Using the orthogonal array with grey relational analysis to optimize the laser hybrid welding of a 6

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Usingtheorthogonalarraywithgreyrelationalanalysistooptimizethelaserhybridweldingofa6061-T6Alalloysheet

HRKimandKYLee*

SchoolofMechanicalEngineering,YonseiUniversity,Seoul,RepublicofKorea

Themanuscriptwasreceivedon27November2007andwasacceptedafterrevisionforpublicationon24April2008.DOI:10.1243/09544054JEM1070

Abstract:Amethodologyfordeterminingtheoptimumprocessconditionsassociatedwith

Nd:YAGlaser–gasmetalarchybridweldingof6061-T6Alalloysheetispresented.Theweld-

abilityisdependentonvariousprocessparameterswhichincludetheweldingwiretype,shield-

inggas,laserpower,laserfocus,travellingspeed,weldingwirefeedrate,rootopening

tolerance,andvoltage.Experimentsareperformedwithdesignatedweldingconditions

obtainedusinganL18orthogonalarray.Fortheevaluationofweldability,comparingtheresult

oftheultimatetensilestrengthontheweldzoneisessential.Inordertodeterminetheopti-

mumweldingconditions,agreyrelationalanalysisiscarriedoutthroughtheresultoftheulti-

matetensilestrengthforeachweldingexperiment.Basedontheresultsofthegreyrelational

analysis,ingtheanalysisofvariance

approachthesignificantweldingparametersarefound.Theresultsshowthattheoptimum

weldingconditionsdeterminedusinggreyrelationalanalysisaremuchbetterthantheoriginal

preliminarysetofexperimentalconditions.

Keywords:laserhybridwelding,aluminiumalloy,orthogonalarray,greyrelationalanalysis,

variance

1INTRODUCTION

Aluminiumhasalowspecificdensityandagoodcor-

rosionresistancewhenintheatmosphere,water,oil,

andmanychemicalsthatisduetotheexistenceofa

thinoxidefilmonthesurfaceofthemetal.The

6061-T6aluminiumalloyisextensivelyusedin

applicationsthathavemediumtohigh-strength

requirementsandgoodtoughnesscharacteristics.

However,thepresenceofthesurfaceoxide(thatis

stableuptotemperaturesof2000 C)meansthat

porosityeffectscanbecreatedintheweldzone.

Thus,anappropriateweldingtechniqueisrequired.

Alloy6061-T6iseasilyweldedandjoinedbyusing

variousweldingtechniques.Hybridweldinghas

attractedconsiderableattentionintheliterature

[1–5].Thisisduetoitsmanyadvantagessuchas

increasedjoinpenetration,improvedrootopening

*Correspondingauthor:SchoolofMechanicalEngineering,

YonseiUniversity,134Sinchon-dong,Seodaemum-gu,Seoul

120-749,RepublicofKorea.email:KYL2813@yonsei.ac.k

JEM1070ÓIMechE2008tolerance,misalignmenttolerance,increasedweldingspeed,andenhancedprocessstability.Taguchi[6]andRoss[7]proposedtheuseoforthogonalarraystoeffectareductioninthenumberofexperimentsevenwhenconsideringalldesignatedparameters.ThegreysystemtheoryproposedbyDeng[8–10]dealswithasystemwhichhasincompleteanduncer-taininformation.Greyrelationalanalysisisbasedonthegreysystemtheoryandcanbeusedtoanalysecomplicatedperformancecharacteristics[11–13].Theuseofgreyrelationalanalysisleadstothecrea-tionofanoptimumvalueofasinglegreyrelationalgradewithqualitativeindicesofaperformancechar-acteristic.Theuseofthistechniquereducestheamountoftimerequiredtoverifyproductquality.Themainfocusofthisstudyistoexplorethepos-sibilityofusinggreyrelationalanalysistooptimizetheweldingparametersforNd:YAGlaser–gasmetalarchybridweldingof6061-T6aluminiumalloy.Basedontheresultsofthegreyrelationalanalysis,asetofoptimumweldingparametersisobtained.Adesignofexperiment(DOE)approachisthenProc.IMechEVol.222PartB:J.EngineeringManufacture