friction wear and surface testing pdf

Friction Wear And Surface Testing Pdf

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The surface properties of a bulk material are not accepted totally and independently. The tribology is the most important field that comprises the component design with static and dynamic relations for a reliability and performance. Hence, it is believed that the surface contacts, atmosphere, and lubrication significantly change the wear resistance of the material surface.

Friction, Lubrication, and Wear

The surface properties of a bulk material are not accepted totally and independently. The tribology is the most important field that comprises the component design with static and dynamic relations for a reliability and performance.

Hence, it is believed that the surface contacts, atmosphere, and lubrication significantly change the wear resistance of the material surface. However, the wear process is more complicated, in that a surface wear properties based on many tribological factors namely sliding type, mode of loading and working atmosphere.

In this chapter, will explore the tribology fundamental, friction, various lubrication, wear types and mechanism on the wear process. Tribology is defined as the science of sliding two surfaces in relative motion.

It comprises the investigation and application of the wear, friction and lubrication. The term called tribology has been realized for thousands of years. This is an interdisciplinary area and related with materials, wear, friction, surface analysis, wear mechanism and working atmosphere [ 1 ]. Also, the surface properties of the base material cannot be measured totally as independent. It involves the component shape with contact types i. The wear resistance of the material is mainly depending on the loading type, sliding and working environment.

However, the phenomena are more complicated, in that a surface wear properties based on many tribological factors namely sliding type, mode of loading and working atmosphere [ 2 ]. Further, the wear behavior examination includes wear rate, coefficient of friction, volume loss, worn-out morphologies examination and studies of the mechanical properties and microstructure.

From the above literature, it has been recognized the importance of tribological properties. The main objective of this chapter is to study the tribology fundamental, friction, lubrication, wear, mechanism. The friction and wear are mainly dependent on the characteristics of two sliding surfaces. The difficulty to predict and to clarify with more accuracy such phenomena reveals the complex nature of the surfaces, which can be evaluated through material properties such as microstructure, presence of organic molecules and oxides, water vapor, geometrical irregularities and other impurities which can be adsorbed from the atmosphere.

Hence, while the two bodies are coming in to closer contact, the significant features of their sliding surfaces define the nature of the interaction, which includes mechanical character, with the development of a stress-strain on the sliding area, with the strong establishment of physical or chemical bonds [ 6 ].

To calculate the contact stresses, the smooth surface concept can be introduced, i. Generally, the formation of smooth surfaces is difficult at a molecular level. The relation for contact stresses and deformations can be obtained through theoretical analysis which is developed by Hertz for linear elastic bodies.

This can be employed while the two bodies are in frictional or elastic contact, with the assumption that the contact body radius is higher while compared with contact zone size. This kind of contact can be seen while bearing sliding on shafts and between wire and tool in drawing processes. For example, with the presence of point contact in rolling bearing between seat and ball , whereas a line contact happens in gears between tooth and tooth.

In another case, the contact area has a limited extension and it can be easily determined. The conformal contact between a plane and the base of a cylinder a and nonconformal contact between a plane and sphere b.

In the case of polymers, the deformation behavior can be occurred that is affected by plastic, elastic and viscoelastic processes. In polymer plate the viscosity influence is mainly noticeable while holding the amorphous phase and the heat may be higher than glass transition temperature. Further, the loss of energy is related to the viscoelastic loading and unloading processes.

This energy dissipation may create the temperature on the material due to lesser thermal conductivity of material. However, the creation of plastic deformation is stable.

Besides, the plastic processes and viscoelastic are based on the temperature and while increasing the temperature their intensity also increased [ 7 ]. The material behaves with ductile way; the provided contact load can be induced the plastic deformation. At the same time, the equivalent stress at the critical point influence the material uniaxial yield stress. In this case, the material is not as elastic stage; however, it must be an elastic-plastic condition [ 8 ].

In this case, the sphere has a higher hardness while compared with plane. If the applied load is increases, the plastic zone size can be increased. The applied load is taken out while the contact pressure with the below specific limit, then with the same magnitude of additional load, which are applied possibly, results the increase in elastic deformation only.

Elasto-plastic a complete plastic, b brittle-type contact, and c between plane and a sphere. The frictional forces can be recognized as good or bad, without this friction, there is no possibility to use vehicle tires on a road, walking on the road or pickup objects.

In some cases, such as machine application like clutches, vehicle brakes and transmission of power belt drives , friction is increased. But, in many cases like rotating and sliding components such as seals and bearings, friction is unwanted. The higher friction makes more material loss i. In these kinds of working atmosphere, the friction is reduced [ 9 ].

The term friction is called as the force resisting the relative motion of two mating surfaces in contact with a fluid. The two sliding surfaces move relative to each other, the friction between the mating surfaces converts the kinetic energy in to heat or thermal energy.

