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关于裂纹尖端塑性区的实验研究(Ⅰ)(英文).docx

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关于裂纹尖端塑性区的实验研究(Ⅰ)(英文) ExperimentalStudyonPlasticZoneatCrackTip(PartI) Introduction Thebehaviorofmaterialsunderstress,especiallyatthepointofcracking,isofgreatsignificanceinunderstandingthemechanicalpropertiesofmaterials.Inparticular,theplasticzoneatthecracktip,whichplaysacrucialroleinthebehaviorofthematerialduringfracture,hasattractedmuchattention.Inthispaper,wepresentanexperimentalstudyontheplasticzoneatthecracktip,focusingontheeffectofloadingrateandmaterialsonthesizeandshapeoftheplasticzone. ExperimentalProcedure MaterialsandSpecimens Twomaterials,copperandsteel,wereselectedfortheexperiment.Thecopperspecimenswereintheformofrectangularbarswithdimensionsof20mmx5mmx1.5mm,whilethesteelspecimenswereintheformofroundbarswithadiameterof10mm.ThespecimenswerepreparedwithaV-shapednotchinthecenterofthegaugesection,withadepthof1mmandawidthof0.5mm. ExperimentalSetup Thespecimenswereloadedintensionusingaservo-hydraulictestingmachine,equippedwitha50kNloadcell.Theloadingwasappliedataconstantrate,rangingfrom0.01mm/minto1000mm/min.Thespecimenswerealsoloadedinbothmonotonicandcyclicloadingconditions. ExperimentalProcedure Adigitalcamerawasusedtocaptureimagesofthecracktipbeforeandaftertheloadingtest.Theimageswereanalyzedusinganimageprocessingsoftwaretodeterminethelengthandwidthoftheplasticzone.Theplasticzonewasdefinedastheareawherethereissignificantplasticdeformation,anditischaracterizedbythepresenceofslipbandsordeformationtwins. ResultsandDiscussion EffectofLoadingRateonPlasticZone Figure1showstheeffectofloadingrateontheplasticzonesizeofcopperandsteelspecimens.Forbothmaterials,theplasticzonesizeincreasedwithincreasingloadingrate,whichisconsistentwithpreviousstudies.Atlowloadingrates,theplasticzonewaslimitedtothevicinityofthecracktip,whileathighloadingrates,theplasticzoneextendedtoagreaterdistancefromthecracktip.Thisisbecauseathighloadingrates,thematerialexperiencesahigherstrainrate,leadingtoanincreaseinthestrainratesensitivityofthematerial. EffectofMaterialonPlasticZone Figure2showsthe