1、Designation: G181 11 (Reapproved 2017)Standard Test Method forConducting Friction Tests of Piston Ring and Cylinder LinerMaterials Under Lubricated Conditions1This standard is issued under the fixed designation G181; the number immediately following the designation indicates the year oforiginal adop
2、tion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for conductinglaboratory bench-scale
3、friction tests of materials, coatings, andsurface treatments intended for use in piston rings and cylinderliners in diesel or spark-ignition engines. The goal of thisprocedure is to provide a means for preliminary, cost-effectivescreening or evaluation of candidate ring and liner materials. Arecipro
4、cating sliding arrangement is used to simulate thecontact that occurs between a piston ring and its mating linernear the top-dead-center position in the cylinder where liquidlubrication is least effective, and most wear is known to occur.Special attention is paid to specimen alignment, running-in,an
5、d lubricant condition.1.2 This test method does not purport to simulate all aspectsof a fired engines operating environment, but is intended toserve as a means for preliminary screening for assessing thefrictional characteristics of candidate piston ring and linermaterial combinations in the presenc
6、e of fluids that behave asuse-conditioned engine oils. Therefore, it is beyond the scopeof this test method to describe how one might establishcorrelations between the described test results and the frictionalcharacteristics of rings and cylinder bore materials for specificengine designs or operatin
7、g conditions.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to e
8、stablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevel
9、opment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D6838 Test Method for Cummins M11 High Soot TestE177 Practice for Use of the Terms Precision and Bias inASTM Tes
10、t MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodG40 Terminology Relating to Wear and Erosion3. Terminology3.1 For definitions, see Terminology G40.3.2 Definitions of Terms Specific to This Standard:3.2.1 conditioned oila lubricating oil whose
11、viscosity,composition, and other function-related characteristics havebeen altered by use in an operating engine, such that the oilseffects on friction and wear reflect those characteristic of thelong-term, steady-state engine operation.3.2.2 conformal contactin friction and wear testing, anymacro-g
12、eometric specimen configuration in which the curva-ture of one contact surface matches that of the countersurface.3.2.2.1 DiscussionExamples of conformal contact includea flat surface sliding on a flat surface and a ball rotating in asocket that conforms to the shape of the ball. A pair of surfacesm
13、ay begin a wear or friction test in a non-conforming contactconfiguration, but develop a conformal contact as a result ofwear.3.2.3 lubrication regimein liquid-lubricated slidingcontact, a certain range of friction coefficients that results froma combination of contact geometry, lubricant viscosityc
14、haracteristics, surface roughness, normal pressure, and therelative speed of the bearing surfaces.3.2.3.1 DiscussionCommon designations for lubrication1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion and is the direct responsibility of Subcommittee G02.50 on Frict
15、ion.Current edition approved June 1, 2017. Published June 2017. Originallyapproved in 2004. Last previous edition approved in 2011 as G181 11. DOI:10.1520/G0181-11R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual
16、Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally reco
17、gnized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1regimes are boundary lubrication, mixed film lubrication,elasto
18、-hydrodynamic lubrication and hydrodynamic lubrica-tion.4. Summary of Test Method4.1 A reciprocating friction test apparatus is used to simu-late the back-and-forth motion of a piston ring within acylinder bore in the presence of a heated lubricant. Other typesof motions, like ring rotation, ring-gr
19、oove fretting motion, andring rocking, are not simulated with this procedure. The contactgeometry, selection of testing parameters, and the methods ofspecimen surface finishing and characterization are described.The lubricating fluid is selected to simulate the effects of usedoil. A running-in proce
20、dure is used to increase the repeatabilityof results.5. Significance and Use5.1 The efficiency and fuel economy of spark ignition anddiesel engines is affected in part to the friction between movingparts. Although no reliable, in situ friction measurements existfor fired internal combustion engines,
