STP 1199 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 Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Library of Congress C a t a l o g l n s - i n - P u b l i c a t l o n D a t a Trlbology : wear test selection for design and application / A.W Ruff 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 George), 1935III Series: ASTM special technical publication ; 1199 TJI075.T784 1993 93-37460 621.8'9 dc20 CIP 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 Photocopy Rights Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by the AMERICAN SOCIETY FOR TESTING AND MATERIALS for users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $2.50 per copy, plus $0.50 per page is paid directly to CCC, 27 Congress St., Salem, MA 01970; (508) 744-3350 For those organizations that have been granted a photocopy license by CCC, a separate system of payment has been arranged The fee code for users of the Transactional Reporting Service is 0-8031-1856-2/93 $2.50 + 50 Peer Review Policy 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 November1993 Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Foreword 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 Dec 1992 The symposium was sponsored by ASTM Committee G-2 on Wear and Erosion A W Ruff of the National Institute for Standards and Technology (NIST) in Gaithersburg, MD and Raymond G Bayer, a Consultant in Vestal, NY, presided as symposium chairmen and are editors of the resulting publication Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions Contents OverviewmA W R U F F A N D R G B A Y E R vii Development of a Wear Test for Adiabatic Diesel Ring and Liner M a t e r i a l s - - w A G L A E S E R A N D P A G A Y D O S Friction Characteristics of Plastic Plain Bearings at Low Velocity K G BUDINSKI 17 Laboratory and Robot Wear Test Selection for Computer Peripherais R G BAYER Realizing Bench Test Solutions to Field Tribology Problems by Utilizing Tribological Aspect NumbersmR M VOITIK 31 45 Extreme Pressure and Anti-Wear Properties of Lubricants: A Critical Study of Current Test Methods and Suggestions for the Future M A PLINT AND A F A L L I S T O N - G R E I N E R Comparison of Laboratory Abrasion Tests and Field Tests of Materials Used in Tillage Equipment P A S W A N S O N 60 80 The Miller N u m b e r - - A Review J E MILLER AND J D MILLER 100 Test Method and Applications for Slurry E r o s i o n - - A Review H MCI CLARK 113 A Retrospective Survey of the Use of Laboratory Tests to Simulate Internal Combustion Engine Materials Tribology ProblemsmP J BEAU 133 Laboratory Wear Tests for Qualifying Automotive Air-Conditioning Lubricants for Use with Refrigerant HFC-134a 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 Wear Set-Up for Simulation of Knee J o i n t - - s BAHADUR 173 The Use of S u r f a c e L a y e r Activation to Measure Ring Wear in an Operating Heavy Duty Diesel Engine J J TRUHAN AND C B COVINGTON 177 Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Overview ASTM'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 scientific 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 testing, 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 connection 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 primarily 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-forpapers was not limited to the Committee or to ASTM 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, not meet the requirements of simulative testing for an application Simulation testing includes critical use conditions, such as contact pressure, 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 An important consideration in all the presentations was the identification of critical use conditions It is hoped that by reading vii Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized viii OVERVIEW 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 A W Ruff National Institute of Standards and Technology, Gaithersburg, MD 20899; symposium chairman and editor R G Bayer 4609 Marshall Drive, West; Vestal, NY 13850; symposium chairman and editor Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions autho W.A Glaeser I and P.A Gaydos I DEVELOPMENT MATERIALS OF A WEAR TEST FOR ADIABATIC DIESEL RING AND LINER REFERENCE: Glaeser, W.A and Gaydos, P.A., "Development of a Wear Test for Adiabatic Diesel Engine Ring and Liner Materials," Triboloqy: Wear Test Selection for DesiQn and Application ASTM STP 1199, A.W Ruff and Raymond G Bayer, American Society for Testing and Materials, Philadelphia, 1993 ABSTRACT: A high temperature