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1
Tan, Adin Ming, Yehuda Weizman, Firoz Alam, and Franz Konstantin Fuss. "The Coefficient of Friction of Soccer Balls." Proceedings 49, no. 1 (June 15, 2020): 92. http://dx.doi.org/10.3390/proceedings2020049092.
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Nine soccer balls were tested for their friction against a leather sheet, using a force plate. An average normal force of 63.6 N was applied and the movement of the ball had an average velocity of 15 mm/s. Each test was repeated 15 times and the average Coefficient of Friction (COF) was reported. The following results were obtained: Jabulani (COF: 0.62 ± 0.05); Fracas (COF: 0.41 ± 0.01); Ordem 3 (COF: 0.63 ± 0.02); Teamgeist (COF: 0.38 ± 0.01); Brazuca (COF: 0.45 ± 0.01); Kopanya (COF: 0.39 ± 0.01); React (COF: 0.37 ± 0.01); Finale 15 (COF: 0.39 ± 0.06); Vintage T-panel leather ball (COF: 0.41 ± 0.02). Overall, the COF of all balls tested ranged between 0.37 and 0.62. The Finale 15 ball showed a decreasing COF trend with repeated trials and the React ball produced pronounced slip-stick phenomenon.
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Fiagbe, Yesuenyeagbe A. K., and Emmanuel W. Ramde. "FRICTION COEFFICIENT OF MUNICIPAL SOLID WASTE COMPONENTS." International Journal of Engineering Technologies and Management Research 7, no. 7 (July 7, 2020): 1–7. http://dx.doi.org/10.29121/ijetmr.v7.i7.2020.702.
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Engineering properties of materials includes coefficient of friction (COF) which are basic in design performance of engineering systems. The COF can be considered as very important in design of handling tools. Various types of handling tools and equipment are used at various stages of disposal and treatment of MSW and COF is one critical property. This paper presents estimate of COF of municipal solid waste components. The components of the municipal solid waste are paper, plastic, organic and others. The estimation of the COF was done using an inclino-tribometer. Waste from 16 sample locations were used with 6 surfaces which are considered to be of relevant. It was estimated that Formica surface has the least COF values and range from 0.269 and 0.312 with ‘others’ – formica surface tribosystem being the least. It was also found that paint application on wooden surface with oil paint would increase COF as compared to applying emulsion on same wooden surface. The study pointed out that polishing with vanish is the best way to reduce COF in wood surfaces. It was also observed that painting metal surfaces with oil paint will increase the COF than when the same metal was left unpolished or unpainted.
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Varriale, Francesco, Stefano Candeo, Gabriele Riva, Jens Wahlström, and Yezhe Lyu. "A Brake System Coefficient of Friction Estimation Using 3D Friction Maps." Lubricants 10, no. 7 (June 23, 2022): 134. http://dx.doi.org/10.3390/lubricants10070134.
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The coefficient of friction (COF) is one of the core factors in the evaluation of brake system performance. It is challenging to predict the COF, since it is strongly influenced by several parameters such as contact pressure (p), slip rate (v) and temperature (T) that depend on the driving conditions. There is a need for better models to describe how the brake friction varies under different driving conditions. The purpose of this research is to study the possibility of using 3D friction pvT-maps to estimate the COF of a disc brake system under different driving conditions. The 3D friction pvT-maps are created by filtering results of material tests conducted in a mini-dyno inertia bench. The COF measured under different driving cycles in an inertia dyno bench with the full brake system are compared with the COF estimated by the friction maps coming from the reduced scale dyno bench to investigate the validity of the simulation approach. This study shows that mini dyno bench is suitable to obtain a tribological characterization of the friction pad–disc rotor contact pair and is able to replace the full inertia dyno bench to investigate the brake system performance.
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Fang, Kun. "Frictional Performance of Polyphenyl Ester Modified Polytetrafluoroethylene." Materials Science Forum 1080 (January 30, 2023): 33–39. http://dx.doi.org/10.4028/p-g7gf9i.
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This paper mainly studied the coefficient of friction (COF), wear performance and frictional vibration performance of polyphenyl ester modified polytetrafluoroethylene under dry friction and water lubrication friction conditions. Polyphenyl ester modified polytetrafluoroethylene composites were prepared by blending 20% polyphenyl ester with polytetrafluoroethylene, and the COF, wear performance and frictional vibration properties of such composites were tested. The results showed that: (1) Under dry friction conditions, as the specific pressure between the friction pairs increased, the volume of wear and the thickness of the wear increased, the COF decreased at first and then increased, the frictional vibration increased and stabilized after the pressure of 0.5 MPa. (2) Under water-lubricated friction conditions, as the specific pressure between the friction pairs increased, the COF increased, and the frictional vibration increased and stabilized after the pressure of 0.5 MPa; (3) The wear resistance of polyphenyl ester modified polytetrafluoroethylene composite under water-lubricated friction was better than that under dry friction, the COF was less than that under dry friction, and the total level of frictional vibration was slightly lower than that under dry friction. Therefore, in order to reduce frictional vibration and improve service life, the working pressure should be reduced, and the lubrication performance between the friction surfaces should be improved. Under water-lubricated friction, the maximum working pressure of the polyphenyl ester modified polytetrafluoroethylene composite system is recommended not to exceed 0.8 MPa.
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Eun, Jinsu, Jaejin Ryue, Sangsoo Park, and Kikwang Lee. "A Novel Method to Measure the Static Coefficient of Friction for Socks." Sensors 22, no. 15 (July 25, 2022): 5525. http://dx.doi.org/10.3390/s22155525.
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Mechanical testers have commonly been used to measure the frictional properties of socks. However, the friction values may be susceptible to the level of stretchiness of tested fabrics or human variability. Thus, the aim of this study was to propose a novel method that enables friction measurement of socks in a sock-wearing condition with less human variability effects. Five socks with different frictional properties were chosen. Three experimental ramp tests were performed with an artificial structure shaped like the foot-ankle complex (last) and a ramp tester to quantify the static coefficient of friction (COF) at the foot against sock, at the sock against an insole, and the foot wearing socks against the insole, respectively. The angle where the last slipped while the ramp surface was gradually inclined was used to compute the static COF values for each sock. The reliability was 0.99, and COF values ranged from 0.271 to 0.861 at the foot-sock interface, 0.342 to 0.639 at the sock-insole interface, and 0.310 to 0.614 in the third test. Socks with different frictional properties were successfully distinguished each other. Thus, the suggested protocol could be a reliable option for measuring the static COF values in the tension similar with it found in a sock-waring condition with reduced effects of human variability.
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Schanner, Jonathan, Roman Funke, Andreas Schubert, and Alexander Hasse. "Investigating the Friction Behavior of Turn-Milled High Friction Surface Microstructures under Different Tribological Influence Factors." Journal of Manufacturing and Materials Processing 6, no. 6 (November 15, 2022): 143. http://dx.doi.org/10.3390/jmmp6060143.
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The coefficient of friction (COF) is an important parameter for mechanical engineers to consider when designing frictional connections. Previous work has shown that a surface microstructuring of the harder friction partner leads to a significant increase in the COF. However, the impact of the changes in the tribological system on the COF are not known in detail. In this study, the tribological influence factors such as the nominal surface pressure, the material pairing, lubrication, and the surface properties of the counterbody are investigated. Microstructuring is applied by turn-milling of an annular contact surface of cylindrical specimens. A torsional test bench is used to measure the torque depending on the displacement of the two specimens, thus enabling the determination of the COF. All tests with the microstructured specimens result in higher COF than the reference test with unstructured samples. The manufacturing process of the counterbody surface, the nominal surface pressure, and the materials in contact have a significant influence on the COF. While lubrication reduces friction in the case of unstructured specimens, the COF does not change significantly for microstructured samples. This proves that the deformative friction component dominates over the adhesive. Microstructuring the harder friction partner increases the transmittable torque in frictional connections and reduces the sensitivity towards possible contamination with lubricants.
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do Vale, Joao Luiz, Carlos Henrique da Silva, and Giuseppe Pintaude. "Energetic coefficient of friction applied to cylinder liners lab tests." Industrial Lubrication and Tribology 72, no. 9 (December 18, 2019): 1103–8. http://dx.doi.org/10.1108/ilt-08-2019-0324.
