chromium interlayer. Linear reciprocating sliding wear tests were performed with ball-on-flat contact geometry to evaluate the tribological performance of the coated alloy. The tests were performed under different normal loads for a period of 105 cycles at a frequency of 5 Hz. The friction force between the contact pair and displacement of the ball were simultaneously observed using a force transducer and laser displacement sensor. Optical microscopy was used to quantify the wear volume by measuring the wear scar diameter on both the specimen and the counterbody. Scanning electron microscopy (SEM) was employed to study the morphology of the wear scar. The characteristic behavior of the AlCrN coating such as bonding strength, wear volume, wear rate, and coefficient of friction with the chromium interlayer was evaluated and compared with the coating directly applied over the substrate. The coating on the textured surface, with the chromium interlayer showed better tribological performance. [ABSTRACT FROM AUTHOR]

Understanding the scratch behaviour of the composite materials is of primary importance. The scratch behaviour of glass fibre reinforced polyester composite was investigated. A new scratch device is designed and developed. Scratch tests at room temperature were carried out, using conical indenter and constant scratching velocity. The main aim of this study is to investigate the effects of tribological parameters on wear mechanisms and friction coefficient. Particularly, the effects of the normal load and the attack angle were presented. The different wear scenario of the composite material during the scratch test was deduced, then supported by an analysis of the glass fibre reinforced polyester composite wear modes using scanning electron microscopy (SEM) observations was performed. The correlation between tribological parameters and wear mechanisms was highlighted through the composite scratch map. Results were compared with those previously published associated with the metallic and the polymeric materials. [ABSTRACT FROM AUTHOR]

The subject of the paper includes theoretical considerations, the conducting of experimental tests, and the analysis of exposed test results related to determination of the coefficient of static friction of previously heat-treated contact pairs. One contact element is previously, before the procedure of determining the coefficient of static friction, heated at temperatures in the range of ambient temperature to 280°C and then cooled down to ambient temperature. The results of experimental tests of five different materials show that depending on the heat treatment of one contact element, there is a significant decrease in the coefficient of static friction. The authors of the paper consider that the reasons for the decreasing coefficient of static friction are related to oxide formation and changes in the surface layer of the contact element which is previously heat-treated. [ABSTRACT FROM AUTHOR]

In the present study, friction coefficient and wear rate of gear fiber reinforced plastic (gear fiber) and glass fiber reinforced plastic (glass fiber) sliding against mild steel are investigated experimentally. In order to do so, a pin on disc apparatus is designed and fabricated. Experiments are carried out when smooth or rough mild steel pin slides on gear fiber and glass fiber disc. Experiments are conducted at normal load 10, 15 and 20 N, sliding velocity 1, 1.5 and 2 m/s and relative humidity 70%. Variations of friction coefficient with the duration of rubbing at different normal loads and sliding velocities are investigated. Results show that friction coefficient is influenced by duration of rubbing, normal load and sliding velocity. In general, friction coefficient increases for a certain duration of rubbing and after that it remains constant for the rest of the experimental time. The obtained results reveal that friction coefficient decreases with the increase in normal load for gear fiber and glass fiber mating with smooth or rough mild steel counterface. On the other hand, it is also found that friction coefficient increases with the increase in sliding velocity for both of the tested materials. Moreover, wear rate increases with the increase in normal load and sliding velocity. The magnitudes of friction coefficient and wear rate are different depending on sliding velocity and normal load for both smooth and rough counterface pin materials. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It has been shown theoretically and experimentally that the friction properties of rubber are controlled by multiple parameters, such that coefficient of friction (COF) calculations for rubber differ from the traditional, metallic-based laws of friction. A previously formulated hypothesis details a unified theory of rubber friction that incorporates adhesion forces, surface deformation hysteresis, bulk deformation hysteresis and cohesion losses from rubber wear. This paper discusses experimental data that support the theory of surface deformation hysteresis (F Hs) and the implications for footwear testing. The experimental results indicate that surface deformation hysteresis on smooth test surfaces can contribute 6.5–42% of the total frictional forces depending on the applied load and outsole compound. This contribution is specific to the experimental dataset reported, and can vary with the rubber compound used. The data also show that F Hs is a constant, resulting in a decreasing contribution to the total COF (µ T) with increasing normal load. The combination of these two facts has implications in the establishment of standard test methods and the application of minimum COF requirements for footwear. [ABSTRACT FROM AUTHOR]

