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WeldingDeformationandResidual StressPrevention

WeldingDeformation andResidualStress Prevention

SecondEdition

NinshuMa

JoiningandWeldingResearchInstitute,OsakaUniversity,Osaka,Japan

DeanDeng

CollegeofMaterialsScienceandEngineering,ChongqingUniversity, Chongqing,China

NaokiOsawa

DepartmentofNavalArchitectureandOceanEngineering,Osaka University,Osaka,Japan

SherifRashed

JoiningandWeldingResearchInstitute,OsakaUniversity,Osaka,Japan

HidekazuMurakawa

JoiningandWeldingResearchInstituteOsakaUniversity,Osaka,Japan

YukioUeda

JoiningandWeldingResearchInstitute,OsakaUniversity,Osaka,Japan

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Preface

Sincearcweldingwasinventedinthelate19thcentury,weldinghasbeenwidelyused asanessentialtechnologyformetaljoininginconstruction.Generally,weldingproducesdeformationandresidualstressinweldedproducts,whichinfluencesthequality andperformanceoftheseproducts.Weldingheatinputisfromtheweldingarcorlaser beamorelectronbeam.Thisheatinducesmeltingofthemetalandconductsinthe joint.Localexpansionandcontractioninthejointresultinweldingdeformation andresidualstress.Manyengineersandresearchershaveexpendedgreateffortsto findwaystocontroltheseincidents.However,weldingdeformationandresidual stressstillremainasdifficultengineeringproblems.Thisisbecausethephenomena associatedwithweldingarecomplexandinterdisciplinary.

Afterthedigitalcomputerwasinvented,newcomputationaltheoriesandmethods weredeveloped,oneofwhichisthefiniteelementmethod.Thismethodisapowerful numericalanalysistooltosolvecomplexproblems.Theauthor’sresearchgrouphas developedmanycomputationalmethodsofanalysisforweldingmechanicsbasedon thefiniteelementmethod.

In1971,UedaandYamakawa [1] succeededinanalysisofthermalelastic-plastic behaviorofbuttjointsoftwoplatesduringweldingandpublishedapaperonthis pioneeringwork.Sincethen,thegrouphascontinuedtoanalyzevarioustypesof weldedjoints,includingmultipassjointsofverythickplates.Withtheseefforts, thegroupestablishedasimulationmethodofthermalelastic-plasticbehaviorof weldedjoints.

Inparallelwiththeseanalyses,theyexaminedtheaccuracyoftheanalysis,comparingwithresidualstressesmeasuredonexperimentalmodels.Duringthisprocess, theypaidspecialattentiontothesourceofresidualstress,calledinherentstrain,and developedaveryefficientmethodtopredictweldingresidualstressanddeformation. Additionally,theypresentedanewrationalmeasuringmethodofthree-dimensional residualstressinthickweldedjoints,utilizingaspecialfeatureoftheinherentstrain method,whichtheydiscovered.Themethodsofanalysis,prediction,andmeasurementofwelddeformationandresidualstresshavebeenfurtheradvanced,andaframeworkofcomputationalweldingmechanicshasbeenestablished [2].

Safetyrequirementsforweldedstructuresarebecomingincreasinglystrict.To meettheserequirements,engineersengagedinstructuraldesignandqualitycontrol oftenneedtoanticipateweldingdeformationandresidualstresseswithhigheraccuracy.Thischangingengineeringenvironmentrequiresthemtohavemoreopportunitiestoconductweldinganalysisutilizingcommercialsoftware,eithergeneralor specializedforwelding.Inordertousesuchsoftwareandevaluatetheoutputeffectively,inexperiencedengineersneedabasicunderstandingofweldingmechanicsand goodpracticeinhandlingthesoftware.

Thefirstedition [3] ofthisbookwaswrittentomeetthisdemand,anditprovided thefollowingelements:

1.Thegenerationmechanismofweldingdeformation,residualstress,andinherentstrainwas illustratedusingasimplethree-barmodel,andthroughtheillustration,basictheorieswere formulatedandanalysisprocedureswerepresented.

