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Study of wear in self-lubricating composites for application in seals of electric motors
Abstract
Investigations of wear resistance of polymers and polymers with additives, using the pin-on-disk apparatus with a campanula has been carried out in the present work. Normal load, velocity and air relative humidity were considered variable in the wear tests. The friction and the wear mechanisms are briefly reviewed. Various polymeric materials containing solid lubricants inside its microstructure were investigated. The self-lubricating characteristics of the added charge as well as the polymeric matrix were considered in the composite selection. Discs of pure PTFE (Teflon), composites PTFE + graphite, PTFE + MoS 2 + glass fibres, PTFE + bronze were tested against pins of quenched and tempered SAE 1045 steel. Pins of PTFE + MoS 2 + glass fibres were also tested against 1045 steel disks. In all tests, debris and flakes of worn materials were deposited on the pin counter face and these particles defined the wear mechanism. Through the analyses of micrograph taken by scanning electron microscopy, the following conclusion can be drawn: friction and wear in polymers are fundamentally different from the mechanisms which occurs in metals and ceramics, although they are due to the same wear micro-mechanisms: micro-plowing, micro-cutting and flake delamination. A very important conclusion on wear resistance of polymers and composites is its strong dependence on the environmental relative humidity and normal load. Variations observed in the relative air humidity from 50 to 70% can duplicate the lost volume by wear and, consequently, to double the wear rate. Among the tested materials, the composites PTFE with additive graphite or MoS 2 and glass fibres have shown the greatest sliding wear resistance.
... Self-lubricating materials are widely used for the production of self-lubricating bearings in the automotive [20], aviation [21], power [22], electronics and household appliances [23] industries. They should meet a number of requirements, the most important of which are resistance to abrasive wear, low friction coefficient, low thermal expansion coefficient and good thermal conductivity [24][25][26][27]. ...
In this work, epoxy composites filled with flake graphite of various size (less than 10 µm and less than 45 µm) were produced. The aim of the research was to develop a self-lubricating material with favorable tribological properties, i.e., reduced friction coefficient compared to unfilled epoxy resin and limited abrasive wear. The research material was produced using technical epoxy resins based on bisphenol A. The detailed process of composite production was described, and typical technological problems were considered. The addition of graphite led to an increase in dynamic viscosity, which positively limits the phenomenon of sedimentation, but an increase in the filler content also led to an increase in the porosity of the material. A series of tests have shown that the addition of graphite above 5% by weight allows for a reduction in the friction coefficient from 0.6 to 0.4 and significantly reduces the material's tendency to abrasive wear.
... The PV limit of composite E is reached to 9.5 MPa·m/s (1 m/s) and 15 MPa·m/s (2 m/s), respectively. It is suitable to operate in high velocity conditions and 2 m/s is the best.[3]has reported in his literature has invistegated Normal load, velocity and air relative humidity were considered variable in the wear tests. ...
... Various polymers can be reinforced with solid lubricants like graphite, MoS2, PTFE etc. PTFE is one of the generally used solid lubricants that could reduce the coefficient of frict ion. Marcelo Kawakame et al. [ 4] investigated that the composites PTFE with additive g raphite or MoS2 and glass fibers have shown the greatest sliding wear resistance. The reinforced PTFE with 15% g lass fiber and 5% of the solid lubricant MoS2 additive have shown better results than that of the PTFE with 15% graphite addit ive. ...
Application of lubricant is a problem in many cases, apart from external lubrication; it is always being useful if the material itself has self-lubricating properties. Such kind of materials are GCI & PTFE+Graphite composites. In these, Graphite flakes acts as solid lubricant & when load is applied, these layers slide over another & provide lubrication. PTFE+Graphite is well known for its self-lubricating properties and widely employed in applications, where dry lubrication & good thermal stability are needed. Primary aim of this work is to study & compare tribological properties of proposed self-lubricating materials. Tests are conducted on the POD apparatus using GCI disc and pin & PTFE+Graphite pin & AISI 1045 Steel disc specimens under different conditions. Later, linear Regression models are developed using input and output variables for both GCI Pin on GCI disc and PTFE filled with Graphite Pin on AISI 1040 Steel disc. Validation of the proposed mathematical equation wa s done by comparing experimental and predicted values of the experimentation and in all cases percentage error was found in between 0-6%. ANOVA was also performed on the experimental results to assess the conformity of the suggested mathematical model with 99% confidence levels. © 2016, Bangladesh University of Engineering and Technology. All rights reserved.
