Vibration Analysis of Cracked Composite Bending-torsion Beams for Damage Diagnosis.pdf

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1、VibrationAnalysisofCrackedCompositeBending-torsionBeamsforDamageDiagnosisKaihongWangDissertationsubmittedtotheFacultyoftheVirginiaPolytechnicInstituteandStateUniversityinpartialfulfillmentoftherequirementsforthedegreeofDoctorofPhilosophyinMechanicalEngine

2、eringDanielJ.Inman,ChairmanDonaldJ.LeoGyuhaeParkHarryH.RobertshawMahendraP.SinghNovember29,2004Blacksburg,VirginiaKeywords:vibrationanalysis,crackedcomposite,bending-torsioncoupling,crackdetection,crackedcompositewing,flutteranddivergence,Info-gapmodeling

3、Copyright2004,KaihongWangVibrationAnalysisofCrackedCompositeBending-torsionBeamsforDamageDiagnosisKaihongWang(ABSTRACT)Ananalyticalmodelofcrackedcompositebeamsvibratingincoupledbending-torsionisdeveloped.Thebeamismadeoffiber-reinforcedcompositewithfiberan

4、glesineachplyalignedinthesamedirection.Thecrackisassumedopen.Thelocalflexibilityconceptisimplementedtomodeltheopencrackandtheassociatedcompliancematrixisderived.Thecrackintroducesadditionalboundaryconditionsatthecracklocationandtheseeffectsinconjunctionwi

5、ththoseofmaterialpropertiesareinvestigated.Freevibrationanalysisofthecrackedcompositebeamispresented.Theresultsindicatethatvariationofnaturalfrequenciesinthepresenceofacrackisaffectedbythecrackratioandlocation,aswellasthefiberorientation.Inparticular,thev

6、ariationpatternisdifferentasthemagnitudeofbending-torsioncouplingchangesduetodifferentfiberangles.Whenbendingandtorsionalmodesareessentiallydecoupledatacertainfiberangleifthereisnocrack,thecrackintroducescouplingtotheinitiallyuncoupledbendingandtorsion.Ba

7、sedonthecrackmodel,aeroelasticcharacteristicsofanunsweptcompositewingwithanedgecrackareinvestigated.Thecrackedcompositewingismodeledbyacrackedcompositecantileverandtheinertiacouplingtermsareincludedinthemodel.Anapproximatesolutiononcriticalflutteranddiver

8、gencespeedsisobtainedbyGalerkin’smethodinwhichthefundamentalmodeshapesofthecrackedwingmodelinfreevibrationareused.Itisshownthatthecriticaldivergence/flutterspeedisaffectedbytheelasticaxislocation,theinertiaaxislocat