Sk Hwt 01 Introhistory Ss08
Transcript of 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
Introduction and History2 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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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Introduction and History3 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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
Introduction and History4 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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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Introduction and History5 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
The first recorded Tribologist2400 B. C.
03136_igelSource: D. Dowson, History of Tribology, 1979
Sliding bearing
Introduction and History6 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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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Introduction and History7 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
Leonardo da Vinci,Italy (1452-1519)
- wear path of hiscranes wasfollowing thesteady load vector
Introduction and History8 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
Leonardo da Vinci, Italy (1452-1519)- friction (03137)
Horizontal and inclindes planes
Appearant areas of conatactFrictional torques
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Introduction and History9 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
Leonardo da Vinci, Italy (1452-1519)- ball bearings for large doors and cranes
Introduction and History10 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
Guillaume Amontons,France (1663-1705)
Charles Augusti n Coulom b,France (1736-1806)
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Introduction and History11 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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
Introduction and History12 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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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Introduction and History13 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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=
Introduction and History14 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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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Introduction and History15 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
contact mechanics ofmoving elastic bodies
sphere-on-plane Simple caseE1=E2, 1= 2
)c1(a
F
2
212
Nmax,t
+
=
+=
21
4
8
3c
Introduction and History16 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
contact mechanics ofelastic bodies
sphere-on-plane flat-on-plane cone-on-plane
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Introduction and History17 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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!
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Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
Tendency to adhere depends on free surface energy and on surface roughness!
N
NNo
F
RFRRF
a
a2
)3(363 +++=
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Introduction and History19 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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
Introduction and History20 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
Richard Stribeck , Germany (1861-1950)- Influence of surface roughness and lubrication onfriction
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Introduction and History21 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
Stribeck curve withboundary, mixed andfluid-film lubricationregimes
Introduction and History22 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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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Introduction and History23 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
Char les Hacket , England 1803 (King George III, 1760)- wear of coins in England- gold, silver, copper
Introduction and History24 uni-due..de/wt
Universitt Duisburg-EssenLotharstr 1, 47057 Duisburg, Germany
WerkstofftechnikMaterials Science & Engineering
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