apparatus has been developed for determining the wear characteristics of refractory materials for piston ring and cylinders in low heat loss advanced diesel engines Operation of the apparatus has demonstrated good simulation with actual engine experience Ceramic materials and coatings evaluated include zirconias, silicon carbide, silicon nitride, and two chromium oxides Both liquid and solid lubricants have also been evaluated with ceramic materials in the apparatus KEYWORDS: Wear, coefficient of friction, piston rings, diesel engines INTRODUCT high temperature, ceramics, ION In 1983, the U.S Department of Energy, OTS, initiated a long range program to develop an industrial ceramics technology base for components for adiabatic diesel engines One part of the program involved the investigation of the wear mechanisms of ceramics u n d e r advance diesel engine operating conditions The adiabatic diesel engine was recommended by ASME as a potential energy saver This was based on the principle that the higher the operating temperature of a diesel engine, the greater the thermal efficiency of the system It was recognized that heat could be lost through the exhaust and regeneration systems were also considered The ideal engine would have an insulated combustion chamber and no cooling system The elimination of the conventional water cooling system would also save energy and cost It was estimated that cylinder temperatures in the adiabatic engine would reach 460 - 850°C [i] thus precluding conventional motor oils and requiring ceramic cylinder liners, piston crowns, piston rings and valves In addition, it was determined that engine life would be increased owing to the superior wear resistance of ceramics Battelle Columbus Laboratories I Copyright © 1993 by ASTM International www.astm.org Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized TRIBOLOGY Further, it was s u g g e s t e d that use of ceramics as h i g h t e m p e r a t u r e m a t e r i a l s w o u l d be b e t t e r than superalloys to save on s t r a t e g i c m a t e r i a l s like cobalt, c h r o m i u m and tungsten It was d e t e r m i n e d that data on the wear c h a r a c t e r i s t i c s of m o n o l i t h i c ceramics o p e r a t i n g under Diesel c o n d i t i o n s was sparse , if not n o n e x i s t e n t D e s i g n e r s r e q u i r e d data on the wear b e h a v i o r of ceramics for d i e s e l o p e r a t i n g conditions W o u l d t h e y o p e r a t e at all under the s l i d i n g speeds and t e m p e r a t u r e s w i t h o u t l u b r i c a t i o n ? What k i n d of wear might be e x p e c t e d and what s t r u c t u r e s and t r e a t m e n t s w o u l d be r e q u i r e d for this application W o u l d t h e r m a l shock be a problem? W o u l d the new t o u g h e n e d ceramics (PSZ) be a p p r o p r i a t e ? What f r i c t i o n a l p r o p e r t i e s w o u l d these m a t e r i a l s have? P i n - o n - d i s k e x p e r i m e n t s had b e e n p e r f o r m e d on c e r a m i c s s l i d i n g against c e r a m i c s at e l e v a t e d temperatures[2], [3], [4] a n d these results were encouraging However, the sliding v e l o c i t i e s and the e n v i r o n m e n t e x p e c t e d in diesel c o m b u s t i o n chambers were not simulated Early e x p e r i m e n t s w i t h high speed sliding contact c e r a m i c a g a i n s t ceramic for rocket seals h a d d e m o n s t r a t e d problems of surface c r a c k i n g and spalling from t h e r m a l shock[5] B a t t e l l e was c o n t r a c t e d by DOE, Oak Ridge, to u n d e r t a k e a p r o g r a m to d e t e r m i n e the basic wear m e c h a n i s m s of ceramics for a d v a n c e d diesel engines A m a j o r part of the research was to d e v e l o p a w e a r test m a c h i n e and use it for s t u d y i n g the b e h a v i o r of m o n o l i t h i c ceramics o p e r a t i n g u n d e r p i s t o n ring - c y l i n d e r liner conditions[6], [7] DESIGN OF THE CERAMIC WEAR TEST MACHINE Aside f r o m the p r e d i c t e d r i n g - c y l i n d e r t e m p e r a t u r e s for an i n s u l a t e d diesel c o m b u s t i o n chamber, ring loads, s l i d i n g v e l o c i t i e s and g a s e o u s e n v i r o n m e n t were also considered The f o l l o w i n g c o n d i t i o n s were set as goals in the design: R i n g t e m p e r a t u r e s 300 ~ - 650~ R i n g contact l o a d i n g N / m m - 50 N / m m M a x i m u m s l i d i n g v e l o c i t y ~15 m/s Gaseous e n v i r o n m e n t d i e s e l exhaust B e c a u s e of the high cost of o b t a i n i n g