boeing spec. d6254000006, finite element modeling guide for aircraft structural analysis198902)外语英文电子书

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1、oThestructureisthenanalyzedby:(a)Generatingasolutionwithsymmetricboundaryconditionsintheplaneofsymmetryandwiththesymmetricalcomponentsoftheappliedloads.(b)Generatingasecondsolutionwithantisymmetricboundaryconditionslntheplaneofsyrrrnetryandwiththeantisy

2、mmetricalcomponentsoftheappliedloads.(c)Superimposingtheresultsfromsteps(a)and(b)toobtainthefinalnonsymrnetricalsolution.Useofsymmetryinperformingstructuralanalysesisillustratedbyexamplesinthefollowingsection.40.5.4ExampleUsesofSymmetryFigure40.5-3shows

3、asymmetricstructureinwhichsymmetrycanbeexploitedforalinearanalysis.pRelativetotheplaneA-Athereis:(/oSymmetricgeometryI·....·..........·....·oSymmetricelasticproperties·••·········-•...-·•••••1•••••....oSymmetricsupports~6Thus,amodelofhalfofthestructure

4、canbeused.Theunsymmetrical(asymmetrical)loadingistreatedbysuperpositionofthefollowingsymmetriccaseandantisymmetriccase.SymmetricCaseP/2----------t~--""'"P/2oSymmetricloadingp=:::~--_____.I~.~------r~r-------"II..••••••oSymmetricdisplacements•II..:•:I:I.

5、.~~..........-----""oSymmetricboundary::~.................._____•r::.JL________I1.•••••========~........~....conditionsinplaneA-A~~----------------~~~IA~AntisymmetricCase~~~~:::;;;-!A_-----?__--toAntisymmetricloadingtilI"....·..----'.-IIII..··+IIII..l··

6、oAntisymmetricdisplacementsIIIIIIIIIIIII··IIIIII..-"..."~""~.......-~~:::::::::=::::::~oAntisymmetricboundary1----------------A-conditionsinplaneA-AIATFigure40.5-3StructureinWhichSymmetryCanbeExploited40.1406-25400-0006Figure40.5-4showsastructureinwhich

7、symmetrycannotbeexploited.RelativetotheplaneA-Athereis:pJA/oSymmetricgeometry/l/........,··•t·••..·....·oSymmetricelasticproperties······~....·...•.!I•••......···oNon-symmetricsupports--Thus,amodelofthecompletestructuremustbeused.Figure40.5-4Structurein

8、WhichSymmetryCannotbeExploitedFigure40.5-5showsastructurehavingmultiplesymmetrieswhichsatisfythesymmetrycriteriaforbothlinearandnonlinearanalyses.RelativetotheplanesXOZandYOZthereis:ZyoSymmetricgeometryoSymmetricelasticproperties