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MechanicsofMaterialsinModern ManufacturingMethodsand ProcessingTechniques
MechanicsofAdvancedMaterialsSeries
TheMechanicsofAdvancedMaterials bookseriesfocusesonmaterials-andmechanics-relatedissuesaroundthe behaviorofadvancedmaterials,includingthemechanicalcharacterization,mathematicalmodeling,andnumerical simulationsofmaterialresponsetomechanicalloads,variousenvironmentalfactors(temperaturechanges, electromagneticfields,etc.),aswellasnovelapplicationsofadvancedmaterialsandstructures. Volumesintheseriescoveradvancedmaterialstopicsandnumericalanalysisoftheirbehavior,bringingtogether knowledgeofmaterialbehaviorandthetoolsofmechanicsthatcanbeusedtobetterunderstand,andpredictmaterials behavior.Itpresentsnewtrendsinexperimental,theoretical,andnumericalresultsconcerningadvancedmaterialsand providesregularreviewstoaidreadersinidentifyingthemaintrendsinresearchinordertofacilitatetheadoptionof thesenewandadvancedmaterialsinabroadrangeofapplications.
Serieseditor-in-chief:VadimV.Silberschmidt
VadimV.SilberschmidtisChairofMechanicsofMaterialsandHeadoftheMechanicsofAdvancedMaterials ResearchGroup,LoughboroughUniversity,UnitedKingdom.HewasappointedtotheChairofMechanicsofMaterials attheWolfsonSchoolofMechanicalandManufacturingEngineeringatLoughboroughUniversity,UnitedKingdomin 2000.Priortothis,hewasaSeniorResearcherattheInstituteAforMechanicsatTechnischeUniversitatMunchenin Germany.EducatedintheUSSR,heworkedattheInstituteofContinuousMediaMechanicsandInstitutefor Geosciences[both—theUSSR(later—Russian)AcademyofSciences].In1993 94,heworkedasavisitingresearcher, FellowoftheAlexander-von-HumboldtFoundationatInstituteforStructureMechanicsDLR(GermanAerospace Association),Braunschweig,Germany.In2011 14,hewasAssociateDean(Research).HeisaChartedEngineer, FellowoftheInstitutionofMechanicalEngineersandInstituteofPhysics,wherehealsochairedAppliedMechanics Groupin2008 11.HeservesasEditor-in-Chief(EiC)oftheElsevierbookserieson MechanicsofAdvanced Materials.HeisalsoEiC,associateeditor,and/orservesontheboardofanumberofrenownedjournals.Hehas coauthoredfourresearchmonographsandover550peer-reviewedscientificpapersonmechanicsandmicromechanics ofdeformation,damage,andfractureinadvancedmaterialsundervariousconditions.
Serieseditor:ThomasBohlke
ThomasBohlkeisProfessorandChairofContinuumMechanicsattheKarlsruheInstituteofTechnology(KIT), Germany.HepreviouslyheldprofessorialpositionsattheUniversityofKasselandattheOtto-von-Guericke University,Magdeburg,Germany.HisresearchinterestsincludeFE-basedmultiscalemethods,homogenizationof elastic,brittle-elastic,andvisco-plasticmaterialproperties,mathematicaldescriptionofmicrostructures,and localizationandfailuremechanisms.Hehasauthoredover130peer-reviewedpapersandhasauthoredorcoauthored twomonographs.
Serieseditor:DavidL.McDowell
DavidL.McDowellisRegents’ProfessorandCarterN.Paden,Jr.DistinguishedChairinMetalsProcessingatGeorgia TechUniversity,UnitedStates.HejoinedGeorgiaTechin1983andholdsadualappointmentintheGWWSchoolof MechanicalEngineeringandtheSchoolofMaterialsScienceandEngineering.HeservedastheDirectorofthe MechanicalPropertiesResearchLaboratoryfrom1992to2012.In2012hewasnamedFoundingDirectorofthe InstituteforMaterials(IMat),oneofGeorgiaTech’sInterdisciplinaryResearchInstituteschargedwithfosteringan innovationecosystemforresearchandeducation.HehasservedasExecutiveDirectorofIMatsince2013.Hisresearch focusesonnonlinearconstitutivemodelsforengineeringmaterials,includingcellularmetallicmaterials,nonlinearand time-dependentfracturemechanics,finitestraininelasticityanddefectfieldmechanics,distributeddamageevolution, constitutiverelations,andmicrostructure-sensitivecomputationalapproachestodeformationanddamageof heterogeneousalloys,combinedcomputationalandexperimentalstrategiesformodelinghighcyclefatigueinadvanced engineeringalloys,atomisticsimulationsofdislocationnucleationandmediationatgrainboundaries,multiscale computationalmechanicsofmaterialsrangingfromatomisticstocontinuum,andsystem-basedcomputationalmaterials design.AFellowofSES,ASMInternational,ASME,andAAM,heistherecipientofthe1997ASMEMaterials DivisionNadaiAwardforcareerachievementandthe2008KhanInternationalMedalforlifelongcontributionstothe fieldofmetalplasticity.Hecurrentlyservesontheeditorialboardsofseveraljournalsandiscoeditorofthe InternationalJournalofFatigue.
