Astm stp 1199 1993

Tribology: Wear Test Selection for Design and Application A... This publication, Tribology: Wear Test Selection for Design and Application, contains papers presented at the symposium of

Tribology: Wear Test Selection for Design and Application

A W Ruff and Raymond G Bayer, Editors

ASTM Publication Code Number (PCN)

04-011990-27

AsT

1916 Race Street

Philadelphia, PA 19103

Trlbology : wear test selection for design and application / A.W

and Raymond G Bayer, editors

(STP ; 1199)

Includes bibliographical references and index

ISBN 0-8031-1856-2

I Trlbology I Ruff, Arthur W II Bayer, R G (Raymond

Copyright ©1993 AMERICAN SOCIETY FOR TESTING AND MATERIALS, Philadelphia, PA All rights reserved This material may not be reproduced or copied, in whole or in part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of the publisher

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Each paper published in this volume was evaluated by three peer reviewers The authors addressed all of the reviewers' comments to the satisfaction of both the technical editor(s) and the ASTM Committee on Publications

To make technical information available as quickly as possible, the peer-reviewed papers in this publication were printed "camera-ready" as submitted by the authors

The quality of the papers in this publication reflects not only the obvious efforts of the authors and the technical editor(s), but also the work of these peer reviewers The ASTM Committee on Publications acknowledges with appreciation their dedication and contribution to time and effort on behalf of ASTM

Printed in Baltimore, MD November 1993

This publication, Tribology: Wear Test Selection for Design and Application, contains

papers presented at the symposium of the same name, held in Miami, FL on 9 Dec 1992

The symposium was sponsored by A S T M Committee G-2 on Wear and Erosion A W Ruff

of the National Institute for Standards and Technology (NIST) in Gaithersburg, M D and

Raymond G Bayer, a Consultant in Vestal, NY, presided as symposium chairmen and are

editors of the resulting publication

Realizing Bench Test Solutions to Field Tribology Problems by Utilizing

Extreme Pressure and Anti-Wear Properties of Lubricants: A Critical Study of

Current Test Methods and Suggestions for the F u t u r e - - M A PLINT AND

A Retrospective Survey of the Use of Laboratory Tests to Simulate Internal

Laboratory Wear Tests for Qualifying Automotive Air-Conditioning Lubricants for Use with Refrigerant H F C - 1 3 4 a - - s I TSEREGOUNIS, J A SPEAROT, V G

R O U N D S , J A B A K E R , A N D B C S E R R I A N N E 149 Friction and W e a r Set-Up for Simulation of Knee J o i n t - - s BAHADUR 173 The Use o f S u r f a c e L a y e r Activation to Measure Ring Wear in an Operating Heavy Duty Diesel E n g i n e - - J J TRUHAN AND C B COVINGTON 177

A S T M ' s Committee on Wear and Erosion has sponsored numerous symposia in subject areas such as wear, solid particle erosion, cavitation, and wear modeling The focus of those symposia and the resulting Special Technical Publications (STPs) involved numerous sci- entific and engineering subjects, as well as the matter of test methodology One important area that has not been covered so far is the connection between laboratory testing and actual operating performance of systems or components The connection between laboratory test- ing, test results, and final design and performance is a crucial one in the practical application

of tribology science and engineering

The very nature of wear makes this connection a complex one It is well recognized that wear, as well as erosion and friction, is not intrinsic to any material or set of materials but depends on the application parameters, such as load, pressure, temperature, environment, and so forth, as well as the material properties Knowledge of the functional dependencies

of wear on such parameters is often qualitative, incomplete, and in some cases, not known

at all As a result, the validity or accuracy of any extrapolation of laboratory test results to specific applications is generally a major concern In view of this, the Committee felt that

it would be desirable to organize a symposium specifically focusing on the successful con- nection of laboratory test results and application performance It was hoped that this would help to identify some methods for establishing or ensuring valid connections of this kind, or

at least, would provide some guidance

Since the problem of relating laboratory test results to application performance is pri- marily faced in industry, strong industrial participation in the symposium was necessary While a wide cross section of U.S industry is represented in the Committee, the call-for- papers was not limited to the Committee or to A S T M membership As a result, 12 papers focusing on wear test selection for design and application were accepted and presented at the symposium, primarily from industry sources

A common problem in addressing design and application issues concerning wear and erosion is the selection of one or more tests that will reliably rank or select materials among those of initial interest, and also provide some measure of relative performance of the materials in the application As indicated in several prior STPs~concerning the selection and use of tests for different categories of materials, simulation of the application is a key to the connection of test results with actual performance Often standard wear tests, including the tests developed by the Committee, do not meet the requirements of simulative testing for an application Simulation testing includes critical use conditions, such as contact pres- sure, contact geometry, and the specific environment, which generally are not duplicated

in standard tests Frequently it takes an expert in wear and erosion phenomena to correctly design or select the simulative test required