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Purpose This paper aims to present a proposal for evaluating the coefficient of friction (COF), under a reciprocating test that considers the energy dissipated by the friction force. In addition, this new parameter is compared to average COF, which is often used to evaluate COF in reciprocating tests. Design/methodology/approach Samples of compacted graphite iron were extracted directly from an internal combustion engine block. The piston ring used was a nitrided martensitic stainless steel with an asymmetrical profile, and the lubricant oil was the SAE 30 CF, controlled at 40°C. Different testing conditions were carried out in a CETR-UMT-Bruker tribometer, varying loads between 25-125 N, frequencies between 1-12.5 Hz and track length between 3-10 mm. Three maps comparing the average COF and the energetic definition were built, allowing to discuss their similarities. Findings In general, both parameters had similarities especially for low frequencies and small tracks. However, for test conditions that imposed higher accelerations (i.e. longer track lengths and higher frequencies), the energetic COF (COFe) was lower than the average COF (COFa) and presented better agreement in Stribeck-like curves – independent on the experienced lubrication regime along the stroke. As the COFe can be interpreted as a weighted average of instantaneous COF in relation to in-track displacements, an immediate consequence is that instantaneous COF closest to mid-stroke is considered more significant. Furthermore, perturbations associated with the intrinsic accelerations of the movement test are minimized in the COFe formulation. Originality/value The energetic COF parameter (COFe) is presented and compared to the average COF. The new parameter presented less data dispersion and is attractive to evaluate the COF behavior in reciprocating tests, as its formulation minimizes perturbations associated with the intrinsic accelerations of the movement (mainly in the initial and final part of the track where the acceleration has its greatest magnitude). Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0324
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Swensen, Eric E., Jerry L. Purswell, Robert E. Schlegel, and Ronald L. Stanevich. "Coefficient of Friction and Subjective Assessment of Slippery Work Surfaces." Human Factors: The Journal of the Human Factors and Ergonomics Society 34, no. 1 (February 1992): 67–77. http://dx.doi.org/10.1177/001872089203400108.
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Research was conducted to determine how well subjects could distinguish between surfaces with different coefficient of friction (COF) values and to evaluate how well subjective ratings of slipperiness correlated with the actual COF values. Thirty-three ironworkers experienced in working and walking on steel surfaces and 23 university students inexperienced with these tasks participated in the study. Subjective slipperiness ratings for a variety of climbing and walking conditions were obtained from the subjects. It was found that subjects could identify differences in the slipperiness of four types of steel coatings tested in the study. There was a high correlation between the subjective ratings and the measured COF values. Subjects did not slip at a COF of 0.41 but did lose footing at a COF of 0.20.
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Chen, Xiang, Zhong Han, Xiuyan Li, and K. Lu. "Lowering coefficient of friction in Cu alloys with stable gradient nanostructures." Science Advances 2, no. 12 (December 2016): e1601942. http://dx.doi.org/10.1126/sciadv.1601942.
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The coefficient of friction (COF) of metals is usually high, primarily because frictional contacts induce plastic deformation underneath the wear surface, resulting in surface roughening and formation of delaminating tribolayers. Lowering the COF of metals is crucial for improving the reliability and efficiency of metal contacts in engineering applications but is technically challenging. Refining the metals’ grains to nanoscale cannot reduce dry-sliding COFs, although their hardness may be elevated many times. We report that a submillimeter-thick stable gradient nanograined surface layer enables a significant reduction in the COF of a Cu alloy under high-load dry sliding, from 0.64 (coarse-grained samples) to 0.29, which is smaller than the COFs of many ceramics. The unprecedented stable low COF stems from effective suppression of sliding-induced surface roughening and formation of delaminating tribolayer, owing to the stable gradient nanostructures that can accommodate large plastic strains under repeated sliding for more than 30,000 cycles.
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Li, Kai Way, Hsuan Cheng Lin, Ching Chung Chen, Li Wen Liu, and Chih Yong Chen. "Measurements of Friction Coefficient on Kitchen Floors in Restaurants." Applied Mechanics and Materials 303-306 (February 2013): 773–76. http://dx.doi.org/10.4028/www.scientific.net/amm.303-306.773.
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Friction measurements in the field were conducted in twelve restaurants in Taiwan. Four restaurants for each of the Chinese style, western style, and western style fast food restaurant were visited. The Brungraber Mark II slipmeter was adopte to measure the coefficient of friction (COF) in three areas in each of the restaurant. The results showed that three, two Chinese style and one western style, of the restaurants had mean COF lower than 0.5, a safety standard commonly adopted in the USA. Engineering/managerial interventions are required for those restaurants as far as employee safety is concerned. The fast food restaurants had more consistent COF levels than those of the other two types of restaurants as these restaurants only operate down-stream food preparation in the store. The Chinese style restaurants had significantly (p<0.05) lower COF than those of the western style restaurants. This was consistent with the commonly belief that Chinese style cuisine is much greasy, in general, as compared to those of western cooking.
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Hsu, Yao Wen, and Kai Way Li. "The Measurements of Friction Coefficient on Ramps among Different Floor Materials." Applied Mechanics and Materials 303-306 (February 2013): 790–93. http://dx.doi.org/10.4028/www.scientific.net/amm.303-306.790.
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This study investigates the influences of slopes on objective friction measurements of different floor materials. It is known that a person is more likely to slip when walking on a slope than when walking on a level surface. In term of the prevention of falls for elders and MMH (manual material handling) workers, slope is more commonly in the design of barrier-free environments. However, it could be a potential environmental risk of slip accidents. The environmental problems were generally caused by poor floor slipperiness. The coefficient of friction (COF) is one of important objective indexes to assess floor slipperiness. It is worthy to investigate that the influences of slope on COF. Thus, COF measurements under different slopes, floor materials and surface conditions were conducted in this study. The data were analyzed to investigate the influence of slope on objective friction measurements of floors. The results showed that the rougher surface and dry conditions had the higher COF values. The different slopes result in significant COF values; however, there is no significant trend. Therefore, there should be more warning signs and slip resistance facilities or accessories to reduce the chance to slip and fall on the slopes.
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Ur Rehman, Zia, M. Gulzar, and Muhammad Kamran Shaukat. "Effect of Temperature on Friction Behavior of Epoxy Resin Composite Coatings for Sliding Contact." Pakistan Journal of Engineering and Technology 5, no. 4 (December 29, 2022): 1–7. http://dx.doi.org/10.51846/vol5iss4pp1-7.
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Epoxy composite coatings are used to reduce friction in mechanical components. The epoxy composites at high temperatures cause serious frictional effects due to poor surface characteristics. Hence, there is a need to find a substitute to improve their frictional behaviour in high-temperature conditions. Adding fillers and lubrication are key solutions to improve tribological properties. In this research work, diglycidyl ether of bisphenol A (DGEBA) epoxy resin was coated on steel, and silica powder (5% by weight) was used as filler. The experiments were conducted under dry and lubricated conditions with and without filler. The coefficient of friction (COF) was examined at different temperatures. The results show that the COF increases with an increase in temperature. In addition, the minimum average COF was observed in the case of epoxy coating with the filler under lubrication conditions. For that case, up to 94.4% decrease in COF was observed as compared to epoxy coating without filler under dry conditions, a 48.33% decrease in COF to epoxy coating without filler under lubricated conditions and a 17.98% decrease in COF than epoxy coating with the filler under dry condition was perceived. Scanning Electron Microscopy (SEM) and surface roughness analyses were also conducted to examine the surface of the specimen after the experiment. A worn and rougher surface was observed in the case of epoxy without filler under dry conditions. The more coefficient of friction at high temperatures is due to the thermal degradation of the epoxy matrix at high temperatures, which results in a rougher surface.
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Setiyana, Budi, Muhammad Khafidh, Mohammad Tauviqirrahman, Rifky Ismail, Jamari, and Dirk Jan Schipper. "Friction and Wear Pattern of Silica-Reinforced Styrene-Butadiene Rubber (SBR) in Sliding Contact with a Blade Indenter." Lubricants 9, no. 11 (November 17, 2021): 110. http://dx.doi.org/10.3390/lubricants9110110.
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This study investigated the friction and wear pattern of silica-reinforced Styrene-Butadiene Rubber (SBR) in sliding friction with a steel blade indenter. The experiments were conducted using a pin-on-disc tribometer at various applied loads and examined under dry and wet contact conditions. Analysis was focused on investigating the coefficient of friction and length of wear pattern spacing. Related to coefficient of friction identification, the abrasion theory was applied here. In addition, the stick-slip theory to identify the wear pattern spacing was also applied. Results of the experiments show that the overall coefficient of friction (COF) decreases along with the increasing applied loads. The COF in wet conditions is much lower at the beginning of sliding time than the COF in dry conditions. The wear pattern spacing increases with increasing loads. However, it seems that there is no significant difference in pattern spacing between the dry and wet contact condition. In general, the experimental results agree qualitatively with the analytical results.