2.AFEMprogram,UserQ&A,and21setsofsampledatawereprovidedtopracticethebasic analysisofheatconduction,deformation,andresidualstressduetoweldingunderbasic planestressandplanedeformationconditions.

3.Examplesofstrategicmethodsandprocedurestosolvevariouswelding-relatedproblems encounteredintheprocessofconstructionwerepresented.

4.Appendicesprovideddatabasesforweldingresidualstressesinvarioustypesofjoints, temperature-dependentmaterialproperties,andthebasicthree-dimensionalequations, amongotherdata.

Tenyearshavepassedsincethefirsteditionwaspublishedin2012.Newtechnology hasbeendevelopedandmorewelding-relatedproblemsareyieldingtocomputational analysisandsynthesis.Itwasthoughttobeappropriatetoupdatethefirsteditionand addnewmaterialaddressingweldingmechanics-relatedproblems.

Inthesecondedition,thefirstthreechaptersarethesameasthoseinthefirstedition.In Chapters1,2,and3,themechanismofproductionofresidualstress,deformation,andinherentstrainduringweldingisillustratedusingthesimplethree-bar modelundergoingtypicalweldingthermalcycles.Therelationalexpressionsbetween themarederived.Throughtheillustration,withtheaidoftheinherentstrainmethod, thefundamentaltheoryofmeasurementofresidualstressisformulated,andtheproceduresofpredictionofresidualstressanddeformationarepresented.Consideringthe factthatthree-dimensionalfiniteelementanalysisiscommonlyusednowadays, Chapters4,5,and6 ofthefirsteditionweredeletedinthesecondedition.

Inthenew Chapter4 ofthesecondedition,variousadvancedcomputingmethods ofweldingthermal-mechanicsareintroduced,includingheatsourcemodels,andthe finiteelementmethodforheattransferandthermalstressanalysis.In Chapter5,thermalelastic-plastic-creepbehaviorisintroducedusingasimplebarmodel,andwelding residualstressdistributionsintypicaljointsarediscussedbasedonsimulationresults andmeasureddata.In Chapter6,practicalanalysismethodsincludingmodeling methodsforweldingassemblydeformationareintroduced. Chapter7 presentspredictionexamplesofweldingdeformationforlarge-scalestructuralmodelsandcoversthe influenceofconstraintconditionsandfabricationsequencesonstructuraldeformation. Chapter8 discussesnumericallycomputedandexperimentallymeasuredresidualstressanddeformationinadditivemanufacturing,suchas3Dmetalprintingand surfaceimprovementtechniques. Chapter9 reusesSections7.1–7.6from Chapter7 of thefirstedition,presentingstrategicanalysisofweldingresidualstressfor manufacturingproblemssuchaswelding-inducedcracking,andimplementstheinfluenceofresidualstressonfatiguesafetyaswellasbucklingbehaviorofweldedstructuresinthenewSections9.6–9.10.InAppendix,adatabaseofweldingresidual distributionsinvariousweldedjointsissummarized.

Thissecondeditionofthebookhasbeenwrittenforthepracticingengineerwho wishestoutilizecomputationalanalysisandpredictionofweldingresidualstressand deformationintheirpracticalwork,aswellasforresearcherswhoareengagedwith weldingmechanics-relatedproblems.Theauthorsbelievethattheeffortsofthe readersshouldcontributetodevelopingtheirowncomputationalanalysis-based manufacturing.

NinshuMa

DeanDeng

NaokiOsawa

SherifRashed

HidekazuMurakawa

YukioUeda

References

[1] Y.Ueda,T.Yamakawa,Analysisofthermalelastic-plasticstressandstrainduringwelding byfiniteelementmethod,Trans.Jpn.Weld.Soc.2(2)(1971)90–100.

[2]Y.Ueda,Apioneerofcomputationalweldingmechanicsandultimatestrengthanalysis (ISUM),halloffame,ShipsOffshoreStruct.(2020), https://doi.org/10.1080/ 17445302.2020.1855500

[3] Y.Ueda,H.Murakawa,N.Ma,WeldingDeformationandResidualStressPrevention,first ed.,Butterworth-Heinemann,Elsevier,2012.ISBN978-0-12-394804-5.

