Bayer R.G. Mechanical Wear Fundamentals and Testing, Revised and Expanded

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Table 10.1 ( Continued )

Standard (committee) Title Materials (parameters measured) Test conﬁguration

D2047 (D-21 on

polishes)

Static Coefﬁcient of Friction of Polish

Coated Floor Surfaces as Measured

by the James Machine

Flooring materials vs. shoe heels

and soles ( m

and m

)

D2394 (D-7 on wood) Simulated Service Testing of Wood

and Wood-base Finish Flooring

Wood and wood-base ﬂooring vs.

sole leather (m

and m

)

D2714 (D-2 on

lubricants)

Calibration and Operation of Alpha

Model LFW-1 Friction and

Wear Testing Machine

Steel ring vs. block lubricated with

standard oil (m

)

D3028 (D-20 on plastics) Kinetic Coefﬁcient of Friction

of Plastic Solids and Sheeting

Plastic sheets or solids vs. other solids

and m

)

D3108

(D-13 on textiles)

Coefﬁcient of Friction,

Yarn to Solid Material

Textile yarns vs. solids (m

)

D3247 (D-6 on paper) Coefﬁcient of Static Friction of

Corrugated and Solid Fiberboard

Self-mated cardboard (m

)

D3248 (D-6 on paper) Coefﬁcient of Static Friction of

Corrugated and Solid Fiberboard

(inclined plane method)

Self-mated cardboard (m

)

Table 10.1 ( Continued )

Standard (committee) Title Materials (parameters measured) Test conﬁguration

D3334 (D-13 on textiles) Testing of Fabrics Woven from

Polyoleﬁn Monoﬁlaments

Self-mated woven fabric (m

)

D3412 (D-13 on textiles) Coefﬁcient of Friction,

Yarn to Yarn

Continuous ﬁlament and spun

yarns self-mated (m

and m

)

E303 (E-17 on traveled

surfaces)

Measuring Surface Frictional

Properties Using the British

Pendulum Tester

Rubber vs. pavement (BPN,

British Pendulum Number)

E510 (E-17 on

traveled surfaces)

Determining Pavement Surface

Frictional and Polishing

Characteristics Using a Small

Torque Device

Rubber vs. pavement (TN,

torque number)

E670 (E-17 on traveled

surfaces)

Side Force Friction on Paved

Surfaces Using the Mu-Meter

Tires vs. pavement (m)

fry

F

wet

)

Table 10.1 ( Continued )

Standard (committee) Title Materials (parameters measured) Test conﬁguration

E707 (E-17 on

traveled surfaces)

Skid Resistance of Paved Surfaces Using

the North Carolina State University

Variable Speed Friction Tester

Rubber tires vs. pavement

(VSN, variable speed number)

F489 (F-13 on footwear) Rating of Static Coefﬁcient of Shoe

Sole and Heel Materials as Measured

by the James Machine

Leather and rubber sole and heel

material vs. walking surfaces (m

)

F609 (F-13 on footwear) Test Method for Static Slip Resistance

of Footwear, Sole, Heel or Related

Materials by Horizontal Pull

Slipmeter (HPS)

Footwear materials vs. walking

surfaces (m

)

F695 (F-13 on footwear) Evaluation of Test Data Obtained by

Using the Horizontal Slipmeter or the

James Machine for Measurement of

Static Slip Resistance of Footwear,

Sole, Heel, or Related Materials

Footwear materials vs. walking surfaces

(reliable ranking of footwear for slip

resistance)(m

)

F732 (F-4 on medical

and surgical materials)

Reciprocating Pin-on-Flat Evaluation of

Friction and Wear Properties of Poly

meric Materials for Use in Total

Joint Prostheses

Materials for human joints (m

)

Table 10.1 ( Continued )

Standard (committee) Title Materials (parameters measured) Test conﬁguration

G143 (G-2 on wear

and erosion)

Measurement of Web=Roller

Friction Characteristics

Plastic ﬁlms and other ﬂexible web

materials vs. roller surfaces (m

and m

)

G164 (G-2 on wear

and erosion)

Determination of Surface

Lubrication on Flexible Webs

Lubricated ﬂexible web materials

vs. steel (detection of lubricant ﬁlm

on surface) (m

)

Source: Refs. 1–4.

Figure 10.3 Examples of friction behavior in sliding tests. ‘‘A’’ illustrates a friction curve where the

force required to initiate sliding, F

, is higher than the average force needed to sustain motion, F

The static and dynamic coefﬁcients are generally based on these two values, respectively. ‘‘B’’ illus-

trates a tribosystem which does not exhibit a higher breakaway force. This system has a single value

for the coefﬁcient of friction, based on F, the average force to sustain motion. Stick-slip behavior is

illustrated in ‘‘C’’. In this case, the peak value is used to determine the static coefﬁcient of friction.