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Riva, Gabriele, Francesco Varriale, and Jens Wahlström. "A finite element analysis (FEA) approach to simulate the coefficient of friction of a brake system starting from material friction characterization." Friction 9, no. 1 (August 14, 2020): 191–200. http://dx.doi.org/10.1007/s40544-020-0397-9.
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Abstract The coefficient of friction (COF) is one of the most important parameters to evaluate the performance of a brake system. To design proper brake systems, it is important to know the COF when estimating the brake force and resulting torque. It is challenging to simulate the COF since friction in disc brakes is a complex phenomenon that depends on several parameters such as sliding velocity, contact pressure, materials, and temperatures, etc. There is a lack of studies found in the literature focusing on simulation of the COF for a full brake system based on tribometer material characterization. The aim of this work is therefore to investigate the possibility to use a finite element analysis (FEA) approach combined with a COF pv-map to compute the global COF of a disc brake system. The local COF is determined from a pv-map for each local sliding velocity and contact pressure determined by the FEA. Knowing the local COF, the braking force of the entire brake system and the global COF can be evaluated. Results obtained by the simulation are compared with dyno bench test of the same brake system to investigate the validity of the simulation approach. Results show that the simulation is perfectly in line with the experimental measurements in terms of in-stop COF development, but slightly higher with a positive offset for every braking.
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Liew, W. Y. H., Sebastian Dayou, M. Azlan Bin Ismail, Nancy J. Siambun, and Jedol Dayou. "Dry Sliding Behaviour of AlCrN and TiN Coatings." Advanced Materials Research 576 (October 2012): 559–62. http://dx.doi.org/10.4028/www.scientific.net/amr.576.559.
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This paper examines the friction behaviour of AlCrN and TiN PVD coatings in atmospheric air and vacuum using a ball-on-disc and a reciprocating tribotesters. Comparative study on the coating sliding in air and in high vacuum environment provides important insight on the effect of oxidation on the friction behaviour of the coatings. Other important factors such as load, sliding velocity, temperature effects on the frictional behaviour of these coatings were also investigated. In the ball-on-disc tests carried out in vacuum, (i) TiN gave lower coefficient of friction (COF) than AlCrN, indicating that TiN was more lubricous, (ii) higher speed resulted in lower COF, and (iii) the COF of both coatings were lower than that produced in air. In ambient air, (i) AlCrN gave lower COF than TiN with high wear debris retention on the sliding interface due to the effect of oxidation, and (ii) higher speed resulted in lower COF, similar to that observed in vacuum. In the reciprocating tests, at low load, increasing the temperature from room temperature to 150 °C resulted in a reduction in the COF. However, at high load, the temperature virtually did not affect the COF. Higher nominal load resulted in lower COF while higher speed resulted in higher COF.
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Cheng, Yi-Ching, Chang-Mou Wu, Po-Chun Lin, Wen-You Lai, Po-Hsun Chen, and Tzong-Der Way. "Friction behaviors of staple carbon fiber composites." Modern Physics Letters B 34, no. 07n09 (March 10, 2020): 2040002. http://dx.doi.org/10.1142/s0217984920400023.
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This study aims to examine the frictional behavior of staple carbon fiber composites (sCFCs). The staple carbon fiber reinforced polycarbonate (PC) composites were prepared by film stacking for two different impregnation levels. Mechanical properties such as tensile and flexural strengths and moduli and static/dynamic friction coefficient (COF) were determined. The COF and temperature as a function of wearing cycles for sCFCs subjected to different applied pressures were also determined by a disk-on-disk sliding wear test machine. The less impregnated sample exhibited superior tribological performance owing to its rough surface and low frictional heat generation.
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Shen, Bin, and Fang Hong Sun. "Influence of Surface Morphology of Diamond Films on their Frictional Behaviors in Dry and Water Environments." Advanced Materials Research 53-54 (July 2008): 331–36. http://dx.doi.org/10.4028/www.scientific.net/amr.53-54.331.
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The influence of surface morphology of diamond films on their friction behaviors was investigated under both ambient air and water environments. The diamond films with three different surface morphologies were deposited on the Co-cemented tungsten carbide (WC-6wt%Co) substrate using hot filament chemical vapor deposition (HFCVD) method and their frictional behavior were studied on a ball-on-plate type reciprocating friction tester, where the ball-bearing steel was used as the counterface materials. The coefficient of friction (COF) of diamond films showed strong surface morphology dependence, those samples with smaller diamond grain size and smoother surface finish represented lower COF in both dry and water lubricating conditions. Water lubricating was significantly favor to decrease the COF of diamond films, which might mainly due to the lubricating effect of physisorbed water layer formed on the sliding interface. In addition, the transferred materials layer adhered on the worn surface of diamond films were supposed to be another factor that was beneficial for reducing the COF.
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Chu, Yanqiu, Jing Xu, and Changsheng Li. "Preparation and Coefficient of Friction of YBa2Cu3O7-δ/Graphene Oxide Composites." International Journal of Surface Engineering and Interdisciplinary Materials Science 4, no. 2 (July 2016): 23–33. http://dx.doi.org/10.4018/ijseims.2016070102.
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YBa2Cu3O7-d/graphene oxide (YBCO/GO) composite materials were fabricated by using powder metallurgy process combined with cold isostatic pressing (CIP) technique. The coefficient of friction (COF) of YBCO matrix composites with addition of 0, 0.5, 1.0 and 2.0 wt% GO were reported for the first time. The friction behavior was observed by means of the ball-on-disk technique with a steel ball used as the counterpart in ambient atmospheric and dry sliding condition. The measured properties were then assessed with respect to sliding speed and the mass fraction of the GO additives. GO is able to reduce COF and brittleness for YBCO ceramic. The excellent performance offers materials with 0.5 wt% GO, which has the lowest COF and lightest wear track.
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Varriale, Francesco, Gabriele Riva, Jens Wahlström, and Yezhe Lyu. "A Mesoscopic Simulation Approach Based on Metal Fibre Characterization Data to Evaluate Brake Friction Performance." Lubricants 10, no. 3 (February 25, 2022): 34. http://dx.doi.org/10.3390/lubricants10030034.
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The coefficient of friction (COF) is an important parameter when evaluating brake system performance. It is complex to predict friction due to its dependence on parameters, such as sliding velocity, contact pressure, temperature, and friction material mixtures. The aim of this work is to evaluate the macroscopic COF of a disc brake system under specific braking conditions by a meso-scale approach, using a cellular automaton simulation where the friction material mixture is modelled starting from its basic components. The influence of the local components in contact is taken into account. Simulated COF values are in line with the experimental values.
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Khaday, Samsiya, Kai-Way Li, Lu Peng, and Ching-Chung Chen. "Relationship between Friction Coefficient and Surface Roughness of Stone and Ceramic Floors." Coatings 11, no. 10 (October 15, 2021): 1254. http://dx.doi.org/10.3390/coatings11101254.
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Slips and falls are common occupational incidents worldwide. The friction on a floor surface is one of the critical environmental factors affecting the risk of a slip. In this research, we conducted friction measurements on stone and ceramic floor tiles under dry, wet, and water–detergent (WD) solution covered conditions using a horizontal pull slip meter (HPS). Our purposes were to quantify the slip resistance of commonly used stone and ceramic floors under different surface conditions and to validate the curvilinear relationship between the coefficient of friction (COF) and surface roughness of the floors proposed in the literature. The COF data were analyzed together with a surface profile parameter (Ra) of the floor samples. The results showed that the COFs of the stone floors were significantly (p < 0.0001) higher than those of the ceramic floors. All the floors under the dry conditions were slip resistant when adopting the ANSI 1264.2 criterion. Two and five ceramic floors were not slip resistant under the wet and WD solution covered conditions, respectively. Three polynomial regression equations were established to describe the relationship between the COF and Ra. The curvilinear functions of these models indicate that the three-zone (initial growth, steady-growth, and plateau) concept concerning the COF–Ra relationship in the literature was valid when static COF values measured using an HPS were adopted. In addition, the three-zone concept was valid not only on WD solution covered surfaces but also on dry and wet surfaces.
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Hu, Ningning, Xiuheng Zhang, Xianghui Wang, Na Wu, and Songquan Wang. "Study on Tribological Properties and Mechanisms of Different Morphology WS2 as Lubricant Additives." Materials 13, no. 7 (March 26, 2020): 1522. http://dx.doi.org/10.3390/ma13071522.