ceramic s p e c i m e n s of c o m p l e x shape, it was e s s e n t i a l that the specimens be of simple geometry It was also important that the m i c r o s t r u c t u r e s and densities of the s p e c i m e n be c o n s i s t e n t from one specimen to another F r i c t i o n of s l i d i n g r i n g - l i n e r contacts n e e d e d to be measured The ambient t e m p e r a t u r e was to be m e a s u r e d and its level m a i n t a i n e d d u r i n g an experiment In addition, it was c o n s i d e r e d important to Value is l o a d per inch width of p i s t o n ring Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions au GLAESERAND GAYDOSON DEVELOPMENTOF A WEARTEST I._m/~"Ring"specimens / / / / Load / / / / / / / / / / ~ ~ Figure I i n d e r " specimens Test Specimen Configuration and Loading Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 165 TSEREGOUNIS ET AL ON LABORATORY WEAR TESTS Measured 200-Hr Compressor Rating 75 70 [] [] 65 60 DD 55 Index of Determination = 0.64~D"" 50 [] [] 45 I [] Data 40 35 35 Regression I I I I I I I 40 45 50 55 60 65 70 75 Predicted 200-Hr Compressor Rating Figure Correlation between measured and predicted compressor ratings in long-term compressor durability tests and formulations with good laboratory wear characteristics are appropriate for testing in compressors (provided that they fulfill other requirements for AC lubricants) On the other hand, oils which produce high wear in the laboratory tests will probably not perform well in the model of AC compressor investigated A large portion of the laboratory wear studies was dedicated to testing additives suitable for improving the wear behavior of specific base fluids One of the basestocks extensively studied is U5 (Table IV), a PAG with the general formula: RO-[CH2CH(CH3)O]n[CH2CH20]m-OH This PAG contains equal amounts (by weight) of propylene oxide (PO) and ethylene oxide (EO) units and has a molecular weight of approximately 1600 The results which demonstrate the response of different additives in this basestock will be described in detail later In general, most of the additives evaluated increase the seizure load and, at the same time, decrease the wear produced by the PAG basestock in steel wear tests; some additives reduce brass wear, some make it worse, and a number have no effect on the wear of brass; and none of the additives tested improve the galling and wear in aluminum wear tests Steel-on-Steel Wear Test Resq!ts Figure shows the effect of additives on the wear and load carrying capacity of the PAG basestock The uncertainty of the data is high and most of the data points indicated in Figure represent the average of at least two or three tests The failure load is defined as the point where seizure (machine overtorque limit) occurs due to failure of the lubricant to support the load and prevent significant metal-te-metal contact The standard deviation of a large number of tests on a couple of oils is indicated by the error bars in Figure Uncertainties in the amount of wear of the steel ring and block are also amplified by the fact that wear is a strong function of the applied load Oils with very good steel load carrying capacities which reach the upper machine limit of 431 kg produce more repeatable wear and overtorque load results Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 166 TRIBOLOGY max load 431 kg Total Steel Wear (mg) 6o i 6~ 50 31 40 CFC-12/Mineral Oil 30 J 44 HFC-134/Mineral Oil \ r2~7~ 84 | r3 2~ 41 10 35 34 ~ J I " 100 37 40 42 ~ 132 ! 39 26 36 ! 300 ' b 450 Seizure Load (kg) Figure Effect of additives on the seizure load and total wear in the laboratory steel-on-steel, continuous rotation test Each number #~dicates the average of data obtained for the specific additives in the PAG (Table V) The arrowheads indicate that the max load was reached for the specific additives without failure The error bars in the data for the PAG and the r l oil blend indicate standard deviations of a large number of runs The diamond points #ldicate data obtained for the mineral oil run with both (CFC-12 and HFC-134a) refrigerants for comparison Many additives increase the seizure load and decrease the wear of steel in this particular PAG base fluid Specifically, molybdenum compounds in combination with fatty acids appear to be the most effective Phosphorous-containing additives increase the seizure load, but are not very effective in decreasing wear This may not be a detriment, however, as predicted by the Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No TSEREGOUNIS ET AL ON LABORATORY