Since such expertise may not be available in an organization, consultants are frequently called upon to develop such testing protocol While this might seem a costly approach, the alternative to simulative testing is to use full-scale component or system testing, which is often too time consuming and expensive

One of the aims of the symposium and this STP was to show by example how successful simulative testing has been accomplished Specific examples are presented from a number

of applications involving different forms of wear, including some from such specialized areas

as computer peripherals, engines, and prosthetic devices A n important consideration in all the presentations was the identification of critical use conditions It is hoped that by reading

vii

the examples presented in the papers contained in this STP, readers can find guidance in

addressing their individual wear problems

The existence of this common theme in these papers suggests that it might be possible to

develop a standard guide for the selection and development of simulative laboratory wear

tests Such a guide would likely comprise a check list of considerations, with appropriate

weighing and priorities indicated For example, the matter of contact area and pressure

would be treated, with discussion on the sensitivity of some materials, for example, polymers,

to small contact area or high pressure Conformity of contact, that is, the closeness of the

geometric shapes, would be another important area It is hoped that such a document,

developed using the broad range of experience in wear and erosion application encompassed

in the Committee membership, would serve the technical community in this important area

of design and application It is anticipated that the Committee soon will initiate activity

pursuant to the development of such a standard

Finally, the chairmen of this symposium gratefully acknowledges the contribution of all

the presenters and of the discussors during the meeting, as well as the contributions of the

reviewers of the papers contained in the STP It is hoped that all who participated gained

a clearer view of the range of problems concerning end-use applications, and that the readers

of these papers will find them beneficial in resolving their problems

D E V E L O P M E N T OF A W E A R TEST F O R A D I A B A T I C D I E S E L R I N G A N D L I N E R

M A T E R I A L S

REFERENCE: Glaeser, W.A a n d Gaydos, P.A., " D e v e l o p m e n t of a W e a r Test for A d i a b a t i c Diesel Engine Ring a n d Liner M a t e r i a l s , " Triboloqy: W e a r Test S e l e c t i o n for D e s i Q n a n d Application A S T M STP 1199, A.W Ruff a n d

R a y m o n d G Bayer, A m e r i c a n Society for T e s t i n g a n d Materials,

Philadelphia, 1993

ABSTRACT: A high t e m p e r a t u r e apparatus has b e e n d e v e l o p e d for

d e t e r m i n i n g the wear c h a r a c t e r i s t i c s of refractory m a t e r i a l s for p i s t o n ring a n d cylinders in low heat loss a d v a n c e d diesel engines O p e r a t i o n

of the a p p a r a t u s has d e m o n s t r a t e d g o o d simulation w i t h actual engine experience C e r a m i c m a t e r i a l s a n d coatings e v a l u a t e d include

zirconias, silicon carbide, silicon nitride, a n d two c h r o m i u m oxides Both l i q u i d a n d solid lubricants have also b e e n e v a l u a t e d with ceramic

i n v o l v e d the i n v e s t i g a t i o n of the wear mechanisms of ceramics u n d e r

a d v a n c e d i e s e l engine o p e r a t i n g conditions

The a d i a b a t i c diesel engine was r e c o m m e n d e d b y ASME as a p o t e n t i a l

e n e r g y saver This was b a s e d on the p r i n c i p l e that the higher the

o p e r a t i n g t e m p e r a t u r e of a diesel engine, the g r e a t e r the thermal

e f f i c i e n c y of the system It was r e c o g n i z e d that heat c o u l d be lost

t h r o u g h the exhaust a n d r e g e n e r a t i o n systems were also considered The ideal engine w o u l d have an i n s u l a t e d combustion c h a m b e r and no c o o l i n g system The e l i m i n a t i o n of the c o n v e n t i o n a l water c o o l i n g system w o u l d also save e n e r g y a n d cost

It was e s t i m a t e d that cylinder t e m p e r a t u r e s in the adiabatic engine w o u l d reach 460 - 850°C [i] thus p r e c l u d i n g c o n v e n t i o n a l m o t o r oils a n d requiring c e r a m i c cylinder liners, p i s t o n crowns, piston rings

a n d valves In addition, it was d e t e r m i n e d that engine life w o u l d be

i n c r e a s e d o w i n g to the superior w e a r resistance of ceramics

B a t t e l l e Columbus Laboratories

I

Load

I._m /~"Ring" specimens

/ /

/ / / / / / / / / / / /

specimens Figure I Test Specimen Configuration and

Loading

Figure 2 Ring and cylinder specimens after test

Figure 3 Photograph of Battelle high temperature diesel engine wear

apparatus

of the rig H e a t i n g e l e m e n t s w e r e m o u n t e d in t h e c h a m b e r a n d exhaust

g a s f r o m a s m a l l d i e s e l e n g i n e (E) w a s p i p e d i n t o the c h a m b e r The d e a d