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In the present work, the relationship curve of the coefficient of friction (COF) with varying loads of different morphology WS2 lubricating additives in the friction process at various sliding speeds was studied. On this basis, wear marks and elements on the wear surfaces after friction were analyzed, and then the anti-wear and mechanism effects of WS2 of different forms in the lubrication process were discussed. Meanwhile, the Stribeck curve was used to study the lubrication state of the lubricating oil in the friction process. It was revealed that the COF of lubricating oil containing lamellar WS2 decreased by 29.35% at optimum condition and the minimum COF was concentrated at around 100 N. The COF of lubricating oil containing spherical WS2 decreased by 30.24% and the minimum coefficient was concentrated at 120 N. The extreme pressure property of spherical WS2 was better than that of lamellar WS2, and the wear resistance of spherical WS2 was more stable when the load was over 80 N. The different morphology of WS2 additives can play anti-wear and anti-friction roles within a wide range of sliding speeds.
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Yap Jun Heng, Nurul Farhana Mohd Yusof, Lee Ann Yen, Shazlina Abd Hamid, and Nurul Nadzirah Mohd Yusof. "A Contact Characteristic of Roller Bearing with Palm Oil-based Grease Lubrication." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 89, no. 2 (December 7, 2021): 139–49. http://dx.doi.org/10.37934/arfmts.89.2.139149.
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Grease lubricants are widely used in rolling contact applications to reduce friction between two rolling surfaces. Improper lubrication may cause high contact stress and deformation to the bearings and lead to machine failure The purpose of this study is to investigate the coefficient of friction produced by newly developed palm oil-based grease and to investigate the contact characteristics in lubricated roller bearings. In this work, the coefficient of friction of new greases was evaluated experimentally and the values were compared with the conventional mineral oil-based grease to investigate the friction performance. The friction test was performed using a four-ball tester. The finite element model was developed based on the roller bearing geometry and the simulation was carried out the evaluate the contact characteristic. The experimental result shows that the palm oil grease formulation A had the least coefficient of friction, followed by palm oil grease formulation B, mineral grease and food grade grease. This indicates that palm oil-based grease has the potential to be applied in rolling contact applications due to low friction characteristics. Finite element analysis shows that the maximum von Mises stress and total deformation for frictional contact are higher than the frictionless contact. For the frictional contact analysis with various lubricant COF, similar values were obtained with von Mises stress at 400.69 MPa and 3.4033×10-4 mm deformation. The finding shows that the small difference in grease COF did not affect the rolling contact. The finding also shows that the newly developed biodegradable grease has a similar performance in terms of rolling contact friction and contact characteristic in a condition that the bearing is operating in normal condition.
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Srinivasan, D., M. Meignanamoorthy, Amel Gacem, Mohanavel Vinayagam, Thanakodi Sathish, M. Ravichandran, Suresh Kumar Srinivasan, Magda H. Abdellattif, and Haiter Lenin Allasi. "Tribological Behavior of Al/Nanomagnesium/Aluminum Nitride Composite Synthesized through Liquid Metallurgy Technique." Journal of Nanomaterials 2022 (August 24, 2022): 1–12. http://dx.doi.org/10.1155/2022/7840939.
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Despite its excellent qualities such as hardness, tensile, and yield strength, aluminum alloys are mostly used in aviation fins and car frames. However, wear resistance at maximum load is weak. This effort will now synthesize and investigate the tribological behavior of AA6063- (AlMg0.7Si-) AlN composites. The goal of this experiment is to determine the best wear rate and coefficient of friction for the AA6063-AlN with nanomagnesium composites developed. Weight percent, load (L), sliding velocity (SV), and sliding distance (SD) are the process factors studied, and the output responses are wear rate and friction coefficient. Bottom pouring type stir casting was used to create AA6063-AlN composites with various weight percentages. The various compositions are AA6063, AA6063-4 wt% AlN, AA6063-8 wt% AlN, and AA6063-12 wt% AlN. A pin-on-disc machine inspected the wear rate and friction coefficient of AA6063-AlN composites. Experimentation was done according to L16 orthogonal array (OA). Wear rate (WR) and coefficient of friction (COF) examinations were made to identify the optimum parameters to obtain minimum WR and COF for the AA6063-AlN composite via grey relational analysis (GRA). The contour plot analysis clear displays WR and COF with respect to wt% vs. L, wt% vs. SV and wt% vs. SD. The ANOVA outcomes revealed that wt% is the most vital parameter (85.55%) persuading WR and COF. The optimized parameters to achieve minor WR and COF was found as 12 wt% of AlN, L 20 N, SV 3 m/s, and SD 400 m. The worn surface was analyzed using scanning electron microscope and indicates that addition of AlN particles with matrix reduces the scratches. These articles offer a key for optimum parameters on wear rate and COF of AA6063-AlN composites via Taguchi grey relational analysis.
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Hayden, Lyndsey R., Sarah Escaro, Dewey R. Wilhite, R. Reid Hanson, and Robert L. Jackson. "A Comparison of Friction Measurements of Intact Articular Cartilage in Contact with Cartilage, Glass, and Metal." Journal of Biomimetics, Biomaterials and Biomedical Engineering 41 (April 2019): 23–35. http://dx.doi.org/10.4028/www.scientific.net/jbbbe.41.23.
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The goal of this study was to develop a method of friction testing utilizing cartilage counter surfaces with a complete subchondral bone plate and compare the results to the cartilage on glass and metal (steel) counter surfaces. Articular cartilage surfaces with the underlying subchondral bone intact were not isolated through plug removal. Friction testing was completed using a tribometer (n=16). The coefficient of friction (COF) was measured between the proximal articular surfaces of the second carpal bone when brought into contact with the articular surface of the distal radial facet. The COF of the distal radial facet was obtained with glass and metal counter surfaces. Cartilage-cartilage interfaces yielded the lowest COF when a normal force of 5N and 10N was applied. No statistically significant increase in COF was noted for any combination when an increased normal force was applied (10N), although an increase was observed when glass and metal was in contact with cartilage. COF significantly increased when comparing the cartilage counter surface to metal under an applied load of 5N (p=0.0002). When a 10N load was applied, a significant increase in the COF was observed when comparing the cartilage counter surface to both the glass and metal counter surfaces (p=0.0123 and p < 0.0001 respectively). Results have shown that the described methodology was accurate, repeatable, and emulates physiologic conditions when determining the friction coefficient. The determined COF of cartilage against cartilage is significantly lower than cartilage against metal or glass.
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Kshirsagar, Mrunal P., and Hrishikesh P. Khairnar. "Comparison of the theoretical and experimental coefficient of friction for the brake disc-brake pad system." Tribology and Materials 2, no. 2 (July 2023): 78–87. http://dx.doi.org/10.46793/tribomat.2023.009.
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Contact between the automotive brake pad and the disc is mathematically modelled to estimate the coefficient of friction (COF). The mathematical model is proposed for the prognosis of the COF of brake pad material, by considering the contact mechanics between the interfacing surface and their material properties. The Greenwood-Williamson contact model is applied for rough contact surfaces for the estimation of the real contact radius. A MATLAB program has been formulated for generating the surface of brake pad material by considering its material properties which aid in the analytical evaluation of the COF. The proposed model is further validated with experimentation on pin-on-disc apparatus, as it is considered suitable for friction pad product testing according to previous research. The 25 pins were fabricated as per the ASTM G99 test for testing under varying loads and speeds. The obtained results showed that the range of COF has been between 0.2 and 0.4. The investigation presents an analytical approach for estimating COF and contact radius for brake disc and brake pad, which can be used to design an efficient automotive brake disc-brake pad system under the given load and rotational speed. The artificial neural network (ANN) is modelled for predicting the values of the COF for brake disc-brake pad systems, which can be further used for determining the tribological properties of new friction materials and their compatibility for efficient brake systems.
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Banerji, A., S. Bhowmick, M. J. Lukitsch, and A. T. Alpas. "Friction Behaviour of Multilayered Graphene against Steel." MRS Proceedings 1812 (2016): 1–8. http://dx.doi.org/10.1557/opl.2016.10.
