Friction Coefficient Of Composites Research Articles

Experimental Investigation of the Influence of Various Wear Parameters on the Tribological Characteristics of AZ91 Hybrid Composites and Their Machine Learning Modeling

Abstract In the current work, the AZ91 hybrid composites are fabricated through the utilization of the stir casting technique, incorporating aluminum oxide (Al2O3) and graphene (Gr) as reinforcing elements. Wear behavior of the AZ91/Gr/Al2O3 composites was examined with the pin-on-disc setup under dry conditions. In this study, the factors such as reinforcement percentage (R), load (L), velocity (V), and sliding distance (D) have been chosen to investigate their impact on the wear-rate (WR) and coefficient of friction (COF). This study utilizes a full factorial design to conduct experiments. The experimental data was critically analyzed to examine the impact of each wear parameter (i.e., R, L, V, and D) on the WR and COF of composites. The wear mechanisms at the extreme conditions of maximum and minimum wear rates are also investigated by utilizing the scanning electron microscope (SEM) images of specimen's surface. The SEM study revealed the presence of delamination, abrasion, oxidation, and adhesion mechanisms on the surface experiencing wear. Machine learning (ML) models, such as decision tree (DT), random forest (RF), and gradient boosting regression (GBR), are employed to create a robust prediction model for predicting output responses based on input variables. The prediction model was trained and tested with 95% and 5% experimental data points, respectively. It was noticed that among all the models, the GBR model exhibited superior performance in predicting WR, with mean square error (MSE) = 0.0398, root-mean-square error (RMSE) = 0.1996, mean absolute error (MAE) = 0.1673, and R2 = 98.89, surpassing the accuracy of other models.

Tribological Behavior of Cast Aluminum Matrix Composites After Multiple Remelting

One of the limiting factors for expanding the applications of aluminum alloy castings in many high-tech industries is the insufficient level of tribological properties, especially under conditions of dry and abrasive wear. Reinforcing of aluminum alloys with hard ceramic particles, i.e., transition to aluminum matrix composites, allows significantly increasing their resistance against dry sliding friction, scuffing, and seizure in wide temperature and force intervals of operation. Among the numerous problems related to the industrial implementation of cast aluminum matrix composites, the problem of their recycling takes the important place. This work is aimed at establishing the influence of metallurgical processes during remelting on the change in tribological properties of cast Al-Si-B4C aluminum matrix composites. For this purpose, tribological tests in conditions of dry friction according to the ball-on-disc scheme were used. Reinforcing of an AlSi12 matrix alloy with B4C particles leads to a decrease in the composite friction coefficient and the mass wear in the as-cast state in comparison with an unreinforced matrix alloy. During remelting, the tribological properties of the aluminum matrix composites do not deteriorate. Repeated remelting leads to the improvement in particle distribution uniformity, formation of the Al3BC phase at the matrix/particle interfaces, fragmentation of reinforcing B4C particles due to cyclic thermal loads as well as an increase in the porosity fraction. The changes in the structural-phase composition during remelting have a direct influence on the level of tribological properties. Typical effects associated with dry friction, such as plastic deformation of the matrix material and the formation of areas of adhesion-cohesive fracture, indicative of scuffing, were revealed by SEM analysis of the wear tracks of an unreinforced matrix alloy. For the composite material, these effects manifested to a much lesser extent. A qualitatively similar sliding wear behavior was observed for all composite samples, regardless of the remelting iteration. The study suggests that the formation of a transitional tribolayer may occur during dry sliding friction of aluminum matrix composites, which can reduce the friction coefficient.