P a r t i a l l y s t a b i l i z e d zirconia was s e l e c t e d b e c a u s e of its h i g h

f r a c t u r e toughness a n d h i g h thermal insulating properties L i m i t e d

experience h a d s h o w n PSZ to h a v e g o o d w e a r resistance

A series of experiments w a s p e r f o r m e d at I000 r p m in diesel

exhaust a n d t e m p e r a t u r e f r o m 290 ~ to 540~ M a x i m u m loads w e r e 7.7

N/mm

These experiments s h o w e d that without lubrication, the ceramics

w e r e not a p p r o p r i a t e for e n g i n e parts F r i c t i o n was h i g h - o n the order

of 0.2 to 0.6 a n d the zirconia s p a l l e d badly H i g h t e m p e r a t u r e heat

streaks c o u l d be seen o n t h e cylinder specimens d u r i n g operation A n

example is shown in Figure 4 Some experiments h a d to b e shut down

p r e m a t u r e l y as the specimens deteriorated Typical surface conditions

of the ceramic parts after w e a r are shown in Figures 5 a n d 6

F r i c t i o n levels of the ceramics w e r e m u c h too h i g h for engine

application P i s t o n f r i c t i o n coefficients in c o n v e n t i o n a l engines are

two orders of m a g n i t u d e lower than the above m e a s u r e d values

C a l c u l a t i o n s s h o w that a t e n - f o l d increase in p i s t o n ring friction can

increase f r i c t i o n h o r s e p o w e r to two-thirds or m o r e of a n engine's

h o r s e p o w e r output T h e r e f o r e h i g h ring f r i c t i o n w o u l d defeat the

p u r p o s e of h i g h t e m p e r a t u r e o p e r a t i o n to increase engine e f f i c i e n c y

a n d lubrication w a s c o n s i d e r e d essential

Figure 5 Wear surface of PSZ c y l i n d e r s p e c i m e n showing thermal

shock f r a c t u r e pattern

Figure 6 Surface of s i l i c o n carbide ring s p e c i m e n showing

fracture along edges

Table 2 C o m p a r i s o n of engine w e a r r i g results for oil lubrication a n d

c a l c u l a t e d w e a r for a conventional diesel truck engine

M a t e r i a l T e m p e r a t u r e R i n g l o a d W e a r

R i n g Cylinder Lubricant C N / m m Coeff

Cr Cast iron SAE 30 100 17.5 5 x 10 -9 3

Cr Cast iron SDL-I i00 12.3 8 x 10 -9

Cr203 Cr203 SDL-I 260 14.5 3 x 10 -6

F r i c t i o n c o e f f i c i e n t s for the 100~ SDL-I r u n r a n g e d b e t w e e n

0.03 a n d 0.04 The c h r o m i a r a n w i t h a coefficient of f r i c t i o n b e t w e e n

0.05 a n d 0.08 at 260~ The f r i c t i o n v a l u e s c e r t a i n l y w e r e more w i t h i n

the a c c e p t e d range for engine o p e r a t i o n a n d the w e a r coefficient

m e a s u r e d at I00~ was h i g h e r than diesel e x p e r i e n c e (as shown in the

first line in table 2.) but not objectionable C o m p a r i s o n w i t h actual

diesel o p e r a t i n g f r i c t i o n a n d w e a r v a l u e s showed that the test rig was

s i m u l a t i n g the diesel engine well

A n u m b e r of h i g h temperature liquid lubricants w e r e i n v e s t i g a t e d

in the engine s i m u l a t i o n rig W e a r c o e f f i c i e n t s r a n g e d b e t w e e n

3 x i0 -s for X-IP to 2 x 10 -6 for 0S-124 at 460~ F r i c t i o n coefficients

v a r i e d b e t w e e n 0.02 to 0.19

L i q u i d lubricants a l l o w e d o p e r a t i o n of the ceramic ring and

c y l i n d e r m a t e r i a l s w i t h o u t excessive frictional h e a t i n g a n d d e s t r u c t i o n

of the rings However, the liquid lubricants limited the m a x i m u m

o p e r a t i n g t e m p e r a t u r e s to a r o u n d 460~ the lower limit of adiabatic

diesel operation These operations d i d a l l o w p r e l i m i n a r y e x p l o r a t i o n of

the k i n d of w e a r m e c h a n i s m s w h i c h might bre e x p e c t e d for ceramics

o p e r a t i n g in h i g h t e m p e r a t u r e ring a n d cylinder conditions