Listofsymbols

A Area,cross-sectionalarea

A (exp:4.60)MaterialconstantinNorton-Baileyequation

A (4.121)Materialparameterforbackstresscalculation

A0

[A](4.26)Conductivitymatrix

a WeldpoolradiusintheGoldakheatsourcemodel

a Cracklength

B({T})Residualerror

[B]Strain-displacementmatrix

BF Halfbreadthofflange

Bw Heightofweb

b WeldpoolwidthintheGoldakheatsourcemodel

b KineticparameterinJMAKequation

b Widthoftheshellelementsadjacenttotheweldline

b0 Halfwidthofinherentstrainzoneincaseofinfinitive platewidth

C (4.122)Materialparameterforbackstresscalculation

C0 Radiationconstantforblackbody(Stefan-Boltzmann constant)

[C]e (4.23b)Dampingmatrixofcorrespondingeachelement

[C]Heatcapacitymatrix

[C](4.23)Dampingmatrix

c Specificheat

c (4.113)Propagationspeedofstresswaveinmaterials

c (4.120)Backstress

af, ar WeldpoollengthintheGoldakheatsourcemodel

cij (4.120)Backstresstensor

[D]Elasticitymatrix

Dstrain,[Dstrain] Dtemp,[Dtemp] Dtime,[Dtime]

[De](4.66)Elasticmatrix

[Dep](4.91)Elastic-plasticcorrespondingmatrixunderplastic loadingstate

E Young’smodulus

Continued

Continued

Ep

Elastic-plasticmodulus

e Baseofnaturallogarithm

e ∗ (6.4)Inherentstrain

erav (4.109)Averagedsquarerootindex

ermax (4.109)Maximumerrorindex

F Force,load

F (4.17)Radiationefficiency

F ∗ Sumofexternalforceandthermalload

Fconcentrate (4.112b)Concentratednodalforce

Ff, Fr (4.7)HeatdistributingfactorsintheGoldakheatsource model

Fgravity (4.112b)Gravity-inducednodalforce

FN, FT, FL, Fθ (6.14)Bondingforces

Fp (6.28)Theshareofthetendonforceofeachsideoftheplate

Fpressure (4.112b)Thenodalforceduetoexternalpressure

Fw (6.28)Thewebshareoftendonforce

{F}(4.26)Heatflowmatrix

{Fdamp}(4.112d)Dampingnodalforcevector

{Fext}(4.112b)Externalequivalentnodalforcevector

{Fint}(4.112c)Internalequivalentnodalforcevector

f (4.120)Yieldfunction

f (6.4)Nodalforcevectors

fB (4.59)Fractionofbainite

fM (4.57)Fractionofmartensite

fS (4.11)Fractionoftotalheattransferredontothesurface

fV (4.12)Fractionofvolumetricheatsource

f(R)Fatigueenhancementfactor

G (4.50)Shearmodulus

H (6.23)Webheight

HT (4.86)Thermalsofteningcoefficient

H0 Coefficientofworkhardening

H0 (4.86)Plasticityhardeningtangent

[H ∗]Elasticresponsematrix

[H ∗ ]T Transposedmatrixof[H ∗ ]

h Thickness

I Weldingcurrent

K (4.57)Coefficientof transformation plasticity

[K](4.23)Stiffnessmatrix

K Stressintensityfactor(SIF)

Kc (6.14c)Largecontactstiffness

Kmat Material’sfracturetoughnessinSIFunit

Kr SIFratio

Continued

ΔKeff

EffectiveSIFrange

k Table4.1Thermaldiffusivity

[K]Heatconductionmatrixofwholestructure

[K] 1

(6.5)Inversematrixof[K]

