ASTM D695-2010

StandardTestMethodfor

CompressivePropertiesofRigidPlastics1ThisstandardisissuedunderthefixeddesignationD695;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.

1.Scope*

1.1Thistestmethodcoversthedeterminationoftheme-chanicalpropertiesofunreinforcedandreinforcedrigidplas-tics,includinghigh-moduluscomposites,whenloadedincompressionatrelativelylowuniformratesofstrainingorloading.Testspecimensofstandardshapeareemployed.Thisprocedureisapplicableforacompositemodulusuptoandincluding41,370MPa(6,000,000psi).

1.2ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesinparenthesesareforinformationonly.

NOTE1—Forcompressivepropertiesofresin-matrixcompositesrein-forcedwithorientedcontinuous,discontinuous,orcross-plyreinforce-ments,testsmaybemadeinaccordancewithTestMethodD3410/D3410M.

D4000ClassificationSystemforSpecifyingPlasticMateri-als

D5947TestMethodsforPhysicalDimensionsofSolidPlasticsSpecimens

E4PracticesforForceVerificationofTestingMachinesE83PracticeforVerificationandClassificationofExten-someterSystems

E691PracticeforConductinganInterlaboratoryStudytoDeterminethePrecisionofaTestMethod2.2ISOStandard:3ISO604Plastics—DeterminationofCompressiveProper-ties

3.Terminology

3.1General—ThedefinitionsofplasticsusedinthistestmethodareinaccordancewithTerminologyD883unlessotherwiseindicated.3.2Definitions:

3.2.1compressivedeformation—thedecreaseinlengthpro-ducedinthegagelengthofthetestspecimenbyacompressiveload.Itisexpressedinunitsoflength.

3.2.2compressivestrain—theratioofcompressivedefor-mationtothegagelengthofthetestspecimen,thatis,thechangeinlengthperunitoforiginallengthalongthelongitu-dinalaxis.Itisexpressedasadimensionlessratio.

3.2.3compressivestrength—themaximumcompressivestress(nominal)carriedbyatestspecimenduringacompres-siontest.Itmayormaynotbethecompressivestress(nominal)carriedbythespecimenatthemomentofrupture.3.2.4compressivestrengthatfailure(nominal)—thecom-pressivestress(nominal)sustainedatthemomentoffailureofthetestspecimenifshatteringoccurs.

3.2.5compressivestress(nominal)—thecompressiveloadperunitareaofminimumoriginalcrosssectionwithinthegageboundaries,carriedbythetestspecimenatanygivenmoment.Itisexpressedinforceperunitarea.

1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.Aspecificprecau-tionarystatementisgivenin13.1.

NOTE2—ThistestmethodistechnicallyequivalenttoISO604.

2.ReferencedDocuments2.1ASTMStandards:2D618PracticeforConditioningPlasticsforTestingD638TestMethodforTensilePropertiesofPlasticsD883TerminologyRelatingtoPlastics

D3410/D3410MTestMethodforCompressivePropertiesofPolymerMatrixCompositeMaterialswithUnsupportedGageSectionbyShearLoading

ThistestmethodisunderthejurisdictionofASTMCommitteeD20onPlasticsandisthedirectresponsibilityofSubcommitteeD20.10onMechanicalProperties.CurrenteditionapprovedApril1,2010.PublishedApril2010.Originallyapprovedin1942.Lastpreviouseditionapprovedin2008asD695-08.DOI:10.1520/D0695-10.2ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.

1AvailablefromAmericanNationalStandardsInstitute(ANSI),25W.43rdSt.,4thFloor,NewYork,NY10036,http://www.ansi.org.

3*ASummaryofChangessectionappearsattheendofthisstandard.

Copyright©ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959,UnitedStates.

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3.2.5.1Discussion—Theexpressionofcompressiveproper-tiesintermsoftheminimumoriginalcrosssectionisalmostuniversallyused.Undersomecircumstancesthecompressivepropertieshavebeenexpressedperunitofprevailingcrosssection.Thesepropertiesarecalled“true”compressiveprop-erties.

3.2.6compressivestress-straindiagram—adiagraminwhichvaluesofcompressivestressareplottedasordinatesagainstcorrespondingvaluesofcompressivestrainasabscis-sas.

