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Introduction to "TRIBOLOGY"Introduction to "TRIBOLOGY"

Sunilkumar S Honnungar M.Tech.(Design Engg)

Lecturer, Department of Mechanical Engineering, SDMCET, Dharwad-2

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What is Tribology?What is Tribology?

� The word Tribology is derived from Greek word “TRIBOS” ,means rubbing. Further it is “OLOGY” which means science of “TRIBEN”, which also means science of rubbing surfaces.

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Introduction Introduction � The British Lubrication Engineering working

Group(1966) put the definition as, “ The science and technology of interacting surfaces in relative motion and the practices related thereto”

� The subject TRIBOLOGY generally deals with the technology of lubrication, control of friction, and prevention of wear of surfaces having relative motion under load.

TRIBOLOGYFRICTION WEAR

LUBRICATION

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� Why TRIBOLOGY is so important?

Basically Tribology is an art of providing solutions to the

problems which are of great economic significance, namely

maintenance, reliability, and wear of equipment starting

from house hold appliances to spacecrafts.

� What are the pre requisites to understand TRIBOLOGY?

To have thorough knowledge and understanding of the subject it is necessary to have an in depth knowledge in

many areas such as chemistry of lubricants, physics of

fluid flow, surface topography, contact mechanics,

material science, mathematics, and Mechanical Engineering. Thus the subject Tribology is truly multi disciplinary.

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HistoryHistory� Tribology is relatively new subject and got importance

only during 1966.

� There are evidences of even older than recorded history.

� Our ancestors were concerned with reducing friction in translatory motion(use of wheels 3500 B.C.) Drills were made use of for drilling holes during Paleolithic era (stone age)or producing fire and they were fitted with bearings made from bones or antlers (Branched horn on Stag or deer).

� Potters wheels or stones used for grinding cereals (wheat, jawar, rice etc) clearly indicate the use and knowledge of some type of bearings.

� A tomb in Egypt provides evidences of use of lubricants. A chariot in that tomb still contains some of the original fat used from animal lubricants in it’s wheel bearings.

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History continued…History continued…

� A ball thrust bearing dated about 40 A.D was found in lake Nimi near Rome.

� Leonard-Da-Vinci (1452-1519) first postulated a scientific approach to friction. He deduced a law governing the motion of a rectangular block bearing over a flat surface and introduced the concept of coefficient of friction as the ratio of the friction force to normal load.(η= F/W). But his work remained unpublished for a long time.

� In 1699, Guillaume Amontons rediscovered the laws and is usually credited with the discovery of two laws.

� The first , the friction force resisting sliding at the interface is directly proportional to the normal loads and second, the frictional force does not depend on the apparent area of contact.

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History continued…History continued…

� Later on Charles Augustin Coulomb verified these laws and added third law, that , the friction force is independent of velocity once motion starts. It was Coulomb who made it clear distinguish between static friction and kinetic friction.

� In 1864 Robert Hooke suggested bell-metal bushes to steel shafts in place of wood shoe with iron for wheel bearings.

� In the later part of 18th century the growth of industarialisation brought about further developments.

� The essential laws of viscous flow were postulated by Newton in 1668, any scientific understanding of lubricated bearing operations did not occur until the end of 19th century.

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History continued..History continued..

� The beginning of understanding of principles of

hydrodynamic lubrication was made possible

with the experiments did by Bauchamp Tower

(1884) and theoretical interpretations of

N.P.Petroff (1883) and Osborne Reynolds

(1886). Since then the hydrodyanamic bearing

theory and practice has been extremely rapid

developments to meet the demand for reliable

bearings in new machinery.

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Present importance for Present importance for TribologyTribology

� Wear is much younger member in the Tribology

family than friction and bearing development.

� It was initiated on largely empirical basis and

scientific studies of wear developed only a little

until the mid 20th century.

� More recently the emergence of proximal probe and

high capacity computational techniques has allowed

systematic investigations of interfacial problems

with high resolution in micro and nano-

electromechanical systems (MEMS) and other

industrial applications. These have led to the

development of new field of microtribology or

nanotribology.

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Present importance for Present importance for Tribology Tribology contd..contd..

� This new member in tribology family is concerned wit experimental and theoretical investigations of processes ranging from atomic scale to micro scales, occurring during adhesion, friction, wear and thin film lubrication at sliding surfaces.

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Worn surface of carbon fibre reinforced PEEK composite

abraded at load of 12 N (a) 1500 x magnification (b) 3400 x

magnification.

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Industrial Importance.Industrial Importance.

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Industrial ImportanceIndustrial Importance contdcontd……� Tribology is essential to modern machinery

involving sliding and rolling surfaces. Brakes, clutches, bolts, nuts, driving wheels on automobiles etc.use of friction in a productive manner. Also friction is used in productive manner like writing with pencil, polishing, machining and shaving.

� Unproductive friction takes place in engines, gears, cams, bearings etc. It has been estimated that in the total world’s energy produced, nearly 1/3rd will go as frictional loss in one or other way. Friction and wear usually cost money and material loss, can decrease national productivity and affect quality of life.

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Industrial ImportanceIndustrial Importance contdcontd……

� Wear also causes accidents. Thus the

knowledge of Tribology can lead various

substantial and significant savings without

deployment of large capital investment.

� Research in Tribology leads to increased plant

efficiency, fewer breakdowns,better

performance and above all significant savings.

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QUESTIONS?