[K0 ](6.2)Initialstressmatrix

L Length

Le (4.114)Equivalentlengthofelements

Lr Loadratio

ΔL Longitudinalexpansioninweldingdirection

ΔL ∗ Inherentdeformation,inherentdisplacementinone dimensionalcase

[M](4.110)Massmatrix

m Numberofmeasuredelasticstrains,numberofstrain gages

m (4.58)Kineticparameterin K-M equation

m (4.60)MaterialconstantinNorton-Baileyequation

m Mass

N Numberofcycles

[N](4.22)Shapefunctionmatrix

n (4.14)–(4.17)Normalunitvectorofsurface

n (4.59)KineticparameterinJMAKequation

n (4.60)MaterialconstantinNorton-Baileyequation

P Electricpower

{P}(4.23)Heatfluxmatrix

p (4.75)Hydrostaticpressure

Q Netheatinputperunitlengthofweld

_ Q A , _ Q B Timerateofheatquantity

q Numberofunknowneffectiveinherentstrains

qA, qB Heatflowrate

qS (4.11)Powerdensityinasurfaceheatsourcemodel

qV (4.10)Powerdensityinavolumetricheatsourcemodel

_ q A

Surfaceheatflux

_ q c Heatflowsthroughthemetalwithunitcrosssection intheunittime

q t Heatflowratebyconvection

q t Heattransferperunitareaandunittime

q V Heatgenerationratepervolume

R (4.9)Radiusofahalfsphereofheatingzone

R Stressratio

r Table4.1Distancefromtheweldcenter

r0 (6.14b)Relativedisplacementatmaximumbondingstress

{△ r}(4.108)Residualerrorinducedequivalentnodalforce

S Sumofsquaresoftheresiduals νi

S (4.10)Sectionalarea Continued

S1, S2, S3

(4.23)Heattransferboundaries

ST ∗ Transverseinherentdisplacement

s Cross-sectionalarea

^ s Unbiasedestimateofmeasurementvariance

T Temperature

T0

Initialtemperature

Tav Averagetemperatureincrease

Tm

Tmax

Tmelt

Mechanicalmeltingtemperature

Maximumtemperature

Meltingtemperature

Tref (4.53)Referencetemperature

TY Yieldtemperature

ΔT Temperatureincrement

{Te}(4.22)Nodaltemperaturevector

Tolav, Tolmax (4.109)Acceptabletolerance

t Time

t Fig.5.14Thickness

Δt Timeincrement

U Weldingvoltage

U (6.1)Displacement

U Openingratio

δU (4.102)Internalvirtualwork

u Displacement

uY Displacementwhentemperatureincrementreaches TY

Δu Displacementincrement

Ve (4.23d)Elementvolume

v Weldingspeed

Wp (4.79)Plasticworkperunitvolume

δW (4.104)Externalvirtualwork

x, y, z Coordinates

Z (6.8)Sectionmodulus

α Instantaneouslinearthermalexpansioncoefficient

α0 Averagevalueoflinearthermalexpansion coefficient

αL (5.4)Coefficientofthermalexpansion

β Equivalentheattransfercoefficientincludingboth convectionandradiation

β c Heatconvectioncoefficient

β r (4.19)Equivalentradiationheattransfercoefficient

δx

(6.14)Relativedisplacements

Table6.3Inherentdeformations

θ Circumferentialdirectionofpipe

θ (4.24)Weightingfactor

ε Emissivityofthematerial

ε Totalstrain

εa, εb, εc Straininbara,barb,andbarc,respectively

ε c Creepstrain

ε e Elasticstrain

εinh ∗ (6.32)Inherentstrain

εp Plasticstrain

εph (4.45)Phasetransformationstrain

ε T Thermalstrain

εtp (4.55)Transformation-inducedplasticstrain

ε vol (4.55)Phasetransformation-inducedvolumestrain

mε e Measuredelasticstrain

εx ∗ , εy ∗ , εz ∗ , γ yz ∗ (6.6)Componentsofinherentstrain

^

ε ∗ Mostprovablevalueofeffectiveinherentstrain

εp (4.79)Equivalentplasticstrain

ε ∗ x Maximumvalueofinherentstrain

ε ∗ x0 Maximumvalueofinherentstrainincaseof infinitiveplatewidth