WEAR TESTS 167 statistical analyses Antioxidants and nitrogen-containing additives are of limited benefit in reducing steel wear The combination of mineral oil and CFC-12 produces a high seizure load, but relatively high wear as well Tile CI in CFC-12 may result in the formation of antiwear films (chlorides) [_5, _6] which improve the load carrying capacity of the oil, but also increase the corrosive wear of the metal surface These characteristics are not present in a HFC-134a atmosphere To further illustrate the effect of chlorine on steel wear, additional data are presented in Figure These data were collected in early tests in which samples of HFC-134a were obtained from suppliers during a period when the purity of the refrigerant (as indicated by the concentration of residual CI present) was improving due to progressive optimization of the manufacturing process For a number of PAG oils with various EO/PO ratios (but similar viscosities) the failure load increased with increasing CI content in HFC-134a Although the effect is small, the clear trend indicates that small amounts of residual CI in the refrigerant (in the form of intermediate products, see i.e synthesis routes in [7]) result in the formation of chlorides which act as EP thin films Even though this beneficial effect of CI from CFC-12 is no longer available, Figure illustrates that there is a number of additives that can modify the antiwear properties of the PAG basestock to match those of the CFC-121mineral oil combination J I Seizure Load (kg) C o m m e r c i a l PAGs (same chemistry) I I 400 Ethylene O x i d e / P r o p y l e n e Oxide 75125 ,, @-'-'-"-'-"- 6/100 200 _ ~ Ratio ," / O/1O0 i00 o-% I 0.01 I 0.1 I 1o0 Residual Chlorine Content (mass %) Figure Effect of HFC-134a purity on the seizure load in the laboratory, steel-on-steel test Brass-on-Steel Wear Test Results Figure illustrates the effect of additives on the wear (weight loss) and wear scar (width) of the brass block in the brass-on-steel, 30~ tests Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 168 TRIBOLOGY Brass Block Wear (mg) 16o J 140 16 120 100 HFC-134/Mineral Oil 3942 80 4043 37 ' 35 60 33 40 20 Basestock (U5) ~,,-J4 ~"'CFC-12/Mineral Oil Brass Block Wear Scar (mm) F i g u r e Effect of additives on the wear and wear scar width of brass blocks in the laboratory, 30~ oscillation brass-on-steel test See caption of Figure for more details The solid line represents the relation between wear and wear scar as described by Equation A simple relationship exists between the wear and the wear scar in block-on-ring tests given by: BRWR = 0.5 b r (0-sin(~) p ,~ 1/12 b w3/r p (9) Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized TSEREGOUNIS ET AL ON LABORATORY WEAR TESTS 169 where b is either the block or the ring width (whichever is smaller, 8.2 mm in the case of brass tests [ring width]), r is the ring radius (17.5 mm), w is the width of the wear scar on the block (mm), e is the sector angle (rad) corresponding to chord w and radius r, and p is the density of brass (8.93 mglmm3) The approximation in Equation (9) results from the relation: 0-sine ,, 8313! (10) which holds for small angles, The solid line in Figure is the theoretical relation between weight loss and wear scar as described by Equation (9) The data in Figure indicate that, in general, the wear is lower than that predicted by the wear scar This is a result of the softness of the brass block (compared to the steel ring) which both plastically deforms and bulges at the edges, thus showing less wear than that predicted by Equation (9) In cases of high wear this effect is more pronounced The data in Figure also demonstrate that a number of additive chemistries can lower brass wear relative to the base fluid by itself, while others have little effect or make it worse Some of the additives that reduce wear of steel are also beneficial for brass Antioxidants and some metal deactivators, in particular, appear most beneficial in reducing brass wear On tile other hand, ptlosphorous-containing additives appear to be deleterious and increase the wear of brass The combination of H FC-134a/mineral oil produces substantial wear, while that of CFC-12hnineral oil results in very little brass wear [ ' I P I Wear (mg) I I 100 i I Water PAGBasestock(U5) 80 / / / 60 / / / / / ZnDDP I " ,.I 4(] / J~A"" ,~-~J 20IbL'- OoL~q; Figure 10 i ~ ~ \ \ ~ ~ /el-Containing A"~ -Antiwear " / ~ O.i Additive Concentration(mass%) Cu Deactivator 1.0 Effect of selective additives on the wear of brass block in the brass-on-steel