Generally, the term used to describe the friction is the coefficient of friction. It is described in Eq. In a sliding condition, it is normally required to monitor or calculate the frictional behavior during the experiment.

The changes in friction with wear data normally offer the beneficial data regarding modeling and mechanisms. The friction is generally classified as two categories: a static friction and b dynamic friction. In the case of two objects is not sliding each other is called as static friction.

In another hand, both the mating objects sliding relatively to each other is called as dynamic friction [ 10 ]. Generally, the asperities contact in metal surfaces is normally plastic. The metals such as titanium, cobalt, magnesium with hcp hexagonal closed packed crystal lattice provides the coefficient of friction nearly 0.

In addition to that the hcp metals possess a reduced ability to deform plastically with relatively lower temperature. Hence, while sliding the asperity junctions deform with lesser intensity and the adhesion forces is not developed at the junctions [ 11 ]. While sliding between two metal alloys, the coefficient of friction is to be lesser than in the corresponding pure metals.

In the case of steel, the coefficient of friction value is around 0. In ceramics material the contact at the asperities is normally mixed. This may be fully in elastic while the surface roughness shows with less [ 6 ]. Else, if the surface roughness is high, it may be shows with plastic stage. Generally, the coefficient of friction must be independent for the normal applied load in elastic contacts.

For example, the alumina balls sliding on the alumina surface and the friction showed around 0. It can be noted that the friction coefficient in ceramics material with dry atmosphere is lesser around 0. The obtained frictional values are relatively similar to metal alloys and this may seem to be quite surprise. In case, the ceramics material is characterized with higher hardness and elastic modulus, and lesser values of the surface energy [ 12 ].

Besides, the surface energy of ceramics material is reduced through the surface reactions with water vapor and the presence of other substances on the working atmosphere. Hence, the lesser frictional force can be expected from the sliding wear experiment. Though, while continuous sliding with real contact area is notably increases with increase in friction. Further, the applied load is considered as major input parameter in the ceramic material.

If the applied load is increased, the brittle contact may establish, and this will increase the coefficient of friction as much as high around 0. Specifically, the brittle contact can be occurred while the tangential stresses owing to higher friction due to the occurrence of critical microcracks on the surfaces.

This type of microcracks can be seen on the ceramics surfaces normally and producing the defects such as porosity, flaws and inclusions. The cracks can be initiated from the development of asperity because of continuous applied load during the tribological study.

The polymer like polytetrafluoroethilene PTFE is produces very low friction around below 0. Thus, this material behaves as solid lubricant while sliding with counterpart [ 13 ]. Generally, most of the polymer material friction coefficient ranges from 0. In the case of the work of adhesion in polymer was lesser than in ceramics and metals.

However, their stiffness and hardness of the material is lesser, and these two effects are nearly proportional. These experiments were conducted on flat to flat surface contacts with lower sliding speed of 0. So that the thermal effects on the polymers can be avoided [ 14 ]. It can be observed that the coefficient of friction was increased with the work of adhesion. In this kind of working condition, the adhesion was considered as a most important factor in friction determination.

In the case of point or line interactions, the produced deformations may be higher and therefore the effect of viscoelastic can play a major role. The clean surfaces without any rust is freely adsorb traces of other substances from the atmosphere.

In addition, the newly manufactured surfaces normally produce the lesser wear and coefficient of friction while compared with clean surfaces. However, there may be chances of external material on the interface of bulk material which can increase the coefficient of friction during continuous sliding process.

Hence, the lubricants can be applied to reduce the wear rate and coefficient of friction [ 8 ]. The term called lubrication can be applied to two various conditions: namely solid lubrication and fluid film lubrication liquid or gaseous.

In any kind of material, the solid lubricant such as solid film and powder was used to protect the sliding surface from the unexpected damages during the sliding process and reduce the wear rate and coefficient of friction. The solid lubricants were used in sliding applications. For example, the bearing was operated with low speeds and higher loads, and the hydrodynamically lubricated bearings demanding the start and stop processes.

The solid lubricant holds the higher variety of material which can produce the lower wear rate and coefficient of friction [ 15 ]. In addition to that the hard materials also were used as lubricant to reduce the friction and wear in extreme working atmosphere. A thick film of lubrication was maintained in the region between two solid surfaces with no relative motion or lesser motion through an external pumping agency is called as hydrostatic lubrication [ 16 ].

This curve has a lowest with providing the recommendation that higher than one lubrication system is presented. In some cases, the lubrication regimes can be recognized through lubricant film parameter [ 17 ].