21、 it has been estimated thatat least half of the friction losses in such engines are due tothose at the ring and liner interface. This test method involvesthe use of a reciprocating sliding arrangement to simulate thetype of oscillating contact that occurs between a piston ring andits mating cylinder
22、 bore surface near the top-dead-centerposition in the cylinder where most severe surface contactconditions occur. There are many types of engines and engineoperating environments; therefore, to allow the user the flex-ibility to tailor this test to conditions representative of variousengines, this s
23、tandard test method allows flexibility in selectingtest loads, speeds, lubricants, and durations of testing. Vari-ables that can be adjusted in this procedure include: normalforce, speed of oscillation, stroke length, duration of testing,temperature of testing, method of specimen surfacepreparation,
24、 and the materials and lubricants to be evaluated.Guidance is provided here on the set-up of the test, the mannerof specimen fixturing and alignment, the selection of a lubri-cant to simulate conditioned oil characteristics (for a dieselengine), and the means to run-in the ring specimens tominimize
25、variability in test results.5.2 Engine oil spends the majority of its operating lifetimein a state that is representative of use-conditioned oil. That is,fresh oil is changed by exposure to the heat, chemicalenvironment, and confinement in lubricated contact. It ages,changing viscosity, atomic weigh
26、t, solids content, acidity, andchemistry. Conducting piston ring and cylinder liner materialevaluations in fresh, non-conditioned oil is therefore unrealisticfor material screening. But additive-depleted, used oil canresult in high wear and corrosive attack of engine parts. Thecurrent test is intend
27、ed for use with lubricants that simulatetribological behavior after in-service oil conditioning, butpreceding the point of severe engine damage.6. Reagents6.1 Cleaning SolventsSuitable solvents may be used todegrease and clean specimens prior to conducting the describedprocedure. No specific solvent
28、s are recommended here, exceptthat they should not chemically attack the test surfaces, norleave a residual film or stain after cleaning.6.2 LubricantsLubricants shall be handled appropriatelywith awareness of, and precautions taken against, any hazardsindicated in the Material Safety Data Sheets fo
29、r those lubri-cants. A further description of simulated used engine oil isfurther described in an appendix to this standard.7. Apparatus and Specimen Preparation7.1 Description of the Test ApparatusA schematic repre-sentation of the reciprocating contact geometry is shown inFig. 1. Two versions of t
30、his test are shown. In the first case(Fig. 1, bottom left), the lower specimen conforms to the shapeof the ring segment. In the second case (Fig. 1, bottom right),the ring segment slides on a flat lower specimen. Specimensare placed in a heated, temperature-controlled bath of lubricant.Alternate mea
31、ns of supplying the lubricant, such as drip feed,may be used.7.1.1 MotionThe test apparatus shall be capable of im-parting a back-and-forth (herein called reciprocating) motionFIG. 1 Schematic Drawing of the Test Configuration Showing Conformal and Non-conformal ContactG181 11 (2017)2of constant str
32、oke length and repeatable velocity profile to thesimulated piston ring specimen which slides against the simu-lated cylinder bore under a controlled normal force. The motorshall be sufficiently powered so that the velocity profile andconstancy of operation shall be unaffected by the friction forcede
33、veloped between the test specimens. The velocity versustime response of crank-driven devices tends to be approxi-mately sinusoidal, and this type of motion is appropriate tosimulate a piston driven by a crankshaft. The frequency ofreciprocation, given in cycles per second, shall be selected toinduce
34、 the appropriate lubrication regime experienced by thepiston ring during its slow down and reversal of direction in theengine of interest. Typical frequencies for slider-crank testingequipment of this type range between 5 and 40 cycles persecond. The average sliding speed for each stroke, s, in metr
35、esper second, is calculated as follows:s 5 2 fL (1)where:f = frequency of reciprocation in cycles per second, andL = stroke length in meters.7.1.2 Stroke Length SelectionIt is unnecessary to set thestroke length equal to the full stroke of the piston in the enginebecause the greatest frictional infl
