1DiedesignforstampinganotebookcasewithmagnesiumalloysheetsContentSummaryInthepresentstudy，thestampingprocessformanufacturinganotebooktopcovercasewithLZ91magnesiumlithiumalloysheetatroomtemperaturewasexaminedusingboththeexperimentalapproachandthefiniteelementanalysis.Afour-operationstampingprocesswasdevelopedtoeliminateboththefractureandwrinkledefectsoccurredinthestampingprocessofthetopcovercase.Inordertovalidatethefiniteelementanalysis，anactuafour-operationstampingprocesswasconductedwiththeuseof0.6mmthickLZ91sheetastheblank.Agoodagreementinthethicknessdistributionatvariouslocationsbetweentheexperimentaldataandthefiniteelementresultsconfirmedconfirmedtheaccuracyandefficiencyoftheementanalysis.ThesuperorformabilityofLZ91sheetatroomtemperaturewasalsodemonstratedinthepresentstudybysuccessfulmanufacturingofthenotebooktopcovercase.Theproposedfouroperationprocesslendsitselftoanefficientapproachtoformthehingeinthenotebookwithlessnumberofoperationalproceduresthanthatrequiredinthecurrentpractice.ItalsoconfirmsthatthenotebookcovercasescanbeproducedwithLZ91magnesiumalloysheetbythestampingprocess.Itprovidesanalternativetotheelectronicsindustryintheapplicationofmagnesiumalloys.Keywords:Notebookcase；LZ91magnesiumlithiumalloysheet；stamping；Multi-operation；Formability21.IntroductionDuetoItslightweightandgoodperformanceinEMIresistance,magnesiumalloyhasbeenwidelyusedforstructuralcomponentsintheelectronicsindustry,suchascellularphonesandnotebookcases.Althoughtheprevailingmanufacturingprocessofmagnesiumalloyproductshasbeendiecasting，thest-ampingofmagnesiumallsheethasdrawninterestsfromindustrybecauseofitscompetitiveproductivityandperformanceintheeffectiveproductionofthin-walledstructuralcomponents.Asforstampingprocess，AZ31magnesiumalloy(aluminum3%,zinc1%)sheethasbeencommonlyusedfortheformingprocessatthepresenttime,eventhoughitneedstobeformedatelevatedtemperatureduetoitshexagonalclosedpacked(HCP)crystalstructureRecently,themagnesiumlithium(LZ)alloyhasalsobeensuccessfullydeve-lopedtoimprovetheformabilityofmagnesiumalloyatroomtemperature.Theductilityofmagnesiumalloycanbeimprovedwiththeadditionoflithiumthatdevelopstheformationofbodycentered-cubic(BCC)crystalstructure(Takudaetal.,1999a,b；Drozdetal,2004).Inthepresentstudy,thestampingprocessofanotebooktopcovercasewiththeuseofLZsheetwasexamined.Theformingofthetwohingesinthetopcoverofanotebook,asshowninFig.1(aandb),isthemostdifficultoperationinthestampingprocessduetothesmalldistancebetweentheflangesandthesmallcornerradiiattheflanges,asdisplayedinFig.1(c).Thisgeometricomplexitywascausedbyadramaticchangeinthecornerradiuswhentheflangeofgetstooclosetthenotebook,whichwouldeasilycausefracturedefectaroundtheflangeofhingeandrequireamulti-operationstampingprocesstoovercomethisproblem.Inthepresentstudy,theformabilityofLZmagnesiumalloysheetswasinvest-igatedandanoptimummulti-operationstampingprocesswasdevelopedtoreducethenumberofoperationallprocedusingboththeexperimentapproachandthefiniteelementanalysis.3Fig.1Flangeofhingesatnotebooktopcovercase.(a)Hinge,(b)topcovercaseand(c)flangesofhinge.2.Mechanicalpropertiesofmagnesiumcontentoflithiumincreases.ItisalsoobservfromFig.2(a)thatthecurvesofLZ91sheetatroomtemperatureandAZ31sheetat200,Careclosetoeachother.LZ101sheetatroomtemperatureexhibitsevenbetterductilitythanLZ91andAZ31doat200,C.Sincethecostoflithiumisveryexpensive,LZ91sheet,insteadofLZ101sheet,canbeconsideredasasuitableLZmagnesiumalloysheettorenderfavorableformabilityatroomtemperature.Forthisreason,thepresentstudyadoptedLZ91sheetastheblankforthenotebooktopcovercaseandattemptedtoexaminetheformabilityofLZ91atroomtemperature.Inordertodetermineifthefracturewouldoccurinthefiniteelementanalysis,theforminglimitdiagramforthe0.6mmthickLZ91sheetwasalsoestablishedasshowninFig.2(b).alloysheetsThetensiletestswereperformedformagnesiumlithiumalloysheetsofLZ61(lithium6%,zinc1%),LZ91,andLZ101atroomtemperaturetocomparetheirmechanicalpropertiestothoseofAZ31sheetsatelevatedtemperatures.Fig.2(a)showsthestressstrainrelationsofLZsheetsatroomtemperatureandthoseofAZ31sheetsatbothroomtemperatureand200?C.Itisnotedthatthestressstraincurvetendstobelower.4Fig.2Mechanicalpropertiesofmagnesiumalloy.(a)Thestressstrainrelationsofmagnesiumalloy；(b)forminglimitdiagram(FLD)ofLZ91sheet.3.ThefiniteelementmodelThetoolinggeometrieswereconstructedbyaCADsoftware,PRO/E,andwereconvertedintothefiniteelementmesh,asshowninFig.3(a),usingthesoftwareDELTAMESH.Thetoolingwastreatedasrigidbodies,andthefour-nodeshellelementwasadoptedtoconstructthemeshforblank.Themateriallpropertiesandforminglimitdiagramsobtainedfromtheexperimentswereusedinthefiniteelementsimulations.Theothersimulationparametersusedintheinitialrunwere:punchvelocityof5mm/s,blank-holderforceof3kN,andCoulombfrictionc