T h e lubricated experiments a l s o d e m o n s t r a t e d that Cr203 coatings

were feasible for p i s t o n rin~ materials

The i n v e s t i g a t i o n t h e n turned to solid lubricants for higher

t e m p e r a t u r e experiments

'The first line g i v e s values a p p r o p r i a t e to c a l c u l a t e d w e a r coefficient

for a typical diesel t r u c k operation

The first a n d t h i r d s o l i d lubricant f o r m u l a t i o n s s h o w e d low

durability Therefore, the second formulation, d e v e l o p e d b y Boes and

Chamberlain[8], was u s e d in most of the h i g h temperature experiments

This f o r m u l a t i o n c o u l d be m o l d e d into s o l i d ring specimens w i t h enough

strength to survive ring s l i d i n g contact

The c h r o m e c a r b i d e - f l u o r i d e c o m p o s i t i o n was coated o n stainless steel

ring specimens a n d u s e d for the highest temperature o p e r a t i o n

investigated

since t h e h a r d n e s s of the s o l i d lubricant m a t e r i a l s c o u l d not b e

determined, a w e a r factor (volume p e r load-distance) w a s used w e a r w a s

m e a s u r e d as r e d u c t i o n in thickness of the r i n g specimen

This m e a s u r e m e n t w a s u s e d to c o m p a r e p e r f o r m a n c e s of v a r i o u s lubricant

formulations

T h e s o l i d lubricant r i n g material d e m o n s t r a t e d exceptional

f r i c t i o n characteristics F r i c t i o n c o e f f i c i e n t s w e r e almost as low as

the liquid l u b r i c a t e d rings W e a r w a s two to t h r e e orders of m a g n i t u d e

larger than liquid lubricated ceramic rings T h e c o m p o s i t e ring t e n d e d

to chip a n d spall, however, m a k i n g it a p o o r c a n d i d a t e for a ring

material However, it c o u l d be u s e d as a w i p e r r i n g to transfer

lubricant to the c y l i n d e r s u r f a c e to lubricate a ceramic t o p ring

C O N C L U S I O N S

A n a p p a r a t u s has b e e n d e s i g n e d a n d b u i l t to evaluate c e r a m i c ring

a n d cylinder m a t e r i a l s for a d v a n c e d low heat loss diesel engines The

apparatus a l l o w s specimens of simple g e o m e t r y to b e u s e d for w e a r a n d

f r i c t i o n e v a l u a t i o n s u n d e r diesel o p e r a t i n g conditions S i n c e t h e

s l i d i n g velocities, ring unit loading, c o m b u s t i o n chamber t e m p e r a t u r e s

a n d g a s e o u s environment are c l o s e l y simulated, the o p e r a t i n g

c h a r a c t e r i s t i c s of v a r i o u s m a t e r i a l s a n d lubricants c a n b e determined

B a s e l i n e e x p e r i m e n t s w i t h a cast iron liner a n d c h r o m i u m p l a t e d ring

specimens l u b r i c a t e d w i t h engine oil indicated that the w e a r a n d

f r i c t i o n v a l u e s f r o m this a p p a r a t u s are w i t h i n reasonable limits for

actual engine exDerience T h i s i n f o r m a t i o n c a n b e u s e d as a g u i d e to

the d e s i g n of a d i a b a t i c diesel engines

the design of adiabatic diesel engines

ACKNOWLEDGMENTS

This work was supported by U.S Department of Energy, Oak Ridge National Laboratory The input of K.F Dufrane of Battelle is gratefully

appreciated

R E F E R E N C E S

[1] Radovanovic, R., Kamo, R a n d Dufrane, K , " T r i b o l o g i c a l

I n v e s t i g a t i o n for an Insulated Diesel Engine, SAE p a p e r

830319

[2] Scott, H.G., "Friction a n d W e a r of Zirconia at V e r y L o w

S l i d i n g Speeds," Wear of M a t e r i a l s 1985, ~ M E , N e w York City,

[4] Yust, C.S a n d Cargnan, F.J., "Observations o n the S l i d i n g

W e a r of Ceramics," ABLE Transamtions, v 28, 2, 245-252

[5] Sibley, L.B., Mace, A.E., Greiser, D.R a n d Allen, C.M.,

"Characteristics G o v e r n i n g the F r i c t i o n a n d w e a r Behavior

of R e f r a c t o r y M a t e r i a l s for H i g h T e m p e r a t u r e Seals a n d

Bearings," W.A.D.C Tech Renort 60-54, (May 1960)

[6] Dufrane, K.F a n d Glaeser, W.A., "Wear of Ceramics in

A d v a n c e d Heat Engine A p p l i c a t i o n s , " W e a r of Materials 1987,