Serieseditor:ZhongChen
ZhongChenisaProfessorintheSchoolofMaterialsScienceandEngineering,NanyangTechnologicalUniversity, Singapore.InMarch2000,hejoinedNanyangTechnologicalUniversity(NTU),SingaporeasanAssistantProfessor andhassincebeenpromotedtoAssociateProfessorandProfessorintheSchoolofMaterialsScienceandEngineering. SincejoiningNTU,hehasgraduated30PhDstudentsand5MEngstudents.Hehasalsosupervisedover200 undergraduateresearchprojects(FYP,URECA,etc.).Hisresearchinterestincludes(1)coatingsandengineered nanostructuresforcleanenergy,environmental,microelectronic,andotherfunctionalsurfaceapplicationsand(2) mechanicalbehaviorofmaterials,encompassingmechanicsandfracturemechanicsofbulk,compositeandthinfilm materials,materialsjoining,andexperimentalandcomputationalmechanicsofmaterials.Hehasservedasaneditor/ editorialboardmemberforeightacademicjournals.Hehasalsoservedasareviewerformorethan70journalsanda numberofresearchfundingagenciesincludingtheEuropeanResearchCouncil(ERC).Heisanauthorofover300 peer-reviewedjournalpapers.
Materials
MechanicsofMaterialsin ModernManufacturing MethodsandProcessing Techniques
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VadimV.Silberschmidt WolfsonSchoolofMechanical, ElectricalandManufacturingEngineering, LoughboroughUniversity,
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Listofcontributorsxiii
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1Modelingofmetalforming:areview1
UdayShankerDixit
1.1Introduction1
1.2Modelingissuesinvariousmetalformingprocesses2
1.2.1Forging2
1.2.2Rolling4
1.2.3Wiredrawing6
1.2.4Extrusion7
1.2.5Deepdrawing10
1.2.6Bending11
1.3Variousmodelingtechniques13
1.3.1Slabmethod13
1.3.2Slip-linefieldmethod13
1.3.3Visioplasticity14
1.3.4Upperboundmethod14
1.3.5Finitedifferencemethod15
1.3.6Finiteelementmethod15
1.3.7Meshlessmethod17
1.3.8Moleculardynamicssimulation18
1.3.9Softcomputing18
1.4Inversemodeling19
1.5Modelingofmicrostructureandsurfaceintegrity20
1.6Anoteonmultiscalemodelingofmetalforming22
1.7Challengingissues23
1.8Conclusion24 References25
2Finiteelementmethodmodelingofhydraulicandthermal autofrettageprocesses31 UdayShankerDixitandRajkumarShufen
2.1Introduction31
2.1.1Hydraulicautofrettage32
2.1.2Swageautofrettage33
2.1.3Explosiveautofrettage34
2.1.4Thermalautofrettage35
2.1.5Rotationalautofrettage35
2.2Numericalmodelingofelastic plasticproblems37
2.2.1Yieldcriteriaandhardeningbehaviorofthematerial38
2.2.2Approachesfornumericalmodelingofelastic plastic problems42
2.3FEMformulationusingupdatedLagrangianmethod44
2.3.1Derivationoftheweakformoftheequilibrium equation44
2.3.2Formulationofelementalequations46
2.3.3Solutionmethod50
2.4TypicalresultsofFEMmodelingofhydraulicandthermal autofrettage52
2.4.1Resultsofhydraulicautofrettage53
2.4.2Resultsofthermalautofrettage58 2.5Conclusion66
References67
3Mechanicsofhydroforming71 ChristophHartl
3.1Introduction71
3.2Modelingofplasticdeformationintubehydroforming74
3.2.1Rotationallysymmetricaltubeexpansion74
3.2.2Hydroformingofpolygonalcrosssections81
3.2.3Hydroformingoftubebranches85
3.3Determinationofforminglimitsintubehydroforming89
3.3.1Neckingandbursting89
3.3.2Wrinklingandbuckling95
3.4Designofloadingpaths98
3.5Conclusion101 References102
4Electromagneticpulseforming111
VerenaPsyk,MaikLinnemannandGerdSebastiani
4.1Processclassification111
4.2Processprincipleandmajorprocessvariants112
4.2.1Generalsetupandprocessprinciple112
4.2.2Majorprocessvariants113
4.3Calculationoftheprocessmechanics123
4.3.1Analyticalcalculationoftheactingloads123
4.3.2Numericalcalculationoftheprocess126
4.4Advantagesandapplicationfieldsofelectromagnetic pulseforming131
4.4.1Shaping132
4.4.2Joining136
4.4.3Cutting138
4.5Prospectsforfuturedevelopments139 References139
5Damageinadvancedprocessingtechnologies143 ZhutaoShao,JunJiangandJianguoLin
5.1Introduction143
5.1.1Conceptsofdamageanddamagevariables143
5.1.2Damagemechanisms143
5.1.3Advancedmanufacturingtechnology:hotstamping144
5.1.4Conceptandfeaturesofforminglimitdiagram145
