nastran热模态分析normal modes with preload.ppt

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1、Section18NormalModesofPreloadedStructuresSection18NormalModesofPreloadedStructuresNORMALMODESWITHDIFFERENTIALSTIFFNESS……………………………18-3PROBLEM#14-NORMALMODESWITHPRELOAD………………………..…..18-7PROBLEM#14-MODESOFPRELOADEDSTRUCTURE……………………….18-9INPUTFILEFORPROBLEM

2、#14A-MODESWITHOUTPRELOAD……………18-10PARTIALOUTPUTFILEFORPROBLEM#14A-MODESWITHOUTPRELOAD………………………………………………………………………18-11INPUTFILEFORPROBLEM#14B-MODESWITHPRELOADUSINGSOL106…………………………………………………18-12PARTIALOUTPUTFILEFORPROBLEM14B-MODESWITHPRELOADUSINGSOL106…………

3、………………………………………18-13INPUTFILEFORPROBLEM#14C-MODESWITHPRELOADUSINGSOL103…………………………………………...……18-14PARTIALOUTPUTFILEFORPROBLEM#14CMODESWITHPRELOADUSINGSOL103…………………………………………………18-15NormalModesWithDifferentialStiffnessCalculatethemodesofstructureswithprelo

4、ads,largechangesingeometry,and/ornonlinearmaterials.NormalModesWithDifferentialStiffness(Cont.)LargeGeometryChangesu1NonlinearMaterialk1Fk0K0=k1NormalModesWithDifferentialStiffness(Cont.)Proceduresforobtainingfrequenciesofapreloadedstructure.Method1Use

5、SOL106.Includelinearornonlinearmaterialpropertiesasrequiredbymodeling.Ifmaterialislinear,thenonlylinearmaterialpropertiesarereferenced.IncludePARAM,LGDISP,1intheBulkDataSection.Onlytheresidualstructure(SEID=0)maycontainnonlinearelements.Allupstreamsupere

6、lementsmustbelinear.AMethod=XCaseControlCommandabovethefirstsubcasecallsouttheappropriateEIGRLentry.IncludePARAM,NMLOOP,XwhereX<>0.ThenonlinearnormalmodeswillbecomputedatthelastiterationloopofeachsubcaseinwhichaMethodcommandappearsNormalModesWithDiffere

7、ntialStiffness(Cont.)Proceduresforobtainingfrequenciesofapreloadedstructure.Method2UseSOL103.Materialmustbelinear.Twosubcasesarerequired.Thefirstsubcaseisastaticsubcasecallingoutthepreload.Thesecondsubcasecalculatedthemodeswithamethod=xcallout.Theseconds

8、ubcasemustalsocontainastatsub=ycommand,wherey=subcaseIDofthefirstsubcase.Problem#14NormalModesWithPreloadProblem#14-ModesofPreloadedStructureConsiderthesimplysupportedbeamasshownbelow.Calculatethefirstbendingfrequency:Wit