1、Designation: G206 11Standard Guide forMeasuring the Wear Volumes of Piston Ring Segments Runagainst Flat Coupons in Reciprocating Wear Tests1This standard is issued under the fixed designation G206; 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 guide covers and describes a profiling method foruse accurately measuring the wear lo
3、ss of compound-curved(crowned) piston ring specimens that run against flat counter-faces. It does not assume that the wear scars are ideally flat, asdo some alternative measurement methods. Laboratory-scalewear tests have been used to evaluate the wear of materials,coatings, and surface treatments t
4、hat are candidates for pistonrings and cylinder liners in diesel engines or spark ignitionengines. Various loads, temperatures, speeds, lubricants, anddurations are used for such tests, but some of them use a curvedpiston ring segment as one sliding partner and a flat or curvedspecimen (simulating t
5、he cylinder liner) as its counterface. Thegoal of this guide is to provide more accurate wear measure-ments than alternative approaches involving weight loss orsimply measuring the length and width of the wear marks.1.2 This standard does not purport to address all of thesafety concerns, if any, ass
6、ociated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2G40 Terminology Relating to Wear and ErosionG181 Test Me
7、thod for Conducting Friction Tests of PistonRing and Cylinder Liner Materials Under LubricatedConditions3. Terminology3.1 DefinitionsSee Terminology G40.3.2 Definitions of Terms Specific to This Standard:3.2.1 conformal contact, nin friction and wear testing,any macro-geometric specimen configuratio
8、n in which thecurvature of one contact surface matches that of the counter-face.3.2.1.1 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 i
9、n a non-conforming contactconfiguration, but develop a conformal contact as a result ofwear.3.2.2 cylinder bore/cylinder liner, nin an internal com-bustion engine, the cylindrical cavity in which the pistonmoves.3.2.2.1 DiscussionThe terms cylinder bore and cylinderliner are used interchangeably in
10、the description of thismethod. Cylinder liners are most commonly used in heavy-duty engines which are intended to be rebuilt. They are sleeves,generally of a cast iron, which are surrounded on their outersurface by coolant for better heat transfer, and meant to bereplaced when excessively worn. A cy
11、linder bore is machineddirectly into an engine block and is more commonly used inlight-duty engines which are not meant for rebuilding. Thematerial of the cylinder bore is, therefore, the same material asthe engine block, however the inside surface of the bore may ormay not have additional surface t
12、reatment.4. Summary of Guide4.1 A reciprocating wear testing 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. Dependingon the duration and severity of the imposed test conditions,some degree of wear is generally pr
13、oduced on one or bothmembers of the sliding pair. Mathematical models of the wearscar geometry on both the piston ring and cylinder linersurfaces allow the degree of wear to be quantified in terms ofvolume lost. The contact geometry for such tests, in the contextof ring-on-liner frictional behavior,
14、 is exemplified in PracticeG181. That method uses pre-worn-in surfaces, and therefore itdiffers from the present case in which wear loss is based onmeasurements of initial and final profiles of the test specimens.1This guide is under the jurisdiction of ASTM Committee G02 on Wear andErosion and is t
15、he direct responsibility of Subcommittee G02.40 on Non-AbrasiveWear.Current edition approved May 1, 2011. Published May 2011. DOI: 10.1520/G020611.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandard
16、s volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 The practical life of an internal combustion engine ismost often determi
17、ned by monitoring its oil consumption.Excessive oil consumption is cause for engine repair orreplacement and can be symptomatic of excessive wear of thepiston ring or the cylinder bore or both. More wear-resistantmaterials of construction can extend engine life and reduce costof operation. Although
18、components made from more wear-resistant materials can be tested in actual operating engines,such tests tend to be expensive and time consuming, and theyoften lead to variable results because of the difficulty incontrolling the operating environment. Although bench-scaletests do not simulate every a
19、spect of a fired engine, they areused for cost-effective initial screening of candidate materialsand lubricants. The test parameters for those tests are selectedby the investigator, but the end result is a pair of wornspecimens whose degree of wear needs to be accuratelymeasured. The use of curved s
20、pecimens, like segments ofcrowned piston rings, presents challenges for precise wearmeasurement. Weight loss or linear measurements of lengthsand widths of wear scars may not provide sufficient accuracy todiscriminate between small differences in wear. This guide isintended to address that problem.6
21、. Reagents6.1 Cleaning SolventsSuitable solvents may be used todegrease and clean specimens prior to conducting wear testsand cleaning specimens afterward. No specific solvents arerecommended here, except that they should not chemicallyattack the tested surfaces, nor leave a residual film or stain a