... Ceramic materials, because of their excellent technological properties, such as strength, hardness, chemical inertness, and thermal shock resistance, have been used in many technological fields and manufacturing applications. In particular, the various glasses are promising for use in industrial and technological areas [1][2][3][4]. However, several aspects need to be addressed before they can be applied to even more fields of application. ...
The wear behaviour of bare and polymer-coated soda-lime glass specimens sliding against 440C stainless steel counterfaces was investigated with the aid of a pin-on-disk apparatus. The selected polymeric coatings were commercially supplied safety films, which are nowadays extensively applied on glass in the automotive and construction industry. One of their main failures is the degradation of their properties due to wear. In this work, the frictional behaviour of these coatings on glass were evaluated and compared to those of bare soda-lime glass. Correlations have been also made between the worn surfaces and weight loss in order to investigate the effect of wear conditions (speed, load) on the wear behaviour of these tribosystems. In addition, during the dry wear of soda-lime glass sliding against stainless steel counterfaces, the dominant wear mechanisms were found to be localized adhesion and abrasion, whereas, in the case of the multilayered polymeric coatings localized adhesion, deformation and tearing were observed.
... In view of the basic requirements of abradable sealing coatings, several materials have been put forward as lubricant phases, such as lanthanum phosphate (LaPO 4 ) [16], Ti 3 SiC 2 [17], graphite [8,18,19], molybdenum disulfide (MoS 2 ) [20], bentonite [21], etc. These materials share a common characteristic of layered crystal structure but only LaPO 4 possesses the potential of being high temperature thermal isolation material for its high melting point, phase and chemical stability and lower thermal conductivity than YSZ. ...
High temperature gas turbine sealing is an important issue for increasing the thermal efficiency of gas turbine. In this purpose, layered structured LaPO4 has been selected as the soft phase to add into the commercialized thermal barrier coating material 7 wt% yttria stabilized zirconia (7YSZ). The consequent thermal conductivities and mechanical properties versus the content of LaPO4 have been researched systemically in this paper. Phase composition and microstructure of the high-temperature sintered LaPO4/7YSZ composites were characterized. The thermal conductivity decreases significantly due to the second phase effects and the interface thermal resistance was also strongly involved according to the composite model. The hardness decreased by composed LaPO4 phase so that to reduce attrition of the vanes at high temperature. The slight increase of fracture toughness and bending strength in the results were also favored in operation. The experimental results demonstrate that the LaPO4/7YSZ composite will be an excellent candidate abradable sealing material for high temperature gas turbine.
... XPS results (Fig.6) show that the carbon contents in lubricating film is about 63.24% and 95.68%, respectively, far more than the graphite content in composites (8% and 18%). Graphite has good selflubricating properties due to its special crystal structure [23]. During wear process, superficial graphite in composites is stripped and milled into debris under friction and forces. ...
CNTs-Ag-G electrical contact composite material was prepared by means of powder metallurgical method. The influence of the graphite content on sliding wear characteristics of electrical contact levels was examined. In experiments, CNTs content was retained as 1% (mass fraction), and graphite was added at content levels of 8%, 10%, 13%, 15% and 18%, respectively. The results indicate that with the increase of graphite content, the contact resistance of electrical contacts is enhanced to a certain level then remains constant. Friction coefficient decreases gradually with the increase of graphite content. Wear mass loss decreases to the minimum value then increases. With the small content of graphite, the adhesive wear is hindered, which leads to the decrease of wear mass loss, while excessive graphite brings much more worn debris, resulting in the increase of mass loss. It is concluded that wear mass loss reaches the minimum value when the graphite mass fraction is about 13%. Compared with conventional Ag-G contact material, the wear mass loss of CNTs-Ag-G composite is much less due to the obvious increase of hardness and electrical conductivity, decline of friction surface temperature and inhibition of adhesive wear between composites and slip rings.