ASME, N e w York City, 285-291

[7] Dufrane, K.F., "Sliding P e r f o r m a n c e of Ceramics for A d v a n c e d

vol 7, ( 2 ) , A m e r i c a n Ceramic Society, 1986, 1052-1059

Heat Engine," Ceramic E n Q i n e e r i n a a n d ~ i e n c e Proceedings,

[8] Boes, D.J a n d Chamberlain, B., "Chemical Interactions

I n v o l v e d in the Formation of O x i d a t i o n - R e s i s t a n t Solid

Lubricant Composites," A ~ L E TRansactions, 28, 1984,

231-238

w i t h a surface r o u g h n e s s of 0.2/xn Ra The v a r i a b i l i t y of

the f r i c t i o n force is p r o p o s e d as the p a r a m e t e r to be

m e a s u r e d w h e n f r e e d o m from s t i c k - s l i p b e h a v i o r is the

s y s t e m goal

KEYWORDS: friction, c o e f f i c i e n t of friction, p l a s t i c

bearings, p l a i n bearings, ball b u s h i n g s

The static c o e f f i c i e n t s of f r i c t i o n of the v a r i o u s test

couples are p r e s e n t e d in Figure 4 The ball b u s h i n g s

w i t h the lowest spring force (0.I a n d 0.125 m m shims),

had the lowest f r i c t i o n coefficients Two of the p l a s t i c

b u s h i n g s h a d the lowest v a r i a b i l i t y in static c o e f f i c i e n t

of friction, the PTFE l u b r i c a t e d acetal and the oil-

i m p r e g n a t e d UHMWPE The k i n e t i c f r i c t i o n c o e f f i c i e n t s

are c o m p a r e d in Figure 5 The ball b u s h i n g w i t h the

lowest s p r i n g force a l s o has the lowest m e a n k i n e t i c

c o e f f i c i e n t of friction, 0.03 The P o l y i m i d e / P T F E b l e n d

had the h i g h e s t f r i c t i o n coefficient, 0.3

The v a r i a b i l i t y of the f r i c t i o n t h r o u g h a test was

m e a s u r e d b y readings t a k e n every 6 seconds d u r i n g the

test If this v a r i a b i l i t y is a n a l y z e d statistically, the

data s u g g e s t that all ball b u s h i n g couples h a d

e s s e n t i a l l y the same k i n e t i c c o e f f i c i e n t of friction

The d i f f e r e n c e s w e r e not s t a t i s t i c a l l y significant

However, the w a y that we i n t e r p r e t these d a t a is that the

v a r i a b i l i t y as m e a s u r e d by the s t a n d a r d d e v i a t i o n of the

individual readings is an a c c u r a t e m e a s u r e of f r e e d o m

from s t i c k - s l i p b e h a v i o r and u s i n g this premise, the

couple w i t h the most f a v o r a b l e f r i c t i o n c h a r a c t e r i s t i c s

for the a p p l i c a t i o n was the o i l - i m p r e g n a t e d u l t r a h i g h

test of the p o l y i m i d e b u s h i n g s w h e n they h a d e s s e n t i a l l y

zero clearance T y p i c a l f r i c t i o n force traces for the

v a r i o u s test couples are p r e s e n t e d in Figures 6, 7, and

8 It can be seen that the s t i c k - s l i p b e h a v i o r

d i s a p p e a r e d w i t h the p o l y i m i d e b u s h i n g s w h e n there was a

m o d i c u m of c l e a r a n c e b e t w e e n the shaft and bushing

T h e s e r e c o r d i n g s d e m o n s t r a t e w h y a v e r a g e f r i c t i o n

c o e f f i c i e n t s m a y p r o d u c e m i s i n t e r p r e t a t i o n of the s y s t e m

the a c e t a l a n d U H M W P E are the m o s t free of the force

p e r t u r b a t i o n s p r o d u c e d b y s t i c k - s l i p behavior

, :::1,:-I , '- Be B.s.Ing~O.O0~ spring _i_ i~ ~ : - 2 ~ t L

' .Test #1: ~ I ~ t " ~ ""I :., , '- ,t,~:,-,].,I.:

!I~ 9 ~I,~iI ':,:;:!::'I '' p,,C,pTFE Sush,,gs ," I~~i : i-q~I :"i.~.I%

~ulii~ ;i r.4 i~u-~;li~;I~ liil~:,~li ~ I~l: i-J~II

~ ' ~ ' 1 I i I : , ~ l ~ l o J n l " l < ; : 1 ; , I , .1 - I I b : ~ l !

:.,_

.~::,, ~ i ; ! ,-, ,1 ', i! ~: ~ ~,~ I! ~!I~ ~ !,! , ',#! ,: :~ i,i I"i:"":'- , :~ :- ~., , ~ , ~"' ,,," - , - ' .~ ':I: -

9 ,:,-:li :I , :~, ~ ' , "; : ;- i ~ I:I.:!: I Vl

k F - + ~ - I - I + + I PIM B r o n z e B u s h l n g s ~;i=:l-r.+ - ~ - ~ " : l : :

, , ; I ; I.: 'I: '; ::~ii: Y,i::; :++.j +.ti.r[i+,+ib:::l -+ ,,) :+ -+.; :;:.~

?