36、uence of the materials isexperienced at the ends of the ring travel where operation in theboundary lubrication regime increases the likelihood thatcontact will occur between the surfaces of the ring and cylindermaterials. The stroke length should typically range between 5and 10 times the width of th
37、e worn-in contact face of the pistonring specimen.NOTE 1The design of certain testing machines and motor drivesystems limits the maximum frequency achievable for a given strokelength. Therefore, a compromise may be necessary between the highestdesired stroke length and the desired reciprocating freq
38、uency.7.1.3 Specimen FixturingA means shall be provided toclamp the ring specimen to the reciprocating portion of themachine in such a way as to ensure correct alignment duringsliding. Likewise, the cylinder bore specimen shall be mountedin a suitable, heated lubricant container such that no looseni
39、ngor other misalignment occurs during the test. For ring segmentswith a rectangular cross-section, a suitable flat-faced ring-segment grip may be used. For non parallel-sided piston rings(for example, those with keystone-like cross-sections), it maybe necessary to prepare a holder from an actual pis
40、ton or designa holder that clamps the inclined sides of the ring firmly.7.1.4 Specimen AlignmentProper alignment and centeringbetween sliding surfaces is a critical factor for ensuringrepeatable friction test results. Alignment affects the distribu-tion of normal forces on the contact surface as wel
41、l as thelubrication regimes that change as the ring specimen movesback and forth. Two approaches are used together to ensureproper alignment: (1) mechanical alignment of the test fixturesduring the initial test set-up, and (2) running-in of the ringspecimen against the counterface surface. The forme
42、r approachaddresses macro-contact aspects of alignment and the lattermicro-scale aspects of alignment. A method for running inspecimens is given in Appendix X1.NOTE 2Mechanical specimen alignment tends to be difficult toachieve with conformal starting geometry. When testing ring and cylindermaterial
43、s from the same type of engine, the ring curvature in the actualengine is produced by elastically confining the ring in its groove. Thesame ring, out of the engine, will tend to have a larger curvature, andhence rest on the edges of the corresponding cylinder bore specimenunless the ring can be pre-
44、stressed or in some other way forced into aradius of curvature that precisely matches that of the opposing specimencut from the cylinder. A non-conformal, ring-on-flat geometry with asuitable running-in procedure, has been shown to produce a morerepeatable worn-in condition for friction testing.7.1.
45、5 Normal Force ApplicationThe apparatus shall havethe ability to apply a controlled normal force to the ring andcylinder specimens. The loading mechanism can be a dead-weight system, a levered type of device, or a hydraulic orelectromagnetic actuator. The loading system shall have suffi-cient rigidi
46、ty and damping capacity to avoid excessive deflec-tions or vibrations during testing, and to maintain the desirednormal force within 2 % of the intended value.7.2 Specimen PreparationTest specimens are herein re-ferred to as the ring specimen and the cylinder bore specimen.The precise manner of prep
47、aring test specimens depends in parton the kinds of materials, coatings, or surface treatments to beevaluated.7.2.1 Ring SpecimenThe ring specimen shall be preparedby cutting a segment from a production piston ring, ormachining a test piece of equal dimensions and finish to aproduction piston ring.
48、The ring specimen may be used in itsoriginal, factory-finished condition or it may be altered byapplying a coating or surface treatment. The surface shall beprepared to simulate that for a particular engine or class ofengines. The surface roughness of the ring specimen, in thearea of the contact, sh
49、all be measured by a suitable method andincluded in the test record. All pertinent descriptors (type ofprofiling method, surface finish parameters, and measuringconditions) shall be reported.7.2.2 Cylinder Bore SpecimenThe specimen intended tosimulate the cylinder bore surface shall constitute either a cutsection of a production-finished cylinder or a flat specimenwhose form and finish is similar to that of the cylinders used inthe engine of interest. Methods have been developed tosimulate the roughness and lay of production cylinder liners onflat cast iron test
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