... One of the mechanisms for reducing friction coefficient is the generation of a transfer film on the mating surface [1,6,16]. Sometimes it is more advantageous to have a more rigid polymer as matrix and fibers and PTFE in order to obtain optimal tribological conditions [19,37]. Adding materials for increasing thermal conductivity of a composite (PTFE + bronze) [10,21] are able to reduce the thermal regime. ...
Based of the team experience in tribology testing of materials, the authors present an interdisciplinary approach of investigating tribological behaviour of composites, results interpretations, non-destructive analysis methods in order to improve reliability of tribosystems using composites, and to link test results to design solutions.
... Recently researchers tried to study the tribological properties of fiber reinforced composite bearings from different aspects. Kawaakme and Bressan have experimentally investigated the wear resistance of self-lubricating polymeric composites for application in seals of electric motors [3]. Liu and Schaefer have studied the sliding friction of three commercial thermoplastic polymer composites [4]. ...
The self-lubricating properties of some polymeric materials make them very valuable in bearing applications, where the lubrication
is difficult or impossible. Composite bearings combine the self-lubricating properties of polymeric materials with better
mechanical and thermal properties of the fibers. At present, there are few studies about these bearings and their design is
mainly based on manufacturers’ experiences. This study includes an experimental and numerical study of the large-scale testing
of fiber-reinforced polymeric composite bearings. In the first part of this article, a new tribological test setup for large
composite bearings is demonstrated. Besides, a two-dimensional finite-element model is developed in order to study the stress
distribution in the composite bearing and kinematics of the test setup. A mixed Lagrangian–Eulerian formulation is used to
simulate the rotation of the shaft and the contact between the composite bearing and the shaft. Simulation results correspond
closely to the experimental data, and provide careful investigation of the stress distribution in the bearing. In the second
part of this article, three-dimensional quasi-static and two-dimensional dynamic models are studied.
This work exploits the use of different sintering manufacturing techniques for obtaining superior performances in lubricated point contacts. Disc and ball specimens were manufactures varying porosity and pore characteristics. The effect of surface pores in sintered materials was evaluated based on the frictional behaviour under different sliding-rolling conditions and lubrication regimes. Furthermore, lubricant film thicknesses were measured using interferometric technique. Test results showed that the decrease of porosity generally improves tribological performance. Low porosity surfaces can promote friction reduction compared to non-porous reference materials in specific configurations and operating with similar specific lubricant thickness values. This work contributes to an improved understanding of how randomly distributed micro-irregularities could change lubrication conditions, potentially increasing the efficiency of lubricated mechanical systems.
In this study, copper-graphite composites were prepared by powder sintering. The wear resistance and electrical contact endurance of composites with different copper-graphite ratios were investigated and are discussed. The results illuminate that the high electrical contact resistance evolution during fretting wear is related to the graphite content. With a decrease in the copper content, the interaction between graphite and copper increases, and the conductivity decreases. The graphite particles of the flat sample delaminate and form a graphite friction film between the contact surfaces; this friction film has excellent lubricating properties. Thus, the copper-graphite composites with the highest graphite content herein demonstrate good behavior against fretting wear and exhibit poor electrical contact performance. In other words, a relatively high copper content could maintain a decreased and stable contact resistance. The comprehensive performance of composite materials can be effectively developed by designing the copper-graphite ratio.