Figure 9 D e s i g n p r o p o s a l for e l i m i n a t i n g running

clearance effects in p l a i n bearings

S U M M A R Y

The results of these l a b o r a t o r y tests suggest that

p l a s t i c p l a i n b e a r i n g s made from P T F E - f i l l e d acetal or

o i l - i m p r e g n a t e d u l t r a h i g h m o l e c u l a r weight p o l y e t h y l e n e

p r o v i d e f r i c t i o n c o e f f i c i e n t s as low as ball bushings,

but they are s i g n i f i c a n t l y b e t t e r than the ball bushings

in f r e e d o m from s t i c k - s l i p behavior The ball bushings

s e e m to have f r i c t i o n p e r t u r b a t i o n s t h a t m a y be caused by

the ball r e c i r c u l a t i o n system

Potential o p e r a t i n g p r o b l e m s caused by p l a i n - b e a r i n g

running clearance can be dealt w i t h by i n s t a l l a t i o n of

some sort of "antibacklash" device such as the one

i l l u s t r a t e d in Figure 9

In summary, the study indicated that the d e s i g n p r o b l e m

of "erratic motion" could be solved by u s i n g p l a s t i c

p l a i n b e a r i n g s instead of ball bushings It was also

d e t e r m i n e d that it was more a p p r o p r i a t e to rate system

f r i c t i o n c h a r a c t e r i s t i c s by r a n k i n g f r i c t i o n force

v a r i a b i l i t y rather than by r a n k i n g average f r i c t i o n

forces

R E F E R E N C E S

(I) M a c h i n e r y ' s H a n d b o o k 23 Edition, Ryffel, H H., Ed.,

N e w York: Industrial Press IC, 1988, p 482

(2) M e c h a n i c a l E n g i n e e r ' s Handbook, Baumeisterl T.g Ed.,

N e w York: M c G r a w Hill Book Co., 1968, pp 3-40

(3) General M a g n a p l a t e F r i c t i o n Data, London, NJ:

STP 1105, Ludema, K G., Bayer, R A., Blau, P J.~

and Littman, W., Eds., Philadelphia: A m e r i c a n

S o c i e t y for T e s t i n g and Materials, 1991

(7 Bahadur, S., "Dependence of Polymer S l i d i n g Friction

as Normal Load and Contact Pressure," WEAR, 29,

1974, pp 223-226

(8 Polymer M a t e r i a l s for Bearing Surfaces, Warrington,

UK: N a t i o n a l Center of Tribology, 1983, pp 25-26

(9 Sail, E., "A S t a t i s t i c a l A p p r o a c h to R u n - i n and the

D e p e n d e n c e of the Coefficient of F r i c t i o n on

Velocity," WEAR, 39, 1975, pp 29-38

(I0) IPSO/TR 7 1 4 7 - 1 9 8 5 E Plain B e a r i n g s - T e s t i n q of the

T r i b o l o g i c a l B e h a v i o r of Plastics, Geneva:

International O r g a n i z a t i o n for Standardization, 1985

(II) I P S O / T R : / I - 1 9 8 5 Plain Bearings - T e s t i n q of the

T r i b o l o g i c a l B e h a v i o r of B e a r i n q Materials, Geneva:

International O r g a n i z a t i o n for Standardization, 1985

(12) ISO/TR 9993:1989(E) Plain B e a r i n q s T r i b o l o g i c a l

B e h a v i o r of B e a r i n g Materials for L u b r i c a t i o n

Applications, Geneva: International O r g a n i z a t i o n

for Standardization, 1989

LABORATORY RND ROBOT WEAR TEST SELECTION FOR COMPUTER PERIPHERALS

REFERENCE: Bayer, R G., " L a b o r a t o r y and Robot Wear Test S e l e c t i o n f o r

Computer Peripheralsw" T r i b o l o q y : Wear Test S e l e c t i o n f o r Desiqn and

A p p l i c a t i o n , ASTM STP 1199, A W Ruff, and Raymond G Bayer, Eds.,

American S o c i e t y f o r Testing and M a t e r i a l s , P h i l a d e l p h i a , 1993

A~TRACT: This paper discusses unique wear t e s t s used to address wear

problems in computer p e r i p h e r a l s These examples i n c l u d e some f o r

which t r i b o m e t e r s were developed and o t h e r s which i n v o l v e d the use o f

modified machines or machine sub-assemblies The former type t e s t s are

r e f e r r e d to as l a b o r a t o r y wear t e s t s ; the l a t t e r , r o b o t wear t e s t s