Purpose – The present paper seeks to report the effect of duration of rubbing on friction coefficient for different polymer and composite materials. Variations of friction coefficient and wear rate with the normal load are also investigated experimentally when stainless steel (SS 304) pin slides on different types of materials such as cloth-reinforced ebonite (commercially known as gear fiber), glass fiber-reinforced plastic (glass fiber), nylon and polytetrafluoroethylene (PTFE). Design/methodology/approach – A pin on disc apparatus is designed and fabricated. During experiment, the rpm of test samples was kept constant and relative humidity was 70 percent. Findings – Studies have shown that the values of friction coefficient depend on applied load and duration of rubbing. It is observed that the values of friction coefficient decrease with the increase of normal load for glass fiber, nylon and PTFE. Different trend is observed for gear fiber, i.e. coefficient of friction increases with the increase of normal load. It is also found that wear rate increases with the increase of normal load for all the materials. The magnitudes of friction coefficient and wear rate are different for different materials. Practical implications – It is expected that the applications of these results will contribute to the design of different mechanical components of these materials. Originality/value – Within the observed range of applied normal load, the relative friction coefficient and wear rate of gear fiber, glass fiber, nylon and PTFE are experimentally investigated. [ABSTRACT FROM AUTHOR]

The effects of friction on tribo-magnetization mechanisms for self-mated iron pairs under dry friction were experimentally investigated in this study. By comparing the effects of sliding speeds and normal loads on surface magnetization, the physical contradiction in frictional magnetization can therefore be classified. Results showed that severe friction phenomena are the prerequisite conditions for tribo-magnetization to occur. The maximum dynamic saturated value of tribo-magnetization for the self-mated iron pairs during the friction process was found to be only about 18G but rapidly decreased to the range of 0-1G after the test. It was also found that tribo-magnetization decreased significantly with increasing sliding speed. This was due to a rise in surface temperature and the presence of oxide materials at the actual contact areas from higher sliding speeds. The magnetic domains were also randomly oriented due to thermal vibration, which explained surface demagnetization with increasing sliding speed. In general, the average tribo-magnetization was inversely proportional to the sliding speed. Under small normal loads, tribo-magnetization was insignificant. For normal loads exceeding 30 N, the average tribo-magnetization increased linearly with increasing normal load. It was revealed that variations of the average tribo-magnetization coincided with wear losses under heavy normal loads. The reasons were that as the oxide film broke, fresh ferromagnetism was exposed to severe wear and material transfer. The orientation of the magnetic domains was caused by both frictional activation and the earth's magnetic field. Tribo-magnetization was thus significantly increased by friction and wear with increasing normal load. Finally, this study proposed two perspectives on energy and material to clarify the physical contradictions of the tribo-magnetization. [ABSTRACT FROM AUTHOR]

In the present paper the influence of the addition of chromium carbide (CrC) particles on the microstructure, microhardness and abrasive wear behaviour of flame sprayed Ni-Cr-Si-B coatings deposited on low carbon steel substrate has been reported. Wear behaviour of the coatings was evaluated with a pin-on-block wear system against SiC abrasive medium (120 & 600 grades) over a range of normal load (5–20 N). It was observed that the wear behaviour is governed by the material related parameters (microstructure, microhardness of coating) and test parameters (abrasive grit size and normal load). The addition of CrC reduces the wear rate three to eightfold. Wear resistance was greater against coarse abrasives at high loads than against fine abrasives. Heat treatment of both unmodified (1004) and modified powder (1004-10%CrC, 1004-20%CrC) coatings deteriorated the abrasive wear resistance. SEM study of wear surfaces showed that wear of the coatings largely takes place by groove formation, plowing and scoring. Electron probe micro analysis (EPMA) of the coating was carried out for composition and phase analysis. [ABSTRACT FROM AUTHOR]

