金属材料的断裂韧性

Fracturetoughnessofmetallicmaterials杜植SummaryThefracturetoughnessofdifferentmetallicmaterialsisthesame,theresearchtotheductilefractureofthedifferentmaterialsandthefindingoftheinfluencingfactorsplaysanimportantroleinimprovingthetoughnessfractureofmaterialtechnology.Accordingtotheinfluencingfactorsoffracturetoughnessofmetallicmaterials,wecansummarizethefactorsintotwoparts:externalandinternalfactors,thenwegetthefactorsthatinfluencethedynamicfracturetoughnessofmetallicmaterials.IntroductionTheuseofmetalmaterialsaregreatlyincreasedwiththedevelopmentofeconomy.Intheprocessofcomponentdesignanduseoftheworkpiece,themostserioussituationisthefracture,whichwillleadtosafetyaccidentandeconomicloss.Throughtheanalysisofthepastfractureeventofthemetalmaterial,wegetthatlowstressbrittlefractureiscausedbycrackpropagation,especiallythemetallicmaterialfracturegrain,whichisgenerallycausedintheprocessofmetalproductionAccordingtotheinfluencingfactorsoffracturetoughnessofmetallicmaterials,wecansummarizethefactorsintotwoparts:externalandinternalfactors.1.externalfactors1.1geometricfactor:Thegeometricfactorisoneofthemostimportantexternalfactors,Geometricfactorsmainlyincludetwoaspects:samplethicknessandsampleorientation.1)samplethicknessCurrentresearchfindsthatdifferentthicknesswillhaveagreatinfluenceonstressqconstraintsofthefrontcrackandonfracturetoughnessofmetallicmaterials.soweusethesamemetalmaterialsofdifferentthicknessinthefracturetoughnesstest.Theresultsoftheexperimentturnouttobethatthefracturetoughnessofthickspecimensislowerthanthevalueofthinspecimens,thatmeans.Thefracturetoughnessischangingwhenwiththethicknessofmaterialsisdifferent.2)sampleorientationWheninthesamplingtestofmetalmaterials,Theorientationofthespecimenhassomerelationshipwiththefracturetoughnessofmetallicmaterials,ifthedirectionofcrackgrowthinmetalmaterialcracksurfacewesampledandthemetalmaterialisconsistent,thefracturetoughnessofmetallicmaterialswillsignificantlyreduce.ifthedirectionisoppositeordeviate,thefracturetoughnesswillimprove.1.2InfluenceofloadingrateMaterialloadingratehavesomeinfluenceonmetalfracturetoughness,therelationshipbetweenthemcanusuallybeexpressedbyvariablerate.Ifthevariablerateisincreasing,thefracturetoughnesswillreduce.However,ifthestrainrateislarge,andthelocaltemperaturerisetotheformationofadiabaticcondition,thematerialfracturetoughnessvalueswillreboundforthere’snotimetodispersethedeformationheat.1.3TheinfluenceofthetemperatureFracturetoughnessofmetallicmaterialsischange,becausethemetalmaterialitselforinternaldamage,causedbythegradualchangeoftheinternalstructureoftheinternalchangeofvacancyconcentrationmetalparticlesdirectlyresultedinthedamageofmetalmaterial.Domesticsomedocumentsshowthatvacancymigrationmovementiscertain,holeopenpolymerizationofacertainpower.Sothevacancyconcentrationishigher,thecracktip,thegreatertheriskofforminghole,itiseasiertoleadtofracture.Fromthebasicknowledgeofphysics.Givenamaterial,itsitselfhowmuchheatchangeswillalsoaffectthetoughnessofthemetalmaterials.Fracturetoughnessofmetallicmaterialsitselfwillreducewiththeincreaseoftemperature.Metalmaterialisadaptedtothechangeitselfhasatemperaturerange,oncethetemperatureisbeyondthescopeoftheoutsideworld,willbeacertaineffectonfracturetoughnessofmetallicmaterials.Thuswecanconcludethatfracturetoughnessofmetalmaterialandtemperaturehaveagreatrelationship.2.Internalfactors:2.1Theinfluenceofstructure1)MartensiteMetalmaterialsinternalmartensiteandimpactfracturetoughnessofmetallicmaterialsisanimportantinternalfactors.Metalmaterialhardeningaftertemperingmartensitetemperedmartensite,appearinmartensitedon'ttemperbrittlenessofqiancondition,temperingtemperatureandtheintensityofchangecanproducegreatinfluencetothewholemetalmaterials,withtheincreaseoftemperingtemperature,theintensitygraduallydecline.Plasticityandtoughnessincreased.Therefore,throughtheexperimentwecangaintemperedmartensiteafterquenchingtempering,theorganizationofthemetaltoohcomprehensivemechanicalperformancecanachievethebestlevel,atthesametime,italsomakesthematerialyieldstrengthandfracturetoughnessvaluesarebigger.2)BainateBainitewithinmetalmaterialisgenerallydividedintothreekinds,nocarbonbainitic(acicularferrite),upperbainiteandlowerbainite.Usually,internalbainiticwillbecomewidmanstattenbyheating,whichmakesthefracturetoughnessofmetallicmaterialshavebeenconsiderablyreduced.3)AusteniteThetoughnessofausteniticitselfismuchhigherthanthemartensite,soiftheresidualausteniteincertainmetalmaterialsonthemartensiteisequivalenttoimprovefracturetoughnessofmetallicmaterials.2.2TheinfluenceofcarboncontentCarboncontentinthemetalmaterialswillalsobeacertaineffectonfracturetoughnessofmetallicmaterials,akindofcommonphenomenonistheproductionofhighstrengthsteelreducethecarboncontent,inordertoimprovethefracturetoughnessofmetallicmaterial,inordertoachievethegoalofstrengthening.2.3TheinfluenceofalloyelementsTheformationoflathmartensitewasbeneficialtotheimprovementofthefracturetoughness.Insteel,alloyelementsmainlythroughtothesteelstructuretoi