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©2008ANSYS,Inc.Allrightsreserved.1ANSYS,Inc.Proprietary2008InternationalANSYSConferenceGuidelinesforObtainingContactConvergenceJosephTMetrisinTurbomachineryFloridaTurbineTechnologies,Inc.©2008ANSYS,Inc.Allrightsreserved.2ANSYS,Inc.Proprietary•IncorporatedinOctober1998•Morethan170peoplewithanaverageexperiencebaseof19years•Morethan300patentapplicationsfiledsinceincorporationAtAGlance…FTTFTT…AleaderininnovationandtechnicalexcellenceFTA37F–Two-SpoolTurbofanDevelopedfortheArmyforApplicationsRequiringPerformanceandFuelEfficiency•FTTspecializesingasturbine,turbomachinery,andpropulsioncomponents,systems,andengineeringforaircraft,space,industrialpower,andcleanenergyOurVision:•Tobethepreferredsupplierofturbomachinerytechnologyandhardwareintheworld•Developedtheworld’sfirstminiatureturbofanforsmallaircraftrequiringhighfuelefficiencyandperformance•HeadquarteredinJupiter,Floridawithapproximately200,000sqftoffacilitiesforengineering,component&systemassembly&testTurbineRigDeveloped,InstrumentedandAssembledforNASAinFTT’sJupiter,FLFacility©2008ANSYS,Inc.Allrightsreserved.3ANSYS,Inc.ProprietaryDebuggingContactAnalyses•ContactelementsareapowerfulfeatureinANSYS,howeverthenumerousbehavioroptionsandinputscanbedaunting.•Anestimated75%oftheinternalsupportcallsatmycompanyarerelatedtodifficultywithcontactelementconvergence.•Overmanyyears,Ihavedevelopedamethodicalprocessfortroubleshootinganddebuggingcontactanalyses.•Thesetechniquesmayormaynotbeuniquetogasturbineapplications.©2008ANSYS,Inc.Allrightsreserved.4ANSYS,Inc.ProprietaryTypicalTurbomachineryApplications•2Daxisymmetricengineassemblymodels.–SmallModels,many(100+)contactpairs•3Dcomponentassemblymodels–LargeModels,few(1-10)contactpairs©2008ANSYS,Inc.Allrightsreserved.5ANSYS,Inc.Proprietary[K][U]=[Fa]Forcontactproblems,[K]isanonlinearfunctionof[U]Nonlinearequationswrittenas:[Kit][ΔUi]=[Fa]–[Finr]Displacementchangebetweeniterations:{Ui+1}={Ui}+{ΔUi}[Kit]=Jacobianmatrix(tangentmatrix).i=currentequilibriumiterationnumber.[Fa]=Vectorofappliedloads.[Finr]=Vectorofrestoringloads(opposestheinternalnodalloads).[R]=[Fa]–[Finr]Residual,orout-of-balanceforcevector.[R]0.001[Fa]Convergencecriteria(Residualmustbelessthan0.1%oftheappliedload.NewtonRaphsonMethod©2008ANSYS,Inc.Allrightsreserved.6ANSYS,Inc.Proprietary[K][U]=[Fa][Kit][ΔUi]=[Fa]–[Finr]{Ui+1}={Ui}+{ΔUi}NewtonRaphsonMethod1.Duringequilibriumiterations,ANSYSmakesaguessat[ΔUi]2.[Kit][ΔUi]isthencalculatedandideally,shouldexactlyequal[Fa]foraconvergedsolution.Inreality,therewillbesomeout-of-balanceforce[Finr].Considerthatif[Kit]isveryhigh,ahugeforceiscalculatedforabadguessat[ΔUi]3.TheResidualout-of-balanceforcevector[R]=[Fa]–[Finr]iscalculatedandcomparedtoconvergencecriteria[R]0.001[Fa]4.Atthenextiteration,[ΔUi]isadjustedand[R]isrecalculated.5.Iterationscontinueuntilconvergenceisachieved.©2008ANSYS,Inc.Allrightsreserved.7ANSYS,Inc.ProprietaryUnderstandingthesolutionoutputiskeytotroubleshootingconvergenceproblems:Keytermsare:UnderstandingSolutionOutputForceConvergenceValue–Thisistheresidualout-of-balanceforcevector[R]=[Fa]–[Finr]shownpreviously.Criterion–Forceconvergencecriteria[R]0.001[Fa]Theforceconvergencevaluemustbebelowthisvalueforconvergence.MaxDOFInc–Themaximumdisplacementthatoccurredonanynodeinthemodelduringthepreviousiteration.ScaledMaxDOFIncrement–LinesearchparameterxMaxDOFInc.(Thisisthedisplacementvectoractuallyused).©2008ANSYS,Inc.Allrightsreserved.8ANSYS,Inc.ProprietaryALLCURRENTANSYSDATAWRITTENTOFILENAME=crap.rdbFORPOSSIBLERESUMEFROMTHISPOINT2DCONTACTELEMENTS:7CONTACTPOINTSHAVETOOMUCHPENETRATIONFORCECONVERGENCEVALUE=0.8836E+08CRITERION=0.5102E-04EQUILITER1COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=-0.1495E-01LINESEARCHPARAMETER=0.9965SCALEDMAXDOFINC=-0.1490E-01FORCECONVERGENCEVALUE=0.2978E+06CRITERION=1015.EQUILITER2COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=-0.5928E-02LINESEARCHPARAMETER=0.8926E-01SCALEDMAXDOFINC=-0.5291E-03FORCECONVERGENCEVALUE=0.2149E+06CRITERION=1021.EQUILITER3COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=0.2503E-02LINESEARCHPARAMETER=1.000SCALEDMAXDOFINC=0.2503E-02FORCECONVERGENCEVALUE=0.7388E+05CRITERION=1099.EQUILITER4COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=0.1707E-02LINESEARCHPARAMETER=0.2963SCALEDMAXDOFINC=0.5059E-03FORCECONVERGENCEVALUE=0.8894E+05CRITERION=1123.EQUILITER5COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=0.1181E-02LINESEARCHPARAMETER=1.000SCALEDMAXDOFINC=0.1181E-02FORCECONVERGENCEVALUE=0.4430E+05CRITERION=1166.EQUILITER6COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=-0.1707E-03LINESEARCHPARAMETER=0.5845SCALEDMAXDOFINC=-0.9977E-04FORCECONVERGENCEVALUE=0.2803E+05CRITERION=1188.EQUILITER7COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=-0.7212E-04LINESEARCHPARAMETER=1.000SCALEDMAXDOFINC=-0.7212E-04FORCECONVERGENCEVALUE=7756.CRITERION=1214.EQUILITER8COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=-0.1465E-04LINESEARCHPARAMETER=1.000SCALEDMAXDOFINC=-0.1465E-04FORCECONVERGENCEVALUE=1869.CRITERION=1239.EQUILITER9COMPLETED.NEWTRIANGMATRIX.MAXDOFINC=-0.3498E-05LINESEARCHPARAMETER=1.000SCALEDMAXDOFINC=-0.3498E-05FORCECONVERGENCEVALUE=442.6CRITERION=1264.CONVERGED