tests Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 170 TRIBOLOGY Figure 10 demonstrates the effect of changing the concentration of particular additives and/or contaminants on brass wear Water, appears to be deleterious to brass Brass wear increases monotonically with increasing concentration of water in the PAG In the AC system, this may be a concern due to the high affinity of PAG for water which under some circumstances may prevent the desiccant from trapping the water, thus allowing it to circulate with the refrigerant/oil mixture A copper deactivator and a chlorine-containirlg antiwear additive have only small effects on brass wear The optimum concentration of both additives is about 0.1 mass percent A primary alkyl ZDDP demonstrates substantial effects on the wear of brass, having an optimum concentration for minimum wear of approximately 0.2 mass percent Aluminum-on-Steel Wear Test Results Figure 11 depicts the effect of additives on the wear and galling of aluminum in aluminum-on-steel, ~ oscillation tests Of the additives considered in this report, none reduces the wear and galling of aluminum when blended in the PAG base fluid However, the data for mineral oil in either a CFC-12 or an HFC-134a environment show that mineral oil produces very low galling and wear and that no antiwear benefit is obtained from the CI-containing CFC-12 refrigerant These results suggest that base fluid chemistry and viscosity tlave a much more important effect on aluminum wear than does the additive package 100 | @ 80 ,, | @ 60 | ~| | T~ @ Surface Galling (%) | PAG Basestock (U5) (~) @ 20 @ C,FC-12/Mineral Oil ' L I I ~ HFC-134/Mineral Oil I I I , I J Wear (mg) I i 10 w i 12 Figure 11 Effect of additives on the wear and galling of aluminum blocks in the laboratory, 5~ oscillation aluminum-on-steel wear test See caption of Figure for more details Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized TSEREGOUNIS ET AL, ON LABORATORY WEAR TESTS 171 CONCLUSIONS From the data presented in this work the following conclusions can be drawn: 1) Three laboratory wear tests are available for identifying advanced lubricants for use in compressors designed to operate on the refrigerant, HFC-134a as well as to better understand the fundamental wear processes occurring in a refrigerant environment 2) Based on wear and durability considerations only, it is concluded that an automotive air conditioning compressor lubricant should provide: i) optimum kinematic viscosity at 40 ~ and 100~ (about 25 and 170 cSt, respectively) 6; ii) maximum steel seizure loads (higher than about 350 kg); iii) minimum brass wear (lower than about 50 mg); iv) minimum aluminum wear (lower than about mg) 3) A number of additives were blended in a PAG basestock and their performance in the laboratory wear tests can be summarized as follows: i) Many additives increased the failure load and the steel wear in the steel-on-steel tests Phosphorous-containing additives were the most effective ii) Some additives reduced the wear of brass in the brass-on-steel tests Antioxidants and metal deactivators were the most effective while some phosphorous-containing compounds were deleterious on brass iii) None of the additives decreased either the wear or galling of aluminum in the aluminum-on-steel tests 4) Minimizing steel wear in the laboratory wear tests is not a necessary requirement Some controlled steel wear may be beneficial for high seizure loads and low aluminum galling 5) Base fluid chemistry and viscosity changes can be more effective in reducing aluminum wear and galling than additives 6) Statistical analyses using multi-variable regressions have developed equations which can be used to predict the performance of oils in three AC compressor tests based on data from laboratory wear test measurements and oil viscosities ACKNOWLEDGMENTS We would like to thank Richard Lalonde for operating the block-on-ring machines and acquiring most of the data presented in this work Thanks to Shawl Majorski, Maynard Riley, and Lori Vandenberg, who contributed significant efforts in collecting the wear test data Thanks to Richard Hammar for consulting on metallurgical issues related to the wear test development, Zack Gardlund for contributing ideas on formulating PAG base fluids, and Shirley Schwartz for helping interpret laboratory and compressor wear data It should be emphasized that the "working" fluid in the AC compressor is a mixture of oil and refrigerant Therefore, the viscosity of this fluid depends on the solubility of the refrigerant in the oil Thus, oils