外文翻译--磨削过程中应力残留 英文版.pdf

ResidualstressingrindingBogdanW.Kruszynski*,RyszardWojcikTechnicalUniversityofodz,Skorupki6/8,90-924odz,PolandAbstractResultsofinvestigationsonresidualstressinsurfacegrindingarepresentedinthepaper.AcoefficientBcombiningpowerdensityandwheel/workpiececontacttimewasdeveloped.Experimentalset-upandsoftwaretoestimatethecoefficientduringgrindingaredescribedinthepaper.Experimentswerecarriedoutforsurfaceplungegrindingforseveralworkmaterialsinawiderangeofgrindingconditions.TheinfluenceofprocessparametersonthecoefficientBaswellastherelationbetweenBandmaximumresidualstresswereexperimentallyevaluated.Theusefulnessofthecoefficienttopredictresidualstressinsurfacegrindingwasproved.#2001ElsevierScienceB.V.Allrightsreserved.Keywords:Residualstress；Grinding；Wheel/workpiece1.IntroductionGrindingisoneofthemostpopularmethodsofmachininghardmaterials.Becauseitisusuallyoneofthefinalopera-tionsofthetechnologicalprocess,propertiesofsurfacelayercreatedingrindinginfluencedirectlythefunctionalproper-tiesoftheworkpiecesuchasfatiguestrength,abrasiveandcorrosionresistance,etc.Creatingfavourablesurfaceintegrity,especiallyingrind-ingwithaluminiumoxidegrindingwheelsisdifficultduetotwooppositetendencies.Ononehand,highprocesspara-metersarepreferredinordertoincreaseproductivity.Unfortunately,suchparametersusuallyleadtotheincreaseofgrindingpowerengagedincreationofthenewsurfaceoftheworkpiece.Ontheotherhand,theincreaseofgrindingpowermakesgrindingtemperaturesgrow,whichmaycauseaseriousdamagetothesurfacelayercreatedingrinding.Findingacompromisebetweenhighproductivityandadvantageoussurfacelayerpropertiesisextremelydifficultduetothelackofrelativelysimpleanduniversalroutines,amongothers.Becauseoftheimportanceofgrindingopera-tiontheinvestigationsofthisprocessareperformedinmanyresearchcentres.Somegeneralapproachesareobservedintheseinvestigations.Thefirstone,strictlyanalytical4,5,isbasedonthemathematicaldescriptionofphysicalprocessesinvolvedinsurfacelayercreation.Ingrindingthermaleffectsareusuallydescribed.Onthebasisofthecalculationsoftemperaturedistributionintheworkpiece,suchchangesinsurfacelayerlikemicrohardness,residualstresses,microstructure,etc.areestimated5.Suchanapproachisverypromisingbutatthepresentstageitislimitedtotheoreticalinvestigationsbecauseofcomplexcalculationsandstilllimitedknowledgeaboutmaterialbehaviourinextremegrindingconditions.Theexperimentalapproach1,7aimsatfindingacorre-lationbetweengrindingconditionsandsurfacelayerpara-meters.Thisisarelativelysimplemethodwithsomedisadvantages.Experimentalworksareusuallytime-andcapital-consumingwhichlimitstheirapplication.Moreover,thereisalimitedpossibilitytoextrapolatetheexperimentalresultsondifferentgrindingmethodsandgrindingconditions.Thereisalsoathirdapproachtotheproblemofcontrolofsurfacelayercreation,whichinvolvesasearchforsuchgrindingcoefficients,whicharestronglycorrelatedwithsurfacelayerproperties2,4.Therearemanysuchcoeffi-cientsexisting.Themostpopularare:equivalentchipthickness(heq)andpowerdensity(P0).Theformerisprovedtobeusefulingrindingceramics,thelatterisoftenappliedwhengrindingwithaluminiumoxidegrindingwheelsisinvestigated2.Themaindisadvantageofbothcoefficientsisthattocalculatethemitisnecessarytoestimatetheeffectivegrindingdepthoreffectivewheel/workpiececontactlength.Bothvaluesareverydifficulttoestimateon-linegrindingaccurately.Thus,aneasy-to-estimategrindingcoefficient,whichwouldbestronglycorrelatedwithsurfaceintegritypara-meters,isstilllacking.TheinvestigationonthecorrelationbetweenthecoefficientcombiningpowerdensityandtheJournalofMaterialsProcessingTechnology109(2001)254257*Correspondingauthor.0924-0136/01/$seefrontmatter#2001ElsevierScienceB.V.Allrightsreserved.PII:S0924-0136(00)00807-4wheel/workpiececontacttimeandresidualstressinsurfacegrindingisdescribedbelow.2.GrindingcoefficientcombiningpowerdensityandcontacttimeItwasproved3thatresidualstressesinsurfacelayeraftergrindingarecloselycorrelatedwithmaximumgrindingtemperature.Theanalysisofequationsusedfortemperaturecalculationingrinding6indicatesthatitisnotonlythepowerdensitythatinfluencesthegrindingtemperaturebutthereisalsoasecondimportantfactorwheel/workma-terialcontacttime.Insurfacegrindingthecontacttimeoftheparticularworkpiecepointwithheatsource(grindingwheel)canbeeasilycalculatedastclevw(1)whereleisaneffectivewheel/workpiececontactlengthandvwistheworkspeed.TheproposedgrindingcoefficientBisaproductofpowerdensityP0andcontacttimetc:BP0tcPbdlelevwPbdvw(2)wherePisthetotalgrindingpowerandbdthegrindingwidth.Thefirstadvantageofthiscoefficientisthatallquantitiesinthisequation(grindingpower,grindingwidthandwork-speed)areeasytomeasureon-lineinagrindingprocess.3.Experimentalset-upExperimentswerecarriedoutforthefollowinggrindingconditions.workmaterials:carbonsteel0.45%C,28HRC(markedS),alloysteel40H(0.38%C,0.9%Cr,0.28%Ni)48HRC(H),bearingsteelH15(equivalentto100Cr6)62HRC(L)；grindingwheels:38A60J8V(J),99A80M7V(M)；wheelspeed:26m/s(constant)；grindingdepth:from0.005to0.06mm；workspeed:from0.08to0.5m/s；grindingfluid:emulsionornone.Grindingparametersintheseinvestigationswerelimitedbythepowerofthemainwheeldrive,tablespeedregulationrangeandbytheappearanceofunacceptablechangesinthesurfacelayer,microcracksandburns.ToestimatecoefficientBitwasnecessarytomeasuregrindingpower,workspeedandgrindingwidth.Grindingpowerwasmeasuredintwodifferentways:bythemeasure-mentofpowerconsumedbywheelmaindrive(Pm)andsimultaneousmeasurementoftangentialgrindingforceFtandwheelspeedvs.Thegrindingpowercanthenbecalcu-latedasPcFtvs.ThecomparisonoftheresultsobtainedfrombothmethodsisshowninFig.1.Averygoodcorrela-tioncanbeseenfromthisfigure,whichprovesthatmea-surementofpowerconsumptionofwheelmaindriveisaccurateenoughtoestimatecoefficientBinthecasewhenonlygrindingwheelisdrivenbythisdrive.Thewheelspeedwasmeasuredbymeansofdisplacementtransducerandgrindingwidthwastakenasawidthofthesamplebeingground.4.ExperimentalresultsOnthebasisofmeasuredvaluesofP,vwandbdinsurfacegrinding,thecoefficientBwascalculatedineachgrindingtest.Measurementscarriedoutduringgrindingallowed,firstofall,toevaluatetheinfluenceofgrindingconditionsonthecoefficientB,cf.Figs.27.ThelineardependencebetweeneffectivegrindingdepthandBcanbeseenfromFigs.2,4and6.Slopesoftheselinesdependmainlyongrindingwheel