This paper describes the influence of a post spray heat treatment on the microstructure, microhardness and abrasive wear behavior of the flame sprayed Ni-WC (EWAC 1002 ET) coating deposited on the mild steel. Coatings were deposited by using an oxy-acetylene flame spraying torch (Superjet Eutalloy L & T, India). The wear behavior of the coating was evaluated using a pin on disc wear system against SiC abrasive medium of 120 and 600 grades at 5, 10, 15, and 20 N normal load. Results revealed that the influence of normal load on wear is governed by the microstructure, hardness and abrasive grit size. The heat treatment increased average microhardness of the coating. However, it was found that the hardness does not correctly indicate the abrasive wear resistance of Ni-WC coating in an as sprayed and heat treated condition. The heat treatment of the coating improved its abrasive wear resistance against fine abrasive medium while the wear resistance against coarse abrasive was found to be a function of a normal load. At low-normal load (5 and 10 N) the heat treated coating showed lower-wear rate than as spayed coating while at high-normal loads (15 and 20 N) heat treated coating was subjected to higher-wear rate than as sprayed coating. In general, an increase in normal load increased the wear rate. The scanning electron microscopy study indicated that the wear largely takes place by groove formation and scoring of eutectic matrix and the fragmentation of the carbide particles. [ABSTRACT FROM AUTHOR]

Demand for the fabric wipes is growing continuously. Wipes in industry are used for cleaning purpose. Cleaning involves rubbing action, so it is very important to know how much frictional force is encountered during the cleaning action. In this study the effects of normal load, sliding speed on frictional characteristics of nonwoven and woven wipes, both dry and wetted with different liquids, against glass and floor tile surfaces have been reported. With the increase in the normal load the coefficient of friction goes on decreasing for both nonwoven and woven wipes and this trend is observed in both dry and wet wipes. The coefficient of friction of both nonwoven and woven wipes against glass surface is in general higher than the floor tile surface. The wipes wetted with water shows an increase in coefficient of friction as compared to dry sample, but there is reduction in the coefficient of friction when the wipe samples are wetted with vegetable oil. In case of dry wipes, the coefficient of friction in case of nonwoven wipe is higher than the woven wipe. In case of woven wipes, the ranges of coefficient of friction either due to change in liquid type, normal load or sliding speed are in general smaller than that in case of nonwoven fabrics. [ABSTRACT FROM AUTHOR]

The influence of the welding process and post-welding heat treatment on the abrasive wear resistance of iron based hardfacing overlays (Fe - 6Cr - 0.5C) is reported. Overlays were deposited by shielded metal arc (SMA) and tungsten inert gas (TIG) welding processes on structural steel using a commercially available surfacing electrode (BOR-C) 3.15 mm in diameter. Overlays were deposited by the SMA welding process using 250 A dc (straight and reverse polarity) at a constant welding speed ∼15 cm min-1. The abrasive wear resistance of overlays in as welded and heat treated conditions was tested on a pin on disc system against 300 grade waterproof SiC polishing paper at different normal loads (1 - 5 N). Optical microscopy was used to study the microstructure of the overlays. SEM study of the wear surfaces was done to analyse the wear mechanism. It was found that the wear resistance of the coating produced by TIG welding is better than that of coatings deposited by SMA welding. The hardness of the coating adjacent to the interface is found to be comparatively lower than that away from the interface. Post-weld heat treatment improves the abrasive wear resistance. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC) film was deposited on Si wafer by a plasma CVD deposition system using benzene. Tribological properties of the DLC film were evaluated using a ball-on-disk tribo-meter in low (RH 17∼20 %) and high humidity (RH 90∼95 %) conditions in air. The effect of sliding speed (4.2 mm/s to 25 mm/s) and load (1.06 N to 3.08 N) on friction and wear was investigated. The friction behavior of the DLC film was obviously different in low and high humidity. When tested under low humidity conditions, the friction coefficient decreased significantly with increasing speed, and increased with load. However, under high humidity conditions, the friction coefficient increased with the speed and decreased with increasing load. The wear of the DLC film was little influenced by the sliding speed, normal load and humidity; a level of 10-8 mm3/Nm could be obtained in all tests. The formation of a uniform transfer layer would be the main factor which controlled the friction coefficient of the DLC films. Unlike the friction, the wear resistance of the DLC film is not so easy to discuss and may be affected mainly by the tribo-chemical reaction in all the test conditions. [ABSTRACT FROM AUTHOR]

