简介：TheDonnelltheoryofshellwasappliedtodescribeshellmotion.Theinnerandoutershellswerestiffenedbytransversecomponents.Usingdeformationharmoniousconditionsoftheinterface,theeffectsofstiffenersweretreatedasreverseforcesandmomentsonthedoublecylindricalshell.Intheacousticfieldproducedbyvibrationandsoundradiationofthedoubleshell,thestructuredynamicequation,Helmholtzequationinthefluidfieldandthecontinuityconditionsofthesurfaceoffluid-structurecomposethevibrationequationcoupledbythesound-fluid-structure.Theextractofacousticpressurecomesdowntotheextractofcouplingvibrationequation.Thenearfieldacousticpressurecanbesolveddirectlybycomplicatedcalculationalmethods.

简介：Basedonthefundamentaldynamicequationsoffunctionallygradedmaterial(FGM)cylindricalshell,thispaperinvestigatesthesoundradiationofvibrationalFGMshellinwaterbymobilitymethod.ThismodeltakesintoaccounttheexteriorfluidloadingduetothesoundpressradiatedbytheFGMshell.TheFGMcylindricalshellwasexcitedbyaharmoniclineradialforceuniformlydistributingalongthegenerator.TheFGMshellequationsofmotion,theHelmholtzequationintheexteriorfluidmediumandth...

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简介：Wepresentadesignmethodforcalculatingandoptimizingsoundabsorptioncoefficientofmulti-layeredporousfibrousmetals(PFM)inthelowfrequencyrange.PFMissimplifiedasanequivalentidealizedsheetwithallmetallicfibersalignedinonedirectionanddistributedinperiodichexagonalpatterns.Weuseaphenomenologicalmodelintheliteraturetoinvestigatetheeffectsofporegeometricalparameters(fiberdiameterandgap)onsoundabsorptionperformance.ThesoundabsorptioncoefficientofmultilayeredPFMsiscalculatedusingimpedancetranslationtheorem.Todemonstratethevalidityofthepresentmodel,wecomparethepredictedresultswiththeexperimentaldata.Withtheaveragesoundabsorption(lowfrequencyrange)astheobjectivefunctionandthefibergapsasthedesignvariables,anoptimizationmethodformulti-layeredfibrousmetalsisproposed.Anewfibrouslayoutwithgivenporosityofmulti-layeredfibrousmetalsissuggestedtoachieveoptimallowfrequencysoundabsorption.Thesoundabsorptioncoefficientoftheoptimalmulti-layeredfibrousmetalishigherthanthesinglelayeredfibrousmetal,andasignificanteffectofthefibrousmaterialonsoundabsorptionisfoundduetothesurfaceporosityofthemulti-layeredfibrous.