5.2Overviewofformabilityevaluation146
5.2.1Forminglimitprediction146
5.2.2Experimentalmethodsfordeterminingforminglimits147
5.2.3Requirementsforhotstampingapplications149
5.2.4Advancedtestingsystemforhotstampingapplications150
5.3Modelingofdamageevolution151
5.3.1Constitutiveequations151
5.3.2Advanceddamagemodels153
5.3.3Asetofunifiedconstitutiveequationsforhotstamping155
5.3.4Modelingofforminglimitdiagrams156
5.4Damagecalibrationtechniques158
5.4.1Overviewofdamagecalibrationtechniques158
5.4.2Anexampleofusingthermomechanicaluniaxialtestdata159
5.4.3Examplesofusingthermomechanicalmultiaxial tensiletestdata160
5.5Applicationsofdamagemodelingtechniqueforhotstamping162
5.5.1Planestress basedcontinuumdamagemechanics materialmodel162
5.5.2Principalstrain basedcontinuumdamagemechanics materialmodel165
5.5.3Predictionofformabilityinhotforming170 5.6Conclusion171 References171
6Numericalmodelingofthemechanicsofpultrusion173
MichaelSandberg,OnurYuksel,Raphae¨lBenjaminComminal,Mads RostgaardSonne,MasoudJabbari,MartinLarsen,FilipBoSalling, IsmetBaran,JonSpangenbergandJesperH.Hattel
6.1Introduction173
6.1.1Pultrusion173
6.1.2Overviewandmotivationofthechapter175
6.2Resinimpregnation175
6.2.1Saturatedpressure-drivenflow176
6.2.2Resinviscosity177
6.2.3Permeabilityoffiberreinforcements177
6.2.4Unsaturatedimpregnationflow178
6.3Thermochemicalmodeling180
6.3.1Heattransfer180
6.3.2Curekineticsanddifferentialscanningcalorimetry181
6.3.3Modelingconsiderations:simplemodelsandstate-of-the-art182
6.4Thermochemical mechanicalmodelingandresidual stressformation183
6.4.1Theevolutionofmaterialproperties183
6.4.2Mechanicalmodelingstrategies184
6.4.3Assessmentoftheresultantresidualstressfields andtheverification186
6.5Pullingforce189
6.5.1Beforedie-entrance, A0 189
6.5.2Die-entrancetoflowfrontlocation, A1 189
6.5.3Throughliquidandgelstates, A2 190
6.5.4Solidstateanddetachmentfromdiewall, A3 191
6.6Conclusion191 References192
7Modelingofmachiningprocesses197 Ju¨rgenLeopold Nomenclature197
7.1Introduction197
7.2Closed-loopprincipleofmodeling198
7.3Modelingandsimulationtechniques199
7.3.1Slip-linemethod199
7.3.2Finiteelementmodeling(finiteelementmethod)203
7.3.3Complementarymethods209
7.4Modelingandsimulationintheindustry—selectedexamples213
7.4.1Cuttingtooloptimization213
7.4.2High-speedcuttingorhigh-performancecutting213
7.4.3Drymachining213
7.4.4Burrformationandcleanmanufacturing213
7.4.5Cryogenicmachining215
7.5Openissues216
7.5.1Hybridmodelingandclosed-loopdesign216
7.5.2Multiscalemodelinginmachining218
7.5.3Multiscalemodelingincoating-substratesimulation220
7.6Summary222 References222 Furtherreading226
8Mechanicsofultrasonicallyassisteddrilling229 AnishRoyandVadimV.Silberschmidt
8.1Introduction229
8.2Drilling:theoryandmodeling230
8.2.1Kinematicmodeling230
8.2.2Finite-elementmodeling232
8.3Ultrasonicallyassisteddrilling235
8.3.1Experimentalsetupandinstrumentation235
8.3.2Casestudy:drillingincomposites237
8.4Conclusionandoutlook240 References241
9Machininginmonocrystals243
AnishRoy,QiangLiu,KaHoPangandVadimV.Silberschmidt
9.1Introduction243
9.2Mechanicsofsingle-crystalmachining245
9.2.1Single-crystal-plasticitytheory245
9.2.2Computationalimplementation247
9.2.3Criteriaofmaterial-removalmodeling248
9.3Machiningofsingle-crystalmetal248
9.3.1Experimentalprocedure248
9.3.2Finite-elementmodelandmaterialparameters249
9.3.3Simulationandresults250
9.3.4Discussion254
9.4Machiningofsingle-crystalceramicmaterial258
9.4.1Experimentalprocedure258
9.4.2Computationalmodeling259
9.4.3Resultsanddiscussion262
9.5Concludingremarks264 References265
10Microstructuralchangesinmachining269
W.Bai,R.Sun,J.XuandVadimV.Silberschmidt
10.1Introduction269
10.2Microstructuralevolutioninmachining270
10.2.1Microstructuralevolutioninmachinedsurface270
10.2.2Microstructuralevolutioninchip273
10.3Microstructuralmodelsformachining275
10.3.1Mechanismmodelsofmicrostructuralevolution275
10.3.2Calculationofmicrostructuralevolution278