with the same viscosity may result in "working" fluids of different viscosities, dependent upon the degree of oil dilution by the refrigerant Consequently, the optimum viscosity values stated here should only be considered indicative and not absolute requirements for the oils Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 172 TRIBOLOGY REFERENCES 1LU Molina, M J and Rowland, F S., "Stratospheric Sink for Chlorofluoromethanes: Chlorine Atom-Catalyzed Destruction of Ozone," Nature, Vol 249, p 810, 1974 [2] Embler, L R., Layman, P L., Lepkowski, W., and Zurer, P S., "The Changing Atmosphere," Chemical and Engineering News, Vol 64, No 47 p 14, 1986 Skinner, T J and Swadner, R L., "V-5 Automotive Variable Displacement Air Conditioning Compressor', Society of Automotive Engineers Transactions, Vol 94(1), p246, 1985 ~] STATGRAPHICS, Version 2.6, Statistical Graphics Corporation, Rockville, MD, Copyright 1988 Murray, S F., Johnson, R L., and Swikert, M A., "Difluorodichloromethane as a Boundary Lubricant for Steel and Other Metals," Mechanical Engineering, Vol 78, pp 233-236 March 1956 Factor, A and Miranda, P M., "An Investigation of the Mechanism of the R12-OiI-Steel Reaction," Wear, Vol 150, pp 41-58, 1991 [7] Manzer, C E., "The CFC-Ozone Issue: Progress on the Development of Alternatives to CFCs, wScience, Vol 239, p 231, 1990 Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized S Bahadur I FRICTION AND WEAR SET-UP FOR SIMULATION OF KNEE JOINT REFERENCE: Bahadur, S., "Friction and Wear Set-Up for Simulation of Knee Joint," Tribolo~y: Wear Test Selection for DesiEn and AD~li¢ation, ASTM STP 1199, A W Ruff and Raymond G Bayer, Eds., American Society for Testing and Materials, Philadelphia, 1993 ABSTRACT: The tribological problems in a knee joint have been discussed The items examined include the incongruent joint structure, cartilage tissue and its lubrication, kinematics and loading The reasons why the reciprocating pin-on-flat set-up included in the ASTM F73282 (Reapproved 1991 ) standard is not satisfactory for the ranking of candidate materials for joint replacement prostheses are discussed A set-up incorporating both the sliding and rolling motions is suggested as a better system KEY WORDS: Wear, coefficient of friction, knee joint, joint prosthesis INTRODUCTION Since the first successful clinical application of total hip prosthesis in 1962, a number of replacements for hip and knee joints have been performed In these replacement joints, serious tribological problems because of loosening and wear have been observed Whereas wear debris induces loosening through the attack of living tissue, high friction accelerates the loosening process There is a need for better mating joint materials and their tribological evaluation under realistic loading conditions Since the latter requires a servocontrolled machine which is both expensive and slow, the screening of materials should be done in simpler and faster machines as realistically as possible TRIBOLOGICAL CONSIDERATIONS The knee is a modified and incongruent hinge joint that joins the femur to the tibia and to the patella as shown in Fig The femur and tibia bones which are the load-transmitting members have globular (approximating cylindrical shape) ends that provide a form of bearing area The bone ends are covered with a layer of relatively soft articular cartilage The cartilages on the femur and tibia are separated by synovial fluid which provides lubrication between the members The articular surfaces not fit into one another thus giving an incongruent joint The knee joint involves two kinds of motions: rolling and/or sliding, as shown in Fig Pure rolling initiates flexion but sliding progressively takes over rolling so that a combination of rolling and sliding motions is obtained Finally, at the end of flexion pure sliding occurs This suggests that a realistic evaluation of knee joint materials should involve both rolling and sliding motions 1Mechanical Engineering Department, Iowa State University, Ames, Iowa 173 www.astm.org Copyright©1993 Copyright by ASTMby Int'lASTM (all rightsInternational reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 174 TRIBOLOGY As for the loading, the cartilage tissue is subjected to pressures that vary with time This occurs because of the variation of pressure during locomotion and also because articulation often results in regions of the tissue compressing opposite regions for intermittent periods during sliding This is a consequence of joint incongruities The load which is compressive in nature varies