Statistical Analysis of Tribological Properties of Mg(AM50)/GNF-Al2O3sf Hybrid Composites

The present article describes the tribological properties of Mg-based hybrid composites reinforced with graphite nanofiber (GNF) and alumina short fiber (Al2O3sf) that were investigated. The Mg/GNF/Al2O3sf hybrid composites with varying volume fraction of fiber (10 vol.%, 15 vol.%, 20 vol.%) were developed. SEM observations indicate that the GNF cluster distributions within the array of the Al2O3sf network are found to be relatively good. The Taguchi design of the experiment has been applied to conduct the wear test, and the statistical analysis of variance (ANOVA) has been used to evaluate the influence of wear test parameters on the wear loss and coefficient of friction (COF) of the composites. The influence of wear test parameters such as volume fraction of fiber (VF), applied load (AL), sliding distance (SD), and sliding speed (SP) on the wear loss and COF of composites was analyzed under dry sliding conditions. The results of ANOVA indicate that the sliding distance was found to be the prominent factor affecting wear loss, and the applied load influenced the COF most significantly. Furthermore, the composites with 20 vol.% of fiber had lower wear loss than those with 10 vol.% and 15 vol.% of fiber. The COF of composites with 15 vol.% of fiber was found to be slightly lower compared to the 10 vol.% and 20 vol.% of fiber cases. The results imply that the hybridization of GNFs and Al2O3sf, as well as the formation of Mg17Al12 and Al2MgC2 precipitates enhanced the tribological properties of the Mg hybrid composites.

Wear failure mechanism analysis of self-lubricating fabric composites at high temperature

The friction and wear properties of self-lubricating fabric composites were closely related to fiber properties. In this paper, polyimide (PI), polyetheretherketone (PEEK), polyisophthalamide (PMIA) and cyclic aramid (Aramid III) fibers were selected as reinforcing fibers to compare and investigate the friction and wear properties of self-lubricating fabric composites at high temperature. The tribological behavior of self-lubricating fabric composites was evaluated by ball-on-disk friction test. The wear mechanism was investigated by scanning electron microscope and mechanical test. As a result, the composite with PI as warp and weft reinforcing fiber has outstanding wear resistance because of the higher modulus of PI fiber. Its wear rate is 1.29 × 10−8 mm3/(N·mm). It shows that the stronger the rigidity of the reinforcing fiber at high temperature, the better the wear resistance of the composite. However, the friction coefficient of composites with PI as weft reinforcing fibers is about 0.8, which is much higher than that of composites with PMIA, PEEK and Aramid III as weft reinforcing fibers. Their friction coefficients are about 0.1. In addition, the self-lubricating fabric composites with different warp and weft reinforcing fibers were prepared as self-lubricating joint bearing liners to evaluate bearing applications.

TRIBOLOGICAL CHARACTERISTICS OF ANTIFRICTION COMPOSITES OF POLYAMIDE AND ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE

Analysis of current trends in improving the designs of tribo-couplings of agricultural machinery has shown that the use of polyamide 6 as an antifriction material is limited by its low moisture resistance, which leads to a significant deterioration in its elastic-strength and tribological characteristics during moisture saturation. The paper shows the possibility of using ultra-high molecular weight polyethylene as its analogue, which allows increasing the durability of tribo- couplings of hydraulic systems of agricultural machinery. (Research purpose) The research purpose is in to study the processes of friction and wear of polyamide PA 6 composites and ultra-high molecular weight polyethylene nanocomposites with obtaining dependencies linking tribological characteristics (friction coefficient and wear intensity) with operational factors (temperature, sliding speed and contact pressure). (Materials and methods). Polyamide PA 6 of the 210/310 brand was used in the work; composite of the UPA 6-15A brand, consisting of 85 percent polyamide PA 6 and 15 percent fibrous carbon filler; ultrahigh molecular weight polyethylene of the GUR 4120 brand; Tuballmatrixbeta concentrate of activated carbon nanotubes; hydrophobic nanocrystalline silicon dioxide with a dispersion of 20 nanometers, Nafen grade aluminum oxide nanofiber with a dispersion of 10- 20 nanometers. Samples were made to study the elastic-strength and tribological characteristics of composites by thermal pressing on a Gibitre hydraulic press. Samples were tested on the UAI-7000 M bursting machine and the Haake MARS III rheometer. (Results and discussion) The values of the intensity of linear wear and the dependence of the friction coefficients of composites on the sliding speed, contact pressure and temperature of industrial oil I-20A were determined for the conditions of dry friction and friction with lubrication. (Conclusions) The research results have shown that the use of ultrahigh molecular weight polyethylene and nanocomposites based on it as commercial antifriction materials of tribo- couplings is promising and requires further study.