3.2.7compressiveyieldpoint—thefirstpointonthestress-straindiagramatwhichanincreaseinstrainoccurswithoutanincreaseinstress.

3.2.8compressiveyieldstrength—normallythestressattheyieldpoint(seealsosection3.2.11).

3.2.9crushingload—themaximumcompressiveforceap-pliedtothespecimen,undertheconditionsoftesting,thatproducesadesignateddegreeoffailure.

3.2.10modulusofelasticity—theratioofstress(nominal)tocorrespondingstrainbelowtheproportionallimitofamaterial.Itisexpressedinforceperunitareabasedontheaverageinitialcross-sectionalarea.

3.2.11offsetcompressiveyieldstrength—thestressatwhichthestress-straincurvedepartsfromlinearitybyaspecifiedpercentofdeformation(offset).

3.2.12percentcompressivestrain—thecompressivedefor-mationofatestspecimenexpressedasapercentoftheoriginalgagelength.

3.2.13proportionallimit—thegreateststressthatamaterialiscapableofsustainingwithoutanydeviationfrompropor-tionalityofstresstostrain(Hooke’slaw).Itisexpressedinforceperunitarea.

3.2.14slendernessratio—theratioofthelengthofacol-umnofuniformcrosssectiontoitsleastradiusofgyration.Forspecimensofuniformrectangularcrosssection,theradiusofgyrationis0.289timesthesmallercross-sectionaldimension.Forspecimensofuniformcircularcrosssection,theradiusofgyrationis0.250timesthediameter.4.SignificanceandUse

4.1Compressiontestsprovideinformationaboutthecom-pressivepropertiesofplasticswhenemployedunderconditionsapproximatingthoseunderwhichthetestsaremade.

4.2Compressivepropertiesincludemodulusofelasticity,yieldstress,deformationbeyondyieldpoint,andcompressivestrength(unlessthematerialmerelyflattensbutdoesnotfracture).Materialspossessingaloworderofductilitymaynotexhibitayieldpoint.Inthecaseofamaterialthatfailsincompressionbyashatteringfracture,thecompressivestrengthhasaverydefinitevalue.Inthecaseofamaterialthatdoesnotfailincompressionbyashatteringfracture,thecompressivestrengthisanarbitraryonedependinguponthedegreeofdistortionthatisregardedasindicatingcompletefailureofthematerial.Manyplasticmaterialswillcontinuetodeformincompressionuntilaflatdiskisproduced,thecompressivestress(nominal)risingsteadilyintheprocess,withoutanywell-definedfractureoccurring.Compressivestrengthcanhavenorealmeaninginsuchcases.

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4.3Compressiontestsprovideastandardmethodofobtain-ingdataforresearchanddevelopment,qualitycontrol,accep-tanceorrejectionunderspecifications,andspecialpurposes.Thetestscannotbeconsideredsignificantforengineeringdesigninapplicationsdifferingwidelyfromtheload-timescaleofthestandardtest.Suchapplicationsrequireadditionaltestssuchasimpact,creep,andfatigue.

4.4Beforeproceedingwiththistestmethod,referenceshouldbemadetotheASTMspecificationforthematerialbeingtested.Anytestspecimenpreparation,conditioning,dimensions,andtestingparameterscoveredinthematerialsspecificationshalltakeprecedenceoverthosementionedinthistestmethod.Ifthereisnomaterialspecification,thenthedefaultconditionsapply.Table1inClassificationD4000liststheASTMmaterialsstandardsthatcurrentlyexist.

5.Apparatus

5.1TestingMachine—Anysuitabletestingmachinecapableofcontrolofconstant-rate-of-crossheadmovementandcom-prisingessentiallythefollowing:

5.1.1DriveMechanism—Adrivemechanismforimpartingtothemovablecross-headmember,auniform,controlledvelocitywithrespecttothebase(fixedmember),withthisvelocitytoberegulatedasspecifiedinSection9.

