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Table of Contents
                            Preface
Contents
1 Surfaces in Contact
	1.1 Contact Between Ideal Surfaces
		1.1.1 Elastic Contact
		1.1.2 Viscoelastic Contact
		1.1.3 Elastic-Plastic and Fully Plastic Contacts
		1.1.4 Brittle Contact
		1.1.5 Materials Response to the Contact Stresses
	1.2 Surface Roughness
	1.3 Real Area of Contact
	1.4 Adhesion Between Surfaces in Contact
	References
2 Friction
	2.1 Influence of Friction on the Contact Stresses
	2.2 Friction and Plastic Deformation at the Asperities
	2.3 The Adhesive Theory of Friction
	2.4 Friction Between Metals, Ceramics and Polymers
		2.4.1 Metals
		2.4.2 Ceramics
		2.4.3 Polymers
		2.4.4 Final Remarks
	2.5 Friction and Transfer Phenomena
	2.6 Effect of Temperature and Sliding Speed
	2.7 The Stick-Slip Phenomenon
	2.8 Contribution of Abrasion to Friction
	2.9 Effect of Initial Roughness
	2.10 Rolling Friction
	2.11 Friction and Surface Heating
		2.11.1 Evaluation of the Average Surface Temperature
		2.11.2 Evaluation of the Flash Temperature
	References
3 Lubrication and Lubricants
	3.1 Solid Lubricants
		3.1.1 Graphite
		3.1.2 Diamond-Like Coatings
		3.1.3 Molybdenum Disulphide
		3.1.4 PTFE
		3.1.5 Soft Metals
	3.2 Liquid Lubricants
		3.2.1 Mineral and Synthetic Oils
		3.2.2 Greases
	3.3 Fluid Film Lubrication
	3.4 Boundary Lubrication and Scuffing
	3.5 Mixed Lubrication
	3.6 Lubricated Friction in Case of Large Plastic Deformations
	3.7 Lubricant Selection
	References
4 Wear Mechanisms
	4.1 Adhesive Wear
		4.1.1 Adhesive Wear of Ductile Materials
		4.1.2 Adhesive Wear of Brittle Solids
	4.2 Tribo-Oxidative Wear
		4.2.1 Tribo-Oxidative Wear at High Temperatures
		4.2.2 Tribo-Oxidative Wear at Low Sliding Speed
	4.3 Abrasive Wear
		4.3.1 Abrasive Wear of Ductile Materials
		4.3.2 Abrasive Wear of Brittle Materials
	4.4 Wear by Contact Fatigue
		4.4.1 Contact Fatigue Under Fluid Film Lubrication
		4.4.2 Contact Fatigue in Mixed and Boundary Lubrication Regime
	4.5 Wear Testing
		4.5.1 Pin-on-Disc
		4.5.2 Block-on-Ring
		4.5.3 Disc-on-Disc
		4.5.4 Four-Ball Tribometer
		4.5.5 Dry-Sand, Rubber-Wheel Wear Test (DSRW)
		4.5.6 Pin Abrasion Wear Test (PAT)
		4.5.7 Examination of the Wear Products
	References
5 Wear Processes
	5.1 Sliding Wear
		5.1.1 Wear Curves
		5.1.2 Mild and Severe Wear
		5.1.3 Mild Wear of Materials
		5.1.4 The PV Limit
		5.1.5 The Effect of Lubrication
		5.1.6 Control Methods for Sliding Wear
	5.2 Fretting Wear
	5.3 Rolling---Sliding Wear
		5.3.1 S-N Curves and the Role of Material
		5.3.2 The Influence of Lubrication Regime
		5.3.3 The Influence of Sliding
		5.3.4 The Influence of Lubricant
		5.3.5 Control Methods for Rolling-Sliding Wear
	5.4 Abrasive Wear by Hard, Granular Material
		5.4.1 High-Stress Abrasion
		5.4.2 Low-Stress Abrasion
		5.4.3 Control Methods for Abrasive Wear by Hard, Granular Material
	5.5 Erosive Wear
		5.5.1 Solid Particle Erosion
		5.5.2 Erosion by Liquid Droplets
		5.5.3 Cavitation Erosion
	5.6 Process-Oriented Wear Tests
	References
6 Materials for Tribology
	6.1 Steels
		6.1.1 Sliding Wear
		6.1.2 Wear by Contact Fatigue
		6.1.3 Abrasive Wear by Hard, Granular Material
	6.2 Cast Iron
		6.2.1 Sliding Wear
		6.2.2 Wear by Contact Fatigue
		6.2.3 Abrasive Wear by Hard Particles
	6.3 Copper Alloys
	6.4 Aluminium and Titanium Alloys
	6.5 Advanced Ceramics
		6.5.1 Sliding Wear
		6.5.2 Wear by Contact Fatigue
		6.5.3 Abrasive Wear by Hard, Granular Material
	6.6 Cemented Carbides
		6.6.1 Sliding Wear
		6.6.2 Abrasive Wear by Hard, Granular Material
	6.7 Graphite and Diamond
	6.8 Polymers
		6.8.1 Sliding Wear
		6.8.2 Abrasive Wear by Hard, Granular Material
	References
7 Surface Engineering for Tribology
	7.1 Surface Functional Modifications: General Aspects
	7.2 Treatments for Microstructural Modification
		7.2.1 Mechanical Treatments
		7.2.2 Surface Heat Treatments
	7.3 Thermochemical Diffusion Treatments
		7.3.1 Carburizing
		7.3.2 Nitriding
		7.3.3 Other Treatments
	7.4 Conversion Coatings
		7.4.1 Phosphating
		7.4.2 Anodizing
	7.5 Surface Coatings
		7.5.1 Metallic Plating
			7.5.1.1 Hard Chromium Plating
			7.5.1.2 Electroless Nickel Plating
		7.5.2 Thin Coatings
			7.5.2.1 Coating Technologies
			7.5.2.2 Main Types of Thin Coatings
			7.5.2.3 Tribological Properties of Thin Coatings
		7.5.3 Thick Coatings
			7.5.3.1 Thermal Spraying Coatings
			7.5.3.2 Weld Hardfacings
	7.6 Summary
	References
8 Tribological Systems
	8.1 Sliding Bearings
		8.1.1 Oil Lubricated Journal Bearings
		8.1.2 Unlubricated Sliding Bearings
	8.2 The Piston Ring/Cylinder Liner System
	8.3 Cam/Follower System
	8.4 Rolling Bearings
	8.5 Gears
		8.5.1 Damage by Contact Fatigue
		8.5.2 Damage by Sliding and Its Control
	8.6 Contact Seals
	8.7 Automotive Disk Brakes
	8.8 The Wheel/Rail System
	8.9 Cutting Tools
	8.10 The Grinding Process
	8.11 Hot Forging Dies
	8.12 Rolling Rolls
	8.13 Wire Drawing Dies
	8.14 Hot Extrusion Dies
	References
Index
                        