during a cycle of knee movement in a complex manner and can be realistically simulated in a servocontrolled machine only The magnitude of the forces is very high It depends upon the activity and the rate of the activity as shown in Table Table 1: Representative values of forces at knee joint, expressed in multiples of body weight Activity Level walking Stairs 1.1 m/s 1.5 m/s 2.0 m/s 2.7 2.8 4.3 Ascent Descent 4.4 4.9 The cartilage is a complex composite polymeric material that consists of a network of collagen, protein-polysaccharides, living cells and inorganic ions The entire network is swollen with fluid dispersed in the fibrous structure When the tissue is compressed, the fluid is exuded, and when it is unloaded the fluid is imbibed In the latter case, dimensional recovery of the tissue compressed during loading occurs This recovery is governed by the factors related to network elasticity and swelling Such a conspicuous behavior can be approached by a polymeric material only Consistent with this observation, the studies have shown that a polymer-metal combination for knee or hip joint is better than a metal-metal or metal-ceramic mating system ASTM STANDARD There is an ASTM standard F 732-82 (Reapproved 1991) for screening the bearing materials of joint prostheses based on the friction and wear behavior The experimental details of interest given in this standard are: reciprocating pin-on-flat set-up, cylinder end in contact with a flat surface, constant load, bovine blood serum lubricant From the earlier discussion of contact surfaces, the type of motion and loading etc., it is obvious that these conditions are not adequately representative even for preliminary screening of the candidate joint materials It is so because in the standard the motion is purely sliding, the surfaces are congruent and the load is constant in the entire cycle The lubrication mechanism is also different PROPOSED SYSTEM A system with a hinged oscillating link is proposed to better simulate the sliding conditions in a knee joint Here one of the link ends will be attached to a cylindrical specimen which will be loaded against a flat specimen The latter will be supported on springs and will be free to move in the horizontal plane The friction force will be measured by constraining this horizontal motion The normal load and friction force both will be recorded over the entire cycle A system using this concept has been developed and the representative test Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized BAHADUR ON SIMULATION OF KNEE JOINT 175 parameters are given in Table Table 2: Representative test parameters Cyclic frequency Load range Roll angle Linear traverse Linear velocity 1.6 Hz 75-100 N (cyclic) 35~ 0.015 m 0.08 m/s (maximum) The proposed system is simple and fairly inexpensive It duplicates the tribological conditions better than the ASTM system indicated above It is also superior to the other systems, such as the block-on-ring, disk-on-flat, and annulus-on-fiat, which have been used in earlier studies The motion of the contact surfaces in the proposed system is a combination of sliding and rolling both The contact points change continuously during the cycle and the compressive load is cyclic in nature Because of the motion and the changing contact points, the mechanism of lubrication approximates elastohydrodynamic lubrication which is closer to the real situation in an actual knee joint // li~ !iil femur carti]'a~e E - ~ joint e patella cartilage &\~ c~rtJ-lage~ synoviaa - X - ~ ; fluid ~ ~ ~e~a~ea~ar \ tibia" i Fig.i.View of a knee jc~_nt Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 176 TRIBOLOGY I RI = Rolling~ , SI R i ~ ~ -~ Slidina: / Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized John J Truhan and Charles B Covington T H E USE O F S U R F A C E L A Y E R A C T I V A T I O N T O M E A S U R E RING W E A R IN AN O P E R A T I N G HEAVY DUTY DIESEL ENGINE REFERENCE: Truhan, J J and Covington, C B., "The Use of Surface L a y e r A c t i v a t i o n t o Measure R i n g Wear i n an O p e r a t i n g Heavy Duty D i e s e l Engine," Tribology: Wear Test Selection for Design and Avvlication, ASTM STP 1199, A W Ruff and Raymond G Bayer, Eds., American Society for Testing and Materials, Philadelphia, 1993 A B S T R A C T : Surfacelayer activation(SLA) was used to directlymeasure pistonring wear in an operating heavy duty diesel engine A top piston ring was irradiated to measure, in situ, wear rates as a function of lube oil cleanliness using naturally aged oil The relationship between ring