(From Ref. 1. Reprinted with permission from ASM International.)

is the tilt angle. The tilt angle at which sliding starts gives the static coefﬁcient of

friction. The minimum angle, which is needed to just susta in motion, gives the kin-

etic coefﬁcient. For tests involving sliding over a cylindrical mandrel, the following

relationship is used:

m ¼

lnðT

ð10:3Þ

In this equation, T

and T

are the tensions on each side of the mandrel (T

> T

) is the

difference in tension across the mandrel and is wrap angle in radians.

In friction tests where Eq. (10.1) is used, the friction force is usually measured as a

function of time during the test. Figure 10.3 shows two general forms of these data when

plotted as a function of time or sliding distance. Curve A illustrates a situation where the

static coefﬁcient of friction is different than the kinetic coefﬁcient of friction. In this

case, the static coefﬁcient is based on the initial peak value of the force. The kinetic co-

efﬁcient is generally based on a time-average of the force after slip takes place. Some

initial stick-slip behavior is also shown in this curve. Curve B is a general form where

there is no difference between the static coefﬁcient and the dynamic, as well as no

stick-slip. In either case, these two graphs illustrate the fact that the friction force is

not usually constant but ﬂuctuates in these tests. The ability to resolve such ﬂuctuations,

including stick-slip behavior, curve C, and a difference between static and kinetic coefﬁ-

cients, depends on the resolution capability of the measuring system. In addition, the

stiffness of the apparatus can be a factor in stick-slip behavior and differences between

the static and kinetic coefﬁcients. It is possible that both types of curves could be

observed for the same materials with different instrumentation and apparatus stiffness.

When the normal force is not constant, instantaneous values of the coefﬁcient of friction

can be deﬁned by simultaneously measuring the friction and normal. Again the ability to

resolve short-term ﬂuctuations depends on the instrumentation.

An illustration of stick-slip behavior is also shown in Fig. 10.3, curve C. When this

occurs, only the static coefﬁcient of friction can be determined, using the peak values of

the friction force. It is possible that variations in the peak force might be observed over

time, as a result of changing surface conditions.

As with wear test, it is generally recommended that details of the test be reported,

along with the results.

REFERENCES

1. K Budinski. In: P Blau, ed. Friction, Lubrication, and Wear Technology, ASM Handbook. 18.

Materials Park, OH: ASM International, 1992, pp 45–58.

2. Standard Guide for Measuring and Reporting Friction Coefﬁcients. West Conshohocken,

PA: ASTM G115.

3. Standard Test Method for Measurement of Web=Roller Friction Characteristics. West

Conshohocken, PA: ASTM G143.

4. Standard Test Method for Determination of Surface Lubrication on Flexible Webs. West

Conshohocken, PA: ASTM G164.

Appendix

GALLING THRESHOLD STRESS

Material Pair

Threshold Stress

MPa Kpsi

Silicon bronze (Rb 94) Silicon bronze (Rb 94) 28 4

304 SS (Rb 77) 300 44

1020 (Rb 90) 440C SS (Rc 58) 14 2

1034 (Rc 45) 1034 (Rc 45) 14 2

Nitronic 32 (Rb 94) 14 2

4337 (Rc 48) Nitronic 60 (Rb 94) >350 >51

4337 (Rc 51) 4337 (Rc 45) 14 2

Nitronic 60 (Rb 94) >350 >51

201 SS (Rb 94) 201 SS (Rb 94) 105 15

304 SS (Rb 77) 14 2

630 SS [17-4Ph] (Rc 41) 14 2

S24100 (Rc 21) 284 41

Nitronic 32 (Rb 98) 250 36

Waukesha 88 (Rb 77) >350 >51

301 SS (Rb 87) 416 SS (Rc 37) 21 3

440C (Rc 56) 21 3

Nitronic 60 (Rb 94) >350 >51

303 SS (Rb 81) 303 SS (Rb 81) 14 2

304 SS (Rb 77) 14 2

316 SS (Rb 81) 21 3

410 SS (Rc 38) 28 4

416 SS (Rc 37) 60 8

430 SS (Rb 84) 14 2

440C SS (Rc 56) 35 5

630 SS [17-4Ph] (Rc 45) 21 3

Nitronic 32 (Rb 99) >350 >51

Nitronic 60 (Rb 94) >350 >51

303 SS (Rb 85) 303 SS (Rb 85) 138 20

303 SS (Rb 89) Waukesha 88 (Rb 77) >350 >51

304 SS (Rb 77) Silicon Bronze (Rb 94) 300 44

201 SS (Rb 94) 14 2

303 SS(Rb 81) 14 2

(Continued )