Document Text Contents
Page 1

Springer Tracts in Mechanical Engineering

Giovanni Straffelini

Friction and
Wear
Methodologies for Design and Control

Page 2

Springer Tracts in Mechanical Engineering

Board of editors

Seung-Bok Choi, Inha University, Incheon, South Korea
Haibin Duan, Beijing University of Aeronautics and Astronautics, Beijing, P.R. China
Yili Fu, Harbin Institute of Technology, Harbin, P.R. China
Jian-Qiao Sun, University of California, Merced, USA

Page 146

this claims for the necessity of adopting a probabilistic design approach when
dealing with ceramic components that are subjected to contact fatigue loading.

It is quite interesting to consider Eqs. 5.10 and 5.13 together, as shown in the
schematization of Fig. 5.9. Generally speaking, ductile materials possess relatively
low hardness and high fracture toughness. Thus, they fall in region A. On the other
hand, brittle materials possess high hardness and relatively low fracture toughness,
which may also depend on their hardness as well. They fall in region C, and their
endurance limit depends much on defects. In the intermediate region, B, materials
possess intermediate values of both hardness and fracture toughness, and they may
behave in a ductile or brittle manner depending on the presence and size of the
defects. This is the case, for example, of carburized steels. They may achieve very
high hardness values after heat treatment but may show a lower endurance limit
than expected, because of the presence of defects (typically inclusions or
precipitates).

Finally, Table 5.4 shows that polymers typically display limited performances as
concerns contact fatigue (even if they display H2/E values similar to those of
bronzes). Such materials are consequently used in mild loading conditions, against
themselves or metals, typically when additional advantages are attained. For
example, they are often used in mild loaded gears working in dry conditions, when
low noise or high resistance to a specific environment are required. As already
highlighted, polymers are also very sensitive to temperature rises, which may also
occur during a cyclic contact loading due to their viscoelastic behaviour.