10.4Microstructuralevolutioninultrasonicallyassistedcutting279
10.4.1Microstructuralevolutioninmachinedsurfacewith ultrasonicallyassistedcutting283
10.4.2Microstructuralevolutioninchipwithultrasonically assistedcutting288
10.5Conclusion294 Acknowledgments294 References294
11Residualstressesinmachining297
J.C.Outeiro
11.1Introduction297
11.2Fundamentalsofmachiningandresidualstresses298
11.2.1Metal-cuttingdefinitionandenergyconsiderations298
11.2.2Definitionandoriginsofresidualstresses301
11.2.3Techniquesformeasuringresidualstress301
11.3Residualstressesinmachiningoperations303
11.3.1Originofresidualstressesinmetalcutting303
11.3.2Residualstressesindifficult-to-cutmaterials305
11.3.3Effectofrelativetoolsharpnessonresidualstresses319
11.3.4Controlofresidualstressesinmachining322
11.4Modelingandsimulationofresidualstresses324
11.4.1Modelingandsimulationconsiderations324
11.4.2Relevanceofconstitutiveandcontactmodelsin residual-stressprediction326
11.4.3Simulationofresidualstressesforseveral workmaterials335
11.4.4Procedureforcomparingpredictedandmeasured residualstresses341
11.4.5Optimizationofcuttingconditionsforimproved residualstressesandsurfaceroughnessinmachined components344
11.5Influenceofresidualstressonproductsustainability346
11.5.1Introduction346
11.5.2Corrosionresistance348
11.5.3Fatiguestrength352
11.6Conclusion353 References354
12Microstructuralchangesinmaterialsundershockandhigh strainrateprocesses:recentupdates361 SatyamSuwas,AnujBishtandGopalanJagadeesh
12.1Introduction361
12.2Shockwaveandparameters363
12.3Experimentalmethodsforinvestigationofshockwaves365
12.3.1Taylor’simpacttest365
12.3.2Explosiveloadingofmaterials366
12.3.3Flyerplateimpacttest366
12.3.4Split-Hopkinsonpressurebar367
12.3.5Shockimpactinashocktube367
12.3.6Laser-inducedshockgeneration368
12.4Parametersinfluencingmaterialresponsetoshockexposure369
12.4.1Typesofshock-generateddefects369
12.4.2Effectofmaterialparameters371
12.4.3Effectofshockparameters376 12.4.4Otherfactors:residualstrain378 12.5Theoryofdefectgenerationundershock:pasttheoriesand newperspectives380 12.6Conclusion384 References384
13Thermomechanicsoffrictionstirwelding393 MadsRostgaardSonneandJesperH.Hattel
13.1Introduction393
13.2Thermalbehavior396
13.3Microstructuralevolution399
13.4Residualstressesanddistortions400
13.5Materialflow403
13.6Conclusion410 References410
14Modelingoffrictioninmanufacturingprocesses415 UdayShankerDixit,V.Yadav,P.M.Pandey,AnishRoy andVadimV.Silberschmidt
14.1Introduction415 14.2Historyoffrictionmodeling416 14.3Somepopularfrictionmodels418 14.3.1Amontons Coulomb’smodel419 14.3.2Constant-frictionmodel419 14.3.3WanheimandBay’smodel420 14.3.4Asperity-basedfrictionmodel421 14.3.5Plowingmodel434
14.4Frictioninmachining435
14.5Frictionmodelsinmetalforming437
14.6Frictioninsolid-statewelding438
14.7Frictionmodelsformicromanufacturing439
14.8Challengingissuesanddirectionsforfutureresearch439 14.9Conclusion440 Acknowledgment441 References441 Furtherreading444 Index445
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Listofcontributors
W.Bai HuazhongUniversityofScienceandTechnology,Wuhan,P.R.China
IsmetBaran FacultyofEngineeringTechnology,UniversityofTwente,Enschede, TheNetherlands
AnujBisht DepartmentofMaterialsEngineering,IndianInstituteofScience, Bangalore,India
Raphae ¨ lBenjaminComminal DepartmentofMechanicalEngineering,Sectionof ManufacturingEngineering,TechnicalUniversityofDenmark,Lyngby,Denmark
UdayShankerDixit DepartmentofMechanicalEngineering,IndianInstituteof TechnologyGuwahati,Guwahati,India
ChristophHartl THKo ¨ ln-FacultyofAutomotiveSystemsandProduction, UniversityofAppliedSciences,Cologne,Germany
JesperH.Hattel DepartmentofMechanicalEngineering,Sectionof ManufacturingEngineering,TechnicalUniversityofDenmark,Lyngby,Denmark
MasoudJabbari SchoolofMechanical,Aerospace&CivilEngineering,The UniversityofManchester,Manchester,UnitedKingdom
GopalanJagadeesh DepartmentofAerospaceEngineering,IndianInstituteof Science,Bangalore,India