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ABSTRACTFrictional behaviour of multilayered graphene was studied in air with different relative humidity (RH) levels (10–52% RH). Pin-on-disk type sliding tests were performed and the running-in and steady state coefficient of friction (COF) values were measured against M2 tool steel counterface. On increasing the RH, multilayered graphene showed a reduction in steady state COF from 0.11 at 10% RH to 0.08 at 52% RH. The low steady state COF values observed in graphene could be attributed to the transfer layer formed on the M2 tool steel counterface. A sliding-induced structural change was observed in graphene transfer layers which could have facilitated the graphitic transfer layer formation. The multilayered graphene showed a lower steady state COF values at all RH compared to non-hydrogenated diamond-like carbon (NH-DLC) which recorded a steady state COF of 0.47 at 10% RH and 0.25 at 52% RH.
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Wei, Yuan, Jesus Resendiz, Robert Tomkowski, and Xu Liu. "An Experimental Study of Micro-Dimpled Texture in Friction Control under Dry and Lubricated Conditions." Micromachines 13, no. 1 (December 31, 2021): 70. http://dx.doi.org/10.3390/mi13010070.
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Friction control is a vital technology for reaching sustainable development goals, and surface texturing is one of the most effective and efficient techniques for friction reduction. This study investigated the performance of a micro-dimpled texture under varying texture densities and experimental conditions. Reciprocating sliding tests were performed to evaluate the effects of the micro-dimpled texture on friction reduction under different normal loads and lubrication conditions. The results suggested that a micro-dimpled texture could reduce the coefficient of friction (CoF) under dry and lubricated conditions, and high dimple density results in a lower CoF. The dominant mechanism of the micro-dimpled texture’s effect on friction reduction was discussed, and surface observation and simulation suggested that a micro-dimpled texture could reduce the contact area at the friction interface, thereby reducing CoF.
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Chen, Zhengpu, Carl Wassgren, and Kingsly Ambrose. "Measurements of Grain Kernel Friction Coefficients Using a Reciprocating-Pin Tribometer." Transactions of the ASABE 63, no. 3 (2020): 675–85. http://dx.doi.org/10.13031/trans.13748.
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Highlights A tribometer was used to measure the friction coefficients of corn and wheat kernels. Both static and dynamic friction coefficients were measured for particle-wall interaction. Data analysis processes were developed to calculate dynamic friction coefficients for inter-particle interaction. Abstract. Various devices have been developed to measure the coefficient of friction (COF) of grain kernels; however, the majority of these tests measure the particle-wall COF at a bulk level. A method that can accurately measure both particle-wall and inter-particle COFs at a single-particle level remains to be developed. The objective of this study was to explore the feasibility of using a reciprocating-pin tribometer to measure static and dynamic COFs between grain kernels and between grain kernels and wall materials. In this study, the methodology of the test was developed, and representative data from the particle-wall and inter-particle friction tests were reported. It was found that the static COFs of corn-steel, corn-acrylic, wheat-steel, and wheat-acrylic are 0.24 ±0.05, 0.22 ±0.03, 0.32 ±0.02, and 0.29 ±0.03, respectively. The dynamic COFs of corn-steel, corn-acrylic, corn-corn, wheat-steel, wheat-acrylic, and wheat-wheat are 0.22 ±0.06, 0.16 ±0.01, 0.09 ±0.02, 0.30 ±0.02, 0.20 ±0.02, and 0.18 ±0.04, respectively. The current study demonstrates that the reciprocating-pin tribometer is suitable for measuring the particle-wall and inter-particle COFs of grain kernels. Keywords: Coefficient of friction, Grain kernel, Reciprocating-pin tribometer
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Ma, Zhiwei, Changsong Zheng, Cenbo Xiong, Liang Yu, Yujian Liu, and Cunzheng Zhang. "Friction-Wear Characteristics of Carbon Fiber Reinforced Paper-Based Friction Materials under Different Working Conditions." Materials 15, no. 10 (May 20, 2022): 3682. http://dx.doi.org/10.3390/ma15103682.
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To study the friction and wear performance of carbon fiber reinforced friction materials under different working conditions, paper-based friction materials with different fibers were prepared. Experiments on the SAE#2 test bench were conducted to study the infectors including friction torques, surface temperature, coefficient of friction (COF), and surface morphologies. The results were analyzed, which indicated that the carbon fiber reinforced friction material could provide a higher friction torque and a lower temperature rising rate under the applied high pressure and high rotating speed conditions. As the pressure increased from 1 MPa to 2.5 MPa, the friction torque of plant fiber reinforced material increased by 150%, the friction torque of carbon fiber reinforced material increased by 400%, and the maximum temperature of plant fiber reinforced and carbon fiber reinforced material reached the highest value at 1.5 MPa. Thus, carbon fibers not only improved the COF and friction torque performance but also had advantages in avoiding thermal failure. Meanwhile, carbon fiber reinforced friction materials can provide a more stable COF as its variable coefficient (α) only rose from 38.18 to 264.62, from 1 MPa to 2.5 MPa, which was much lower than the natural fiber reinforced friction materials. Simultaneously, due to the good dispersion and excellent mechanical properties of PAN chopped carbon fibers, fewer pores formed on the initial surface, which improved the high wear resistance, especially in the intermedia disc.
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Martinelli, Giovanni, Paolo Plescia, and Emanuela Tempesta. "“Pre-Earthquake” Micro-Structural Effects Induced by Shear Stress on α-Quartz in Laboratory Experiments." Geosciences 10, no. 5 (April 27, 2020): 155. http://dx.doi.org/10.3390/geosciences10050155.
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This paper presents the results of measurements performed on α-quartz subjected to shear stress in dry conditions, to understand the relationship between the shear intensity and the resulting physical and chemical effects. If a shear stress of intensity higher than 100 MPa is applied continuously to alpha quartz crystals, they will tend to lose their crystallinity, progressively reduce their friction coefficient (Cof) and change into a low-order material, apparently amorphous under X-ray diffraction, but with a structure different from silica glass. Raman and Pair Distribution Function analyses suggested a structure like cristobalite, a silica polymorph well-known for its auxetic behavior, i.e., having a negative Poisson ratio. This elastic parameter pre-eminently controls the friction coefficient of the material and, if it is negative, the Cof lowering. As a result, the increase in low crystallinity cristobalite is sufficientto explain the lowering of the quartz friction coefficient up to values able to contribute, in principle, to the triggering processes of active faults. This allows hypothesizing a slip induction mechanism that does not include the need to have the interposition of layers of hydrated silica, as invoked by many authors, to justify the low friction coefficients that are achieved in shear stress tests on rocks abundant in quartz.
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Trzepieciński, Tomasz, Ján Slota, Ľuboš Kaščák, Ivan Gajdoš, and Marek Vojtko. "Friction Behaviour of 6082-T6 Aluminium Alloy Sheets in a Strip Draw Tribological Test." Materials 16, no. 6 (March 14, 2023): 2338. http://dx.doi.org/10.3390/ma16062338.
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Aluminium alloy sheets cause many problems in sheet metal forming processes owing to their tendency to gall the surface of the tool. The paper presents a method for the determination of the kinematic friction coefficient of friction pairs. The determination of coefficient of friction (COF) in sheet metal forming requires specialised devices that ‘simulate’ friction conditions in specific areas of the formed sheet. In this article, the friction behaviour of aluminium alloy sheets was determined using the strip drawing test. The 1-mm-thick 6082 aluminium alloy sheets in T6 temper were used as test material. Different values for nominal pressures (4.38, 6.53, 8.13, 9.47, 10.63, and 11.69 MPa) and different sliding speeds (10 and 20 mm/min.) were considered. The change of friction conditions was also realised with several typical oils (hydraulic oil LHL 32, machine oil LAN 46 and engine oil SAE 5W-40 C3) commonly used in sheet metal forming operations. Friction tests were conducted at room temperature (24 °C). The main tribological mechanisms accompanying friction (adhesion, flattening, ploughing) were identified using a scanning electron microscope (SEM). The influence of the parameters of the friction process on the value of the COF was determined using artificial neural networks. The lowest value of the COF was recorded when lubricating the sheet metal surface with SAE 5W40 C3 engine oil, which is characterised as the most viscous of all tested lubricants. In dry friction conditions, a decreasing trend of the COF with increasing contact pressure was observed. In the whole range of applied contact pressures (4.38–11.69 MPa), the value of the COF during lubrication with SAE 5W40 C3 engine oil was between 0.14 and 0.17 for a sliding speed of 10 mm/min and between 0.13 and 0.16 for a sliding speed of 20 mm/min. The value of the COF during dry friction was between 0.23 and 0.28 for a sliding speed of 10 mm/min and between 0.22 and 0.26 for a sliding speed of 20 mm/min. SEM micrographs revealed that the main friction mechanism of 6082-T6 aluminium alloys sheet in contact with cold-work tool steel flattens surface asperities. The sensitivity analysis of the input parameters on the value of COF revealed that oil viscosity has the greatest impact on the value of the COF, followed by contact pressure and sliding speed.