5.3.2 The Influence of Lubrication Regime

Figure 5.10 schematises the role of the lubrication regime (i.e., of the Λ factor) on
the rolling-sliding wear. Fatigue life is seen to increase with Λ reaching a plateau
for Λ ≈ 3, when fluid film lubrication is attained. A further increase in Λ does not

Hardness H

E
nd

ur
an

ce
l

im
it

p
en

d

Increasing c

A B CFig. 5.9 Schematic diagram
showing the correlation
between the endurance limit
and materials’ hardness

5.3 Rolling—Sliding Wear 135

Page 147

flb10.eps


lead to an appreciable increase in the fatigue life. If Λ is lower than about 1.5,
adhesive wear becomes more important, and the two wear mechanisms may have a
competitive role (wear is important also in pure rolling because of the presence of
micro slip). In this case, a simplified approach is typically adopted, and fatigue life
is firstly assessed. After checking that it is sufficiently long for the given applica-
tion, wear is considered, and the component wear life for an allowable depth of
wear is then verified. However, it is possible that the two mechanisms interact in a
negative or positive way. For instance, wear may produce a surface damage that
favours the surface nucleation of fatigue cracks. Alternatively, wear may remove,
partially or entirely, the surface cracks nucleated by contact fatigue. The subsequent
crack propagation is thus delayed and the overall rolling-sliding resistance is
increased [25]. Different parameters must be balanced in order to take advantage of
wear in limiting contact fatigue damage, and this perspective is limited to a
restricted number of systems.

Most of the experimental investigations carried out so far to assess the role of Λ
on the contact fatigue of materials have been focussed on steels. The researches
reported by Niemann are well known [26]. The Author proposed the following
relationships for various types of steels under pure rolling: pend = 3 H for a line
contact (H is in kg/mm2 and pend in MPa), and pend = 5.25 H for a point contact (the
difference can be clearly attributed to the statistical effects described in Sect. 4.4.1).
If Λ > 3, Eq. 5.9 can be then used, with n > 16. Table 5.6 reports simplified
relations for the evaluation of pend as a function of the lubrication regime, and the

0 1 2 3 4

Contact
fatigue life

Wear rate

Λ

Fig. 5.10 Scheme showing rolling-sliding damage mechanisms as a function of Λ factor

Table 5.6 Typical pend and n values for steels and in line contact for N50 (from different literature
sources)

pend (MPa) n range

Rolling-sliding with boundary lubrication
(Λ < 0.5, μ > 0.1)

1.7 H <8

Rolling-sliding with mixed lubrication 2.25 H (or: 2.76 H −70) 8–16

Rolling-sliding with fluid film lubrication
(Λ > 3, μ < 0.07)

3 H >16

136 5 Wear Processes

http://dx.doi.org/10.1007/978-3-319-05894-8_4

Page 291

Severe oxidation, 92, 93, 120, 161
Severe wear, 77, 117–120, 123, 170, 181–183,

192, 196, 213, 225
Shape factor, 143
Shot peening, 130, 150, 207, 211
Sialon, 179
Silicon carbide, 45, 110, 179, 181, 183, 184,

188
Silicon nitride, 42, 43, 79, 134, 179, 183, 184,

262
Simplified tests, 104, 105
Sliding, 2, 21–23, 25–37, 39, 43, 49, 53, 65,

77, 85–88, 93, 115, 130, 137, 141, 159,
160, 162, 169, 178, 181, 183, 186, 192,
195, 207, 209, 213, 219, 225, 240, 241,
249, 273

Sliding bearings, 57, 122, 177, 186, 237, 245
Sliding speed, 21, 26, 32, 36, 42, 43, 55, 79,

90, 94, 107, 117, 118, 162, 192, 213,
238

Soft metal, 19, 38, 67, 79, 246
Solid lubricants, 30, 35, 40, 61–63, 67, 78, 88,

141, 184, 216, 218, 262, 267
Solid particle erosion (SPE), 149–152, 156,

196, 217
Sommerfeld number, 238
Spalling, 8, 102, 104, 131, 140, 153,

210, 248
Specific energy for cutting, 258
Specific grinding energy, 264, 265
Specific heat, 55, 56, 189
Specific wear coefficient, 107, 118, 120, 122,

160, 170, 177, 179, 181, 213, 214, 217,
219, 225, 227, 231, 267, 270, 272

Spur gears, 247
Sputtering, 222
Static friction force, 21
Steady-state, 24, 38, 118, 124, 128, 238, 239
Steady-state stage, 38, 124
Steels, 31, 45, 52, 70, 121, 129, 133, 136, 142,

146, 151, 159, 162–165, 167, 171, 177,
184, 189, 202, 209, 212, 215, 229, 241,
244

Stellites, 233, 251
Stick regime, 127, 129
Stick-slip, 21, 43, 44
Strain-induced martensitic transformation, 160,

167
Stress intensity factor, 102, 103, 134
Stress intensity threshold, 134

Stress relieving, 160
Strip drawing process, 81, 82
Stylus profilometer, 11
Super-hard ceramics, 262
Surface distress, 80, 82
Surface energies, 16
Surface engineering, 115, 148, 201, 204, 228,

