闭孔泡沫铝的孔壁机械性能

Cellwallmechanicalpropertiesofclosed-cellAlfoamInsuJeona,*,KiyotakaKatoub,TsutomuSonodab,TadashiAsahinab,Ki-JuKangaaSchoolofMechanicalSystemsEngineering,ChonnamNationalUniversity,300Yongbong-dong,Buk-gu,Gwangju500-757,RepublicofKoreabMaterialsResearchInstituteforSustainableDevelopment,NationalInstituteofAdvancedIndustrialScienceandTechnology(AIST),Shimoshidami,Moriyama-ku,Nagoya463-8560,JapanarticleinfoArticlehistory:Received3March2008Receivedinrevisedform11August2008abstractThemechanicalpropertiesofthecellwall,suchastheelasticmodulus,0.2%offsetyieldstressandpower-lawhardeningexponentoftheclosed-cellAlfoamaredeterminedusingbothexperimentalmeasurementsandfiniteelementanalyses.A6612cm3ingotofthecellwallbasematerial,whichissampledfrommeltedAl-1.5wt.%Caalloybeforefoam-ing,isprepared,anditsmechanicalpropertiesareinitiallymeasuredtosetthelimitvaluesofthemechanicalpropertiesoftheAlcellwall.Two555mm3Alfoamspecimensofcompletelydifferentstructuresarefabricated,anddirectlymodeledforthefiniteelementanalysisbyusingamicrofocusX-rayCTsystem,3Dreconstructionprogram,3Dscanneddataprocessingsoftware,andcommercialmeshgenerationprogram.Subsequently,uniax-ialcompressiontestsarecarriedoutonthespecimens,andthenumericalsimulationsofthesetestsareperformedusingthefiniteelementmodels.Forthesimulations,variousmechanicalpropertiesforthecellwallselectedfromthemeasuredpropertiesofthebasematerialareused.Then,theAlcellwallmechanicalpropertiesarepreciselydeterminedbycomparingthecomputedforce–displacementcurveswiththemeasuredones.Finally,theeffectsofeachmechanicalpropertyonthecompressivebehaviorofthefoammaterialareanalyzed.2008ElsevierLtd.Allrightsreserved.1.IntroductionAsafunctionallightweightmaterial,closed-cellAlfoamiswidelyusedintransportationapplications,militaryequipment,machinetoolsandsoon.Therefore,themechanicalperformancesofthefoammaterial,includingitseffectiveelasticmodulus,compressivestrength,anden-ergyabsorptioncapacity,havebecomeanimportantsub-jectofresearch.Muchresearchhasbeendoneonperformanceimprovementofthefoammaterial.Twomainstreamsofresearchhavebeendevelopedsubsequently:first,theanalysisofthesignificanteffectsofgeometricparametersrelatedtothecellstructureontheperfor-manceofthefoammaterial(Miyoshietal.,1999,2000;SimoneandGibson,1998a;Grenestedt,1998;GrenestedtandTanaka,1999;MarkakiandClyne,2001;JeonandAsahina,2005),andsecond,theanalysisontheeffectsofthecellwallmaterialpropertiesontheperformanceofthefoammaterial(Jeonetal.,submittedforpublication).Withrespecttotheeffectsofthegeometricparameters,decreasedcellsizeandincreasedthicknessofthecellwallincreasethecompressivestrengthofthealuminumfoammaterial(Miyoshietal.,1999,2000).Furthermore,cellfacecurvaturesandcorrugationsdecreasetheelasticmodulusandplasticcollapsestress(SimoneandGibson,1998).Thewavyimperfectionandcellshapevariationdecreasethestiffnessoffoammaterials(Grenestedt,1998;GrenestedtandTanaka,1999).Theeffectsofcellwallmicrostructures,whichareformeddifferentlydependingontheproductionprocessesandthecompositionofthecellwallrawmaterials,onthecompressiveresponseofclosed-cellfoamswerealsopresented(MarkakiandClyne,2001).Recently,theeffectsofintrinsicstructuraldefectsof0167-6636/$-seefrontmatter2008ElsevierLtd.Allrightsreserved.doi:10.1016/j.mechmat.2008.08.002*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](I.Jeon).MechanicsofMaterials41(2009)60–73ContentslistsavailableatScienceDirectMechanicsofMaterialsjournalhomepage:(JeonandAsahina,2005).Withrespecttotheeffectsofthematerialpropertiesofthecellwall,researchresultshavenotbeenextensive.Jeonetal.(submittedforpublication),however,demonstratedtheeffectsofcellwallplasticproperties,suchasthe0.2%yieldstressandpower-lawhardeningexponent,ontheen-ergyabsorptioncapacityoftheclosed-cellAlfoam.Theyalsocomparedthestress–straincurvemeasuredfromtheauniaxialcompressiontestona101010mm3closed-cellAlfoamwiththestress–straincurvesobtainedfromnumericalsimulationsofthetest.Althoughtheplas-ticpropertiesofthecellwallcontributesignificantlytothemechanicalperformanceofthefoammaterial,researchonthemeasurementoftheprecisevaluesofthesepropertieshavebeenlimited.AnapproximationmethodwasappliedtomeasuretheyieldstressoftheAlcellwall,whichtakestheyieldstressvaluestobeone-thirdofthecellwallhardness(Sugimuraetal.,1997;SimoneandGibson,1998b;Andrewsetal.,1999).Anothermeasurementmethodusingnanoindenta-tionhasbeenrecentlyintroducedtomeasurecellwallmechanicalproperties(KimandTunvir,2006;Hasanetal.,2008).Thismethod,however,hassomedifficultiesFig.1.(a)A6612cm3basematerialingot,(b)threecylindricalspecimensof25mmheightand12.7mmdiameter,and(c)aspecimenbetweencompressionplatens.Fig.2.Truestress-truestraincurvesofthebasematerial.Table1MeasuredelasticmoduliandelasticlimitstressesofthebasematerialE(GPa)Elasticlimitstress,re(MPa)Comp.testcase#166.0912Comp.testcase#256.249.9Comp.testcase#362.811.6A