Polymeric coatings are ideal materials for the surface modification of many solid substrates. The interfacial properties of these coatings, i.e., surface energy and tribological features, impact a surface’s resulting wettability, repellency, friction, wear, and other performance metrics. To design polymer coatings for various applications, numerous studies have been dedicated to elucidating key structure-property relationships. This review highlights recent efforts to develop such relationships for the various length-scales across which different phenomena arise. For example, the surface energies of polymer coatings have been correlated to molecular aggregation (0.5 nm - 10 nm) and nanoscale phase separation (1 nm - 1 μm), along with microscale phase separation (1 μm - 100 μm) and surface chemistry patterning (10 μm – 500 μm). In a similar vein, the low friction, ultra-low wear performance of polymer composites is highlighted, along with links to microscale phase separation, with emphasis on several studies that have connected micrometer features to improved tribological characteristics, such as reduced friction and wear. The limitations of current structure-property studies with respect to surface coatings also are discussed, and potential methods to overcome these limitations are presented. Finally, an outlook for future structured polymer coatings is provided, along with proposed opportunities for the next generation of polymer-based surfaces.
Ni3Al matrix self-lubricating composites containing multilayer graphene and Ag are successfully prepared by spark plasma sintering (SPS) and laser melting deposition (LMD), which are denoted as NMAS and NMAL, respectively. The sliding wear performances of NMAS and NMAL at 25-500 °C are systematically investigated. NMAL exhibits the lower friction coefficients (0.20-0.40) and considerable wear resistance (2.8-5.0 × 10⁻⁵ mm³ · N⁻¹ · m⁻¹) as compared to NMAS. For the use of spherical prealloyed powders and the manner of layer by layer deposition, the hardness distribution of NMAL is more uniform than that of NMAS. NMAL shows the better tribological properties in comparison to NMAS from 25 to 400 °C because of the good consistency of microhardness. NMAL has excellent tribological behavior at 400-500 °C, while NMAS exhibits poor tribological performance. An explanation for the result is that the lubricating film of NMAL is still intact at 400-500 °C, while the lubricating film of NMAS is cracked and peeled off.
The present attempt in this project is to reduce the vibrations, temperature due to friction, noise and weight of I C engine valve guide by replacing conventional metal valve guide with composite valve guide. Composite materials have been used in automotive components because of their properties such as low weight, high specific stiffness, corrosion resistance, ability to produce complex shapes, high specific strength and good impact energy absorption etc. The Internal combustion engine valve guides are the parts that support the valves in the cylinder head, besides this it keeps lubricating oil from getting sucked into the combustion chamber past the intake valve stem, it keeps exhaust gases from getting into the crankcase past the exhaust valve stem and it also keeps the valve face in perfect alignment with the valve seat. A valve guide test rig is indigenously fabricated. Valve guides are manufactured using the developed composite material (Resin ARL-136, Hardener AH-126 and 4 vol% WS2), on a CNC lathe. The performance of the developed composite guide under varied conditions of speeds, that is, fixed change in rpm and modulated changes in rpm is assessed. Noise, temperature and vibrations are measured. The experimental data revealed that contribution of composite guide in respect of acceleration, velocity and displacement components of vibration is not substantial. A substantial reduction in noise levels is seen. As far as temperature rise due to friction is concerned maximum components fail at elevated temperatures, with composite guides the temperature generated due to friction at higher speeds is less, a considerable weight reduction is also observed.
Consistent and concise literature about self-lubricating metallic composites containing MoS2 is very scarce in particular those analyzing the possible reactions during processing, which are often neglected or even unknown in a variety of publications. In some situations, the composites present a poor lubricating behavior not related to environmental parameters or surface properties, but due to the simple fact that the solid lubricant added is not there anymore, i.e. it has reacted with the matrix or other additives. This review compiled publications from 1945 up to 2017 about the research developments in metal matrix self-lubricating composites containing MoS2. Information on the tribological properties of such composites according to the varied matrixes, contents, processing conditions, testing temperatures and atmospheres are presented.