ANALISA KAMPAS REM CAKRAM KOMPOSIT CANGKANG KEMIRI, SERBUK ALUMINIUM, SERAT KELAPA DAN POLIURETAN DENGAN TEKANAN 3 TON

Nowadays, the fulfillment of materials with certain characteristics is very much needed along with the rapid development of technology. Coconut fiber material is a lightweight but strong composite material. Dried coconut fibers can be used as resin reinforcement because of their rigid structure as well as candlenut shells whose hardness can also be used. The purpose of this study was to find the best composite brake canvas composition from candlenut shells and coconut fiber by going through a series of wear and friction coefficient tests with comparisons of Honda Genuine Part and After Market brake pads. This brake canvas material consists of candlenut shell, coconut fiber and added with aluminum powder and polyurethane (isocyanate and polyol) with a certain percentage. The results of this study are the wear value of composite brake pads is higher than AM brake pads and lower than HGP brake pads, namely for pad A: 1.1179 x 10 B and at B: 1.02402 x 10¯⁵. For the lowest composite temperature, and the lowest After Market rotation pressure. Meanwhile, the composite friction coefficient is lower than Honda Genuine Part and higher than After Market

Comparison of dry sliding tribological behavior of SS 316L impregnated with MoS2 vs h-BN solid lubricants: A statistical point of view

The main aim of this paper is to statistically discuss the friction and wear behavior of 316L stainless steel (SS316L) composites added with h-BN and MoS2 solid lubricant under different running conditions at room temperature. The SS316L composites added with h-BN and MoS2 were produced by the powder metallurgy method. The mixture of SS316L composites with 15 and 20 vol% of h-BN and MoS2 were cold compacted into ∅ 30 mm cylinder parts. Then sintered in the sintering furnace under H2 atmosphere for 60 min. Brinell's hardness and dry-sliding wear behavior of the sintered SS316L composites were investigated using a pin-on-disc testing machine. The factorial experimental design was employed to investigate the influence of specific independent variables on dry sliding wear, testing at sliding speeds of 0.1 and 0.2 m/s, applied load of 3 and 5 N and sliding distance varying from 100 to 200 m. The effects of tested variables on the specific wear rate and coefficient of friction were analyzed from both statistic plots and physical analyses of worn surface with SEM micrographs. The results showed that the MoS2 added composite resulted in greater wear resistance than h-BN added composite. The wear resistance and friction coefficient on dry sliding wear test also depended on the interaction effect of sliding distance, sliding speed and applied load which are relative to the formation of tribofilm on sliding interfaces. In addition, sliding speed influence to the formation of tribofilm showed significantly high levels of wear resistance and friction coefficient of composites. The statistical design of this experiment enabled us to collect and analyze wear data which provided a greater understanding of the complex mode/mechanism of sliding wear of SS316L self-lubricating composites.

Effect of Transfer Films on Friction of PTFE/PEEK Composite

Abstract This paper investigates the effect of transfer films on friction coefficient of polytetrafluoroethylene (PTFE)/polyetheretherketone (PEEK) composite. Friction experiments were carried out first to investigate transfer-film development during sliding contact of PTFE/PEEK composite with different PTFE volume fractions on a steel counterface. Quantitative relationships between PTFE/PEEK composite friction coefficient and constituent material mechanical properties are then established to facilitate the subsequent investigation of friction mechanisms and influence of transfer films on the composite friction. A micromechanics-based friction theory is developed for predicting PTFE/PEEK composite friction coefficient. The effect of transfer films on composite friction is accounted for based on two distinctly different mechanisms—one with solid-state film lubrication and the other with PTFE as a solid-state lubricant on the top surface of transfer films. The friction theory is first validated through the excellent agreement obtained between the theoretical predictions and the in-house experimental results on PTFE/PEEK composite with up to 20% PTFE (by volume). The validity of the theory is further demonstrated by comparing the theoretical predictions with the test data reported by other researchers in the literature.

