ABAQUS分析收敛控制.docx
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ABAQUS分析收敛控制.docx
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ABAQUS分析收敛控制
AbaqusAnalysisUser'sManual
7.2.1 Convergenceandtimeintegrationcriteria:
overview
NumerouscontrolparametersareassociatedwiththeconvergenceandintegrationaccuracyalgorithmsinAbaqus/Standard.Theseparametersareassigneddefaultvaluesthatarechosentooptimizetheaccuracyandefficiencyofthesolutionforawidespectrumofnonlinearproblems.Youcanchangethesolutioncontrolparameters,asdescribedinthefollowingsections:
∙Abriefsynopsisofthemoreimportantsolutioncontrolparameters,togetherwithadescriptionofthecircumstancesinwhichtheycanbeusedeffectively,isprovidedin“Commonlyusedcontrolparameters,”Section7.2.2.Thissectionislikelytobethemostusefulforthegeneraluserandshouldbereadfirst.
∙Abaqus/Standardincorporatesanempiricalalgorithmdesignedtosolvetheequilibriumequationsofnonlinearsystemsaccuratelyandeconomically.Thecriteriausedtoestablishconvergenceofnonlinearincrementsandtheautomaticadjustmentofincrementsizebasedontheconvergenceratearedescribedin“Convergencecriteriafornonlinearproblems,”Section7.2.3.
∙Abaqus/Standardallowsyoutochoose“timeintegrationaccuracyparameters”inproblemsthathaveaphysicaltimescale.Thealgorithmsthatusetheseparametersforautomaticallycontrollingtimeincrementsizesaredescribedin“Timeintegrationaccuracyintransientproblems,”Section7.2.4.
∙Abaqus/CFDallowsyoutochoosethecontrolparametersusedinanAbaqus/CFDtoAbaqus/StandardortoAbaqus/Explicitco-simulationtoalleviateinstabilityandmeshdistortionduringtheanalysis.
Modifyingthedefaultsolutioncontrols
Thedefaultvaluesforthesolutioncontrolparametersneednotbeadjustedformostcases.Youcanresetthem,however,withinastepdefinition.
Valuesgivenforthesolutioncontrolparametersremainineffectfortheremainderoftheanalysisoruntiltheyarereset.
Input File Usage:
*CONTROLS
The*CONTROLSoptioncanberepeated,ifnecessary,withdifferentparameters.
Abaqus/CAE Usage:
Stepmodule:
Other
GeneralSolutionControls
Edit:
toggleonSpecify
Resettingalldefaultsolutioncontrols
Youcanrestoreallsolutioncontrolparameterstotheirdefaultvalues.
Input File Usage:
*CONTROLS,RESET
Abaqus/CAE Usage:
Stepmodule:
Other
GeneralSolutionControls
Edit:
toggleonResetallparameterstotheirsystem-defineddefaults
7.2.2 Commonlyusedcontrolparameters
Products:
Abaqus/Standard Abaqus/CFD Abaqus/CAE
References
∙“Convergenceandtimeintegrationcriteria:
overview,”Section7.2.1
∙*CONTROLS
∙“Customizinggeneralsolutioncontrols,”Section14.15.1oftheAbaqus/CAEUser'sManual
Overview
Solutioncontrolparameterscanbeusedtocontrol:
∙nonlinearequationsolutionaccuracy;
∙timeincrementadjustment;and
∙FSIstabilizationandmeshdistortioninanAbaqus/CFDtoAbaqus/StandardortoAbaqus/Explicitco-simulation.
Thesesolutioncontrolparametersneednotbechangedformostanalyses.Indifficultcases,however,thesolutionproceduremaynotconvergewiththedefaultcontrolsormayuseanexcessivenumberofincrementsanditerations.Afterithasbeenestablishedthatsuchproblemsarenotduetomodelingerrors,itmaybeusefultochangecertaincontrolparameters.
Thissectionpresentsabriefsynopsisofthemoreimportantsolutioncontrolparameters,togetherwithadescriptionofthecircumstancesinwhichtheycanbeusedeffectively.
Valuesgivenforthesolutioncontrolparametersremainineffectfortheremainderoftheanalysisoruntiltheyarereset.Youcanrestoreallsolutioncontrolparameterstotheirdefaultvalues(see“Convergenceandtimeintegrationcriteria:
overview,”Section7.2.1).
Terminology
Inthissectiontheword“flux”meansthevariablewhosediscretizedequilibriumisbeingsoughtandforwhichtheequilibriumequationsmaybenonlinear:
force,moment,heatflux,concentrationvolumetricflux,orporeliquidvolumetricflux.Theword“field”referstothebasicvariablesofthesystem,suchasthecomponentsofthedisplacementinacontinuumstressanalysisortemperatureinaheattransferanalysis.Thesuperscript
referstoonesuchtypeofequation.ThefieldsandcorrespondingfluxesavailableinAbaqus/Standardarelistedin“Convergencecriteriafornonlinearproblems,”Section7.2.3.
Definingtolerancesforfieldequations
Solutioncontrolparameterscanbeusedtodefinetolerancesforfieldequations.Youcanselectthetypeofequationforwhichthesolutioncontrolparametersarebeingdefined,asshowninTable7.2.2–1.Thedefaulttolerancescanberesetiftheanalysisdoesnotrequirehighaccuracyintheconvergencecriteria.
Table7.2.2–1Selectingthefieldequation.
Equilibriumequation
Inputfile
Abaqus/CAE
DOF
Allactivefields
FIELD=GLOBAL
Applytoallapplicablefields
all
Forceandbimoment
FIELD=DISPLACEMENT
Displacement
1,2,3,7
Moment
FIELD=ROTATION
Rotation
4,5,6
Heattransfer
FIELD=TEMPERATURE
Temperature
11,12,13,...