_

ε c Creepstrainrate

ε c Equivalentcreepstrainrate

Δε Strainincrement

Δε1 P Plasticstrainincrementduringheatingprocess

Δε2 P Plasticstrainincrementduringcoolingprocess

Δmε e Observationerrors

η Efficiencyofheatinput

κ Thermaldiffusivity

λ Thermalconductivity

Δλ (4.51)Plasticityloadingvariable

μ (4.31)Correctionfactor

ν Poisson’sratio

{ν}Residuals

σ Stress

σ (4.17)Stefan-Boltzmannconstant

σ b (5.2)Bendingstress

σ ex, min, σ ex, max Minimumandmaximumstressduetoexternal loading

σ m (5.1)Through-thicknessmembranestress

σ max (6.14)Maximumbondingstress

σ N, σ T, σ L, σ θ (6.14)Bondingstresses

σ R Weldingresidualstress

σ se (5.3)Self-equilibratingstress

σ x, σ y, τxy Componentsofstress

σ Y Yieldstress

σ yield Table8.3Yieldstrength

mσ Measuredstress

σ Equivalentstress

^

Mostprovablevalueofresidualstress

σ 0 (4.57)Stressdeviation

Δσ Stressincrement

ρ Density

ωmin (4.14)Minimumradialeigenvalue

JWSJapanWeldingSociety

JWRIJoiningandWeldingResearchInstitute,Osaka University,Japan

Acknowledgments

TheauthorsexpresstheirspecialappreciationtoProfessorEmeritusYukioUedaand HidekazuMurakawa,ProfessorNinshuMafortheirencouragementinwritingthesecondeditionbyimplementingnew Chapters4–9 andenhancedAppendixcombining Chapters1–3 ofthefirstedition.Theauthorswishtoacknowledgetheircolleagues andstudentswhoengagedintheassociatedresearch,theresultsofwhichareused inthisbook.SincerethanksareextendedtoElsevier’sScienceandTechnology EditorialandBookProductionteamsfortheirstrongsupportinpublishingthisbook. Finally,andmostimportantly,theauthorswouldliketoacknowledgethesupportof theirfamilymembers,withoutwhomthisbookwouldneverhavebeencompleted.

Appendix:Databaseoftypical residualstressdistributions invariousweldedjoints

TableA.1 Listofresidualstressdatabaseinvariousweldedjoints.

SectionBaseplateorweldedjoints

A.1 Residualstressesinbasemetals

Relevant sectionReferences

A.1.1ResidualstressinTMCPsteel [1,2]

A.1.2ResidualstressinTMCPsteelinducedbybead weld [1,2]

A.1.3Explosivecladsteel [3]

A.1.4Cylinderthickplatebycoldbending [4]

A.2 Residualstressesinweldedjointsofplates: Two-dimensional

A.2.1Butt-weldedjoints [5,6]

A.2.2Longbutt-weldedjoint [7]

A.2.3Build-upmembersofT-shapeandI-shape [7]

A.2.4Build-upmembersofT-shape,experiment [8]

A.2.5Slitwelds [9]

A.3 Multipassbuttweldsofthickplates:Threedimensional [9.5]

A.3.1Residualstressclassification [10]

A.3.2Residualstressmeasuredbyexperiment [11]

A.4 Electronbeamwelds,thickplate [12]

A.5 Firstbeadofbuttjoint:RCCtestspecimen [9.1] [13,14]

A.6 Multipassweldedcornerjoint [9.4] [15]

A.7 Filletwelds:Three-dimensional

A.7.1Straightfilletwelds [16]

A.7.2Filletweldsatthejointofwebandflange[9.3] [17,18]

A.8 Repairweldofthickplate:Threedimensional [19]

A.9 Circumferentialweldedjointofpipes [9.6]

A.9.1Heatsinkwelding [20]

A.9.2Penetrationpipejointsinnuclearreactor [21–23]

A.10 Thinplatebutt-weldedjoint [24]

A.11 Electroslagweldedjoint [25] Continued

358Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints

TableA.1 Continued

SectionBaseplateorweldedjoints

Relevant sectionReferences

A.12 Dissimilarmetalplatebutt-weldedjoint [26]

