analyses of sandwich beams and plates with viscoelastic cores (phd thesis, 2001)(216s)外语英文电子书

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1、ABSTRACTTitleofDissertation:AnalysesofSandwichBeamsandPlateswithViscoelasticCoresGangWang,DoctorofPhilosophy,2001Dissertationdirectedby:AssociateProfessorNormanM.WereleyDepartmentofAerospaceEngineeringAhybriddampingschemeusingpassiveconstraineddampinglayers(PCLD),andsurfacebonded

2、piezoceramicactuatorswasproposedforinteriorcabinnoiseandvibrationcontrolinhelicopters.Inordertoevaluatetheperformanceofthesetreatments,weneedtounderstandthedynamicbehaviorofsandwichstructures.Theanalysesofsandwichstructuresarecomplicatedbythefrequencydependentstiffnessanddampingpr

3、opertiesofviscoelasticmaterials.Themethodsdevel-opedinthisthesisspecificallydealwithfiniteelementmethodsandassumedmodesmethodstothisproblem.Aspectralfiniteelementmethod(SFEM)wasdevelopedinthefrequencydomainforsandwichbeamanalysis.Theresultsofnaturalfrequenciesandfre-quencyresponsesf

4、ortwocantileveredbeamswithdifferentspanofPCLDtreat-mentswerepresentedandvalidatedbyexperimentalresultsandotheranalyses;includingtheassumedmodesmethod(AM),andconventionalfiniteelementmethod(CFEM).TheSFEMmethodimplicitlyaccountsforfrequencydepen-dentstiffnessanddampingofviscoelasticma

5、terials.However,CFEMandAMmethodhavetouseadditionalinternaldissipationcoordinatestoaccountfortheseproperties.TheGolla-Hughes-McTavish(GHM)dampingmethodwasusedinbothanalyses.AlsoSFEMimprovesaccuracyoffrequencypredictionscomparedtotheresultsofCFEMandAMmethodbecauseofitshigherorderin

6、terpolationfunctions.WeexpectedtoextendSFEMmethodtotwo-dimensionalsandwichplatestructures.Butitisextremelydifficulttosolvethegoverningequationsforasandwichplate.AnalternativemethodwasdevelopedtoupdatethetraditionalAMmethodbyusingplatemodeshapes.Theplatemodeshapefunctionsweresolvedd

7、irectlybasedontheKantorovichvariationalmethodforbothtransversebendingandin-planevibrationofisotropicrectangularplates.TheseplatemodeshapeswereemployedtocalculatesandwichplatesinAMmethod.Theresultsofnaturalfrequencies,lossfactorsandfrequencyresponsefunctionswerecalculatedandvalida

8、tedbyexperimentaldataandtheresultsbyusin