FE MODEL VALIDATION FOR STRUCTURAL DYNAMICS

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1、ImperialCollegeofScience,TechnologyandMedicineUniversityofLondonFEMODELVALIDATIONFORSTRUCTURALDYNAMICSbyGanChenAthesissubmittedtotheUniversityofLondonforthedegreeofDoctorofPhilosophyDynamicsSectionDepartmentofMechanicalEngineeringLondon,SouthKensingtonApril20011AbstractThisthesisdescribesstudieso

2、ffiniteelement(FE)modelvalidationmethodsforstructuraldynamics.ThereareusuallydiscrepanciesbetweenpredictionsofthestructuraldynamicpropertiesbasedonaninitialFEmodelandthoseyieldedbyexperimentaldatafromtestsontheactualstructure.Inordertomakepredictionsfromthemodelsuitableforevaluatingthedynamicprop

3、ertiesofthestructure,andthustooptimiseitsdesign,themodelhastobevalidated.Theprocessofmodelvalidationandtheindividualstepsthatmakeupthisprocessarestudiedthroughtheoreticalanalysisandcasestudies.Ageneralstrategyformodelvalidationispresentedintheintroductiontothethesis,describingthevalidationprocess

4、asasequenceofdistinctsteps.Astudyofthestrategypresentedattheendofthethesisshowsmultipleapproachesformodelvalidation.UsingexperienceobtainedfromvalidatingmodelsofexamplestructuresforconstructingandvalidatingthemodelofanewdesignofasimilarstructurecouldacceleratetheprocessofFEmodelvalidation,andther

5、eforebenefitindustrybyreducingthetimeofthedesign-examine-redesignloop.Throughcasestudies,anewperspectiveontheperformanceofmodelupdatingispresentedinthisworkshowingthatmodelupdatingcanonlyminimisethediscrepanciescausedbyparametererrorsinthemodel.However,modelupdatingprocedurescannotreducediscrepan

6、ciescausedbydiscretisationerrorsand/orconfigurationerrorswithoutlosingthephysicalmeaningoftheupdatingparameters.Inordertomakesurethatamodelissuitableforbeingsubjectedtotheupdatingstep,themodelmustfirstbeverified.Twoverificationmethods,aconvergencecheckbyusingtwodifferentformulaeforconstructingthe

7、massmatrixofeachelementandaconfigurationcheckbyprojectingexperimentalmodeshapesontothesubspacespannedbyFEmodelpredictedeigenvectors,areproposedtodealwithdiscretisationerrorsandconfigurationerrorsrespectivelyinFEmodels.