wear rate and contamination level in the oil was obtained for different particle size ranges By the use of a wear model, ring wear rates were used to estimate ring life The predicted wear calculated by SLA correlated very well to the actual wear as determined by profile traces KEYWORDS: Wear, surface layer activation, diesel engines, filtration INTRODUCTION Surface layer activation (SLA) is a potentially powerful wear testing technique because it allows wear to be measured in an actual operating system real time In diesel engine research, wear can be measured in situ with no artificial contaminant added so that realistic wear rates can be measured as a function of lubricant condition and engine operatingvariables such as load and speed This sammary represents a small portion of the ongoing research to determine the effectiveness of filtration on engine life RESULTS AND DISCUSSION A chromium plated top piston ring was irradiated around the face to produce Mn54 The ring was installed in a heavy duty diesel engine and run under steady state conditions of full load and speed The loss of activity due to wear was calculated by comparison to a calibration curve representing the activity gradient in the plating Lubricating oils aged in the field and in test ceils were run in the test engine to determine the amount of wear they produced in 24 hours of operation Figure shows a typical 24 hour experiment The cleanliness levels of the used oils were determined by passing them through a series of successively finer screens The differential pressure across the screens as they plug is a measure of the particulate contaminant level Figure shows the relationship between ring wear rate and oil cleanliness for contaminants 15 micrometers and larger As can be seen, the cleaner the lube oil, representing different levels of filtration, the lower the wear rate These rates, measured for realistic levels of contamination, can be used to predict part life with the application of a wear model The model should define the amount of wear that could be tolerated and maintain functionality along with corrections for areas of accelerated I Fleetguard Corporation Copyright 1993 by ASTM lntcrnational 177 www.astm.org Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 178 TRIBOLOGY wear such as near the gap Figure shows the results of the application o f a wear model to the data in Figure The model predicts that the ring, ideally, would have a life approaching 1.6 million kilometers if a high efficiency filtration system is used throughout its life On the other hand, a poorer level of filtration could reduce the life to about 600,000 kilometers, roughly the current expected life to overhaul These estimated part lives, o f course, assume that a constant level of filtration is maintained throughout the whole period Extended tests showed that ring wear depended little on the degradation of the oil chemistry and was more affected by oil cleanliness This lack of dependence on oil chemistry would probably not extend to more heavily loaded ferrous engine components such as found in the valvetrain Profile traces were carried out before and after testing so that a correlation between calculated and actual wear could be determined The results o f that effort are shown in Fig The correlation after approximately 1200 hours of ring use indicate that direct measurement SLA can be accurately done Current test plans will involve the irradiation o f a ring, the corresponding cylinder liner and a part representative o f overhead wear Novel methods for in situ bearing wear measurements are also being considered, however this is more developmental Calculated Wear (micrometers) 12 0.05 Wear Rate (micrometers / h) 0.04 11, 0.03 ~L~r R~m.~n 0,02 0.01 I t , i i , i , i , i , i , I , i i 11 13 15 17 19 21 23 RunningTime (h) 10000 , , , , 100000 No, of Particles / 1OO ml FIG A typical experimental run showing wear vs time la=~ Ring Ufe (1000 km) " Ring Life (1000 h) FIG The relationship between ring wear rate and level of 15 micrometer particles Top 2S 1~0o t400 -e-Rlng Life (1000 Ion) "~Original 20 Profile 1200 1000 15 8OO ) 600 10 400 20/~m SLA Calculated Wear 2OO 1o~o0 No of ~ c l e s / 11111ml FIG The relafionslfip between rin84ife and level of 15 rmcrometer partacles FIG A compa6son between calculated wear by SLA and actual wear by profile trace Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized ISBN 0-8031-1856-2 Copyright by ASTM Int'l (all rights reserved); Tue Dec 29 00:37:55 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further r