5.1.2LoadIndicator—Aload-indicatingmechanismca-pableofshowingthetotalcompressiveloadcarriedbythetestspecimen.Themechanismshallbeessentiallyfreefrominertia-lagatthespecifiedrateoftestingandshallindicatetheloadwithanaccuracyof61%ofthemaximumindicatedvalueofthetest(load).TheaccuracyofthetestingmachineshallbeverifiedatleastonceayearinaccordancewithPracticesE4.

5.2Compressometer—Asuitableinstrumentfordetermin-ingthedistancebetweentwofixedpointsonthetestspecimenatanytimeduringthetest.Itisdesirablethatthisinstrumentautomaticallyrecordthisdistance(oranychangeinit)asafunctionoftheloadonthetestspecimen.Theinstrumentshallbeessentiallyfreeofinertia-lagatthespecifiedrateofloadingandshallconformtotherequirementsforaClassB-2extensometerasdefinedinPracticeE83.

NOTE3—Therequirementsforextensometerscitedhereinapplytocompressometersaswell.

5.3CompressionTool—Acompressiontoolforapplyingtheloadtothetestspecimen.Thistoolshallbesoconstructedthatloadingisaxialwithin1:1000andappliedthroughsurfacesthatareflatwithin0.025mm(0.001in.)andparalleltoeachotherinaplanenormaltotheverticalloadingaxis.ExamplesofsuitablecompressiontoolsareshowninFig.1andFig.2.5.4SupportingJig—AsupportingjigforthinspecimensisshowninFig.3andFig.4.

5.5Micrometers—Suitablemicrometers,readingto0.01mmor0.001in.formeasuringthewidth,thickness,andlengthofthespecimens.

6.TestSpecimens

6.1Unlessotherwisespecifiedinthematerialsspecifica-tions,thespecimensdescribedin6.2and6.7shallbeused.Thesespecimensmaybepreparedbymachiningoperations

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FIG.3SupportJigforThinSpecimen

NOTE1—Devicessimilartotheoneillustratedhavebeensuccessfullyusedinanumberofdifferentlaboratories.DetailsofthedevicedevelopedattheNationalInstituteforStandardsandTechnologyaregiveninthepaperbyAitchinson,C.S.,andMiller,J.A.,“ASubpressforCompressiveTests,”NationalAdvisoryCommitteeforAeronautics,TechnicalNoteNo.912,1943.

FIG.1SubpressforCompressionTests

lengthistwiceitsprincipalwidthordiameter.Preferredspecimensizesare12.7by12.7by25.4mm(0.50by0.50by1in.)(prism),or12.7mmindiameterby25.4mm(cylinder).Whereelasticmodulusandoffsetyield-stressdataaredesired,thetestspecimenshallbeofsuchdimensionsthattheslender-nessratioisintherangefrom11to16:1.Inthiscase,preferredspecimensizesare12.7by12.7by50.8mm(0.50by0.50by2in.)(prism),or12.7mmindiameterby50.8mm(cylinder).6.3Forrodmaterial,thetestspecimenshallhaveadiameterequaltothediameteroftherodandasufficientlengthtoallowaspecimenslendernessratiointherangefrom11to16:1.6.4Whentestingtubes,thetestspecimenshallhaveadiameterequaltothediameterofthetubeandalengthof25.4mm(1in.)(Note4).Forcrushing-loaddeterminations(atrightanglestothelongitudinalaxis),thespecimensizeshallbethesame,withthediameterbecomingtheheight.

NOTE4—Thisspecimencanbeusedfortubeswithawallthicknessof1mm(0.039in.)orover,toinsidediametersof6.4mm(0.25in.)orover,andtooutsidediametersof50.8mm(2.0in.)orless.

FIG.2CompressionTool

frommaterialsinsheet,plate,rod,tube,orsimilarform,ortheymaybepreparedbycompressionorinjectionmoldingofthematerialtobetested.Allmachiningoperationsshallbedonecarefullysothatsmoothsurfacesresult.Greatcareshallbetakeninmachiningtheendssothatsmooth,flatparallelsurfacesandsharp,cleanedges,towithin0.025mm(0.001in.)perpendiculartothelongaxisofthespecimen,result.

