sk hwt 01 introhistory ss08

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here Werkstofftechnik: Tribologie Introduction and History

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Introduction and History1 uni-due..de/wt

Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany

WerkstofftechnikMaterials Science & Engineering

I nt roduction and History of Tribology

Jost-Commission (1966) in England

TRIBOLOGY - Friction- Wear- Lubrication

ancient greek = rubbing

= knowledge




economical losses by wear~ 1-4% of gross national product~ 10% of primary energy is lost by friction and wear

within Germany (direct and indirect costs)

1975 2,5 Billion 1983 5 Billion (of this 1,1 billion in steel industry)2002 40 Billion


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direct costs- new parts- regeneration of worn parts

indirect costs- interruption of production- costs of maintanance- storekeeping

add. costs- more expensive production

- decrease of quality- decrease of productivity- loss of market shares




History of Tribology

predominately friction

recorded since ever- e.g. to make fire

Egyptians, Sumerians (3500-35 A.C.)- leather as bearing material for rolls and wheels- stone transport on wooden rails with lubrication by oil,grease, water- roller bearings since about 330 A.C. in Greece


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The first recorded Tribologist2400 B. C.

03136_igelSource: D. Dowson, History of Tribology, 1979

Sliding bearing




Calculation of the coefficient of friction

03135_igelSource: D. Dowson, History of Tribology, 1979

23.080665.9000,60

800172

F

F

N

T =

==

FT: 172 men each pullingabout 800 N (~ 80 kg)FN: 60 tons 5.9x10

5 N

wood-on-wooddry ~ 0.25 - 0.5wet ~ 0.2


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Leonardo da Vinci,Italy (1452-1519)

- wear path of hiscranes wasfollowing thesteady load vector




Leonardo da Vinci, Italy (1452-1519)- friction (03137)

Horizontal and inclindes planes

Appearant areas of conatactFrictional torques


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Leonardo da Vinci, Italy (1452-1519)- ball bearings for large doors and cranes




Guillaume Amontons,France (1663-1705)

Charles Augusti n Coulom b,France (1736-1806)


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Coulomb-Amontons laws of friction:should be named da Vinci-Amontons-Coulomb laws of

friction

1) the friction force depends on the normal force2) the friction force is independant of the nominal contact area3) static friction is smaller than dynamic friction4) the friction force is independant of the relative speed

2) + 4) are wrong




Heinrich Rudolph Hert z, Germany (1857-1894)contact mechanics of elastic bodies

sphere-on-plane

3 N

E

RF11.1a =

Simple caseE1=E2, 1= 2

32

2N

maxR

EF388.0p =

maxmaxp31.0=

a47.0zm=


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Heinrich Rudolph Hert z, Germany (1857-1894)contact mechanics of elastic bodies

sphere-on-sphere with different radii

3

21

21N

RR

RR

E

F11.1a

+=

Simple caseE1=E2, 1= 2

3

21

212Nmax

RR

RREF388.0p

+=

maxmaxp31.0=

a47.0zm=




E = equivalent Youngs Modulus of Body 1 and Body 2

1,2 = Poissons ratio of body 1 and 2

R = equivalent radius; substitutes two spheres by one sphere and oneflat

21

11

1

RRR+=

21

212EE

EEE

+=

if is the same for both bodies

Notice: With different radii of the two bodies in different directions theformulas become more complicated!


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contact mechanics ofmoving elastic bodies

sphere-on-plane Simple caseE1=E2, 1= 2

)c1(a

F

2

212

Nmax,t

+

=

+=

21

4

8

3c




contact mechanics ofelastic bodies

sphere-on-plane flat-on-plane cone-on-plane


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Richard Stribeck , Germany (1861-1950)- Influence of surface roughness and lubrication onfriction

lubdefad++=

within vacuum = 10in air = 0.5in oil = 0.001

Note: Adhesion increases the contact area!




Tendency to adhere depends on free surface energy and on surface roughness!

N

NNo

F

RFRRF

a

a2

)3(363 +++=


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Richard Stribeck , Germany (1861-1950)- Influence of surface roughness and lubrication on friction

1

1

0

0

lub

)1(

++=

++=

S

S

defad

C

= fraction of real area of contact

C = probability of ploughing0 = shear strength of adhesive bond, 0 = contact stress within adhesive contacts = shear strength of material, s = contact stress within roughness1 = shear strength of lubricant; similar to viscosity, 1 = pressure within lubricant




Richard Stribeck , Germany (1861-1950)- Influence of surface roughness and lubrication onfriction


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Stribeck curve withboundary, mixed andfluid-film lubricationregimes




Predominatly investigated until 1920s- sliding friction- rolling friction- lubrication

Wear is investigated since the 1930se.g. Holm, wear of electrical contacts

except for one thing

MONEY


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Char les Hacket , England 1803 (King George III, 1760)- wear of coins in England- gold, silver, copper




Char les Hacket , England 1803 (King George III, 1760)- wear of coins in England- gold, silver, copper

- Results

- pure Au wears faster than alloyed Cu or Ag- the softer metal wear faster than the harder one- materials transfer from the softer to the harder- Cu vs. Cu show higher wear than non-self-mating contactmaterials- sand or metal chips increase wear with increasing ductility ofcoin materials

sk hwt 01 introhistory ss08

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