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Ningrum, Putri Intan Puspa, Ani Mulyasuryani, and Rakhma Febriani. "The Effect of Slip Polymer Additives on the Characteristics of Polyethylene Films." IJCA (Indonesian Journal of Chemical Analysis) 6, no. 1 (March 16, 2023): 75–84. http://dx.doi.org/10.20885/ijca.vol6.iss1.art8.
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Polymer additive’s function is to improve film quality, including slip additives which function as film surface lubricants. Slip additives affect the physical characteristics of the film as indicated by the coefficient of friction and optical properties. In this research, the influence of slip additives and the aging time of the coefficient of friction (COF) and the optical properties of polyethylene (PE) films have been studied. The optical properties of the film are measured based on the haze value and the gloss value. The additives used in this study were erucamide, stearyl erucamide, and a mixture of the two. Observations were made for 14 days at 23 °C and 50 °C. Measurements of the COF, haze value, and gloss value were carried out on days 0, 1, 3, 7, 10, and 14. The results showed that the lowest COF was produced on films with erucamide additives. Films with erucamide additives had the best friction coefficient value of 0.129 on the 3rd day of aging at 50 °C, a haze value of 4.63% and a gloss value of 56.5 GU.
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Trzepiecinski, Tomasz, and Hirpa G. Lemu. "Effect of Lubrication on Friction in Bending under Tension Test-Experimental and Numerical Approach." Metals 10, no. 4 (April 23, 2020): 544. http://dx.doi.org/10.3390/met10040544.
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This paper is aimed to determine the value of coefficient of friction (COF) at the rounded edge of the die in the sheet metal forming operations using the bending under tension (BUT) test. The experimental part of the investigations is devoted to the study of the frictional resistances of low alloy steel sheet under different strains of the specimen, surface roughnesses of the tool and for different lubrication conditions. Three oils are destined for different conditions of duties in the stamping process. Numerical modeling of the material flow in the BUT test has been conducted in the MSC.Marc program. One of the objectives of the numerical computations is to know the type of the contact pressure acting on the cylindrical surface countersample in the BUT test by assuming the anisotropic properties of the metallic sheet. It has been found that the COF in the rounded edge of the die does not vary with increasing sheet elongation. Taking into account that normal pressure increases with increasing specimen elongation and workpiece material is subjected to strain hardening phenomenon, the COF value is very stable during the friction test. The effectiveness of the lubrication depends on the balance between two mechanisms accompanied by friction process: roughening of workpiece asperities and adhesion of the contacting surfaces. In the case of high surface roughness of tool due to a dominant share of ploughing, all of the lubricants used were not able to decrease the COF in a sufficient extent. The used lubricants were able to reduce the value of friction coefficient approximately by 3–52% in relation to the surface roughness of rolls.
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Kothasiri, Anupama Francy, Srinivasa Rao Chalamalasetti, and Gopalakrishnaiah Peteti. "MULTIPLE PROCESS PARAMETER OPTIMIZATION OF FORWARD EXTRUSION PROCESS ON AA 2024." International Journal of Modern Manufacturing Technologies 13, no. 2 (December 20, 2021): 63–75. http://dx.doi.org/10.54684/ijmmt.2021.13.2.63.
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Extrusion is a simple metal forming process in which a block of metal is forced through a die orifice with a certain shape under high pressure. This extrusion process is influenced by many process parameters such as die angle (DA), ram speed (RS), coefficient of friction (COF), Extrusion ratio, Die land height, work piece diameter and length, material properties etc. In extrusion process, extrusion force is crucial parameter, the flow of metal and hence the extrusion force is significantly influenced by the above parameters which results in quality of the product. The present study numerically investigates the influence of major process parameters such as die angle, ram speed, coefficient of friction on the extrusion process. The AA2024 material is chosen as work piece material and the extrusion force and damage is considered as the output responses. The input process parameters are varied in three levels (Level - 1: 10° DA, 1.6mm/min RS, 0.06 COF; Level - 2: 20° DA, 3.2mm/min RS, 0.08 COF; Level - 3: 30° DA, 4.8mm/min RS, 0.01 COF). Numerical simulations are performed by using DEFORM 3D software. The simulations are conducted as per L27 orthogonal array. From the results it is observed that Increase of die angle, ram speed and coefficient of friction increases the extrusion force. The die angle has highest (86.45%) influence on the extrusion force, then after ram speed (6.60%). The coefficient of friction has insignificant influence (0.55%). It is also noticed that the damage is considerable after the 20° die angle. A multi parameter optimization is also done by using the Grey relation analysis by considering the equal weightage of extrusion force and damage. The optimum levels of input process parameters for the minimum extrusion force and damage is DA level 1, RS level 1, and COF level 3.
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Rodríguez Jiménez, Rebeca Cristal, Julian Hernández Torres, R. Galván Martínez, Luis Zamora Peredo, and Leandro García González. "Hardness and Friction Coefficient Analysis of Electrochemically Anodized Ti-6Al-4V." ECS Transactions 106, no. 1 (January 31, 2022): 163–70. http://dx.doi.org/10.1149/10601.0163ecst.
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Electrochemical anodization was performed for surface modification of Ti-6Al-4V, using an HCl-based electrolyte. The effect of increasing the electrode spacing of the electrochemical cell by 1, 2, and 2.5 cm on the hardness and COF was investigated. Using a 0.5 M solution of HCl and glycerol in different percentages (85, 90, and 95 %), a voltage of 30 V and a time of 5 minutes. The results revealed the growth of nanotubular structures, which contribute to the increase in hardness, obtaining a maximum of 7.1 GPa for the anodized samples and the reduction of COF to a minimum of 0.5. While the heat-treated samples increased their microhardness up to 10.25 GPa.
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Myalski, Jerzy, Marcin Godzierz, Karolina Olszowska, Urszula Szeluga, Sławomira Pusz, Stanisław Roskosz, Hanna Myalska-Głowacka, and Andrzej Posmyk. "Glassy Carbon Open-Celled Foams as a Reinforcement in Polymer Matrix Composites Dedicated for Tribological Applications." Materials 16, no. 5 (February 22, 2023): 1805. http://dx.doi.org/10.3390/ma16051805.
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This work presents the results of a tribological examination of polymer matrix composites reinforced with carbon foams with different porosity. The application of open-celled carbon foams allows an easy infiltration process by liquid epoxy resin. At the same time, carbon reinforcement remains its initial structure, which prevents its segregation in polymer matrix. Dry friction tests, conducted under 0.7, 2.1, 3.5 and 5.0 MPa loads, show that higher friction load results in higher mass loss, but it strongly lowers the coefficient of friction (COF). The change in coefficient of friction is related to the size of the pores of the carbon foam. Open-celled foams with pores size below 0.6 mm (40 and 60 ppi), used as a reinforcement in epoxy matrix, allow to obtain COF twice lower than composite reinforced with 20 ppi open-celled foam. This phenomenon occurs due to a change of friction mechanisms. In composites reinforced with open-celled foams, general wear mechanism is related to destruction of carbon components, which results in solid tribofilm formation. The application of novel reinforcement, in the form of open-celled foams with stable distance between carbon components, allows the decrease of COF and the improvement of stability, even under a very high friction load.
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Wang, Yanshuang, Qingguo Qiu, Pu Zhang, Xudong Gao, Zhen Zhang, and Pengcheng Huang. "Correlation between Lubricating Oil Characteristic Parameters and Friction Characteristics." Coatings 13, no. 5 (May 8, 2023): 881. http://dx.doi.org/10.3390/coatings13050881.
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In order to help one to judge the friction properties of lubricating oils without tests, this paper intends to establish the correlation between the characteristic parameters of lubricating oils and the friction properties. The elastohydrodynamic and boundary friction properties of poly alpha olefin (PAO) synthetic oil, polyol ester oil and paraffin-based mineral oil were tested using a Mini-Traction Machine. Fourier transform infrared microscopy is used to identify material changes before and after friction tests. The kinematic and dynamic viscosities of the three lubricating oils were measured using a petroleum product viscosity tester and a rotating rheometer. The results show that the kinematic viscosity does not directly determine the COF (coefficient of friction) of the lubricating oil, but the higher the dynamic viscosity, the higher the COF of the lubricating oil. The higher the viscosity-pressure coefficient, the lower the viscosity index (the worse the viscosity-temperature performance), and the higher the COF of the lubricating oil, which is related to the adaptability of the molecular structure of lubricating oils to pressure and temperature. PAO synthetic oils and polyol ester oils have excellent friction properties resulting from their strong adaptability to temperature and pressure variations due to the presence of linear chains and flexible groups.