,workspeed(Figs.2and6)andongrindingfluid(Fig.4).ThecorrectnessoflinearapproximationwasprovedinastatisticalwayvaluesofR2werehigherthan0.9inallcases.Fig.1.Comparisonofmeasuredandcalculatedgrindingpower.Fig.2.TheinfluenceofgrindingdepthandgrindingwheelgradeoncoefficientBforcarbonsteel(S).B.W.Kruszynski,R.Wojcik/JournalofMaterialsProcessingTechnology109(2001)254257255TheinfluenceofworkspeedoncoefficientB,Figs.3,5and7,isnotasuniformasthoseobtainedforgrindingdepth.MuchhigherinfluenceofvwonBisobservedforalowerrangeofworkspeeds.ItindicatesthatthereisalimitedpossibilitytoinfluencecoefficientBbychangesoftheworkspeed.Verysimilardependencieswereobtainedforthethirdworkmaterialinvestigatedalloysteel(H).Forallexperiments,inwhichmicrocracksand/orburnswerenotpresent,residualstressdistributionwasmeasuredbymeansofthewell-knownmaterialremovalmethod.Fromresidualstressvs.depthbelowsurfacediagramsobtainedforeachgrindingtest,maximalresidualstressesinthesurfacelayerweredetermined.Usually,residualstressesreachtheirmaximum(tensilevalues)closetothesurfaceondepthsof1020mm.RelationsbetweencoefficientBandmaximumresidualstressforinvestigatedworkmaterialsareshowninFigs.810.Inthesediagramstheresultsaresummarisedforeachworkmaterialregardlessofothergrindingconditions(grind-ingwheelproperties,grindingfluid,grindingparameters).Ineachcasethelineardependencewasassumedwhichwasprovedinastatisticalway(R2from0.8529to0.9074).Itresultsfromthesefiguresthattheslopesofresidualstress-coefficientBlinesarecharacteristicforthegivenworkmaterialandseemtobeindependentofothergrindingconditions.Thehighestslopewasobtainedforbearingsteel(L),Fig.10,andthelowestoneforalloysteel(H),Fig.9.Fig.3.Theinfluenceofworkspeedandgrindingwheelgradeoncoef-ficientBforcarbonsteel(S).Fig.4.TheinfluenceofgrindingdepthandgrindingfluidoncoefficientBforcarbonsteel(S).Fig.5.TheinfluenceofworkspeedandgrindingfluidoncoefficientBforcarbonsteel(S).Fig.6.TheinfluenceofgrindingdepthandgrindingwheelgradeoncoefficientBforbearingsteel(L).Fig.7.TheinfluenceofworkspeedandgrindingwheelgradeoncoefficientBforbearingsteel(L).256B.W.Kruszynski,R.Wojcik/JournalofMaterialsProcessingTechnology109(2001)254257Someadditionalobservationsrecordedduringinvestiga-tionsindicatethatthereisapossibilitytousethecoefficientBtopredictand/orcontrolsuchchangesinsurfacelayerlikemicrocracks,burnsormicrostructurechanges.Additionalinvestigationsarenecessarytoconfirmtheusefulnessofthiscoefficientinothergrindingmethods.5.Conclusions1.ThegrindingcoefficientBcombiningpowerdensityandwheel/workpiececontacttimewasdevelopedtopredictresidualstressinsurfacegrinding.2.AlinearcorrelationbetweencoefficientBandmaxi-mumresidualstresswasfoundexperimentally.Itwasconfirmedforseveralworkmaterials.3.TherelationbetweencoefficientBandmaximumresidualstressseemstobeindependentofgrindingconditions.4.CoefficientBincreaseslinearlywiththeincreaseofgrindingdepthanddecreaseswiththeincreaseofworkspeed.Thisdecreaseshowslessintensityintherangeofhigherworkspeeds.5.ThecoefficientBiseasy-to-estimate,evenon-line,inindustrialpractice.6.ThecoefficientBmaybeusefulinpredictingsuchsurfacelayerpropertiesingrinding