270
Surface heating, 21, 53, 57, 92
Surface rolling, 203, 207
Surface roughness, 10, 11, 14, 21, 33, 37, 48,

66, 77, 82, 108, 139, 189, 192, 213,
217, 219, 229, 231, 238, 244, 246, 248,
250, 262, 269

T
Tangential velocities, 76
Taylor equation, 261
Tempering, 54, 161, 163, 165, 169, 263
Theory of Archard, 86, 89, 260
Thermal conductivities, 55, 57, 120
Thermal diffusivity, 55, 57, 258
Thermal shock, 120, 121, 181, 261
Thermal shock resistance, 181
Thermal spraying, 205, 228, 229, 251
Thermal stresses, 181, 224
Thermoplastics, 122, 144, 191
Thermosets, 191
Thick coatings, 201, 218, 228
Thickeners, 72, 73
Thin coatings, 16, 67, 218, 221–225, 227
Third-body, 40
Three-body abrasion, 44, 47, 95, 98
Thrust bearings, 237
Thrust force, 73–76, 137, 247, 256, 258
Tillage tools, 116, 144, 147
Titanium alloys, 129, 176, 178, 179
Tool steels, 121, 146, 159, 163, 164, 166, 170,

215, 225, 262, 266, 267, 273
Tool wear, 256, 267
Top dead centre, 241, 242
Toyota Diffusion (TD) process, 215
Tractive rolling, 52, 254
Traditional ceramics, 179
Transfer phenomena, 21, 31, 37–39, 49, 50, 89,

177, 269, 273
Transferred layer, 37, 39
Tresca yield stress criterion, 7, 25–27, 260
Tribological compatibility, 17, 31, 88, 192,

240, 261

282 Index

Page 292

Tribological layer, 27, 94
Tribological system, 40, 44–46, 52, 57, 61, 62,

66, 73–75, 78, 80, 82, 85, 88, 104, 110,
115, 119, 122, 125, 129, 131, 142, 144,
150, 154, 169, 178, 201, 222, 237, 244,
245, 256

Tribometers, 105, 155
Tribo-oxidative wear, 31, 90, 93, 94, 111,

117–119, 129, 159, 161, 162, 164, 170,
175, 177, 178, 210, 219, 253

Turning, 12, 256, 258, 260
Two-body abrasion, 44, 46, 48, 96, 98

U
Ultimate tensile strength (UTS), 154
Ultrahigh molecular weight polyethylene

(UHMWPE), 192
Uncompensated acceleration, 256
Unit rolling force, 270, 271
Unlubricated Sliding Bearings, 241
Upsetting, 265–267

V
van der Waals bonds, 15, 17
Viscoelastic contact, 6, 10
Viscosity, 6, 69–72, 75, 76, 78, 80, 81, 138,

140, 195, 238, 246, 267, 269, 272
Viscosity index (VI), 72, 141

W
Water-hammer effect, 154, 155
Water turbines, 150
Wear by contact fatigue, 85, 100, 108, 159,

165, 171, 173, 184, 207, 215, 245
Wear coefficient for abrasive wear, 264
Wear coefficient for adhesive wear, 87, 118,

120, 124, 160
Wear coefficient for erosive wear, 150

Wear coefficient for tribo-oxidative wear, 31,
92

Wear curves, 115, 117, 118, 175
Wear land, 259, 260
Wear maps, 118–120
Wear mechanisms, 85, 100, 105, 115, 118,

120, 131, 136, 177, 234
Wear processes, 27, 85, 86, 115, 131, 155, 159,

169, 229, 234
Wear rate, 68, 87, 90, 93, 98, 110, 115, 117,

118, 122, 128, 139, 143, 146, 147, 152,
154, 175, 178, 186, 187, 189, 192, 196,
219, 220, 226, 232, 253, 260

Wear ring, 272
Wear testing, 86, 104, 147, 155
Wear tracks, 110, 111, 117, 118, 253
Wear transition, 117
Wear volume, 87, 95, 109, 115, 150, 260
Weld hardfacings, 232
Wheel-rail system, 51, 131, 253, 254
Wheel tread, 254, 256
White cast iron, 145, 146, 148, 169, 172, 173
White layer, 13, 162, 212, 213, 215
White metals, 240, 241
Wire drawing dies, 271
Work of adhesion, 16–18, 21, 28, 30, 35, 36,

40, 43, 44, 63, 189, 206, 258, 262
Work piece, 81, 82, 222, 232, 256, 258, 259,

263, 264, 266–269
Worn surfaces, 32, 33, 86, 88, 94, 111, 232

Y
Yield pressure, 7, 14, 46

Z
Zinc dialkil dithiophosphate (ZDDP), 70
Zinc phosphate layers, 216
Zirconia, 179, 181, 229

Index 283

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