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Roupec, Jakub, Filip Jeniš, Zbyněk Strecker, Michal Kubík, and Ondřej Macháček. "Stribeck Curve of Magnetorheological Fluid within Pin-on-Disc Configuration: An Experimental Investigation." Materials 13, no. 20 (October 20, 2020): 4670. http://dx.doi.org/10.3390/ma13204670.
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The paper focuses on the coefficient of friction (COF) of a magnetorheological fluid (MRF) in the wide range of working conditions across all the lubrication regimes—boundary, mixed, elastohydrodynamic (EHD), and hydrodynamic (HD) lubrication, specifically focused on the common working area of MR damper. The coefficient of friction was measured for MR fluids from Lord company with concentrations of 22, 32, and 40 vol. % of iron particles at temperatures 40 and 80 °C. The results were compared with a reference fluid, a synthetic liquid hydrocarbon PAO4 used as a carrier fluid of MRF. The results show that at boundary regime and temperature 40 °C all the fluids exhibit similar COF of 0.11–0.13. Differences can be found in the EHD regime, where the MR fluid COF is significantly higher (0.08) in comparison with PAO4 (0.04). The COF of MR fluid in the HD regime rose very steeply in comparison with PAO4. The effect of particle concentration is significant in the HD regime.
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Yu, Ma, Chen, Li, Ma, and Liu. "Comparison of the Friction and Wear Characteristics between Copper and Paper Based Friction Materials." Materials 12, no. 18 (September 15, 2019): 2988. http://dx.doi.org/10.3390/ma12182988.
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Copper-based friction material (CFM) and paper-based friction material (PFM) are the two most commonly used clutch friction materials. The friction and wear characteristics of these two kinds of friction materials under dry conditions were investigated by the pin-on-disc test over a broad range of applied loads, rotating speeds and ambient temperatures. Before experiments, the running-in test was conducted to stabilize the coefficient of friction (COF) and wear amount of the test samples. After experiments, the metallographic micrographs of the tested samples were presented to investigate the wear mechanisms. Experimental results showed that both the COF and wear depth of the CFM are much greater than these of PFM. The COF of CFM decreases with the increase of applied load, and changes slightly with the variation of rotating speed, whereas it increases first and then decreases with the increase of ambient temperature. However, the COF of PFM decreases dramatically with the increase of the rotating speed and ambient temperature, while it remains stable at first and then decreases slowly as the applied load increases. Additionally, under such three working conditions, the wear depth of CFM changes linearly, while the wear depth of PFM varies greatly. This study can be used as a guide for selecting friction materials for clutches with different applications.
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Yang, Lian Fa, Cong Qiang Wu, and Feng Jun Chen. "COF Measurement of Tubes by Hydraulic Bulging with Radial Crushing." Advanced Materials Research 189-193 (February 2011): 2597–600. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.2597.
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A new method of determining the coefficient of friction (COF) in expansion zone of tube hydroforming (THF) is proposed. The measuring method features that a round tube is hydro-formed into a square one by a radial compression accompanying a constant internal hydraulic pressure p, and the difference ΔL of the two diagonal lengths of the square section of deformed tube is taken as measuring index for COF. The relationships between the ΔL and the p, COF, relative displacement S/S0 of moving punches are established by the finite element (FE) simulation of the forming process. The COF can be determined by matching the indexes ΔL from experiments and simulation. The FE simulation results show that the measuring index ΔL is in exponent proportion to COF and the internal pressure p, it is extremely sensitive to the friction force or COF and conveniently measured and especially under a higher internal pressure.
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Li, Li Xin, Xue Quan Liu, Cun Guang Ding, Yi Li, Fa Chang Li, and Jin Pu Li. "Ti3SiC2 – A New High Temperature Solid Self-Lubricating Additive Agent." Advanced Materials Research 815 (October 2013): 626–31. http://dx.doi.org/10.4028/www.scientific.net/amr.815.626.
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With the additive agent Ti3SiC2, the dry sliding behavior of Cr3C2-Ni and Cr3C2-Ni-Ti3SiC2 composites against GCr15 was investigated with a pin-on-disk tester at 400 °C in air under the load of 200N. Without Ti3SiC2, the dynamic coefficient of friction (COF) curves was fluctuated severely. After adding Ti3SiC2, the COF was decreased from 0.37 to 0.32, and the initial transition region of dynamic COF curve was shortened. These tribological test results showed that Ti3SiC2 was a new kind of solid additive agent with favorable high temperature self-lubricating property, and two possible mechanisms was proposed for its anti-friction ability.
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Trzepieciński, Tomasz, and Marcin Szpunar. "Assessment of the effectiveness of lubrication of Ti-6Al-4V titanium alloy sheets using radial basis function neural networks." Acta Polytechnica 61, no. 3 (June 30, 2021): 489–96. http://dx.doi.org/10.14311/ap.2021.61.0489.
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The aim of the research presented in this article was to determine the value of the friction coefficient using a simple tribological test and to build an empirical model of friction with the use of radial basis function artifi-cial neural networks. The friction tests were carried out on a specially designed friction simulator that allows a sheet metal strip to be drawn between two fixed dies. The test materials were sheets of Ti-6Al-4V titanium alloy with a thickness of 0.5 mm. The friction tests were carried out with variable contact forces of counter-samples with rounded surfaces and in various lubrication conditions. Mineral oils and bio-degradable oils with the addition of boric acid (5 wt %) were tested. Based on the results of friction investigations, neural models of friction were built using RBF artificial neural networks. The good properties of the RBF network 2:2-35-1:1 were confirmed by a high value of the determination coefficient R2 = 0.9984 and a low value of the S.D. ratio equal to 0.0557. It was found that the COF value was the highest for the average values of both the nominal pressure and kinematic viscosity. Over the entire range of nominal pressures applied, SAE10W-40 engine oil ensured the most effective reduction of the COF. The COF value was the highest for the average values of both the nominal pressure and kinematic viscosity.
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Hu, Song, Ge Shi, Qinggang Guo, Long Zheng, Luquan Ren, and Chao Su. "The Tribological Adaptability for Ventral Scales of Dinodon rufozonatum in Dry/Wet/Rough Environments." Coatings 12, no. 1 (December 24, 2021): 20. http://dx.doi.org/10.3390/coatings12010020.
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The ventral scales of Dinodon rufozonatum were investigated to understand the outstanding tribological adaptability in various environments. The coefficient of friction (COF) of ventral scales was measured and changed with the contact conditions. It was discovered that the COF of scales under water-lubrication conditions (WLC) was larger than that under dry conditions (DC). More interestingly, the COF increased first and then decreased as the substrate roughness reduced. The abrasion marks on scales were then observed. The results indicated that the scales in DC wore more gently than that in WLC. Moreover, the degree of wear reduced with the decrease of substrate roughness. The frictional performance of ventral scales enabled the snakes to move more efficiently, quickly, and flexibly in multiple environments.
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Fekete, Gusztáv. "Numerical Wear Analysis of a PLA-Made Spur Gear Pair as a Function of Friction Coefficient and Temperature." Coatings 11, no. 4 (April 1, 2021): 409. http://dx.doi.org/10.3390/coatings11040409.
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Polylactic acid (PLA)-made machine elements exhibit easy machining, biodegradability, and excellent mechanical properties. However, enhancing their wear resistance is still a crucial engineering point, which may be achieved by altering (lowering) their coefficient of friction (CoF). Therefore, the first aim of this paper is to analyze how wear is affected by the alteration of CoF. The second aim is connected to the fact that PLA is sensitive to heat, which also limits its applicability. Accordingly, the next goal is to explore the effect of temperature on wear propagation. This study answers these questions by means of multibody dynamics simulations of a PLA-made spur gear pair. Simulations were carried out under constant torque, while the CoF and the temperature were varied in a normal operation domain (CoF: 0.1–0.05, T = 20–30 °C). The results showed that the wear volume gradually began to decline at approximately 0.085 CoF, whilst convergence to steady-state wear could be observed at 0.05 CoF. In conclusion, alteration of the CoF can lower wear by 35%, in this specific domain, while even a 5 °C rise in temperature causes 40% wear progression. The feasibility of the numerical procedure was validated by comparing numerically and experimentally obtained wear–torque results.