JunJiang DepartmentofMechanicalEngineering,ImperialCollegeLondon, London,UnitedKingdom
MartinLarsen FiberlineCompositesA/S,Middelfart,Denmark
Ju ¨ rgenLeopold TBZ-PARIVGmbH,Chemnitz,Germany
JianguoLin DepartmentofMechanicalEngineering,ImperialCollegeLondon, London,UnitedKingdom
MaikLinnemann FraunhoferInstituteforMachineToolsandFormingTechnology, Chemnitz,Germany
QiangLiu DepartmentofMaterialsEngineering,KULeuven,Leuven,Belgium
J.C.Outeiro Arts&MetiersInstituteofTechnology,CampusofCluny,Cluny, France
P.M.Pandey DepartmentofMechanicalEngineering,IndianInstituteof TechnologyDelhi,NewDelhi,India
KaHoPang WolfsonSchoolofMechanical,ElectricalandManufacturing Engineering,LoughboroughUniversity,Loughborough,UnitedKingdom
VerenaPsyk FraunhoferInstituteforMachineToolsandFormingTechnology, Chemnitz,Germany
AnishRoy WolfsonSchoolofMechanical,ElectricalandManufacturing Engineering,LoughboroughUniversity,Loughborough,UnitedKingdom
FilipBoSalling DepartmentofMechanicalEngineering,SectionofManufacturing Engineering,TechnicalUniversityofDenmark,Lyngby,Denmark
MichaelSandberg DepartmentofMechanicalEngineering,Sectionof ManufacturingEngineering,TechnicalUniversityofDenmark,Lyngby,Denmark
GerdSebastiani imkautomotiveGmbH,Chemnitz,Germany
ZhutaoShao DepartmentofMechanicalEngineering,ImperialCollegeLondon, London,UnitedKingdom
RajkumarShufen DepartmentofMechanicalEngineering,IndianInstituteof TechnologyGuwahati,Guwahati,India
VadimV.Silberschmidt WolfsonSchoolofMechanical,Electricaland ManufacturingEngineering,LoughboroughUniversity,Loughborough,United Kingdom
MadsRostgaardSonne DepartmentofMechanicalEngineering,Sectionof ManufacturingEngineering,TechnicalUniversityofDenmark,Lyngby,Denmark
JonSpangenberg DepartmentofMechanicalEngineering,Sectionof ManufacturingEngineering,TechnicalUniversityofDenmark,Lyngby,Denmark
R.Sun HuazhongUniversityofScienceandTechnology,Wuhan,P.R.China
SatyamSuwas DepartmentofMaterialsEngineering,IndianInstituteofScience, Bangalore,India
J.Xu HuazhongUniversityofScienceandTechnology,Wuhan,P.R.China
V.Yadav DepartmentofMechanicalEngineering,MaulanaAzadNational InstituteofTechnologyBhopal,Bhopal,India
OnurYuksel FacultyofEngineeringTechnology,UniversityofTwente, Enschede,TheNetherlands
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Modelingofmetalforming: areview
UdayShankerDixit DepartmentofMechanicalEngineering,IndianInstituteofTechnologyGuwahati, Guwahati,India
1.1Introduction
Manufacturingofaproductbyplasticdeformationofmetalshasbeenperformed forages.Plasticdeformationcanbeaccomplishedwithorwithoutheatingthe metal.Accordingly,twobroadcategoriesofmetalformingprocessesarehotmetalworkingandcoldmetalworking.Amorerefinedclassificationincludeswarmmetalworkinginbetweenhotandcoldmetalworking.Inmostofthemetalforming processes,deformationiscarriedoutbytheapplicationofamechanicalload;the roleofheatislimitedtoreducingtheflowstress(requiredtostarttheplasticdeformationofthemetal).However,thereareprocesses,wheretheplasticdeformation isachievedbytheheatalone;anexampleislaserbending,whereasheetisbentby laserirradiationthatcreatesasufficientamountofthermalstressestobendthe sheet [1].
Basedonrawmaterial,desiredfinalproductandmetalflowpattern,themetal formingprocessesareclassifiedintobulkandsheetmetalformingprocesses.Bulk metalformingprocessesdeformhighvolume-to-surfacearearatiorawmaterials resultinginachangeofsurfacearea.Inthesheetmetalformingprocesses,theraw materialhasalowvolume-to-surfacearearatio,andmaterialdeformationdoesnot intendtochangethesurfaceareaimplyingthatthesheetthicknessremainsmoreor lessunaltered.Recently,anothercategory,namely,sheet-bulkmetalforminghas beenintroduced [2].Insheet-bulkmetalformingprocesses,thebulkdeformationof sheetiscarriedoutthatinvariablybringsouttheintendedchangesinthethickness aswell.Someexamplesofbulkmetalformingareforging,rolling,extrusion,and wiredrawing.Sheetmetalformingprocessesincludedeepdrawing,bending,and spinning [3].Coining,flowforming,andironingareexamplesofsheet-bulkmetal forming.