Hydrostaticfluid
FIELD=HYDROSTATICFLUIDPRESSURE
HydrostaticFluidPressure
8
Porefluidpressure
FIELD=POREFLUIDPRESSURE
PoreFluidPressure
8
Massdiffusion
FIELD=CONCENTRATION
Concentration
11
Electricalconduction
FIELD=ELECTRICALPOTENTIAL
ElectricalPotential
9
Mechanismanalysis(connectorelementswithmaterialflowdegreeoffreedom)
FIELD=MATERIALFLOW
Unsupported
10
AnalysiscontainingC3D4Helements(allmaterials,exceptcompressiblehyperelasticelastomersandelastomericfoams).
FIELD=PRESSURELAGRANGEMULTIPLIER
Unsupported
N/A
AnalysiscontainingC3D4Helementswithcompressiblehyperelasticorhyperfoammaterials.
FIELD=VOLUMETRICLAGRANGEMULTIPLIER
Unsupported
N/A
Themostsignificantsolutioncontrolparametersforfieldequationtolerances—
and
—mayhavetobemodifiedincaseswheretheresidualsarelargerelativetothefluxesorincaseswheretheincrementalsolutionisessentiallyzero.
Input File Usage:
*CONTROLS,PARAMETERS=FIELD,FIELD=field
Abaqus/CAE Usage:
Stepmodule:
Other
GeneralSolutionControls
Edit:
toggleonSpecify:
FieldEquations:
ApplytoallapplicablefieldsorSpecifyindividualfields:
field
Modifyingtheresidualcontrol
istheconvergencecriterionfortheratioofthelargestresidualtothecorrespondingaveragefluxnorm,
forconvergence.
isdefinedin“Convergencecriteriafornonlinearproblems,”Section7.2.3.Thedefaultvalueis
=5×10–3,whichisratherstrictbyengineeringstandardsbutinallbutexceptionalcaseswillguaranteeanaccuratesolutiontocomplexnonlinearproblems.Thevalueforthisratiocanbeincreasedtoalargernumberifsomeaccuracycanbesacrificedforcomputationalspeed.
Modifyingthesolutioncorrectioncontrol
istheconvergencecriterionfortheratioofthelargestsolutioncorrectiontothelargestcorrespondingincrementalsolutionvalue.Thedefaultvalueis
=10–2.Inadditiontosufficientlysmallresiduals,Abaqus/Standardrequiresthatthelargestcorrectiontothesolutionvaluebesmallincomparisontothelargestcorrespondingincrementalsolutionvalue.Someanalysesmaynotrequiresuchaccuracy,thuspermittingthisratiotobeincreased.
Specifyingtheaverageflux
isthevalueofaveragefluxusedbyAbaqus/Standardforcheckingresiduals.ThedefaultvalueisthetimeaveragefluxcalculatedbyAbaqus/Standard,asdefinedin“Convergencecriteriafornonlinearproblems,”Section7.2.3.Youmay,however,defineaconstantvalue,
fortheaverageflux,inwhichcase
throughoutthestep.
Youmaywishtouseabsolutetolerancesforyourresidualchecks.Theabsolutetolerancevalueisthenequaltotheproductoftheaverageflux,
andtheratio
.Toavoidtestingthemagnitudeofthesolutioncorrection,youcanset
to1.0.
Modifyingtheinitialtimeaverageflux
istheinitialvalueofthetimeaveragefluxforthecurrentstep.Thedefaultvalueisthetimeaveragefluxfromthepreviousstepor10–2ifthisisStep 1.Redefining
issometimeshelpfulwhenacoupledproblemisanalyzedandsomeofthefieldsintheproblemarenotactiveinthefirststep;forexample,ifastaticstepiscarriedoutbeforeafullycoupledthermal-stressstep.
Redefinitionof
canalsobeusefulifthefirststepisessentiallyanullstep;forexample,inacontactproblembeforeanycontactoccurs,theinitialfluxes(forces)generatedarezero.Insuchcases
shouldbegivenasatypicalfluxmagnitudethatwilloccurwhenfield
firstbecomesactive.
Theinitialvalueof
isretaineduntilaniterationiscompletedforwhich
atwhichtimeweredefine
.Thecriterionforzerofluxcomparedto
is
(see“Convergencecriteriafornonlinearproblems,”Section7.2.3).
Ifyouspecifytheaverageflux,
directly,thevaluegivenfor
isignored.
Abaqus/Standardoutput
Thecontrolsineffectforananalysisarelistedinthedata(.dat)andmessage(.msg)files.Nondefaultcontrolsaremarkedby***.Forexample,specifyingthefollowingcontrols:
FieldEquation
Displacement
0.01
1.0
10.0
–
–
1.E–4
Rotation
0.02
2.0
20.0
2.E3
–
–
wouldresultinthefollowingoutput:
CONVERGENCETOLERANCEPARAMETERSFORFORCE
***CRIT.FORRESIDUALFORCEFORANONLINEARPROBLEM1.000E-02
***CRITERIONFORDISP.CORRECTIONINANONLINEARPROBLEM1.00
***INITIALVALUEOFTIMEAVERAGEFORCE10.0
AVERAGEFORCEISTIMEAVERAGEFORCE
ALT.CRIT.FORRESIDUALFORCEFORANONLINEARPROBLEM2.000E-02
***CRIT.FORZEROFORCERELATIVETOTIMEAVRG.FORCE1.000E-04
CRIT.FORDISP.CORRECTIONWHENTHEREISZEROFLUX
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