Investigation on friction and wear behaviors of Cu–Zn composition with doped MoS2 powder under electric field

Molybdenum disulfide (MoS2) as a two-dimensional material and solid lubricant shows good friction properties in many applications. The study used the copper (Cu) and zinc (Zn) powder with doped MoS2 powder to prepare the alloy material through the spark plasma sintering (SPS) technology. The coefficient of friction (COF) and wear of alloys with different doped ratios (0 wt%, 3 wt%, 6 wt%, 9 wt%) of MoS2 were studied by using universal mechanical tester (UMT-5), which was based the ball-on-disk method. The results show that the alloy with 3 wt% MoS2 has the lowest COF, about 0.093. The COF of composites containing 9% MoS2 are close to those of un-doped composites, 0.673 and 0.712, respectively. It is mainly owing to excessive corrosion of Cu by MoS2, resulting in increased COF and wear rate. In addition, the effect of the applied electric field on the COF of the alloy was also investigated. It was found that the electric field can increase the COF and the wear rate of the composites. As the voltage increases, oxidation of the Cu was promoted and FeSx was formed to reduce friction and wear. This work provides a new method for manufacturing and studying electrical contact friction materials.

Influence of wear parameters on friction performance of A356 aluminum – graphite/ granite particles reinforced metal matrix hybrid composites

In this work aluminium-silicon alloy (A356) is strengthened with blends of granite and graphite particles using stir casting technique. Granite particulates, an industrial waste generated while cutting granite stones is used along with graphite particulates which has excellent lubricant properties. The reinforcements are mixed in different weight proportions, to base alloy at 2 and 4 weight percentages. Wear rate and friction for the fabricated composites and alloy is recorded during each sliding test The dry sliding wear of the over different loads with a track diameter of 60 mm and sliding times of 15, 30 and 45 minutes respectively. The techniques of ANOVA and Taguchi are used to study the influence of wear parameters on the friction coefficient of composites by using “MINITAB 18” software with quality characteristics chosen as smaller is better.

Effect of graphene platelets on tribological properties of boron carbide ceramic composites

The friction and wear behaviour of hot pressed boron carbide/graphene platelets (GPLs) composites have been investigated using the ball-on-flat technique with SiC ball under dry sliding conditions at room temperature. The hardness and fracture toughness of the investigated materials varied from 18.21GPa to 30.35GPa and from 3.81MPa·m1/2 to 4.60MPa·m1/2, respectively. The coefficient of friction for composites were similar, however the wear rate significantly decreased ~77% in the case of B4C+6wt.% GPLs when compared to reference material at a load of 5N, and ~60% at a load of 50N. Wear resistance increased with increasing GPLs content in regards to the present graphene platelets, which during the wear test pulled-out from the matrix, exfoliated and created a wear protecting graphene-silicon based tribofilm.

Sliding wear behavior of E-glass-epoxy/MWCNT composites: An experimental assessment

This investigation has evaluated the sliding wear properties of E-glass-epoxy/MWCNT (multiwalled carbon nanotube) composite and Epoxy/MWCNT composite. Four different reinforcements (0, 0.5,1 and 1.5 wt %) of MWCNTs are dispersed into an epoxy resin. Design of experiments (DOE) and Analysis of variance (ANOVA) are employed to understand the relationship between control factors (Percentage of reinforcement, Sliding distance, Sliding velocity and Normal load) and response measures (specific wear rate and friction coefficient). The control variables such as sliding distance (300, 600, 900 and 1200 m) and normal loads of 10, 15, 20 and 25 N and at sliding velocities of 1, 2, 3 and 4 m/s are chosen for this study. It is observed that that the specific wear rate and friction coefficient can be reduced by the addition of MWCNTs. Scanning electron microscopy (SEM) is used to observe the worn surfaces of the samples. Compared with neat epoxy, the composites with MWCNTs showed a lower mass loss, friction coefficient and wear rate and these parameters decreased with the increase of MWCNT percentage. Microscopic investigation of worn out sample fracture surface has revealed that fiber debonding happens when the stresses at the fiber matrix interface exceeds the interfacial strength, causing the fiber to debond from the matrix. The optimum control variables have been derived to reduce both wear and friction coefficient of composites.