Modelingofmetalformingstartedsincethebeginningofthe20thcentury [4]. Initialattemptsweredirectedtoestimatetheloadrequiredforplasticdeformation. Prominentmethodswereslip-linefieldmethod,slabmethod,andupperbound method.Thesemethodsinvolvedseveralassumptionsandwereincapableofprovidingdetailedinformationaboutstress straindistributioninthematerial.Thetechniqueofvisioplasticitywasintroducedinthelate1950stogetdetailedinformation aboutthedeformation.Inavisioplasticitymethodatime-dependentvelocityfieldis MechanicsofMaterialsinModernManufacturingMethodsandProcessingTechniques. DOI: https://doi.org/10.1016/B978-0-12-818232-1.00001-1 Copyright © 2020ElsevierLtd.Allrightsreserved.
calculatedbasedonaseriesofphotographsofagridpatternonthemetalbeingprocessed.Analyticaland/ornumericaltechniquesareusedtoestimatethestress straindistributionandotherderivativeinformation.Thedecade1950 60sawthe emergenceoffiniteelementmethod(FEM).Anumberofarticleswerepublishedin the1970sand1980sonthemodelingofmetalformingprocesses.Thesemethods wereperfectedinthe1990s,andnowadays,thereareseveralcommercialFEM packagesdedicatedtomodelingofmetalformingprocesses.Sincethelasttwodecades,therehavebeenattemptstodevelopadvancedFEMtechniquesandseveral meshlessmethods.However,therequirementofhugecomputationaltimeisahindranceinthepopularizationofthesemethods.
Somedevelopmentshavetakenplaceincarryingoutmicrostructuralmodeling ofmetalformingprocesses.Classicalplasticitytheorycouldaccountfordistinct materialbehaviorbasedonmicrostructuralfeatures.Moleculardynamicssimulations(MDSs)andcrystalplasticityaretworecentlydevelopedmethodsforrealistic simulationofmetalformingprocesses,particularlyformodelingofmicroforming. However,thesemethodsarestillatanascentstageofdevelopmentforsolving metalformingproblems,andthereareseveralcomputationaldifficultiestobe overcome.
Thischapterprovidesanoverviewofmodelingofwell-knownmetalforming processes.Capabilitiesandlimitationsofvariousmodelingtechniquesare highlighted.Finally,thedirectionsforfurtherresearchareprovided.
1.2Modelingissuesinvariousmetalformingprocesses
Whydowemodelmetalformingprocesses?Whatisexpectedoutofamodel?In general,modelingisexpectedtoimprovetheefficiencyofoverallmanufacturing systemandreducethedependenceoncostlyhitandtrialexperiments.Modeling canprovidethefollowingvaluableinformation:(1)requireddeformationload; (2)energyconsumptionintheprocess;(3)stressesonthediesandtools;(4)defects intheprocess;(5)qualityoftheproduct,particularlyintermsofdimensionalaccuracyandsurfaceintegrity;(6)propertiesoftheproduct;(7)stress,strain,strain rate,andtemperaturedistributionintheproductaswellastooling;and(8)life assessmentofthetoolingandmachine.Adequatemodelingcanhelpinthedesign andoptimizationofmetalformingprocess,machines,andtooling.Inthesequel, salientmodelingissuesofpopularmetalformingprocessesarediscussed.
1.2.1Forging
Forgingisaprocessofplasticallydeformingthemetalbypressingandhammering. Itmaybeperformedincold,warm,orhotstateofthemetal.Therearemainlytwo typesofforgingprocesses:(1)opendieorfreeforgingand(2)closeddieor impressiondieforging.Opendieforgingistheprocessofdeformingthemetal betweenmultiplediesthatdonotcompletelyenclosethematerial.Itisoften 2MechanicsofMaterialsinModernManufacturingMethodsandProcessingTechniques
employedtopreformmaterialforsubsequentmetalforming.Thereareseveraldifferenttypesofopendieforgingprocesses. Fig.1.1 showsschematicdiagramsof threetypesofopendieforging—upsetforgingorupsetting,cogging,andorbitalor rotaryforging.Inupsettingthecompleteorpartialportionoftheworkpieceiscompressedbetweenafixeddieandmovingraminordertoincreasethecrosssection ofthedesiredportion.In Fig.1.1A,arodisbeingupsetforgedtomakeahead.In Fig.1.1B,coggingprocessisbeingcarriedoutinordertomakeasteppedbar.Itis basicallyanincrementalforming;aportionoftheworkpieceiscompressedbetween thedies,diesretract,andtheworkpieceisadvancedaxiallyfornextcompression operation. Fig.1.1C depictsupsettingofaworkpiecebyorbitalforging.Herethe lowerdieisfixed.Theupperdierotatesaboutanaxisslightlyinclinedtoworkpiece-axis;hence,atatimeitcompressesonlyasmallportionoftheworkpiece. Thisisalsoanincrementalformingandloadrequirementgetsreduced.
