铝合金5052材料表征Word格式文档下载.docx

铝合金5052材料表征Word格式文档下载.docx

《铝合金5052材料表征Word格式文档下载.docx》由会员分享，可在线阅读，更多相关《铝合金5052材料表征Word格式文档下载.docx（11页珍藏版）》请在冰豆网上搜索。

Chapter3Materialmodelandmaterialcharacterizationofautomotivealuminiumalloy5052H34

3.1preface

Thebasicpropertyofmaterialdecidestheusefunctionofthestructure.intheresearchofcarcrashesandlargedeformationofkeycomponents,thekeypointofsolvingtheproblemistobuildcorrespondingphysics-mathmodelinordertoacquirethespecificmaterialparameters.Asfortheautomotivealuminiumalloyinourresearch,weneedtoconsidertheresponsecharacteristicofthematerialmachanismonconditionofrealimpact（suchasdynamicloading,high-stresscondition,includingprimarydefectsordamage,etc）.Bythisway,numerousperformancetestandfull-sizecomponnetcrashtestneedtobeconducted,whichwouldexhaustgreatlaborpowerandphysicalresources,buttheresultisstilldubious.Withthelimiteddiscretdataobtainbytheexperiment,itcanhardlycoverthespaceofallsolutionofthemodel.Forsomeextremeconditionsuchasshearingstresscondtion,highstrainrate（ε－1≥2×

102）,ithardtopredictitsmachanismresponse.Therefore,thismodelwebuilthasitscomparativelylargelimitations.Butcombinewithnumericalsimulations,itcanexpandthespaceofthemodeleffectively,whileobtaincompletematerialparameters.

Theresultshowsthattheprecisionofnumericalsimulationislargelydependontheprecisionofmaterialparametertoinput.Intheanalysisoflargedeformation,mater

-ialmachanismmustdescribethematerialchangefromelasticdeformation,elastoplasticdeformation,damageprogession,evolvement,fracture,whichismulti-stepmachanismprocedure.Besides,variousstrainrate,anisotropiccausedbyprocessinghistory,etcneedtobetakeintoaccounttoconsideritsaffectionwithconstitutiverelations.Previously,thisisaextremelycomplexproject,wheremanyproblemsisstillunsolved.J.G.BlauelandD.Z.Su,etcsimplyusedtensilebarexperimentcombinedwithfiniteelementtosimulatethecharacterizationofAW6016automotivealuminiumalloyandcrashtestofthetypicalcomponentsinautomobiles.Itpredictsthestaticanddynamicresponseofthealuminiumalloyandkeycomponentsinmacroperspective,andexpandG-T-Nmodelinmicroperspective,whichexplaintheductilefractureofthealuminiumanditsinitiationandevlovementbymachanismofgrowthofvoids,thatcouldbeappliedinengneeringcalculations.FranckLauroandBrunoBennanibuiltdynamicalloadingmachanismmodelonfinite-elementcalculationterrace.Thismodeltakeelasticflowandanisotropicofmicroholes’damageevolvementintoaccount.Therebythiscouldbeusedtopredictsituationofdamageandfractureofmaterialswithobvioustexturedeformationsuchasextrudedaluminiumalloysincircumstancesofdynamicloadingwithlargedeformation.TheotheronecontributionofFrank’sresearchistodevelopiterativealgorithmwhichisaexperimentcombinewithnumericalsimulationtoachievesolvingandcorrectthekeyparameterinmaterialmodel.Thismethodusesnotchtensiledataasthebasicinput,whichcanderiveparameterofG-T-Ndamagemodel,andrevisetheseparametersinconsiderofanisotropicfactors.Eventually,theresultofnumericalsimulationhitoffwithexperiments.Incomparewithothermaterialcharacterizationmethod,thiscouldavoidagreatamountofexperimentexpenses,andimprovingtheefficencyofmodelingrate.Ontheotherhand,thismethoddoesnotconsiderthechangesofdamagemachanismofthematerialsunderlowerstresscondition.Theresultprovedthatwhenthreedimensionstressdegreeisbelow1,withthereducingofstressdegree,shearslipfailurewouldtakethedominentposition,anddamageofvoidtypewillbesupressed.So,toadoptesingledamgemodelwouldlimititsapplicability.

Thischapteristryingtoconductmaterialcharacterization,acquirefractureparameterofthematerialundersimpletension,notchandshearstress,tocarryouttensiletestinconditionofstatic,quasi-staticanddynamicloading,andnumericalsimulation,furthermore,gainmachanicalpropertyunderdifferentstrainrate.Twokindsofdamagemodelwerebuiltinthisbasis,comparetheprecisionofmodelandsphereofapplicationofthesetwo,todescribethedamageandfracturebehaviourinlargedeformationfrommacrophenomenonanmicromachanism.

3.2Researchofmachanicalpropertytestofmaterialunderstaticanddynamicloading.

3.2.1Basicintroductionoftheexperiment

1.overallthinkingoftheexperiments.