Wear and friction behavior of nanosized TiB2 and TiO2 particle-reinforced casting A356 aluminum nanocomposites: A comparative study focusing on particle capture in matrix

In the present study, regarding the theoretical and practical aspects of nanoparticle capture in liquid-state processing of aluminum composite, different volume fractions of [Formula: see text] and [Formula: see text] nanopowders were incorporated into aluminum alloy via stir casting method. Hardness and sliding wear test were carried out to evaluate the mechanical properties of composites. The effects of wear load and reinforcement content on wear rate and friction coefficient of composites were examined. Microstructural studied showed that particle distribution in A356-[Formula: see text] composites was more favorable than that of the A356-[Formula: see text] samples. Results showed that nanoparticles were partially captured by aluminum matrix. With an increase in reinforcement content the amount of porosity and rejected nanoparticles increased. Regarding the wettability features of particles, the amount of introduced [Formula: see text] powders was higher than that of [Formula: see text] particles. A356-[Formula: see text] composites showed higher mechanical properties compared with those of A356-[Formula: see text] samples. Significant improvements in hardness and wear resistance were obtained in A356-1.5 vol.% [Formula: see text] composite. It was observed that the friction coefficient of the composites was lower than that of the non-reinforced alloy. With an increase in normal wear load, wear rate of composites increased and friction coefficient of reinforced samples decreased. Study on surface morphology of the worn surfaces showed both of the mild and sever wear mechanisms. The depth and number of grooves in worn surface of composites decreased with introduction of nanoparticles into matrix. The presence of oxide layers was detected on worn surface. Iron trace was observed in wear debris of samples.

Friction Properties of PTFE Matrix Composites Reinforced by PPS and PPTA Fibers

The polytetrafluoroethylene (PTFE) matrix composites reinforced by polyphenylene sulfide (PPS) fiber and poly-p-phenelenferephthalamide (PPTA) fiber were prepared by the processes of mechanical blending, compression molding and sintering. The fractured surfaces of impacting specimens were examined by scanning electron microscopy (SEM). The tribological properties of the composites were investigated on M-2000 wear tester at dry friction condition. The wear mechanism was also discussed and the wear surfaces were examined by SEM. The result indicates that fibers which diffused in PTFE matrix wind with PTFE molecule chain, and then form grid structure. The load-bearing capacity of composites can be obviously enhanced and the trend of block fragmentation’s slide is inhibited, so that the tribological properties are improved markedly. The friction coefficient of composites is reduced by adding graphite which also prevents fibers leaving. The tribological properties of PTFE matrix composites is greatly improved because of the synergistic effect between fibers and graphite, which has good prospect for low loading application.

Tribological behavior of hybrid PTFE/Kevlar fabric composites with nano-Si3N4 and submicron size WS2 fillers

Hybrid PTFE/Kevlar fabric composite specimens were prepared with nano-Si3N4 and/or submicron size WS2 as fillers. The tribological behaviors of these composites were studied. The morphologies of the worn surface, transfer film and debris were analyzed by means of scanning electron microscopy. In addition, an energy-dispersive X-ray spectrometer was used for analysis of the elemental distribution and content in the transfer film. The results indicate that single nano-Si3N4 fillers can effectively reduce the wear rate of composites, but they do not reduce the friction coefficient. Hybrid Si3N4 and WS2 fillers can significantly reduce the wear rate and friction coefficient of composites.

Development of Electron Beam Cross-Linked PDMS/PTFEM Composites with Low Coefficient of Friction and High Elastic Modulus

Cross-linked composites were synthesized via internal compounding of Polydimethylsiloxane and Polytetraflouroethylene micro-powder (PTFEMP) in various proportions and subsequently cross-linking to different extent by electron beam irradiation. The PTFE micro-powder was generated by degrading PTFE ribbons using gamma radiation in presence of CCl4. Elastic modulus of the composites increasedwith radiation doseupto300kGy. Thecomposi-tes showed greater increase in elastic modulus than pure PDMS. Polymer-filler interaction, XRD and FTIR investigations reflected complex changes in composites during compounding and radiation cross-linking. PTFEMP loading did not affect contact angle much but significantly reduced coefficient of friction for composites.