6.2Thestandardtestspecimen,exceptasindicatedin6.3-6.7,shallbeintheformofarightcylinderorprismwhose

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6.5Whereitisdesiredtotestconventionalhigh-pressurelaminatesintheformofsheets,thethicknessofwhichislessthan25.4mm(1in.),apile-upofsheets25.4mmsquare,withasufficientnumberoflayerstoproduceaheightofatleast25.4mm,maybeused.

6.6Whentestingmaterialthatmaybesuspectedofanisot-ropy,duplicatesetsoftestspecimensshallbepreparedhavingtheirlongaxisrespectivelyparallelwithandnormaltothesuspecteddirectionofanisotropy.

6.7ReinforcedPlastics,IncludingHigh-StrengthCompos-itesandHigh-StrengthCompositesandHighlyOrthotropicLaminates—Thefollowingspecimensshallbeusedforrein-forcedmaterials,orforothermaterialswhennecessarytocomplywiththeslendernessratiorequirementsortopermitattachmentofadeformation-measuringdevice.

6.7.1Formaterials3.2mm(1⁄8in.)andoverinthickness,aspecimenshallconsistofaprismhavingacrosssectionof12.7mm(1⁄2in.)bythethicknessofthematerialandalengthsuchthattheslendernessratioisintherangefrom11to16:1(Note5).

6.7.2Formaterialsunder3.2mm(1⁄8in.)thick,orwhereelasticmodulustestingisrequiredandtheslendernessratiodoesnotprovideforenoughlengthforattachmentofacompressometerorsimilardevice,aspecimenconformingto

D695–10

NOTE1—Coldrolledsteel.

NOTE2—Furnishedfoursteelmachinescrewsandnuts,roundhead,slotted,length31.75mm(11⁄4in.).NOTE3—Grindsurfacesdenoted“Gr.”

FIG.4SupportJig,Details

thatshowninFig.5shallbeused.ThesupportingjigshowninFig.3andFig.4shallbeusedtosupportthespecimenduringtesting(Note6).

NOTE5—Iffailureformaterialsinthethicknessrangeof3.2mm(1⁄8in.)isbydelaminationratherthanbythedesirableshearplanefracture,thematerialmaybetestedinaccordancewith6.7.2.

NOTE6—Round-robintestshaveestablishedthatrelativelysatisfactorymeasurementsofmodulusofelasticitymaybeobtainedbyapplyingacompressometertotheedgesofthejig-supportedspecimen.

8.3Specimensthatbreakatsomeobviousflawshallbediscardedandretestsmade,unlesssuchflawsconstituteavariable,theeffectofwhichitisdesiredtostudy.

9.SpeedofTesting

9.1Speedoftestingshallbetherelativerateofmotionofthegripsortestfixturesduringthetest.Rateofmotionofthedrivengriporfixturewhenthemachineisrunningidlemaybeusedifitcanbeshownthattheresultingspeedoftestingiswithinthelimitsofvariationallowed.

9.2Thestandardspeedoftestingshallbe1.360.3mm(0.05060.010in.)/min,exceptasnotedin10.5.4.

10.Procedure

10.1Measurethewidthandthicknessofthespecimentothenearest0.01mm(0.001in.)atseveralpointsalongitslength.Calculateandrecordtheminimumvalueofthecross-sectionalarea.Measurethelengthofthespecimenandrecordthevalue.10.2Placethetestspecimenbetweenthesurfacesofthecompressiontool,takingcaretoalignthecenterlineofitslongaxiswiththecenterlineoftheplungerandtoensurethattheendsofthespecimenareparallelwiththesurfaceofthecompressiontool.Adjustthecrossheadofthetestingmachineuntilitjustcontactsthetopofthecompressiontoolplunger.

NOTE7—Thecompressiontoolmaynotbenecessaryfortestingoflowermodulus(forexample,700MPato3500MPa(100,000psito500,000psi))materialiftheloadingsurfacesaremaintainedsmooth,flat,andparalleltotheextentthatbucklingisnotincurred.

6.8Whentestingsyntacticfoam,thestandardtestspecimenshallbeintheformofarightcylinder25.4mm(1in.)indiameterby50.8mm(2in.)inlength.