In the present study, dry sliding wear behavior of a newly developed electroless Ni–P–X (X=ZrO2+Al2O3) coating, prepared by in-situ co-precipitation of X and its co-deposition, has been investigated both as-coated and heat treated, at different loads on a pin-on-disc wear monitor with constant sliding speed. The cumulative volume loss for increasing sliding distance is observed to be linear and variation in wear rate has been found to increase linearly with normal load following Archard's law. As-coated and heat-treated samples showed significantly better wear performance than that of the substrate aluminum (AS) in terms of the wear rate, which was also found to be influenced by substrate hardness. The friction coefficient decreases with increasing normal load for both the un-coated and coated aluminum. However, relatively higher values of friction coefficient has been observed for coated and heat-treated samples compared to that for the substrate. [ABSTRACT FROM AUTHOR]

The rail transit system is a large electric vehicle system that is strongly dependent on the energy technologies of the power system. The use of new energy-saving amorphous alloy transformers can not only reduce the loss of rail transit power, but also help alleviate the power shortage situation and electromagnetic emissions. The application of the transformer in the field of rail transit is limited by the problem that amorphous alloy is prone to debris. this paper studied the stress conditions of amorphous alloy transformer cores under different working conditions and determined that the location where the core is prone to fragmentation, which is the key problem of smoothly integrating amorphous alloy distribution transformers on rail transit power supply systems. In this study, we investigate the changes in the electromagnetic field and stress of the amorphous alloy transformer core under different operating conditions. The finite element model of an amorphous alloy transformer is established and verified. The simulation results of the magnetic field and stress of the core under different working conditions are given. The no-load current and no-load loss are simulated and compared with the actual experimental data to verify practicability of amorphous alloy transformers. The biggest influence on the iron core is the overload state and the maximum value is higher than the core stress during short circuit. The core strain caused by the side-phase short circuit is larger than the middle-phase short circuit. [ABSTRACT FROM AUTHOR]

The friction of hydrogenated diamond-like carbon (H-DLC) films was evaluated under the controlled environments of humid air and vacuum by varying the applied load. In humid air, there is a threshold applied load below which no obvious friction drop occurs and above which the friction decreases to a relatively low level following the running-in process. By contrast, superlubricity can be realized at low applied loads but easily fails at high applied loads under vacuum conditions. Further analysis indicates that the graphitization of the sliding H-DLC surface has a negligible contribution to the sharp drop of friction during the running-in process under both humid air and vacuum conditions. The low friction in humid air and the superlow friction in vacuum are mainly attributed to the formation and stability of the transfer layer on the counterface, which depend on the load and surrounding environment. These results can help us understand the low-friction mechanism of H-DLC film and define optimized working conditions in practical applications, in which the transfer layer can be maintained for a long time under low applied load conditions in vacuum, whereas a high load can benefit the formation of the transfer layer in humid air. [ABSTRACT FROM AUTHOR]

Coatings are normally employed to meet some functional requirements. There is a kind of self-generated coating during use, such as the transfer layer during sliding, which may greatly affect the tribological behavior. Although the transfer layer has aroused much attention recently, the formation of the transfer layer closely depends on the service conditions, which need to be further studied. In this paper, the effects of sliding speed, normal load, and duration of wear test on the transfer layer thickness during friction of Ni/PTFE (Polytetrafluoroethylene) composites were experimentally investigated. The formation mechanism of transfer layer and the relationships between tribological properties and transfer layer thickness were analyzed in detail. It was found that the transfer layer thickness increased with increases of sliding speed and normal load; and after a period of wear test, the transfer layer thickness remained stable. The transfer layer thickness correlates linearly with the friction coefficient and wear volume of the PTFE composites. With the increase of the transfer layer thickness, the friction coefficient decreased, while the wear volume increased, which means that a uniform, thin, and stable transfer layer is beneficial for the reduction of friction and wear of the polymeric composites. [ABSTRACT FROM AUTHOR]