1

2

3

4

.

V2

V

V1

V

5

Wear

situation

Motion/With

or Without Slip

Lubed or

Unlubed

With or

Without

Particles

Typical Mechanisms1

Adhesive Single-Cycle

Deformation

Repeated -

Cycle

Deformation

Chemical Thermal

Sliding2 Unidirection Lubed Without

Unlubed Without 5 6

Lubed With

Unlubed With 5 6

Reciprocating

(large

amplitude)

Lubed Without

Unlubed Without 5 6

Lubed With

Unlubed With 5 6

Reciprocating

(small

amplitude)

Lubed Without

Unlubed Without 5

Lubed With

Unlubed With 5

Rolling3 With slip Lubed Without

Unlubed Without

Lubed With

Unlubed With

Without slip Lubed Without

Unlubed Without

Lubed With

Unlubed With

Impact4 With slip Lubed Without

Unlubed Without

Lubed With

Unlubed With

Without slip

(compound

impact)

Lubed Without

Unlubed Without

Lubed With

Unlubed With

1 Except in hostile environments, where thermal and chemical wear mechanisms can be

significant and dominate the wear behaviour. 2 Repeated-cycle deformation mechanisms tend to be dominant, but chemical mechanisms

can be significant; with particles, abrasive wear can be dominant; mild to severe wear

transitions with load and speed common in unlubricated situations; lubrication generally

required for metal and metal-ceramic pairs; galling and fretting are forms of sliding wear. 3 Mildest wear situation; repeated-cycle deformation mechanisms tend to be dominant;

wear increases with slip and particles; with particles and slip abrasive wear can be

dominant; smooth surface particles preferred. 4 Repeated-cycle deformation mechanisms tend to be dominant; gross plastic deformation

generally unacceptable, unless in short life applications; stresses should be in the elastic

range for lives greater than 106 impacts; wear increases with slip. 5 With metals. 6 With polymers.

6

Asperity Contact Mutual aperity deformationand formation opf adhesive bond

Brittle fracture

Ductile fracture

7

Two-Body Abrasive Wear

Two-Body Abrasive Wear, with Embedded Particles

Three-Body Abrasive Wear

8

High impact velocity; soft

material

High impact velocity; very brittle

material

Slow crack growth in deformed

layers

Impact wear as a form of oxidative

wear

High Impact Energy

Ductile Extrusion from Contact

High Impact Energy

Cracks

BrittleFracture

PlasticallyDeformedLayers Oxygen

Removal ofOxide LayersAfter Impact

Metal

9

Oxide

1 2 3

Regrowth

(a) (b)

10

11

"Running-in"

Wear

Volu

me

Time or Sliding Distance

12

h

KPS V

13

Unlubed

GoodLube

GoodLube

GoodLube

GoodLube

PoorLube

PoorLube

PoorLube

PoorLube

Unlubed

Unlubed

Unlubed

Unlubed

Unlubed Lubed

Lubed

2 -Body

Rampant Benign - EP Action

High Abr.Concentr.

3 - Body Low Abr.Concentr.

ADHESIVEWEAR

ABRASIVEWEAR

CORROSIVEWEAR

FRETTING

IdenticalMetals

CompatibleMetals

Partly CompatibleMetals

Incompatible Metals

Non-metal on Metal or Non-Metal

Excellent Lube

Excellent Lube

ExcellentLube

WEAR COEFFICIENT

10-1 10-2 10-3 10-4 10-5 10-6

14

Wear Mechanism Model Parameters

h

KPS V

n KNvV

9

'

01

2000

m

y

r N

'

r

h

PSk V

tan2

15

nA

VQ ~

AH

FF N~

0

0~

a

vrv

where:

V = Wear volume

An = Apparent contact area

FN = Normal load

H = Hardness of the softer material

v = Sliding velocity

r0 = Radius of the pin

a0 = Thermal diffusivity of the material

16

0.0 0.2 0.4 0.6 0.8 1.00

500

1000

1500

2000

2500

UIC60 900A vs R7 Wear Map

Severe

Mild

Severe -

Catastrophic

Transition

Catastrophic

Rail Head/Wheel TreadRail Gauge/Wheel Flange

Conta

ct P

ressure

(M

Pa)

Sliding Velocity (m/s)

17

18

INC

REA

SIN

G C

OM

PLE

XIT

Y

19

20

Unidirectional sliding

Unidirectional or

oscillatory sliding

Unidirectional sliding

Unidirectional sliding

Unidirectional sliding

Unidirectional sliding or

unidirectional sliding plus

oscillatory motion

Unidirectional sliding

Normal impact and

normal impact plus

sliding

Reciprocating sliding

Unidirectional sliding

Oscillatory sliding

Small amplitude

oscillatory sliding

(fretting motion)

Small amplitude

oscillatory sliding

(fretting motion)

Pure rolling and rolling

plus sliding

Unidirectional sliding

21

Operational

Parameters

Structure of Test

Configuration

Tribometric

Characteristics

Type of motion

Contact geometry

Load

Velocity

Temperature

Duration

Friction force

Friction coefficient

Noise, vibrations

Temperature

Wear

Contact conditions

Surface characteristics

Surface topography

Surface composition

(4)

(3)

(1)

(2)

(1) Triboelement(2) Triboelement(3) Lubricant(4) Atmosphere

22

23

24