Several o f the t e s t s are r e l a t e d to the wear associated w i t h paper,

p r i n t e r r i b b o n s , and magnetic tape Because o f the low wear r e s i s t a n c e

o f these m a t e r i a l s , s p e c i a l t e s t c o n f i g u r a t i o n s are r e q u i r e d to

c h a r a c t e r i z e the wear r e s i s t a n c e o f much harder m a t e r i a l s to wear by

these m a t e r i a l s Tests, used to addressed c o n d i t i o n s of s l i d i n g ,

combined impact and s l i d i n g , and combined s l i p and r o l l i n g in computer

a p p l i c a t i o n s , are also described The c o r r e l a t i o n o f these t e s t s w i t h

f i e l d performance, the m o d i f i c a t i o n o f these t e s t s f o r d i f f e r e n t types

o f m a t e r i a l s , and the r e l a t i o n s h i p of these t e s t s to engineering wear

models are discussed The general methodology t h a t was used in the

development and s e l e c t i o n o f these t e s t s is also presented These

t e s t s were used in s e v e r a l ways to support machine development and

product engineering programs associated w i t h impact and non-impact

p r i n t i n g , check s o r t i n g , magnetic r e c o r d i n g , and e l e c t r o n i c packaging

One was to determine wear c o e f f i c i e n t s needed f o r wear l i f e p r o j e c t i o n s

of components and designs A second was the ranking o f m a t e r i a l s i n

terms of t h e i r wear r e s i s t a n c e to support m a t e r i a l s e l e c t i o n A t h i r d

was the e v a l u a t i o n o f the e f f e c t s of d i f f e r e n t design parameters on

wear, such as alignment, roughness, shape, and load

KEY~]R~: wear t e s t s , wear t e s t methods, computers, computer

p e r i p h e r a l s , magnetic tapes, paper, r i b b o n s , p r i n t e r s , check s o r t e r s ,

e l e c t r i c a l connectors, motors, magnetic heads

In general there are p r i m a r i l y two f a c t o r s which i n f l u e n c e the

s e l e c t i o n of wear t e s t s One is the n a t u r e of the wear s i t u a t i o n The

other i s the i n f o r m a t i o n or data t h a t i s desired from the wear t e s t s

The f i r s t comes from the general need to s i m u l a t e the a p p l i c a t i o n in

I C o n s u l t a n t , 4609 Marshall Dr W., V e s t a l , NY 13850

31

the wear t e s t [ s The second i s r e l a t e d to the goal o f the wear

study, e g m a t e r i a l development, design use, fundamental i n f o r m a t i o n ,

e t c [ e , 5 ] This o f t e n r e f l e c t s the n a t u r e o f the group i n v o l v e d

Consequently, the t e s t s discussed in t h i s paper r e f l e c t not o n l y the

nature o f the wear problems encountered in computer p e r i p h e r a l

equipment but the design goals set f o r these types of products, as w e l l

as the background of the personnel addressing these wear problems

A wide range of wear s i t u a t i o n s are encountered i n p r i n t e r s ,

check s o r t e r s , storage devices, and o t h e r pieces o f equipment t h a t are

p e r i p h e r a l elements in computer systems Some of these i n v o l v e common

mechanical elements, such as gears, b e a r i n g s , and cams Others i n v o l v e

unique elements and i n t e r f a c e c o n d i t i o n s , which may be l i m i t e d to a

s i n g l e machine but more l i k e l y to a type o f machine F r e q u e n t l y the

duty c y c l e s , motions, loading c o n d i t i o n s , and r e q u i r e d t o l e r a n c e s

associated w i t h the common mechanical elements tended to make these

s i t u a t i o n s unique, as w e l l While some wear t e s t i n g was r e l a t e d to

common mechanical elements, the ma3ority was r e l a t e d to components and

design s p e c i f i c a l l y associated w i t h computer p e r i p h e r a l s

APPLICATION CHARACTERISTICS

L i f e Requirements

For most s i t u a t i o n s performance was a d v e r s e l y a f f e c t e d by small

amounts o f wear Allowed wear depths in these a p p l i c a t i o n s were

g e n e r a l l y less than Ie5 ~m and in some cases less than 50 Hm In most

cases the component was expected to perform s a t i s f a c t o r i l y f o r several

years, e g 5 to 10 years, w i t h o u t maintenance The number o f

o p e r a t i n g c y c l e s associated w i t h many o f these l i f e t i m e s was o f t e n in

the range o f 100 m i l l i o n or more In c e r t a i n s i t u a t i o n s they were much

less For example, less than I00 cycles o f o p e r a t i o n s were o f t e n

r e q u i r e d f o r e l e c t r i c a l c o n t a c t s Components such as l a t c h e s and