Friction and wear performance of copper–graphite surface composites fabricated by friction stir processing (FSP)

Copper–graphite composites which have low friction coefficient can be used as bearing materials in lieu of materials containing lead which cause environmental problems. So far, some methods such as powder metallurgy and centrifugal casting have been employed to produce these composites. In this study, friction stir processing (FSP) was used to produce copper–graphite surface composites. Five tools with different pin profile were employed in order to achieve a comprehensive dispersion. Results show that the tool with triangular pin gives rise to a better dispersion of graphite particles. Furthermore, four copper–graphite composites containing different graphite content were prepared using triangular tool through repeating the process passes. Friction and wear performance of the composites were studied using a pin-on-disc tribometer. It was indicated that the friction coefficients of composites were lower than pure annealed copper and decreased with increase in graphite content. The reduction in friction coefficient is due to decrease in metal–metal contact points, originated from the presence of graphite particles as a solid lubricant. Wear loss of the composites was also decreased with increase in graphite content. This is related to change in wear mechanism from adhesive to delamination wear and reduction of friction coefficient.

Torsional Wear Behavior of Monomer Casting Nylon Composites Reinforced with GF: Effect of Content of Glass Fiber

The torsional wear behavior of monomer cast (MC) nylon composites reinforced with different glass fiber (GF) contents was studied. Different composites exhibited differently shaped torque–angular displacement curves. The composite friction coefficient was the main factor affecting the torsion contact regime, and the torsional wear behavior was influenced by the torsion contact regime. Serious wear characterized by a groove with an approximately 1.5–4 mm radius that occurred in the contact zone on the steel surface. The mass of MC nylon composite samples increased after the torsional wear test in the partial slipping regime, and the mass of pure MC nylon was reduced in the slipping regime.

Research on Friction and Wear Properties of MC Nylon/ Carbon Nanotubes Composites

In this article, MC nylon/carbon nano tubes (CNTs) composites were prepared by in-situ polymerization method. The friction and wear properties were determined. The sample wear surface morphology carried out by scanning electron microscope (SEM) and the wear mechanism was investigated. It was found that the friction coefficient of composites has decreased with the amount of CNTs increasing in the composites. Addition amount of CNTs is up to 0.3% (weight percent), abrasion index decreased to minimum. The abrasion index of the sample of wearing a long time is smaller than that of the sample of wearing a short time. The sample with wearing less time mainly take place adhesive wear, however, mainly happen abrasive wear and adhesive wear for wearing time is longer. Further more, carbon nano tubes (CNTs) are not only improve the wear resistance of composites but also improve the mechanics performance.

Friction and wear properties of copper matrix composites reinforced by tungsten-coated carbon nanotubes

Carbon nanotubes (CNTs) were coated by tungsten layer using metal organic chemical vapor deposition process with tungsten hexacarbonyl as a precursor. The W-coated CNTs (W-CNTs) were dispersed into Cu powders by magnetic stirring process and then the mixed powders were consolidated by spark plasma sintering to fabricate W-CNTs/Cu composites. The CNTs/Cu composites were fabricated using the similar processes. The friction coefficient and mass wear loss of W-CNTs/Cu and CNTs/Cu composites were studied. The results showed that the W-CNT content, interfacial bonding situation, and applied load could influence the friction coefficient and wear loss of W-CNTs/Cu composites. When the W-CNT content was 1.0 wt.%, the W-CNTs/Cu composites got the minimum friction coefficient and wear loss, which were decreased by 72.1% and 47.6%, respectively, compared with pure Cu specimen. The friction coefficient and wear loss of W-CNTs/Cu composites were lower than those of CNTs/Cu composites, which was due to that the interfacial bonding at (W-CNTs)-Cu interface was better than that at CNTs-Cu interface. The friction coefficient of composites did not vary obviously with increasing applied load, while the wear loss of composites increased significantly with the increase of applied load.