Ag-MoS2 composite brushes were fabricated by means of powder metallurgy method. The friction coefficient, wear volume loss and contact voltage drop were studied. The mechanics of the electrical sliding wear was discussed. The results show that there is no difference between the friction coefficient with and without current. The positive pole corrosion happens and the material transfer from the positive pole to the negative pole, thus the wear volume loss of the positive brush is more than that of the negative brush and the wear volume loss of the brush without current is between them. The contact voltage drop of positive brush is higher than that of the negative brush because the film of MoS2 is thicker and the electric conduction pots are more in the surface of the positive brush.
Background: Silver-matrix composite is usually used as a kind of electrical conductive material, which has excellent properties in electrical and heat conducting. MoS2, which used as a common solid lubricating material, has unique anti-frictional and lubricating properties in the process of wearing. Ag-MOS2 composites using in the area of electrical sliding wear were fabricated by adding MOS2 to the silver-matrix. Objective: Ag-MOS2 composites with different content of MOS2 were produced to gain the mixture ratio for best properties by the experiments of mechanical and wear test. Design, Time and Setting: The controlled experiment was performed at the Department of Material Science and Engineering, Hefei University of Technology from April to May 2008. Materials: Silver powder (Bengbu Gold and Silver Article Factory, China) and MOS2 powder (Sinopharm Chemical Reagent Co., Ltd., China) were used in this study. Methods: Ag-MoS2 composites for five different contents were fabricated by powder metallurgy method, which included the processes of powder mixture, drying, initial pressure, sintering, and second pressure. MOS2 contents were the MOS2 composite of 12.0%,13.5%,15.0%,16.5%,18.0% silver- MOS2. Main Outcome Measures: Flexural strength was measured by versatility mechanical testing machine. The microstructures of the composites after sintering were observed by an optical microscope. The electrical sliding friction and wear properties were tested by the electrical wear test machine. The worn surfaces of the samples were observed by a scanning electron microscope. Results: With the increase in MOS2, the flexural strength decreased, the resistivity increased, and the wear loss decreased first, and then increased, which comes the lowest point when the MOS2 content was 15%. Conclusion: When the content of MoS2 is 15%, the average properties was the best.
Four kinds of Cu-based composites with different mass ratios of graphite and WS2 as lubricants were fabricated by hot-pressing method. Electrical sliding wear behaviors of the composites were investigated using a block-on-ring tribometer rubbing against Cu-5%Ag alloy ring. The results demonstrated that 800 °C was the optimum sintering temperature for Cu-graphite-WS2 dual-lubricant composites to obtain the best comprehensive properties of mechanical strength and lubrication performance. Contact voltage drops of the Cu-based composites increased with increasing the mass ratio of WS2 to graphite. The Cu-based composite with 20% graphite and 10% WS2 showed the best wear resistance due to the excellent synergetic lubricating effect of graphite and WS2. The reasonable addition of WS2 into the Cu-graphite composite can remarkably improve the wear resistance without much rise of electrical energy loss which provides a novel principle of designing suitable sliding electrical contact materials for industrial applications.
New self-lubricating bronze matrix composites were prepared for seals and the tribological mechanisms in antiwear hydraulic oil were explored. The tribological behavior of bronze matrix composites tribotesting against an AISI 52100 steel ball was investigated with a ball-on-disc tribotester over a wide range of applied load and sliding speed. The obtained results showed that the tribological properties of composites were markedly improved. The alumina enhanced the strength and wear resistance of composites. However, the friction coefficient increased due to the addition of alumina. Silver was an effective solid lubricant. The tribological properties of the new self-lubricating composites were improved because of the synergistic effect of silver and Al2O3.
This paper presents an analysis of several 3D parameters based on bearing area curve in order to use the information for establishing the influence of sliding regime against steel on the tribological behavior of a composite class with polyamide matrix and 1% of black carbon. There were done pin-on-disk tests for different concentrations of micro glass spheres (MGS): 2.5, 5, 10, 20, 30 and 50% (wt), respectively. The polymer was tested under similar conditions in order to have a reference basis and to point out the improvement in tribological behavior when adding this reinforcement material. The surface topographies were registered with the help of PRO500 3D (stylus) Profilometer. The test parameters in dry regime were: sliding speed 0.5, 1.0 and 1.5 m/s, average pressure 1, 2 and 3 MPa, respectively. There were analyzed the influence of MGS concentration and sliding regime on wear as mass loss of the composite discs, after 10,000 m of sliding, the friction coefficient and several 3D parameters related to the bearing area curve, determined from raw profiles (surface bearing index – Sbi, core fluid retention index – Sci, valley fluid retention index, Svi, reduced summit height, Spk, core roughness depth, Sk, and reduced valley depth, Svk).
Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protec-tive atmosphere at 700 • C and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.
Modified PTFE oil seal is studied: non-linear finite element model of sealing interface is established to simulate the distribution
of contact stress and the grinding condition. The friction and wear properties of PTFE composite are investigated in different
loads under dry and oil-lubricated conditions. The worn surfaces of the tested samples and grinding ring are observed with
optical microscope, as an effort to analyze the wear mechanisms. The result shows that forced location of oil seal can be
visually displayed by finite element analysis. Radial force increases with increasing magnitude of interference. Simulant
results fit well with the actual situation. Under dry condition, friction coefficient increases with load increasing at low
speed and decreases at high speed but is stable and affected little by loads under oil-lubricated condition.
Ag-MoS2 composite brushes were fabricated by means of powder metallurgy process. The composite was detected by the method of XRD after sintering, and the worn surface of the brush was analyzed by XPS after the wearing experiments with current. Results showed that the components of the composite didn't change during sintering, but the surface components of it changed upon wearing and some matters such as MoO3 and MoO2 were produced. At the same time, Cu2O, CuO and Cu2S were detected due to the adhesion transfer of elemental Cu from the slipping ring to the brush surface and the reaction between the elemental Cu and the ambient air molecules. During electrical sliding wearing, the surface film can reduce the friction coefficient and be beneficial to the frictional performance of the material.
In the present work, friction coefficients and wear rates of polyester composites reinforced by graphite fiber with different diameters and impregnated by vegetable oils (Corn, Olives, and Sunflower oil) were measured to develop new engineering materials with low friction coefficients and high wear resistance which can be used in industrial applications as bearing materials. It was found thatcomposites of 10 vol.% corn oil and 10 vol.% graphite fibers show relatively low friction coefficientsand low wear rates. Corn and sunflower oil display good tribological behavior of the polyester composites.
Metal matrix composite coatings with potential self-lubricating properties were produced on plain steel substrates using the plasma transferred arc technique (PTA). Layers of approximately 1mm thickness and with various compositions were obtained with additions of MoS2 and MnS compounds, which are known to act as solid lubricants in a number of applications. Following the microstructural characterization, the tribological behavior of the coatings was investigated using pin-on-disk experiments. Experimental results indicated that the addition of MnS was effective in reducing the friction coefficient and the wear rate of the coatings in comparison to the steel substrate, whereas the MoS2 was ineffective, due to its instability and subsequent redistribution of Mo and S elements during the solidification process.
