Tribology is the study of the science and technology of interacting surfaces in relative motion and encompasses the study and application of friction, wear, lubrication and related design aspects. To further understand tribology, it is important to understand the definitions behind friction, wear and lubrication. Friction is the resistance to relative motion between two bodies in contact. It is not a material property but a system property. Scientists believe it occurs due to the electromagnetic attraction between charged particles in two surfaces that are touching.

There are several types of friction, including:. Friction is not considered a fundamental force. It is a non-conservative force meaning that work done against friction is path dependent. Wear is the gradual removal, damaging or displacement of material at solid surfaces. When it comes to wear, the common types are:. Given the various types, tribology also illustrates how Wear can undergo many changes in time or undergo changes in operational conditions.

Lubrication is the control of friction and wear by introducing a friction-reducing film between moving surfaces in contact. This film, aka lubricant, can be a solid, fluid or plastic substance with oil and grease being the most common. Lubricants have several functions, including reducing friction, preventing wear, protecting equipment from corrosion, controlling temperature and contamination, transmitting power and providing a fluid seal.

When it comes to lubrication, there are three different types referred to as regimes: boundary, mixed and full film. Boundary lubrication exists where there are frequent starts and stops, and also where shock-loading conditions are present. For example, some oils contain additives — such as extreme pressure EP or anti-wear AW — to help protect surfaces in case full films cannot be recognized due to load, speed or other factors. Full-film lubrication exists in two forms: hydrodynamic and elastohydrodynamic.

Hydrodynamic lubrication HL occurs when two surfaces in sliding motion are fully separated by a film of fluid. Elastohydrodynamic lubrication EHL is very similar to HL but occurs when the surfaces are in a rolling motion relative to each other. This results in greater pressure on the film.Tribology is the science of wear, friction and lubrication, and encompasses how interacting surfaces and other tribo-elements behave in relative motion in natural and artificial systems.

This includes bearing design and lubrication. Tribology is not an isolated science, but rather a complex, multidisciplinary endeavor where advances are made by collaborative efforts of researchers from fields including mechanical engineering, manufacturing, materials science and engineering, chemistry and chemical engineering, physics, mathematics, biomedical science and engineering, computer science, and more.

One of the most important pillars of tribology is the system analytical and system related thinking. Friction and wear are not material properties.

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They are responses to a specific tribological system which typically includes a bearing, shaft and lubricant combination and as such are influenced by a wide range of factors. The tribological sub-system in Figure 1 provides an overview of common factors which affect friction and wear values:. The collective stress includes the technical and physical load parameters including load, sliding speed and duration along with the movement and temperature conditions stressing the system-structure.

The system-structure is determined by the property profiles of the substantial elements including the base, opposing body and ambient and the intermediate medium. The greatest challenge is that friction and wear values cannot be easily transferred from one system to another eg from a tribological test rig to a real application.

Comparisons between measured values are only feasible when based on a very similar tribological system. The tribological behavior of materials can ony be estimated for specific applications based on modeling and simulation testing provided the specific operating conditions of the application and test environment are the same. Friction can be described on the macroscopic level by the basic laws of friction from physicists Guillaume Amontons and Charles-Augustin de Coulomb.

These physicists found a linear relationship between resulting friction force and applied normal load. Based on this, a dimensionless main parameter can be derived, called the coefficient of friction. It is defined by the ratio of the resulting friction force and applied normal force. However, the actual mechanism of sliding friction occurs at a microscopic level, which means tribological theories on friction also involve the topography of the surfaces.

tribological properties definition

The tribologist differentiates between the real contact area and the nominal contact area geometric dimensionswhich accounts for any voids or non-contacting portions of a solid element.

The mechanisms responsible for the energy transforming process in the near surface area include:. These wear mechanisms include:. Friction and wear mechanisms are strongly affected by the structure of the tribological system as well as on the induced collective stress:.

Friction and wear mechanisms do not occur in an isolated fashion, but rather through a superposition of mechanisms that is challenging to quantify and control for.

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This superposition occurs in tribo-technical systems in non-detectable proportions and in proportions that vary across time and place, making it nearly impossible to calculate friction and wear processes in a tribo-contact. This is why tribological tests are so crucial for estimating tribological behavior. If we want to interpret and understand tribologically-measured data and mechanism-oriented research, we need complete knowledge of the acting mechanisms in a tribo-contact.

Tribologists classify friction, wear and lubrication conditions according to the following schedules:. Tribological testing allows us to gain information about tribo-performance of materials to drive new and better material designs.

We can then target material compositions to achieve specific and better tribological properties. Tribological test results and surface analytical methods help us estimate the tribo-performance including friction and wear, failure mechanisms, kinetics of transfer films of existing materials and new prototypes based on various factors and influences. This information helps us see and understand variables like the effects of various material compositions including filler, filler concentration, synergetic effects of fillers, material structure as well as the impact of other elements of they system structure.

