The coupling thermal mechanical and microstructural model fo

The coupling thermal mechanical and microstructural model for the FEM simulation of cross wedge roll

JournalofMaterialsProcessingTechnology172(2006)

202–207

Thecouplingthermal–mechanicalandmicrostructuralmodelfor

theFEMsimulationofcrosswedgerolling

XuetongLia, ,MintingWangb,FengshanDua,b

b

CollegeofMechanicalEngineering,YanshanUniversity,Qinhuangdao066004,PRChina

KeyLaboratoryofMetastableMaterialsScienceandTechnology,YanshanUniversity,Qinhuangdao066004,PRChina

Received30April2003;receivedinrevisedform13September2005;accepted19October2005

a

Abstract

ThemicrostructuralevolutionmodelsonAISI5140wereobtainedusingtheGleeble-3500thermo-mechanicalsimulator.Simulationonthecrosswedgerolling(CWR)processhasbeencarriedoutontheplatformof niteelementsoftwareDEFROM-3Dwiththermo-mechanicandmicrostructuralevolutioncoupled.Anddistributionsofthedifferent eld-variablesduringthewholerollingprocessfromthekni ng,guiding,stretchingtosizingstage,suchaseffectivestrain,effectivestrainrateandtemperature,wereobtained.Meanwhile,three-dimensional(3D)distributionofaustenitegrainsizeofworkpiecewasalsoachieved.Itissigni canttounderstandthenet-shapedmechanismandoptimizeCWRtechnology.

©2005ElsevierB.V.Allrightsreserved.

Keywords:CWR;Finiteelementmethod(FEM);Microstructuralevolution;Grainsize

1.Introduction

TheCWRtechniqueisatypicalrotaryformingmethod,whosemanyintegratedvirtuescamefrombothforgingprocessandmetallurgicalrollingtechnology.Owingtosinglecontin-uouslocallargedeformationforworkpiece,CWRhashighproductivity.However,justthisdeformationstylealsoleadstosomeproductdefects[1,2]andsomeengineeringproblems,suchasnecking,surfacespiralandinnerporousvoidandcracks,etc.So,itishelpfulforCWRtechniquedevelopmenttounderstandtherelationshipsamongrollingforces,deformationandinnermicrostructureevolution.Thoughmanyresearchersmadegreateffortsonaboveproblems[3–11]andmicrostructuralevolutionsimulationsforotherformingprocesseshavebeenmade[12,13],fewliteraturesontwo-rollCWRwerereported.

BasedonthesoftwareDEFROM-3D,asimulationmodelfortheCWRprocesshasbeendevelopedbymeansof3Drigid-viscoplasticFEMinthisstudy.Inthismodel,manyfactorsincludingthermal,mechanicalandmicrostructuralevolutionaretakenintoaccountcomprehensively.Themicrostructuralevolu-tionmodelsonAISI5140wereobtainedusingtheGleeble-3500

thermo-mechanicalsimulator.Anddistributionsofthediffer-ent eld-variableswereobtainedaftersimulation.Theseresultsareusefultounderstandthenet-shapemechanismandoptimizeCWRtechnology.

2.FEMandmicrostructuremodelsofCWR

TheCWRreferstoametalformingprocessinwhichacylin-dricalbilletisplasticallydeformedintoanotheraxisymmetricalshapebytheactionofwedgeshapetoolsmovingtangentiallyrelativetoeachother[9].Theroundedbarsareprolongedfreelyintheaxisdirection,andatthesametimeitscross-sectionareaisreducedduringtheformingprocess.

FEMsoftwareDEFORMdevelopedbyBattelColumbuslabintheUnitedStateswasusedtoestablishsimulationmodelfortheCWRprocess.Basedonrigid-viscoplastic niteelementthe-ory,aCWRmodelwiththermo,mechanicsandmicrostructurecoupledhasbeendevelopedandsolvedsuccessfully.Thetech-niqueofautomaticremeshinginDEFORMcanrelievemeshsingularityduringthe niteelementsimulationprocess.2.1.FEMmodel

Correspondingauthor.Tel.:+863358074553.E-mailaddress:xtli@http://(X.Li).

Thereliabilityofthewholesimulationresultsisdirectlyin uencedbytheaccuracyofFEMmodeldeveloped.Andthe

0924-0136/$–seefrontmatter©2005ElsevierB.V.Allrightsreserved.doi:10.1016/j.jmatprotec.2005.10.011

The coupling thermal mechanical and microstructural model for the FEM simulation of cross wedge roll

X.Lietal./JournalofMaterialsProcessingTechnology172(2006)202–207

203

Fig.1.CWRFEMmodel.

geometryprecisionof nalproductdependsmainlyontoolsdesign.CWRtoolsarecharacterizedbymulti-segmentstructureand3Dhigher-ordersurface,whichmakeitdif culttoconstructsolidmodel.Inthispaper,toolssolidmodelbasedonfeatureshasbeensetupwiththeaidofgeneralCADsoftwarePro-E.Consideringhightemperaturedeformation,apartwasde nedasplasticbody.TodecreasecomputerCPUtime,toolswerede nedasrigidbody.FEMmodelofCWRisshowninFig.1.Themaincalculationconditionsareasfollows:workpiecediameter(d0),22mm;workpiecelength(b),35mm;rolldiame-ter(D),500mm;rotationalspeedofroll(ω),10rpm;workpieceinitialtemperature(T0),1000 C;surfaceemissivity(ξ),0.7;areareduction( A),40%;formingangle(α),28 ;spreadingangle(β),6 ;steppedtiltangle(θ),45 .2.2.Microstructrualevolutionmodel

PhysicalsimulationonAISI5140wascarriedoutusingtheGleeble-3500thermo-mechanicalsimulator.Thechemicalcom-positionsofthematerialtestedinweightpercentaredescribedindetailinTable1.

Basedontheresultsfromthermo-simulationexperiments,dynamicrecrystallizationofmediumcarbonsteelAISI5140forCWRprocessoccursunderthedeformationtemperaturefrom1100to900 Candstrainrate10.0–0.1s 1.Theactiva-tionenergyofdynamicrecrystallization,whichiscorrespondingwiththepeakstress,is370.6kJ/mol.TherelationshipbetweenpeakstressσporpeakstrainεpandfactorZisexpressedas:σp=2.626×10 9Z 6.08

(1)

Table1

Chemicalcompositionsofthesample(wt.%)

ElementsC

SiMnPSCrContent

0.41

0.28

0.62

0.018

0.02

0.88

εp=5.162×10 3Z0.128

(2)

whereZisZener Hollomanparameterasfollows.

Z=˙ε

expQ1

RT

(3)

TheexponentialrelationalexpressionbetweendynamicrecrystallizationgrainsizedandZiswrittenas:d=25004.8Z 0.211

(4)

Themodelforrecrystallizationkineticsisobtainedbyobservingthequenchingmicrostructureofthedeformedsam-plesofAISI5140underthedifferenttemperature,strainandstrainrate:

Xv=1 exp[ 20.691(ε ε0)3.492]

(5)

3.Resultsanddiscussion

FEMsimulationapplicationontheCWRprocesscanprovideeffectivefoundationsforanalysisonpartformingprocessanddeterminationofproperparametersoftooldesign,aswellasdi …… 此处隐藏：15522字，全部文档内容请下载后查看。喜欢就下载吧 ……