MECHANICAL MODELS OF CELLULAR SOLIDS, PARAMETERS (2)

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1、ARTICLEINPRESSInternationalJournalofImpactEngineering34(2007)3–27www.elsevier.com/locate/ijimpengMechanicalmodelsofcellularsolids:ParametersidentificationfromexperimentaltestsMassimilianoAvalle,GiovanniBelingardi,AndreaIbbaDipartimentodiMeccanica,PolitecnicodiTorino,CorsoDucadegliAbruzzi24,1

2、0129Torino(TO),ItalyReceived21January2006;accepted30June2006Availableonline18September2006AbstractCellularmaterialshavelargeuseinmanycomponentsactingasimpactenergyabsorbers.Thesecomponentshavetobedesignedonthebasisofthekindofimpact,oftheinvolvedenergyamountandofthemaximumadmissibleload.Thech

3、oiceofthemostsuitabledensityfortheselectedtypeoffoamisbasedonstress–strainbehaviour,obtainedbymeansofexperimentaltestsand/ormodels.Onlyafewmicro-mechanicalmodels,astheGibsonmodel,takeintoaccountthedensityeffects.Thesemodelscouldresultquitecomplextomanagebecauseoftheneedof,atleast,aroughanaly

4、sisoftheactualfoamstructure.Conversely,mostofthemodelsusedfornumericalsimulationsarephenomenologicalmodelsandhavesimpleparameteridentificationbasedonfittingofexperimentaldata,buttheydonotaccountfordensityeffect.Experimentaluniaxialcompressiontestsperformedforseveraltypesoffoams,namelyEPP,PUR(B

5、ayfillEA),EPSandPPO/PS(NorylGTX),atdifferentdensitylevelsareusedinordertoidentify,withanoptimisationproceduredevotedtotheminimisationofthefittingresidualevaluatedbytheleastsquaremethod,theparametersoffourcellularsolidmodels.Theconsideredmodelsarefour:theGibsonmodel[GibsonLJ,AshbyMF.Cellularsol

6、ids.Structureandproperties.Cambridge:CambridgeUniversityPress;1997],theRuschmodel[RuschKC.Load-compressionbehaviorofflexiblefoams.JApplPolymSci1969;13:2297–311;RuschKC.Energy-absorbingcharacteristicsoffoamedpolymers.JApplPolymSci1969;14:1133–47;RuschKC.Load-compressionbehaviorofbrittlefoams.J

7、ApplPolymSci1970;14:1263–73],amodifiedversionoftheGibsonmodelandanewempiricalmodel.Thethirdandfourthmodelshavebeendevelopedinordertobetterfittheexperimentalstress–straincurve.Theobtainedimprovementsintermsofweightedsumofthesquarederrorsareshown.Theex