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MMW-1A Vertical Universal Friction Wear Test Machine is similar to Test machine in main application and functions, it's widely used as machine in design and develop hydraulic oil, combustion engine oil, gear oil etc.. Perhaps the most versatile commercial system for evaluating friction, wear, characteristics of materials, coatings, and lubricants. Numerous Standard Test Application Specific Custom testing programs are possible due to user selected contact motions, velocities, temperatures, contact pressures, and test specimen materials allow one test apparatus to meet many test specifications and simulate a broad range of field applications. Applications include research and development, quality control, product qualification and the evaluation of physical and performance characteristics of materials, coatings, 3nd lubricants. Test studies and a number of technical publications confirm exceptional correlation with field service.

Sliding Friction/Wear

Our research. The machine has both point contacts and line contacts Reciprocating wear rig - fully computer controlled with a frequency range of 2 to 50 Hz, stroke of 0. Capable of a vast range of loads from 0.

This article discusses the tests designed specifically to evaluate the adhesion, friction, and wear behavior of various material systems. It tabulates the characteristics of common types of wear and mechanical surface damage. The article also considers the displaying and analyzing of adhesion, friction, and wear test data.

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Friction, Lubrication, and Wear

Supported by the expertise of Surface Engineering and Tribology at the Catholic University of Leuven, and by cooperations with international research institutes such as Tekniker Spain and Centre Tudor Luxembourg. We use certified specimens and train our operators regularly, complying with ISO Talk to us about your specific needs. Capable of simulating a variety of field conditions, the Falex Block-on-Ring Test Machine evaluates the friction and wear characteristics of materials and lubricants in research, quality control, and technical service applications. Tests are typically performed using a flat HP block for single line contact, but conforming blocks for area contact may also be used.

The surface properties of a bulk material are not accepted totally and independently. The tribology is the most important field that comprises the component design with static and dynamic relations for a reliability and performance. Hence, it is believed that the surface contacts, atmosphere, and lubrication significantly change the wear resistance of the material surface. However, the wear process is more complicated, in that a surface wear properties based on many tribological factors namely sliding type, mode of loading and working atmosphere. In this chapter, will explore the tribology fundamental, friction, various lubrication, wear types and mechanism on the wear process.

Tribometers | Friction and Wear Loss Testing Equipment

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Our specially designed interchangeable jigs enable users to perform various types of wear testing by simply changing the jig of the instrument. The interchangeable jigs allow our tribometers to be built much smaller in size and less costly than the leading brands in the industry. Also, our Windows compatible measurement software makes your wear testing even more convenient. All the data are saved in CSV Excel format for your convenience. Tribometers are available in single-purpose, multi-purpose , universal , and also as a customized system such as our cam and tappet wear tester which is a modified version of a block-on-ring tester to better simulate real-life camshaft and valve operation of an internal combustion engine.

Wear test is carried out to predict the wear performance and to investigate the wear mechanism. We may use an example to describe the difference among each type of test. A new surface engineering SE technology has been developed, which could be potentially used to improve the wear resistance of parts for a metal-on-metal hip joint for human body. Perhaps the ideal and logical sequence of wear testing in this example will be as follows:. Stage 1 Laboratory test with small samples are initially carried out under testing conditions simulated insofar as conveniently possible to determine whether the surface engineering technology warrants further consideration, and if so, to find out under what treatment conditions, the highest wear resistance improvement can be achieved. Stage 2 In the next stage, the optimised surface treatment condition will be used to treat some real joint parts, e. Stage 3 Only when the surface treated parts have survived the simulation tests, and indeed show considerably improved wear resistance yet without losing other properties e.

Basic friction angle is an essential parameter when estimating shear strength of rock joints, according to Barton's equation and other approaches. Nevertheless, there is still no standard procedure to estimate it by means of laboratory testing. This study investigates the influence of tilting rate on basic friction angle results, as well as the impact of previous wear on the surfaces when carrying out various tilt tests on the same surfaces. An experimental program including 5 tilting rates, 5 joints for every rate and 5 tests for every joint was carried out in rock samples of moderately weathered granite. Interpretation of results suggest that whereas tilt rate does not significantly affect results of basic friction angle, surface wear and the number of test performed on every sample may play a meaningful role. These observations are finally discussed with the aim of suggesting a guideline for testing procedures focusing on rock engineering purposes. Rock joints and other discontinuities control the behaviour of rock masses being, therefore, essential to understand how they behave.

Friction, Lubrication, and Wear

The materials testing lab at Nova Werke AG offers testing and consulting services both for internal research and development and external customers. At Nova laboratory we can conduct several tribological systems to investigate coatings and surface engineered materials subjected to friction and wear for their application in harsh environments, e. Our dedication to the highest levels of customer service and excellence helps us to solve complex wear and friction problems related to coating solutions.

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