7.Conditioning

7.1Conditioning—Conditionthetestspecimensinaccor-dancewithProcedureAofPracticeD618unlessotherwisespecifiedbycontractorrelevantASTMmaterialspecification.Conditioningtimeisspecifiedasaminimum.TemperatureandhumiditytolerancesshallbeinaccordancewithSection7ofPracticeD618unlessspecifieddifferentlybycontractormaterialspecification.

7.2TestConditions—Conductthetestsatthesametempera-tureandhumidityusedforconditioningwithtolerancesinaccordancewithSection7ofPracticeD618unlessotherwisespecifiedbycontractortherelevantASTMmaterialspecifica-tion.

8.NumberofTestSpecimens

8.1Atleastfivespecimensshallbetestedforeachsampleinthecaseofisotropicmaterials.

8.2Tenspecimens,fivenormaltoandfiveparallelwiththeprincipalaxisofanisotropy,shallbetestedforeachsampleinthecaseofanisotropicmaterials.

10.3Placethinspecimensinthejig(Fig.3andFig.4)sothattheyareflushwiththebaseandcentered(Note8).Thenutsorscrewsonthejigshallbefingertight(Note9).Placetheassemblyinthecompressiontoolasdescribedin5.3.

NOTE8—Around-robintest,designedtoassesstheinfluenceof

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FIG.5CompressionTestSpecimenforMaterialsLessthan3.2mmThick

specimenpositioninginthesupportingjig(thatis,flushversuscenteredmounting),showednosignificanteffectoncompressivestrengthduetothisvariable.However,flushmountingofthespecimenwiththebaseofthejigisspecifiedforconvenienceandeaseofmounting.4NOTE9—Around-robintestontheeffectoflateralpressureatthesupportingjighasestablishedthatreproducibledatacanbeobtainedwiththetightnessofthejigcontrolledasindicated.

10.4Ifonlycompressivestrengthorcompressiveyieldstrength,orboth,aredesired,proceedasfollows:

10.4.1Setthespeedcontrolat1.3mm/min(0.050in./min)andstartthemachine.

10.4.2Recordthemaximumloadcarriedbythespecimenduringthetest(usuallythiswillbetheloadatthemomentofrupture).

10.5Ifstress-straindataaredesired,proceedasfollows:10.5.1Attachcompressometer.

10.5.2Setthespeedcontrolat1.3mm/min(0.050in./min)andstartthemachine.

10.5.3Recordloadsandcorrespondingcompressivestrainatappropriateintervalsofstrainor,ifthetestmachineisequippedwithanautomaticrecordingdevice,recordthecompleteload-deformationcurve.

10.5.4Aftertheyieldpointhasbeenreached,itmaybedesirabletoincreasethespeedfrom5to6mm/min(0.20to0.25in./min)andallowthemachinetorunatthisspeeduntilthespecimenbreaks.Thismaybedoneonlywithrelativelyductilematerialsandonamachinewithaweighingsystemwithresponserapidenoughtoproduceaccurateresults.11.Calculation

11.1CompressiveStrength—Calculatethecompressivestrengthbydividingthemaximumcompressiveloadcarriedbythespecimenduringthetestbytheoriginalminimumcross-sectionalareaofthespecimen.Expresstheresultinmegapas-calsorpounds-forcepersquareinchandreporttothreesignificantfigures.

11.2CompressiveYieldStrength—Calculatethecompres-siveyieldstrengthbydividingtheloadcarriedbythespecimenattheyieldpointbytheoriginalminimumcross-sectionalarea

ofthespecimen.Expresstheresultinmegapascalsorpounds-forcepersquareinchandreporttothreesignificantfigures.11.3OffsetYieldStrength—Calculatetheoffsetyieldstrengthbythemethodreferredtoin3.2.11.

