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1、EngineeringFractureMechanicsVol.21,No.I,pp.3148.19850013-7944/85$3.00+.ooPrintedintheU.S.A.PergamonPressLtd.FRACTURECHARACTERISTICSOFTHREEMETALSSUBJECTEDTOVARIOUSSTRAINS,STRAINRATES,TEMPERATURESANDPRESSURESGORDONR.JOHNSONHoneywellInc.,DefenseSystemsDivision,Edina,MN55436,U.S.A.andWILLIA
2、MH.COOKAirForceArmamentLaboratory,EghnAirForceBase,FL32542,U.S.A.Ahstrac-ThispaperconsidersfracturecharacteristicsofOFHCcopper,Armcoironand4340steel.Thematerialsaresubjectedtotorsiontestsoverarangeofstrainrates,Hopkinsonbartestsoverarangeoftemperatures,andquasi-statictensiletestswithvar
3、iousnotchgeometries.Acumulative-damagefracturemodelisintroducedwhichexpressesthestraintofractureasafunctionofthestrainrate,temperatureandpressure.Themodelisevaluatedbycomparingcomputedresultswithcylinderimpacttestsandbiaxial(torsion-tension)tests.INTRODUCTIONWHENMATERIALSaresubjectedtod
4、ynamicloadingconditionssuchashighvelocityimpact,explosivedetonationormetalformingoperations,awiderangeofstrains,strainrates,temperaturesandpressuresmaybeexperienced.Insomeinstancestherehasbeenatendencytodistinguishdynamicmaterialpropertiesfromstaticmaterialproperties.Theunderlyingassump
5、tionisthatthedifferencesbetweenthedynamicandstaticpropertiesmustbeduetostrainrateeffectsonly.Oftenassociatedwithhighstrainrates,however,arelargestrains,hightemperaturesandhighpressures.Therefore,itisimportantthattheeffectsofeachvariablebeproperlyassessed,ratherthanassumingalldistinguish
6、ingcharacteristicsareduetostrainratealone.ThispaperconsidersfracturecharacteristicsofOFHCcopper,Armcoironand4340steel.Aseriesoflaboratorytestshasbeenperformedtodeterminetheeffectsofstrainrate,temperatureandpressureonthestraintofracture.Acumulative-damagefracturemodelisdevelopedandevalua
7、tedwithanindependentseriesoftestsandcomputations.TESTDATAAdescriptionofthethreematerialsisgiveninTable1.AllofthetestspecimenswerefabricatedfromthesamematerialstockandtheheattreatmentwasalwaysasspecifiedinTable1.ThetorsiontestdataareshowninFig.1.ThetorsiontesterisdescribedinRef.