A.13 Controllingresidualstressesusinglowtemperaturetransformationfillermetal [27,28]

A.14 Penetrationnozzleweldedjoint [29,30]

A.15 Circumferentialweldedjointofpipes [31]

A.16 Electronbeamweldwithmultielectron beamheating [32]

A.17 Extrathickplatemultipassbuttjointwith 430MPayieldstrength [33]

A.18 Extrathickplatemultipassbuttjointwith 390MPayieldstrength [34]

A.19 Butt-weldedjointofpipes [35]

A.20 Dissimilarmetalnozzlejoint [36]

A.21 LapjointmeasuredbyX-raydiffraction method [5.3] [37]

A.1. Residualstressesinbasemetals

A.1.1.ResidualstressinTMCPsteel

Doc.No.1.1BasemetalofTMCP [1,2] (Figs.A.1.1–A.1.4).

ProductionTMCPMediumthickMaterial:Highstrengthsteel

ExperimentMeasurementbyLxspecimenandLyspecimenusingstressrelease method.

Components σ x ¼ inrollingdirection, σ y ¼ intransversedirection. CharacteristicsTensileresidualstressinthemiddleofthickness,compressiveoneon upperandlowersurfacesofplate

Cut lines

Steel plate

Lx and Ly specimens h =12,16, 20 mm

Strain gauge

Fig.A.1.1 TMCPplateformeasurement.

Fig.A.1.2 ResidualstressesofTMCP(12mmthick).

Fig.A.1.3 ResidualstressesofTMCP(16mmthick).

360Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints

Fig.A.1.4 ResidualstressesofTMCP(20mmthick).

A.1.2.ResidualstressinTMCPsteelinducedbybeadweld

Doc.No.1.2Residualstressinducedbybeadweld [1,2] (Figs.A.1.5andA.1.6).

Weld.cond. Bead weldSingle Medi. thick Material:Highstrength steel

AnalysisThermalEl-PlanalysisbyFEM.

Components σ x ¼ inrollingandweldingdirection, σ y ¼ intransversedirection.

CharacteristicsOntheuppersurface,thecomputedresidualstresseswithandwithoutthe effectoftheinitialrollingstressareshownin Fig.A.1.5.Theinfluenceof initialrollingstressontotalresidualstressisschematicallyshownin Fig.A.1.6.Itcanbeapproximatelyexpressedbytheinfluencefactor α, whichis0.0intheweldedmetalandHAZ,1.0intheelasticdeformation zone,and0.0to1.0intheplasticdeformationzone,respectively

Fig.A.1.5 ResidualstressesofTMCPinducedbybeadwelds.

Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints361

Fig.A.1.6 Influencefactor α ofinitialrollingstressonresidualstress.

A.1.3.Explosivecladsteel

Doc.No.1.3Explosivecladsteel [3] (Figs.A.1.7andA.1.8).

ProductionExplosivelycladdingThinNi/SUS304

ExperimentMeasuredbyinherentstrainmethod.

Components σ x ¼ inexplosivedirection, σ y ¼ transversedirectionto σ x CharacteristicsVeryhightensileresidualstressattheinterfaceofthejointanddecreases rapidlyashortdistanceaway

Fig.A.1.7 LxandLyspecimensformeasurement(Ni/SUS304explosivecladsteel).

362Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints

Fig.A.1.8 Measuredresidualstressattransversecross-section(Lmethodofinherentstrainmethod).

A.1.4.Cylinderthickplatebycoldbending

Doc.No.1.4Cylindricalthickplatebycoldbending [4] (Fig.A.1.9).

ManufactureColdbendingThickplate80kgf/mm2 HT

ExperimentInherentstrainmethod

Components σ θ M ¼ circumferential, σ z M ¼ axial

CharacteristicsSimilartoresidualstressdistributionofabeamsubjectedtoelasticplasticcoldbending

(a) Geometry of cylindrical thick plate subjected to cold bending (b) Residual stresses in thickness direction Mθ specimen Mz specimen

Fig.A.1.9 Residualstressesduetocoldbendinginshellplate.