hinges also tended to have lower l i f e requirements

Loadinq and Geometry

In computer and computer p e r i p h e r a l a p p l i c a t i o n s p a r t s are

g e n e r a l l y s m a l l , e g dimensions order o f c e n t i m e t e r s or less Loads

tend to be l i g h t , e g g e n e r a l l y in the range o f 1 to 10 N For some

s i t u a t i o n , higher loads, e g up to 50 N, might occur f o r short p e r i o d s

o f time Stress l e v e l s can be high because o f the small s i z e and non-

conforming shapes of the components Motions encountered are r o l l i n g ,

s l i d i n g , impact, and m i x t u r e s o f these

M a t e r i a l s

A l l types of m a t e r i a l s and c o a t i n g s tended to be used in these

a p p l i c a t i o n s , e g metals, ceramics, p l a s t i c s , elastomers, composites,

e l e c t r o - p l a t e s , v a p o r - d e p o s i t e d c o a t i n g s , e t c Where p o s s i b l e

l u b r i c a t i o n is used i n these a p p l i c a t i o n s and may i n v o l v e the use o f

o i l s , greases, or s o l i d l u b r i c a n t s However, the amount o f l u b r i c a n t

a v a i l a b l e to the i n t e r f a c e i s g e n e r a l l y s m a l l With o i l s i t is

t y p i c a l l y in the form of a t h i n f i l m on the c o n t a c t i n g surfaces [ 4 , 5 ]

TE5T PURPOSES

In general the deslgn goal of the wear studies or evaluations was

to insure a minimum wear l i f e , while s a t i s f y i n g other design

requirements, such as f u n c t i o n , cost, and m a n u f a c t u r a b i l i t y Wear

performance was considered an i n t e g r a l p o r t i o n of the design This

f r e q u e n t l y required the development engineer to make t r a d e - o f f s in

parameters which a f f e c t wear, so that the a l l the design requirements

could be simultaneously s a t i s f i e d To support such an approach i t was

necessary to do wear t e s t s f o r a v a r i e t y of purposes In a d d i t i o n to

ranking m a t e r i a l s , wear t e s t s were done to i n v e s t i g a t e the e f f e c t o f

various design f a c t o r s on wear, to c h a r a c t e r i z e and understand wear

behavior under s p e c i f i c c o n d i t i o n s , to determine c o e f f i c i e n t s

associated with various models f o r wear, and to formulate engineering

models f o r wear In our case the general nature of the approaches to

wear concerns resulted from the natural pressure of development

engineers f o r such information and the background of the t r i b o l o g i s t s

involved, who tended to be mechanical engineers and p h y s i c a l

s c i e n t i s t s , rather than material s c i e n t i s t s and engineers

TEST ~PPARRTUS AND METHODS

A l l of these elements tended to have a profound e f f e c t on the

s e l e c t i o n of the t e s t methods and apparatus used In general standard

wear t e s t methods and equipment were not used to evaluate wear behavior

f o r these a p p l i c a t i o n s There were three major reasons f o r t h i s One

was s i m u l a t i o n In some cases the wear s i t u a t i o n was so unique that a

standard t e s t or apparatus did not e x i s t f o r i t In others cases i t

was f e l t that these apparatus could not provide adequate simulation in

terms of loads, s i z e , shapes, and counterface c o n d i t i o n s

The second reason was that i t was g e n e r a l l y concluded that

standard t e s t methods could not provide the information wanted from the

wear t e s t s Since i n i t i a l wear behavior tended to be ignored in

standard t e s t s , these t e s t methods were g e n e r a l l y not s u i t a b l e f o r the

small amounts of wear which were of i n t e r e s t These methods tend to be

more s u i t a b l e f o r m a t e r i a l comparison than e v a l u a t i n g the e f f e c t s of

other parameters on wear Frequently a presumption of l i n e a r i t y

between wear volume and/or load and s l i d i n g distance i s implied with

these methods, which may or may not be v a l i d

The t h i r d reason was that in most cases i t would have been

necessary not only to modify the t e s t method but to modify the

apparatus, as w e l l In general i t was concluded that i t was more

convenient and expedient to develop unique equipment and t e s t methods

which would meet the s p e c i f i c requirements, rather than attempt the

m o d i f i c a t i o n s

Because of the large range of c o n d i t i o n s encountered, t h i s

approach led to the development and use of a number of unique t e s t

c o n f i g u r a t i o n s and t e s t methods When proper s i m u l a t i o n could not be

provided by a m o d i f i c a t i o n of e x i s t i n g equipment, a new apparatus was

developed or a machine, such as a p r i n t e r , was modified so that wear

t e s t s could be performed with i t With t h i s approach e x i s t i n g wear