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Li, Kai Way, and Chan Chi Lin. "Effects of Floor Material, Surface Condition, and Foot Moving Speed on the Coefficient of Friction on the Floor." Applied Mechanics and Materials 303-306 (February 2013): 2704–7. http://dx.doi.org/10.4028/www.scientific.net/amm.303-306.2704.
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A laboratory study was conducted to measure the coefficient of friction between the foot and the floor under three surface and two foot sliding speed conditions. A force platform was adopted to measure the ground reaction force (GRF) of the foot on the floor. The coefficient of friction was calculated as the ratio of vertical and horizontal GRF. Five male subjects were recruited. They were requested to slide their right foot on the tested floor which was mounted on the force platform. The results indicated that floor material, surface condition, and foot sliding speed were all significant factor affecting the COF. Ceramic tile had lower COF under all surface and sliding speed conditions as compared to steel, wood, and vinyl tiles.
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Trzepiecinski, Tomasz, and Hirpa G. Lemu. "Recent Developments and Trends in the Friction Testing for Conventional Sheet Metal Forming and Incremental Sheet Forming." Metals 10, no. 1 (December 25, 2019): 47. http://dx.doi.org/10.3390/met10010047.
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Friction is the main phenomenon that has a huge influence on the flow behavior of deformed material in sheet metal forming operations. Sheet metal forming methods are one of the most popular processes of obtaining finished products, especially in aerospace, automobile, and defense industries. Methods of sheet forming are carried out at different temperatures. So, it requires tribological tests that suitably represent the contact phenomena related to the temperature. The knowledge of the friction properties of the sheet is required for the proper design of the conditions of manufacturing processes and tools. This paper summarizes the methods used to describe friction conditions in conventional sheet metal forming and incremental sheet forming that have been developed over a period of time. The following databases have been searched: WebofKowledge, Scopus, Baztool, Bielefield Academic Search Engine, DOAJ Directory of Open Access Journals, eLibrary.ru, FreeFullPdf, GoogleScholar, INGENTA, Polish Scientific Journals Database, ScienceDirect, Springer, WorldCat, WorldWideScience. The English language is selected as the main source of review. However, in a limited scope, databases in Polish and Russian languages are also used. Many methods of friction testing for tribological studies are selected and presented. Some of the methods are observed to have a huge potential in characterizing frictional resistance. The application of these methods and main results have also been provided. Parameters affecting the frictional phenomena and the role of friction have also been explained. The main disadvantages and limitations of the methods of modeling the friction phenomena in specific areas of material to be formed have been discussed. The main findings are as follows—The tribological tests can be classified into direct and indirect measurement tests of the coefficient of friction (COF). In indirect methods of determination, the COF is determined based on measuring other physical quantities. The disadvantage of this type of methods is that they allow the determination of the average COF values, but they do not allow measuring and determining the real friction resistance. In metal forming operations, there exist high local pressures that intensify the effects of adhesion and plowing in the friction resistance. In such conditions, due to the plastic deformation of the material tested, the usage of the formula for the determination of the COF based on the Coulomb friction model is limited. The applicability of the Coulomb friction model to determine the COF is also very limited in the description of contact phenomena in hot SMF due to the high shear of adhesion in total contact resistance.
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Nikam, Manoj D., Dipak Shimpi, Kiran Bhole, and Sachin A. Mastud. "Design and Development of Surface Texture for Tribological Application." Key Engineering Materials 803 (May 2019): 55–59. http://dx.doi.org/10.4028/www.scientific.net/kem.803.55.
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Surface texturing is a process of fabricating specific patterns on a surface to enhance surface properties such as friction, contact area, air aspiration, wear, hydrophobicity, etc. Fabricating surfaces with planned micro features is an effective method to improve tribological performance of the interacting surfaces. Laser surface texturing process is one of the best suitable processes for producing micro-patterns. Micro textures are imparted on HSS discs using CO2 laser, varying the shape and dimensions of the resulting dimples affecting the frictional coefficient and wear. Experiments have been accomplished to determine effects of textural variations such as areal density of dimples, dimple shape, area of dimples and depth of dimples on the Coefficient of Friction (COF) and Wear. Effects of lubrication conditions (Dry and Wet), pin material (MS, SS, EN31), applied load (25N, 50N, 75N) and Sliding velocity (400 rpm, 800 rpm and 1200 rpm) are evaluated on COF and Wear. Tests have been performed on pin-on-disk apparatus along guidelines of Taguchi L18 Orthogonal Array, keeping constant sliding distance of 940 m (about 10,000 cycles). Experimentally, it is found that wet lubricated, circular shaped dimples, with areal density 7.5%, dimple area 0.09 mm2 with MS material pin provides best results. This experimental analysis has been performed to test the applicability, efficiency and reliability of the textured surfaces.
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Hussain, Abrar, Vitali Podgursky, Dmitri Goljandin, Mart Viljus, Maksim Antonov, Andrei Bogatov, and Illia Krasnou. "Tribological and Mechanical Properties Investigations of Post-Consumer Cotton Textiles." Solid State Phenomena 320 (June 30, 2021): 97–102. http://dx.doi.org/10.4028/www.scientific.net/ssp.320.97.
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In this manuscript surface roughness, coefficient of friction (COF) and tensile properties of a post-consumer cotton fabric are evaluated. Fabric roughness, COF, effective tensile force and breaking force measured by optical profilometer, CETR tribometer and Instron tensile machine, respectively. The results proved that COF could rely on fabric pattern. Moreover, microscopically roughness influences on friction and tensile properties due to surface defects. It was found that increase in roughness of textile cotton relates to increase of number of random directional fibers. These fibers intensify friction and reduce tensile properties. The reduced values of tensile (140.49 N), breaking (123.23 N) and effective tensile force (251.43 N) of warp direction are greater than values of tensile (79.54 N), breaking (67.97 N) and effective tensile force (179.69 N) of weft direction. These effects can lower cutting performance of post-consumer textile.
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Liu, Mengmeng, Lihui Wang, Caixia Zhang, Yanhong Cheng, Congbin Yang, and Zhifeng Liu. "Regulation Mechanism for Friction Coefficient of Poly(vinylphosphoric acid) (PVPA) Superlubricity System Based on Ionic Properties." Nanomaterials 12, no. 13 (July 5, 2022): 2308. http://dx.doi.org/10.3390/nano12132308.
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Adjustable lubrication aims to achieve active control of the relative motion of the friction interface, providing a new idea for intelligent operation. A new phenomenon of sudden changes of friction coefficient (COF) in the poly(vinylphosphoric acid) (PVPA) superlubricity system by mixing different lubricants, was found in this study. It was found that anions were the critical factor for the COF change. The change degrees of the COF were investigated by a universal micro tribometer (UMT). A quartz crystal microbalance (QCM)-D was used to analyze the adsorption quantity of anions on the PVPA surface. The hydratability of the PVPA interface was controlled by changing the anionic properties (the amount of charge and structure), thus regulating the COF. The adsorption difference of anions is an important reasoning of how anionic properties can regulate the hydratability. It was analyzed by molecular dynamics simulation. For anions carrying different numbers of charges or double bonds, the adsorption quantity of anions was mainly affected by the adsorption degree on the PVPA surface, while the adsorption quantity of anions with different molecular configuration was synergistically regulated by the adsorption degree and adsorption area of anions on the PVPA surface. This work can be used to develop smart surfaces for applications.
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Abdo, Jamil, and Amer Al-Yhmadi. "The Effect of Controlled Frequency and Amplitude of Vibration on Friction." Solid State Phenomena 147-149 (January 2009): 380–86. http://dx.doi.org/10.4028/www.scientific.net/ssp.147-149.380.
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An in-house pin-on-disc apparatus is designed and constructed to perform the tests and the design of experiments technique is utilized to determine the effect of vibration, amplitude of vibration, surface roughness, and sliding speed and their cross influence on coefficient of friction for 304 stainless steel and Alloy 6061 Aluminum. The design is performed using response surface method (RSM). The coefficient of friction (CoF) is analyzed as a nonlinear function of the factors and predicted by a second-order polynomial equation. Results suggested that the presence of vibration affect the friction function CoF considerably for both metals. The friction function linearly decreases with the increases of vibration and amplitude of vibration, non-linearly decreases with the increases of sliding speed and linearly increases with the increases of the surface roughness until the middle range is reached and then there is non-linearly decrease thereafter. Similar trends of friction functions are observed for Alloy 6061 Aluminum with a reduction of almost 15% except for the case with amplitude of vibration where the variation showed more significant affect on the friction function when Alloy 6061 Aluminum disk is used.