The effect of 20 wt% polytetrafluoroethylene (PTFE) fillers on the friction and wear properties of thermoplastic polyimides (TP) are investigated, under dry sliding in line contact against steel under 50 to 200 N, 0.3 to 1.2 m/s, and 60 to 260°C. Besides the lubricating mechanisms of PTFE based on mechanical shear, the thermal and tribophysical interactions in the sliding interface are considered in this research by using thermoanalytical measurements, Raman spectroscopy, and calculating the maximum polymer sliding temperature T*. The effect of hydrolysis of the TP bulk material, causing high friction at 100 to 140°C, is covered by PTFE. A transition at pv-values 2.2 MPa m/s (T* = 120°C) is due to thermally controlled sliding of PTFE, while a transition at pv-values 3.2 MPa m/s (T* = 180°C) remains controlled by degradation of the TP bulk material into monomer fractions. The reduced coefficient of friction in the presence of PTFE leads to smaller degradation and orientation of the molecular back-bone and side-chains within the TP structure. The formation of a homogeneously mixed transfer film is only observed at 180 to 260°C. The PTFE forms a fibrillar structure during wear at high sliding velocities, while they wear as separate particles at high normal loads. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers
The internal lubrication of 15 vol% graphite flakes added to polyimide was investigated during sliding at 50–200 N normal loads, 0.3 m/s and 23–260 °C, showing that chemical reactions in the polyimide bulk have an important effect on the sliding efficiency of the graphite. The latter are illustrated by Raman spectroscopy, thermo-analytical measurements and mass spectroscopy. At low temperatures (23–100 °C), transfer consists of pure graphite and mechanical shear prevails. At intermediate temperatures (120–180 °C), transfer consists of coexistent polyimide and graphite. A regime with decreasing friction is related to hydrolysis reactions in the bulk polyimide, lowering the effective water content in the sliding interface. At higher temperatures (180–260 °C), transfer consists of mixed polyimide–graphite. A low friction regime is related to imidisation of the bulk polymer and interfacial water supply, favouring the graphite lubricating properties. The graphite debris morphology occurs as flakes (low temperature) or powders (intermediate temperatures), likely resulting from cleavage between the basal planes or embrittlement across the basal planes.
This book presents the current understanding of the influences of microstructural parameters on wear. The effects of microstructure become more pronounced as the surface contact of two solid bodies becomes closer and these effects can be substantially reduced by oxide layers and lubricant films. The chapters include a general review of microstructure and properties of materials; classification of wear processes, wear mechanisms for grooving wear, sliding wear in metals, polymers, ceramics and composites; and rolling sliding wear and erosive wear of metals. (H.C.B.)
A novel materials-selection procedure has been developed and implemented in software. The procedure makes use of Materials Selection Charts: a new way of displaying material property data; and performance indices: combinations of material properties which govern performance. Optimisation methods are employed for simultaneous selection of both material and shape.
The aim of this research was to investigate and analyze the wear of polymers by use of an empirical wear equation. A dimensional analysis was carried out to develop an equation in which the volume of polymer material worn during sliding on a horizontal pin-on-disk machine was expressed in terms of the operating conditions, properties of the polymer, and counterface roughness. Both a linear and a non-linear relationship of volume loss with other variables was considered in evaluating a dimensionless wear coefficient. It was concluded that a better correlation with the variables was obtained using a non-linear relationship.
Preface * Introduction * Surface topography and surfaces in contact * Friction * Lubricants and lubrication * Sliding wear * Wear by hard particles * Wear and design * Surface engineering in tribology * Materials for bearings * Author index * Subject index.
The application of advanced materials in various areas of contemporary technology can lead to improvements in the function, quality and performance of engineering components and systems. In this paper, an overview of the developments in high performance materials, both organic and inorganic based, is given. This includes thin hard coatings because of their increasing importance in tribological improvements. For these types of materials the requirements for tribo-engineering applications are analysed. Research results from BAM concerning ceramics and ceramic composites, polymers and polymer composites as well as hard coatings illustrate the friction and wear behaviour of these materials and their potential for tribo-engineering applications.
Although wear resistance is not a materials property, many of the factors which determine the tribological behaviour of materials can be defined. This review discusses these factors, together with recent developments in bulk materials for tribological applications, including composites and intermetallics. Advances in surface engineering and the possibilities of “smart” tribological materials are also reviewed.
Along with the extensive application of polymers for tribological purposes, the understanding of polymer tribology is becoming increasingly important. A broad overview of the general area of polymer tribology is presented in this paper. The progress in understanding the field over the past decade is reviewed under the three topics of rubber tribology, plastic tribology and tribology of polymer composites. It is hoped that this paper will serve as a valuable source of reference for future tribologists.
A novel materials selection procedure containing a database of quantitative and qualitative data for a wide range of engineering materials was implemented in software. The management system provided an interactive graphical selection environment appropriate for mechanical engineering design using performance indices in the selection of materials with optimum properties and section shape.
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