Inthecloseddieforgingorimpressiondieforging,metaliscompressedinthe encloseddies.Inthisprocessthemetalisfullycompactedtoacquiretheshapegovernedbythediecavities.Excessmaterialcomesoutasflashandistrimmed.
4MechanicsofMaterialsinModernManufacturingMethodsandProcessingTechniques
Usually,themassofflashcanbeasmuchas20%. Fig.1.2 showsaschematicof closeddieforgingwithflashgeneration.Flash-lessforgingisalsopossiblebut requiresacarefultoolingdesign.
Inforgingprocess,strainratemaylieintherange10 3 10 2 s 1,depending onwhetheritispressforgingorhammerforging.Inthecoldforgingtheeffective Coulomb’scoefficientoffrictionrangesfrom0.05to0.15and0.1to0.5inhot forging.Inmostofthecases,Coulomb’sfrictionmodelisinappropriate.Frictional behaviormaychangefromstickingtoslidingwhilemovingoutwardlyfromcenter inadirectionnormaltotheload.
Estimationofforgingloadhasbeenthefocusofattentioninforging.Another interestistofindoutflowpatternsinordertodesigndies.Forgingprocesssuffers fromvariousdefectsthatneedtobecontrolled.Surfacecrackingmayoccurdueto thermomechanicaleffects.Poormaterialflowmaycausefoldingoroverlappingof oneregionofmetalontoanothercausingcoldshut.Itmayalsoresultinunderfillingofdiecavities.Surfacemaygetroughenedduetothedeformationofcoarse grains,whichiscalledorangepeeldefect.Althoughforgingloadestimationtechniquesaresufficientlyrefined,predictionofdefectsisstillachallengingtask.
Thesimplestopendieforging,namelyupsettingisoftenusedasabenchmarktest forstudyingthematerialandfrictionbehavior.Inatypicalcompressiontestthespecimeniscompressedbetweentwolubricatedplatenstofindoutthedeformation behaviorofmetals.Inaringcompressiontestahollowcylinderspecimeniscompressedbetweentwoplatesandfrictionisestimatedbasedonthechangeinthehole diameter.Inthecylindricalspecimenofaringcompressiontest,typicallythehole diameterishalfoftheouterdiameterandheightisone-thirdtheouterdiameter.
1.2.2Rolling
Rollingshapesmaterialsbypassingitbetweencounterrotatingrolls.Ithasbeenin wideusesincethe14thcentury.Inthisprocess,slabs,billets,blooms,orrodsare
Figure1.2 Closeddieforging.
rolledintoplates,sheets,strips,rods,andtubes.Theprofilescanalsobeproduced byrolling.Becauseofthelimitationofthemaximumpossiblereductioninone pass,usuallymultipassrollswithanumberofstandsinseriesareemployed.Thisis calledtandemrollingandisschematicallydepictedin Fig.1.3.Ithasthreestands; ineachstand,therearetwowork-rollsandtwobackuprollstopreventwork-roll deflection.Rollingcanbeemployedwithorwithoutfrontandbacktensions. Rollingprocesslooksdeceptivelysimple.However,arealisticsimulationneeds tofocusonthefollowingthreecomplextasks:
1. properelastic plasticmodelingofthematerialtobeprocessed,
2. modelingoffrictionbehaviorwithaproperassessmentofneutralzoneinwhichthedirectionoffrictionalstresseschangesfromfacilitatingthemovementofthematerialtoopposingit,and
3. applicationofelasticitytheoryforestimatingtherollflatteningandrolldeflection.
Apropermodelofrollingprocessestimatestherolltorque,rollseparatingforce, androllpressuredistributionaccurately.Thecommondefectsinrollingprocessare edgecracking,wavyedge,centralburst,andalligatoring.Edgecrackingrefersto crackingattheedgesoftherolledproductsandoccursbecauseofnonhomogeneous deformationduetowrongdesignofrollsorimpropermanagementoffriction. Wavyedgeoccursmainlybecauseofrolldeflection.Duetononuniformrollgap, edgestendtoelongatemorethanthecenter.Tomaintaincontinuity,edgesgetcompressedandproduceawavypattern.Centralburstisaductilefracturethatinitiates fromavoidatthecenter.Inalligatoringacrackformsalongthecentralplaneand splitstheends.Excessivefrontorbacktensionmaycausethetearingofthesheet. Manytimes,rollingprocessisemployedforimprovingthematerialproperties. Asymmetricsheetrolling,inwhichthesurfacespeedofrollsorfrictiondifferson thetwosidesofthesheet,hasbeenusedtoimprovethemicrostructure [5,6].In temperorskin-passrolling,0.5% 4%reductioninthesheetthicknessiscarried outtoprovideadegreeofhardeningtosheet,topreventstretcherstrainsorLu ¨ ders band,andtoimprovethesurfaceintegrityofthesheet [7].Accumulativerollbondingisaseveredeformationprocess [8].Inthisprocessasheetispassedbetween twocounterrotatingcylinderstoimpart50%reductiontoit.Elongatedsheetiscut intotwopiecesofequallengthandstackedtogethertomakeitofsamedimension
Figure1.3 Atandemrollingmill.
