一种人工电磁材料解析模式.pdf

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1、PHYSICALREVIEWB79,195109
2009AnalyticmodelofelasticmetamaterialswithlocalresonancesXiaomingZhouandGengkaiHu*SchoolofAerospaceEngineering,BeijingInstituteofTechnology,Beijing100081,PeoplesRepublicofChina
Received6January2009;revisedmanuscriptreceived6April2009;published12May2009

2、AuniÞedanalyticmodelforeffectivemassdensity,effectivebulkmodulus,andeffectiveshearmodulusispresentedforelasticmetamaterialscomposedofcoatedspheresembeddedinahostmatrix.Theeffectivematerialpropertiesarederiveddirectlyfromtheaveragesoflocalmomentum,stress,andstraindeÞnedinasingle

3、doublycoatedsphere.Itisshownthattheeffectivematerialparameterspredictedbytheproposedmodelareinexcellentagreementswiththecoherent-potentialapproximationresultsatlowÞllingfractionswheretheanisotropyofperiodicstructurescanbeneglectedforelasticwaves.Theadvantageoftheproposedmethodis

4、thatitcanrevealclearlythephysicalmechanismfornegativeeffectivematerialparametersinducedbytheresonanteffect.Itisfoundthatnegativeeffectivemassdensityisinducedbynegativetotalmomentumofthecompositeforapositivemomentumexcitation.Negativeeffectivebulkmodulusappearsforcompositeswithan

5、increasing
decreasingtotalvolumeunderacompressive
tensilestress.Negativeeffectiveshearmodulusdescribescompositeswithaxisymmetricdeformationunderanoppositeaxisymmetricloading.Numericalexamplesarealsogiventoillustratethesemechanisms.TheseÞndingsmaybeusefulindesignofelasticmetama

6、terials.DOI:10.1103/PhysRevB.79.195109PACSnumber
s:43.20.
g,43.35.
d,43.40.
sI.INTRODUCTIONNegativeeffectivemodulusofelasticmetamaterialsisdistinctfromthenegativestaticstiffnessobservedintheRecently,therehasbeenagrowinginterestinanalyzing1Ð8bucklingstateofcompressedstructures.2

7、4Theformerisin-thepropertyofelasticmetamaterials,whicharetheducedbythelocalresonanteffect,asdemonstratedinahol-elasticwavecounterpartsofelectromagnetic
EMmetamaterials.9Ð11Generallyspeaking,metamaterialsarelowwaveguideattachedbyanarrayofsubwavelengthHelm-holtzresonators.2,25The

8、effectivecomplianceofHelmholtzcompositeswhosebu