Asfortheautomotivealminiumalloy5052H3.4,itismainlyusedinweldproductioninbearingweightcomponentofcar-body,inactualcollisiondesign,thesestructurewouldmostlyhavelargeelasticdeformationbeforefailure.Therefore,it’snotenoughformaterialcharacterizationonlyconsideringtosatisfystrengthdemand,therheologicalfutureofmaterialinlargeelasticdeformation,suchasworkhardening,anisotropicandfacturefeaturesofprimarydamageandevolvement,etc.Whilethesemachnicalpropertiesaretiedupwithinsidefactorssuchasmicrostruture,distribution,andoutsidefactorsofworkingtemperature,loadingrateandstresscondition.Asforspecificaluminiumalloy,itsorganizationstructureisfixed,buttheworktemperatureandloadingconditionvarieswiththeactualimpactprocess,soweneedtoconductaseriesofsysmaticalexperimentsoncharacterizationofthiskindofaluminiumalloy.Takeresearchinmachanicalresponseunderstaticanddynamiccondition.Onthissense,thisisaproject,whichneedsparticularcategoryandunifyrequirements.

2.Basicinformationofspecimens

Inaccordancewiththeactualimpactcondition,weneedtotakestaticanddynamicloadingmachanicalpropertytestinaluminiumalloy5052H43,theexperimentwasdividedintofivegroups,whichissmoothtensiletest,notchtensiletest,doublenotchsheartest,Iosipescusheartest,dynamictensileloadingtest.SerialnumberofthetestspecimensandexperimentconditionareshowinTable.3.1,sizesofthespecimensareshowinFig.3.2,thespecimensarecutfromoriginalplatebyusing（电火花技术）,thedistributionofallthespecimensonplatecanbeseenonFig3.1.Asfortheserialnumberofthespecimens,takingPT1-UT-S1Qasanexampleforexplanation:

3.2.2Staticuniaxialtesniletest

3.2.2.1experimentequipment

Uniaxialsmoothtensiletestisoneofthebasicmachanicalpropertytest,whichismainlyusedtomeasureflowcurveofmaterialandstrengthindex.Theprimaryaimofthistestistomeasuretheactualstress-straincurveandfractureparameter,inordertoprovidewithmaterialpropertyforfollowingnumericalsimulation.Soastoexpandthescaleofthetestdata,obtainpracticaldataasmuchaspossible,theexperimentadoptedtwosetsofequipments.oneisthestrength-displacementdetectsystem,whichusesextend-measurementdisplacement,alsoloadingsensortomeasureload,whichisownedbyInstron1886tensiletestmachine.

Anothersetofmachineisopticaldeformationmeasuresystem,includingstaticcamera,digitaltransitioncardandfollowingimageprocessingsoftwareanddiagramcalculationsofteware.Thesystemisequipedwithtwosetsofdigitalcamera,theshootingangleisseperativelyperpendiculartofrontsideandlateralsideofthespecimens,distributtedby90degrees.Thereforeitcoulddetectchangesinwidthandthicknessdirectionimmediatelywhenthespecimenisinthetensileprocess,withdynamicimagedetectingtoacquirechangesinspecimensection,sowecouldcalculatetheminiumsectionsizeAi,accordingtotheformulationinfigure3.2tocalculatetheactualstress,strainintensileprocess,whichcouldgetstress-strainrelationofthetensilespecimensafternecking.Fig3.3istheschematicchartoftheexperimentequipments.Thesetwosetsofequipmentsworkscollaboratively.Thecommonstress-displcementismainlyresponsibleforrecordingofwholecourseloadingdetectionandelasticdeformationandpartialductiledeformation（beforemaxmiumloading）,whiletheopticaldetectingsystemaimatrecordingofdetectionofelasticandductile（beforefracture）deformation.

WecanseefromChaper2.3.3thatthetruestrainofaluminiumalloy5052H34is9.6%correspondtostaticmaxmiumtensileloadatroomtemperature,andfracturestrainεfis73%atfracturing,atthistime,thesedatasegementisundetectablebyusingordinarytensileexperiment,andtherewillbesevereerrorinthecomingupnumericalsimulation.Bycontrast,segmentdataafterneckingcanberepairedifopticaldetectingsystemisused,andthemaxmiumtruestraincanbemeasuredupto56.1%.Themeasureproblemofstress-straincurvecanbefixedbylinearinterpolation.ComparisonofCurvesofspecificmaterialsandprecisionofnumericalsimulationwillbediscussedinthischapterinrelateddiagrams.

3.2.2.2Discussion

1Relationshipsofstress-strain

ThetruecurvesbytwosetsofdifferentkindsofdetectingsystemcanbeshowinFig3.4,wecanseethatthedatascaleofoptialdeformationsystemcoveredwider,whilethecomplexityandcostsofthisdetectingsystemisrelativelyhigher.

2Materialcharacterizationofrelativityofanisotropicandstresscondition

Specimenofsmoothtensiletestiscutfromthedirectionofverticalandparalleltotherollingdirection,theengineeringstress-striancurvescanbeseeninFig.3.5.Fromtheresult,theexperimentdisplayedexcellentrepitivenessandstablityofdatarecording.Curvesreactthatverticalyeildstressis22Mpahigherthanparallelyieldstress,tensilestrengthis26Mpahigher,whichdemostratesparticularanisotropic.Thesizeanddistributionofgrainsisregularfromfurtherresearchinmicrostructure.First,griansizesofthesufaceislargerthancentergrains（Fig.3.6）.sec

-ondly,therearecertaingrainorientationinthecenterofthematerial（Fig.3.7）.Partofthegrainintheaxisalong