11.4ModulusofElasticity—Calculatethemodulusofelas-ticitybydrawingatangenttotheinitiallinearportionoftheloaddeformationcurve,selectinganypointonthisstraightlineportion,anddividingthecompressivestressrepresentedbythispointbythecorrespondingstrain,measurefromthepointwheretheextendedtangentlineintersectsthestrain-axis.Expresstheresultingigapascalsorpounds-forcepersquareinchandreporttothreesignificantfigures(seeAnnexA1).11.5Foreachseriesoftests,calculatetothreesignificantfiguresthearithmeticmeanofallvaluesobtainedandreportasthe“averagevalue”fortheparticularpropertyinquestion.11.6Calculatethestandarddeviation(estimated)asfollowsandreporttotwosignificantfigures:

¯2!/~n21!s5=~(X22nX

(1)

where:

s=estimatedstandarddeviation,X=valueofsingleobservation,n=numberofobservations,and

¯=arithmeticmeanofthesetofobservations.X

NOTE10—ThemethodfordeterminingtheoffsetcompressiveyieldstrengthissimilartothatdescribedintheAnnexofTestMethodD638.

SupportingdatahavebeenfiledatASTMInternationalHeadquartersandmaybeobtainedbyrequestingResearchReportRR:D20-1061.

412.Report

12.1Reportthefollowinginformation:

12.1.1Completeidentificationofthematerialtested,includ-ingtype,source,manufacturer’scodenumber,form,principaldimensions,previoushistory,etc.,

12.1.2Methodofpreparingtestspecimens,12.1.3Typeoftestspecimenanddimensions,12.1.4Conditioningprocedureused,

12.1.5Atmosphericconditionsintestroom,12.1.6Numberofspecimenstested,12.1.7Speedoftesting,

12.1.8Compressivestrength,averagevalue,andstandarddeviation,

12.1.9Compressiveyieldstrengthandoffsetyieldstrengthaveragevalue,andstandarddeviation,whenofinterest,

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TABLE1Precision,CompressiveStrength

(ValuesinUnitsofMegapascals)

MaterialAcetal

Polystyrene

Linen-filledphenolic

ATABLE2Precision,CompressiveModulus

(ValuesinUnitsofGigapascals)

RD5.99.821.0

MaterialAcetal

Polystyrene

Linen-filledphenolic

AAverage100106158

SrA1.11.43.7

SRB2.13.57.5

rC3.13.910.4

Average3.283.886.82

SrA0.140.070.23

SRB0.250.740.90

rC0.390.200.64

RD0.702.072.52

Sristhewithin-laboratorystandarddeviationfortheindicatedmaterial.Itisobtainedbypoolingthewithin-laboratorystandarddeviationsofthetestresultsfromalloftheparticipatinglaboratories:

Sr=[[(S1)2+(S2)2+...+(Sn)2]/n]1/2.

BSRisthebetween-laboratoriesreproducibility,expressedasastandarddeviation,fortheindicatedmaterial.Cristhewithin-laboratoryrepeatabilitylimit,r=2.83Sr.DRisthebetween-laboratoryreproducibilitylimit,R=2.83SR.Sristhewithin-laboratorystandarddeviationfortheindicatedmaterial.Itisobtainedbypoolingthewithin-laboratorystandarddeviationsofthetestresultsfromalloftheparticipatinglaboratories:

Sr=[[(S1)2+(S2)2+...+(Sn)2]/n]1/2.

BSRisthebetween-laboratoriesreproducibility,expressedasastandarddeviation,fortheindicatedmaterial.Cristhewithin-laboratoryrepeatabilitylimit,r=2.83Sr.DRisthebetween-laboratoryreproducibilitylimit,R=2.83SR.

12.1.10Modulusofelasticityincompression(ifrequired),averagevalue,standarddeviation,12.1.11Dateoftest,and12.1.12Dateoftestmethod.

13.PrecisionandBias

13.1Table1andTable2arebasedonaround-robintestconductedin1987inaccordancewithPracticeE691,involvingthreematerialstestedbysixlaboratoriesforTestMethodD695M.Sincethetestparametersoverlapwithintolerancesandthetestvaluesarenormalized,thesamedataareusedforbothtestmethods.Foreachmaterial,allofthesampleswerepreparedatonesource.Eachtestresultwastheaverageoffiveindividualdeterminations.Eachlaboratoryobtainedtwotestresultsforeachmaterial.(Warning—Thefollowingexplana-tionsofrandR(13.2-13.2.3)areonlyintendedtopresentameaningfulwayofconsideringtheapproximateprecisionofthistestmethod.ThedatainTable1andTable2shouldnotberigorouslyappliedtoacceptanceorrejectionofmaterial,asthesedataapplyonlytothematerialstestedintheroundrobinandareunlikelytoberigorouslyrepresentativeofotherlots,formulations,conditions,materials,orlaboratories.UsersofthistestmethodshouldapplytheprinciplesoutlinedinPracticeE691togeneratedataspecifictotheirlaboratoryandmaterialsorbetweenspecificlaboratories.Theprinciplesof13.2-13.2.3wouldthenbevalidforsuchdata.)