astheoriginalsheet.Itisfurtherpassedthroughtherolltoimpart50%reduction. Theprocedureisrepeatedseveraltimes,whichresultsinproperlybondedthin stackedsheetswithalargeaccumulatedstrain.Withthisprocedure,grainsizegets reformed,andstrengthgetsimproved.
1.2.3Wiredrawing
Wiredrawingprocesspullsawirethroughadietoreduceitscrosssection.Itcan becarriedoutinthepresenceofabacktensionthathelpsinreducingthediepressureandprovidingdimensionalstability.Theoreticallymaximumpossiblereduction inonepassis63%,butapracticallimitis45%.Hence,forgettinghigherreduction, multistagewiredrawingisemployed. Fig.1.4 depictsaschematicoftwo-stage wiredrawingprocesstoreducethecross-sectionalareaofwirefrom Ai to Af.Wire drawingisusuallycarriedoutatroomtemperature,butoccasionallywarmwire drawingisalsoperformed.
Roddrawingissimilartowiredrawing.Hereinsteadofawire(diameterless thanabout6mm),arodispulledthroughdies.Incaseoftubedrawing,atubeis drawnoveramandrel.Intube,sinkingnomandrelisusedandouterdiameter reducedwithincreaseinlength;tubethicknessmayreduceorincreasedepending ontheprocessparameters.
Diedesignisveryimportantinwireorroddrawing.Mostoftheresearchers haveoptimizedthedieshapewithanobjectiveofminimizingenergy.However,the shapeofdiehasalargebearingonthequalityoftheproduct.Certaindieshapes, althoughmayincreasetherequiredpower,reducethedefectsandimprovethe mechanicalpropertiessuchastensilestrengthandhardnessofthedrawnwire/rod. Thereareseveraltypesofdefectsinawire/roddrawingprocess.Somedefectssuch asscabs(irregularlyshapedflattenedprotrusions)occurduetodefectiverawmaterial.Somedefectsoccurduetofaultydesignofdieandprocess.Forexample,a combinationoflargedieangleandsmallreductionresultsinthenarrowingofplasticzoneinthevicinityofcenterlineandenhancesthechanceofcentralburst [9]. FrictionisundesirableinwiredrawingandusuallytheCoulomb’scoefficientof frictionrangesfrom0.01to0.1withproperlubrication.Inthedrywiredrawingthe
lubricantiscoatedonthewirebeforeenteringthedie.Inthewetdrawing,dieand wirearesubmergedinthelubricants.Itisalsoimportanttocontroltheresidual stressesinthewirebyproperdesignofthedieandprocess.Recentlydielessdrawingofwiresandtubesisalsogainingimportance [10].
1.2.4Extrusion
Inextrusionprocesstherawmaterialiscompressedthroughadietoreducethe cross-sectionalareaofthematerialortogeneratespecialprofileofthecrosssection.Theoretically,thereisnolimittothemaximumpossiblereductioninextrusion.Theextrusioncanbeperformedincold,warm,orhotstateofthemetal. Therearealotofvariantsoftheextrusionprocess.Intheforwardordirect extrusionthemetalflowsinthedirectionoframmotion. Fig.1.5 showsaschematicdiagramoftheprocess.Toavoidstickingoframwithrawmaterial,adummy blockisinsertedinbetween.Movementofmaterialthroughthecontainercausesa lotoffrictionbetweenthecontainerwallandrawmaterial.Toalleviatethisproblem,backwardorindirectextrusionisused,inwhichtheramandextrudedmaterial moveindifferentdirectionsasshownin Fig.1.6;however,theramneedstobehollow,whichweakensit.Inlateralextrusion,materialflowssideways,usuallyperpendiculartorammotion;ithelpstoreducethefrictionallosses.Aschematic diagramisshownin Fig.1.7,wherelateralextrusionistakingplacefromboth sides,butitcantakeplacefromonesideaswell.Inimpactextrusion,materialis extrudedwiththeimpactforceoftheram. Fig.1.8 showsaschematicofimpact extrusionusedtomakeathin-walledtubeopenatoneend.Inhydrostaticextrusion (Fig.1.9)therawmaterialisplacedinasealedchambercontainingliquidanda movingrampressurizestheliquid;therawmaterialisforwardextrudedbythepressureoftheliquid.Hydrostaticextrusionreducesthefrictionandalsoenhancesthe ductilityoftherawmaterial.Inthemulti-holeextrusion(Fig.1.10)thediehas morethanoneopening,causingmorethanoneproducttobeextruded
Extruded rod