A.2. Residualstressesinweldedjointsofplates:Two-dimensional

A.2.1.Butt-weldedjoints

Doc.No.2.1Classificationofpatternsofresidualstressdistributions [5,6] (Figs.A.2.1–A.2.3).

Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints363

WeldingButtjointSingleSubmergedarcweldingMildsteel

AnalysisThermalel-planalysisbyFEM

Components σ x ¼ inweldingdirection

CharacteristicsTransversedistributionsoflongitudinalresidualstressmaybeclassified intotypicalthreetypes(A,B,C)

EachpatterndependsonL/Banddistancefromtheends.Summaryis showninfigures

Fig.A.2.1 Butt-weldedjoint.

L/B: large (Region 3)

Fig.A.2.2 ChangeofstressdistributionswithvariationofL/B(Figs.A.2.3andA.2.4).

(a)
(c)

Fig.A.2.3 Typesofstressdistributionpatterns.

ThetypeoftransversedistributionoflongitudinalresidualstressdependsonL/B andthedistancefromtheends.Achangeofpatternisinfluencedbythedistancefrom theends,asshownin Figs.A.2.2andA.2.4 andsummarizedin TableA.2.

Fig.A.2.4 Classificationofpatternsofresidualstressdistribution. 364Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints

TableA.2 Classificationoflongitudinalresidualstresses.

Transversedistribution RegionL/B

TypeA:Effectofshearlagfromtheends:large.

TypeB:Effectofin-planebending:large.

TypeC:Effectofshearlagandin-planebendingiscompensatedorvanishes.

Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints365

A.2.2.Longbutt-weldedjoint

Doc.No.2.2Predictingmethodofresidualstressoflongweldedjoints [7] (Figs.A.2.5 andA.2.6).

WeldingButtSingleSubmergedarcMildsteel

TheoreticalpredictionLongitudinalresidualstressdistributionintransversecrosssectionatthemiddlelength(basedontheoreticalanalysis)

Components σ x ¼ inweldingdirection

CharacteristicsPredictingequationforinherentstraindistributionintransverse section.Residualstressiscalculatedbyelasticanalysisregarding inherentstrainasinitialstrain EquationisafunctionofL/B,heatinput,andkindofsteel

Fig.A.2.5 Butt-weldedjoint. (a) Assumed

Fig.A.2.6 Assumedinherentstrainandpredictedresidualstressdistributions.

366Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints

Thepredictionfortheinherentstrainregionis: ζ ¼ ε ∗ x =εYW ¼ 1+ 0:27αT av εYB ξ ¼ b=b0 ¼ 1 0 27αtav εYB , where

ε ∗ x :maximuminherentstrainintheweldedzone

εYW, εYB:yieldstrainsofweldedzone(weldmetalandHAZ)andbasemetal yieldstressdividedbyYoung’smodulus:

b:halfwidthofinherentstrainzone

b0:halfwidthofinherentstrainzoneincaseofinfinitiveplatewidth Tav:averagetemperatureincrease b0 ¼ αQ 2επ p ecρhεYB T av ¼ Q 2cρhB

A.2.3.Built-upmembersofTshapeandIshape

Doc.No.2.3Built-upmembersofTshapeandIshape [7] (Figs.A.2.7–A.2.9).

WeldingFilletSingleSubmergedarcMildsteel

PredictionandFEManalysis1.Predictionbyelasticanalysis(EA)usingassumed inherentstrain(Doc.No.2.2)

2.Thermal-elastic-plasticanalysis(TEPA)byFEM Components σ x ¼ inweldingdirection

CharacteristicsPredictionofweldingresidualstressbyelasticanalysis. VerificationofthepredictedresidualstressbyTEPAof FEM

Appendix:Databaseoftypicalresidualstressdistributionsinvariousweldedjoints367

Web Flange

Added flange

Fig.A.2.7 Built-upmembersofTshapeandIshape.

Fig.A.2.8 Comparisonofweldingresidualstressesofbuilt-upmemberofTshapeobtainedby TEPAandEAwithassumedinherentstrain.

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