22、ftercleaning.7. Apparatus and Specimen Preparation7.1 Description of the Test ApparatusAny dimensionalmetrology instrument that is capable of measuring the length,width, and depths of the subject wear scars, and the curvaturesof the regions that surround and contain them, may be used.These include s
23、tylus-type profiling instruments, optical orlaser-based interferometric instruments, and the like. It is theresponsibility of the user to ensure that the dimensionalmeasurement apparatus used has been correctly calibrated.7.1.1 Specimen PreparationThe test specimens shall besolvent cleaned and free
24、from debris or other measurement-complicating artifacts.7.1.2 Specimen FixturingA suitable shall be used toclamp the specimens in the proper orientation for profiling anddimensional measurement without touching the area subjectedor to be subjected to wear.8. Procedure8.1 The current procedure, examp
25、les of its use, and com-parison with other methods for measuring wear, have beenpublished elsewhere.3Wear measurements for ring and linerspecimens are separately described in the following para-graphs. It is the users responsibility to determine which of thefollowing procedures best suits the wear s
26、car geometry pro-duced in the reciprocating test method that was used.8.2 Wear Volume of the Piston Ring SpecimenA hypo-thetical piston ring with compound curvatures can be consid-ered as the central slice of an ellipsoid with initial ring radiusroas the minor semi-axis, as illustrated in Fig. 1. Th
27、e wornsurface on the ring usually will not be flat but also hascompound curvatures. The wear scar can be considered as apatch of another ellipsoid whose minor semi-axis is the finalradius rwon the wear scar. The top view of the wear scar is inelliptical shape with scar length across the crown (2b) a
28、nd scar3Qu, J., and Truhan, J. J., “An Efficient Method for Accurately DeterminingWear Volumes of Sliders with Non-flat Wear Scars and Compound Curvatures,”Wear, Vol 261, 7-8, 2006, pp. 848-855.FIG. 1 Schematic Drawing of the RingG206 112width in the conferential direction of the ring (2a), as shown
29、 inFig. 2. Fig. 3 illustrates the side view of the worn surface,showing the curvature change after testing. By measuring thewear scar size (2a and 2b) and ring curvatures (roand rw)before and after testing, the wear volume Vringand maximumwear depth hringcan be obtained by the following formulae:Vri
30、ng5pa3b2ro32rw3 2ro21 b2!=ro2 b21 2rw21 b2!=rw2 b2#(1)hring5 ro rw =ro2 b21 =rw2 b2(2)8.2.1 When the ring specimen has much lower wear resis-tance compared to the flat specimen, the worn surface on ringwill be fairly flat and Eq 1 and Eq 2 can be simplified asfollows:Vring5pa3b2ro3 2ro21 b2!=ro2 b2#
31、 (3)hring5 ro =ro2 b2(4)8.2.2 Please note that when the crown curvature is zero orvery small compared to the ring curvature, the wear scar lengthis restricted by the ring thickness and the above formulae forwear volume calculations will no longer be valid. In this case,the ring surface should be con
32、sidered as cylindrical, as dis-cussed in 8.2.3.2.8.2.3 Special Cases:8.2.3.1 Spherical Ring SurfaceWhen the two compoundcurvatures on a ring specimen are identical, the ring will be thecentral slice of a sphere with a round shape wear scar. The wearvolumes and maximum wear depths can be calculated u
33、sing Eq1-4 with a=b. Note that the calculations in this case can bedirectly applied to commonly used ball sliders.8.2.3.2 Cylindrical Ring SurfaceWhen the crown curva-ture is zero or very small compared to the ring curvature, thering surface should be considered as cylindrical and the wearscar is re
34、ctangular with width 2b and length equal to the ringthickness 2a=t. The worn surface is also cylindrical withradius rw. Although Eq 2 and Eq 9 are still valid for maximumwear depths, different formulae have been derived for wearvolumes. Namely:Vring5 t Sro2arcsinbro rw2arcsinbrw b=ro2 b21 b=rw2 b2D(
35、5)Vflat5 L Frf2arcsin SW2rfD brf2W24G (6)When the ring specimen has far lower wear resistance than theflat specimen, the worn surface on ring will be relatively flat.In that case, the wear volume and maximum wear depth can becalculated by Eq 7 and Eq 4, respectively.Vring5 t Sro2arcsinbro b=ro2 b2D(
36、7)8.3 Wear Volume of a Flat Counterface SpecimenA sche-matic drawing of the wear scar on the flat specimen isillustrated in Fig. 4. Lsis the stroke length of the reciprocatingtest. The length and width of the wear scar on the flat aredenoted as L and W, respectively. The wear scar on the flat iscomp
37、osed of three segments, the cylindrical middle with radiusof rfand the two compound-curvature ends. The wear volumeVflatand maximum wear depth hflatcan be calculated byVflat5 LsFrf2arcsin SW2rfD W2rf2W24G1pL Ls!3WF2rf3 S2rf21W24Drf2W24G (8)hflat5 rfrf2W24(9)FIG. 2 Schematic Top View of the Wear Scar
38、 on the Ring SpecimenG206 1139. Report9.1 Wear measurements, expressed as the volume of mate-rial lost, shall be reported in accordance with the test methodthat was used to generate the wear.9.1.1 In addition to, or in place of the calculated wearvolume, data may be normalized to express wear volume
39、 lossper unit sliding distance per unit applied normal force, orsimilar combined parameters, wear rates, or wear factors.10. Keywords10.1 cylinder liner; piston ring; wear measurementFIG. 3 Schematic Side View of the Wear Scar on the Ring SpecimenFIG. 4 Schematic Wear Scar on a Flat SpecimenG206 114
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43、ee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).G206 115
