1、Designation: G181 11Standard 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 adoption or, in the ca
2、se 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 friction tests of
3、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. Areciprocating sliding arr
4、angement 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,and lubricant condit
5、ion.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 presence of fluids that b
6、ehave 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 operating conditions.1.3 T
7、he 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 establish appro-pri
8、ate safety and health practices and determine the applica-bility of regulatory limitations prior to use.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 Test MethodsE691 Practice for Conducting an
9、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 viscosity,composition, and other function
10、-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-geometric specimen configuration in which
11、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 surfacesmay begin a wear or friction test in a non
12、-conforming contactconfiguration, but develop a conformal contact as a result ofwear.3.2.3 lubrication regimein liquid-lubricated sliding con-tact, a certain range of friction coefficients that results from acombination of contact geometry, lubricant viscosity charac-teristics, surface roughness, no
13、rmal pressure, and the relativespeed of the bearing surfaces.1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion and is the direct responsibility of Subcommittee G02.50 on Friction.Current edition approved May 1, 2011. Published May 2011. Originallyapproved in 2004.
14、Last previous edition approved in 2009 as G18104(2009). DOI:10.1520/G0181-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page ont
15、he ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.3.1 DiscussionCommon designations for lubricationregimes are boundary lubrication, mixed film lubrication,elasto-hydrodynamic lubrication and hydrodynamic lubrica-ti
16、on.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-groove fretting motion, andring rocking, are not simula
17、ted 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 procedure is used to increase the repeatabilityof results.
18、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, it has been estimated thatat least half of the frict
19、ion 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 bore surface near the top-dead-centerposition in the
20、 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 standard test method allows flexibility in selectingte
21、st 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 surface prepara-tion, and the materials and lubricants to be evaluated.
22、Guidanceis provided here on the set-up of the test, the manner ofspecimen fixturing and alignment, the selection of a lubricantto simulate conditioned oil characteristics (for a diesel engine),and the means to run-in the ring specimens to minimizevariability in test results.5.2 Engine oil spends the
23、 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, chemical envi-ronment, and confinement in lubricated contact. It ages, chang-ing viscosity, atomic weight, solids content, acidity, andchemistry. Conduct
24、ing 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 intended for use with lubricants that simulatetribologi
25、cal 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 solvents are recommended here, exceptthat they should no
26、t 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 for those lubri-cants. A further description of sim
27、ulated 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 this test are shown. In the first case(Fig. 1, bot
28、tom 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. SpecimensFIG. 1 Schematic Drawing of the Test Configuration Showing Conformal and Non-conformal ContactG181 112are placed in a heated, t
29、emperature-controlled bath of lubricant.Alternate means 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) motionof constant stroke length and repeatable velocity profile to thesimulat
30、ed 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 forcedeveloped between the test specimens. The velocity versust
31、ime 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 the appropriate lubrication regime experienced by thepi
32、ston 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 metresper second, is calculated as follows:s 5 2 fL (1)where
33、: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 influence of the materials isexperienced at the ends of the
34、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 the worn-in contact face of the pistonring specimen.NOTE 1
35、The 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 frequency.7.1.3 Specimen FixturingA means shall be provided
36、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 looseningor other misalignment occurs during the test. For ring
37、 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 piston or designa holder that clamps the inclined sides of
38、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 well as thelubrication regimes that change as the ring spec
39、imen 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 former approachaddresses macro-contact aspects of alignment a
40、nd 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 cylindermaterials from the same type of engine, the ring curvature in th
41、e 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-stressed or in some other way forced into aradius of cur
42、vature 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.7.1.5 Normal Force ApplicationThe apparatus shall havethe ab
43、ility 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 rigidity and damping capacity to avoid excessive deflec-tions
44、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 preparing test specimens depends in parton the kinds of mate
45、rials, 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. The ring specimen may be used in itsoriginal, factory-fi
46、nished 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, shall be measured by a suitable method andincluded in the
47、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 fl
48、at 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 coupons.3Alternatively, a polished surfacemay be used to simulate the worn condition of
49、 a cylinder borenear at the top-dead-center position. In certain cases, thecylinder bore specimen may be fabricated from experimentalmaterials, coated, or surface-treated. The surface roughness ofthe cylinder bore specimen shall be measured by a suitablemethod and included in the test record. With stylus-typeinstruments, it is traditional to measure and report the surface3Blau, P. J., “Simulation of Cylinder Bore Surface Finish Parameters to ImproveLaboratory-Scale Friction Tests in New and Used Oil,” Engine Systems:Lubricants, Components, Exhaust and Boosting Sys
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