13.2ConceptofrandRinTable1andTable2—IfS(r)andS(R)havebeencalculatedfromalargeenoughbodyofdata,andfortestresultsthatwereaveragesfromtestingoffivespecimensforeachtestresult,then:

13.2.1Repeatability—Twotestresultsobtainedwithinonelaboratoryshallbejudgednotequivalentiftheydifferbymorethanthe“r”forthatthematerial.“r”istheintervalrepresent-ingthecriticaldifferencebetweentwotestresultsforthesamematerial,obtainedbythesameoperatorusingthesameequipmentonthesamedayinthesamelaboratory.

13.2.2Reproducibility,R—Twotestresultsobtainedbydifferentlaboratoriesshallbejudgednotequivalentiftheydifferbymorethanthe“R”valueforthatmaterial.“R”istheintervalrepresentingthecriticaldifferencebetweenthetwotestresultsforthesamematerial,obtainedbydifferentoperatorsusingdifferentequipmentindifferentlaboratories.

13.2.3Anyjudgementinaccordancewith13.2.1and13.2.2wouldhaveanapproximate95%(0.95)probabilityofbeingcorrect.

13.3Therearenorecognizedstandardsbywhichtoesti-matethebiasofthistestmethod.

14.Keywords

14.1compressiveproperties;compressivestrength;modu-lusofelasticity;plastics

ANNEX

(MandatoryInformation)A1.TOECOMPENSATION

A1.1Inatypicalstress-straincurve(Fig.A1.1)thereisatoeregion,AC,thatdoesnotrepresentapropertyofthematerial.Itisanartifactcausedbyatakeupofslack,andalignmentorseatingofthespecimen.Inordertoobtaincorrectvaluesofsuchparametersasmodulus,strain,andoffsetyieldpoint,thisartifactmustbecompensatedfortogivethecorrectedzeropointonthestrainorextensionaxis.

A1.2InthecaseofamaterialexhibitingaregionofHookean(linear)behavior(Fig.A1.1),acontinuationofthelinear(CD)regionofthecurveisconstructedthroughthezero-stressaxis.Thisintersection(B)isthecorrectedzero-6

strainpointfromwhichallextensionsorstrainsmustbemeasured,includingtheyieldoffset(BE),ifapplicable.TheelasticmoduluscanbedeterminedbydividingthestressatanypointalongthelineCD(oritsextension)bythestrainatthesamepoint(measuredfromPointB,definedaszero-strain).A1.3Inthecaseofamaterialthatdoesnotexhibitanylinearregion(Fig.A1.2),thesamekindoftoecorrectionofthezero-strainpointcanbemadebyconstructingatangenttothemaximumslopeattheinflectionpoint(H8).ThisisextendedtointersectthestrainaxisatPointB8,thecorrectedzero-strainpoint.UsingPointB8aszerostrain,thestressatanypoint(G8)

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NOTE1—Somechartrecordersplotthemirrorimageofthisgraph.

FIG.A1.1MaterialwithHookeanRegion

NOTE1—Somechartrecordersplotthemirrorimageofthisgraph.

FIG.A1.2MaterialwithNoHookeanRegion

onthecurvecanbedividedbythestrainatthatpointtoobtainasecantmodulus(slopeoflineB8G8).Forthosematerialswith

nolinearregion,anyattempttousethetangentthroughtheinflectionpointasabasisfordeterminationofanoffsetyieldpointmayresultinunacceptableerror.

SUMMARYOFCHANGES

CommitteeD20hasidentifiedthelocationofselectedchangestothisstandardsincethelastissue(D695-08)thatmayimpacttheuseofthisstandard.(April1,2010)

(1)RevisedSection7.

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