精选优质文档-----倾情为你奉上EffectofPorosityonDeformation,Damage,andFractureofCastSteelR.A.HARDINandC.BECKERMANNAcombinedexperimentalandcomputationalstudyisperformedtoinvestigatetheeffectofcenterlineshrinkageporosityondeformation,damage,andfractureofcaststeelundertensiletesting.Steelplatescontainingshrinkageporosityarecastinsandmolds,machinedintotestcoupons,andtensiletestedtofracture.Theaveragevolumetricporosityinthegagesectionofthespecimenswithporosityrangesfrom0.10to0.27pct.Ductilityinthetestcastingswithporosityismarkedlyreducedwiththepercentelongationdatarangingfrom12.8to19.6pct;vs22pctelongationforthesoundmaterial.Radiographicimagingisusedtomeasureandreconstructtheporosityfieldinthetestspecimens.Thereconstructedporosityfieldisthenusedinafinite-elementstressanalysissimulatingthetensiletesting.Localelasticpropertiesarereducedaccordingtotheporosityfractionpresent.Porousmetalplasticitytheoryisusedtomodelthedamageduetoporosityandthefracture.Goodagreementisobtainedbetweenthemeasuredandpredictedstress–straincurvesandfracturebehaviors.Thereductioninductilityispredictedwellbycomparingthemeasuredandthesimulatedelongations.Thecomputationalmodelingapproachusedinthisstudyallowsforadetailedevaluationoftheeffectofporosity,includingitssize,shape,andlocation,onthefracturebehaviorofsteelcastings.DOI:10.1007/s11661-013-1669-zTheMinerals,Metals&MaterialsSocietyandASMInternational2013I.INTRODUCTIONSTEELcastingsareunder-utilizedbecauseofuncertaintiesintheirperformanceandlackofexpertiseincastingdesign.Discontinuitiesincastings,likeporosity,playanimportantroleincastingunderutilization.Porositycreatesuncertaintyinadesign’srobustness,sincetherearenomethodologiesforincludingitspresenceinthedesign.Asaresult,designersemployoverlylargesafetyfactorstoensurereliabilityleadingtoheaviercomponentsthannecessary.Contributingtotheissue,theprocessesofdesigningandproducingcastingsareusuallyuncoupledexceptforthespecificationofnondestructiveevaluation(NDE)requirements.Unlessmdesignengineershavetestdataorexperienceforapart,theycallforNDErequirementswithoutknowinghowthisrelatestopartperformance.Bypredictingporosityaccuratelyfromcastingsimulationandrealisticallymodelingitseffectsonthepartperformance,engineerscandeveloprobustdesignsthataretolerantoftheporosityandreliable.Inthecurrentstudy,engineeringapproacheshavebeenappliedtosimulatetheeffectofporosityondeformation,damage,andfractureforacaststeelduringtensiletesting,andthesimulationresultsarecomparedwithmeasurements.ThematerialusedinthisstudyisASTMA216GradeWCBsteel.Itisacastcarbonsteelhavingacombinationofgoodductilityandstrength.Ithasthefollowingchemicalcomposition(maximumwtpct):C0.3;Mn1.0;P0.035;S0.035;Si0.6;Cu0.3;Ni0.5;Cr0.5;Mo0.2;andV0.03;andthetotalofCu,Ni,Cr,Mo,andVcannotexceed1.0wtpct.Atroomtemperature,GradeWCBsteelhasayieldstrengthandatensilestrengthof248and485MPa,respectively,and22pctelongationasminimumtensilerequirementsinASTMA216.Failureofsuchductilemetalsoccursonthemicroscopicscalebymechanismsofvoidnucleation,growth,andcoalescence.[1]Voidscanpre-existasmicroporosityandcanalsonucleatefromimperfectionslike专心---专注---专业精选优质文档-----倾情为你奉上second-phaseparticles.Afternucleation,voidsgrowwithincreasinghydrostaticstressandlocalplasticstraining.Asvoidsnucleateandgrow,thevoid(orporosity)volumefractionincreases.Thevoidsbegintointeract,andthep...