It covers rudimentary roller bearings used by the ancient Egyptians, ball bearings used by the Romans 40BC, the roles of heat treatment of hardened steel and oxide-based ceramics. It also covers he development of the first self-lubricating plain metal-polymer bearing by GGB. Tribology plays a central role in applications in which two contacting surfaces move in relation to each other. Some industries place higher demands on tribological systems due to their mission criticality, continuous operation requirements or extreme conditions.

This depends strongly on the application.

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Some applications require low friction e. For most of the applications, minimum wear of the materials is a primary goal. For many applications, a defined sweet spot between low friction levels and good wear performance is often targeted. When designing experiments describing friction and wear, tribological testing can be placed into one of six main categories, from field tests in Category I to simplest laboratory model tests Category VI.Related to tribological: tribologist. The science of the mechanisms of friction, lubrication, and wear of interacting surfaces that are in relative motion.

All rights reserved. References in periodicals archive? Volume 18 of the ASM handbook series provides professional insight on the tribological properties of materials, methods of laboratory testing and analysis, the materials selection process, and field diagnosis of tribology problems. Friction, Lubrication, and Wear Technology.

Less Could be More! Nanoparticles of IF-WS2 Improve Grease Tribological Properties Like no Other

Tribological experiments were performed using a standard four-ball tribometer. Phosphonium-based ionic liquids mixed with stabilized oxide nanoparticles as highly promising lubricating oil additives. An increased interest in using PAs in tribological application is due to its high mechanical strength and structural integrity. For example, it has high adherent strength to substrate, high hardness and thickness, high corrosion resistance, high wear resistance, low environment pollution, relatively low cost, and outstanding tribological performance because of its exceptional oil retention ability [H, 12].

Investigation into mixed and hydrodynamic frictions of PEO coatings and cast iron. The main tribological surface characteristics influencing the speed regularity of USM in steady regimen are macro- and microasperities and friction coefficient fluctuations between rotor surface and friction element.

Impact of the tribological characteristics on the dynamics of the ultrasonic piezoelectric motor. Polyketone compounds are back. Graphene has recently attracted extensive attention because of its excellent properties, such as high thermal conductivity, high young's modulus, large specific surface area, and outstanding tribological properties [].

Synthesis, characterization, and tribological behavior of oleic acid capped graphene oxide. This study focuses on mechanical and tribological properties within 0. Thermoset Composites: Preparation, Properties and Applications. Dictionary browser? Full browser?Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of frictionlubricationand wear.

Tribology is highly interdisciplinary.

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It draws on many academic fields, including physicschemistrymaterials sciencemathematicsbiologyand engineering. People who work in the field of tribology are referred to as tribologists. Peter Jost coined the word in[1] in the eponymous report which highlighted the cost of frictionwear and corrosion to the UK economy. Despite the relatively recent naming of the field of tribology, quantitative studies of friction can be traced as far back aswhen Leonardo da Vinci first noted the two fundamental 'laws' of friction.

He also observed that the force needed to overcome friction doubles as weight doubles. However, da Vinci's findings remained unpublished in his notebooks. The two fundamental 'laws' of friction were first published in by Guillaume Amontonswith whose name they are now usually associated. They state that: [3]. Although not universally applicable, these simple statements hold for a surprisingly wide range of systems.

InCharles Hatchett and Henry Cavendish carried out the first reliable test on frictional wear. In a study commissioned by the Privy Council of the UKthey used a simple reciprocating machine to evaluate the wear rate of gold coins. They found that coins with grit between them wore at a faster rate compared to self-mated coins. Michael J. Neale was another leader in the field during the mid-to-late s. He specialized in solving problems in machine design by applying his knowledge of tribology.

Neale was respected as an educator with a gift for integrating theoretical work with his own practical experience to produce easy-to-understand design guides. The Tribology Handbook[14] which he first edited in and updated inis still used around the world and forms the basis of numerous training courses for engineering designers.

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Duncan Dowson surveyed the history of tribology in his book History of Tribology 2nd edition.Send us feedback. See more words from the same year Dictionary Entries near tribology triboelectricity triboelectric series Tribolium tribology triboluminescence tribometer tribon.

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Tribology Explained

Test your knowledge - and maybe learn something a Login or Register. Save Word. Definition of tribology. Keep scrolling for more. Examples of tribology in a Sentence Recent Examples on the Web In part, because tribology itself is built on unseen forces all around us. First Known Use of tribologyin the meaning defined above.

Learn More about tribology. Time Traveler for tribology The first known use of tribology was in See more words from the same year. Dictionary Entries near tribology triboelectricity triboelectric series Tribolium tribology triboluminescence tribometer tribon See More Nearby Entries. Statistics for tribology Look-up Popularity. More Definitions for tribology. More from Merriam-Webster on tribology Britannica. Comments on tribology What made you want to look up tribology? Get Word of the Day daily email!Reformation and Modern Rituals and Theologies of Baptism: From Luther to Contemporary Practices.

tribological properties definition

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