重庆理工材料成形技术基础课程课件双语PPT之7Sheet-MetalFormingProcesses.ppt

重庆理工材料成形技术基础课程课件双语PPT之7Sheet-MetalFormingProcesses.ppt

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FundamentalofMaterialsForming,-Sheet-MetalFormingProcesses板金成形工艺,INTRODUCTION,Productsmadebysheet-metalformingprocessesareallaroundus;theyincludemetaldesks,filecabinets,appliances,carbodies,aircraftfuselages（机身）,andbeverage（饮料）cans.Sheetformingdatesbackto5000B.C.,whenhouseholdutensils（器具）andjewelryweremadebyhammeringandstampinggold,silver,andcopper.,冲压生产场景,Comparedtothosemadebycastingandbyforging,sheet-metalpartsoffertheadvantagesoflightweightandversatile（万能的）shape.Becauseofitslowcostandgenerallygoodstrengthandformabilitycharacteristics,low-carbonsteelisthemostcommonlyusedsheetmetalForaircraftandaerospaceapplications,thecommonsheetmaterialsarealuminumandtitanium.,OutlineofSheet-MetalFormingProcesses,Figure16.1,CharacteristicsofSheet-MetalFormingProcesses,SHEARING剪切,Beforeasheet-metalpartismade,ablankofsuitabledimensionsisfirstremovedfromalargesheet（usuallyfromacoil）byshearing;thatis,thesheetiscutbysubjectingittoshearstresses,typicallyonesdevelopedbetweenapunchandadie（Fig.16.2a）.TypicalfeaturesoftheshearededgesofthesheetandoftheslugareshowninFigs.16.2bandc,respectively.Notethattheedgesarenotsmooth,noraretheyperpendiculartotheplaneofthesheet.,Themajorprocessingparameters,Themajorprocessingparametersinshearingaretheshapeofandthematerialsforthepunchanddie,thespeedofthepunching,thelubrication,andtheclearance,c,betweenthepunchandthedie.Theclearanceisamajorfactorindetermin-ingtheshapeandthequalityoftheshearededge.,Clearance,Figure16.3（a）Effectoftheclearance,c,betweenpunchanddieonthedeformationzoneinshearing.Astheclearanceincreases,thematerialtendstobepulledintothedieratherthanbesheared.Inpractice,clearancesusuallyrangebetween2%and10%ofthethicknessofthesheet.（b）Microhardness（HV）contoursfora6.4-mm（0.25-in）thickAISI1020hot-rolledsteelintheshearedregion.Source:

H.P.WeaverandK.J.Weinmann.,Punchforce,Theforcerequiredtopunchis,basically,theproductoftheshearstrengthofthesheetmetalbytheareabeingsheared.Frictionbetweenthepunchandtheworkpiececan,however,increasethisforcesubstantially.Themaximumpunchforce,F,canbeestimatedfromtheequationF=0.7TL（UTS）,whereTissheetthickness,Listhetotallengthsheared（suchastheperimeterofahole）,andUTSistheultimatetensilestrengthofthematerial.Astheclearanceincreases,thepunchforcedecreases,andthewearondiesandpunchesisalsoreduced.,ShearingOperations,Severaloperationsbasedontheshearingprocessareperformed.Wefirstdefinetwoterms.Inpunching,theshearedslugisdiscarded（Fig.16.4a）.Inblanking,theslugisthepartandtherestisscrap.Manyoftheoperationsdescribedbelow,aswellasthosedescribedthroughouttherestofthischapter,cannowbecarriedoutoncomputer-numerical-controlledmachines（seeChapter39）withquick-changetoolholders.,ShearingOperations,notching开槽,lancing切缝,Slitting切口,erforating成孔,arting切断,Shearingdies,Fig16.3（a）Effectoftheclearance,c,betweenpunchanddieinthedeformationzoneinshearing.Astheclearanceincreasesthematerialtrendstobepulledintothedieratherthanbesheared.,FineBlanking.,Verysmoothandsquareedgescanbeproducedbyfineblanking（Fig.16.5a）.Thefine-blankingoperationisusuallycarriedoutontriple-actionhydraulicpresses,wherethemovementsofthepunch,ofthepressurepad,andofthedieareseparatelycontrolled.Theprocessusuallyinvolvesaparthavingholesthatarepunchedsimultaneouslywithitsblanking.Suitablesheethardnessistypicallybetween50and90HRB.,FineBlanking精冲,Figure16.5（a）Comparisonofshearededgesproducedbyconventional（left）andbyfine-blanking（right）techniques.（b）Schematicillustrationofonesetupforfineblanking.Source:

FeintoolU.S.Operations.,Slitting（切口）,Slitting.Shearingoperationscanbecarriedoutbymeansofapairofcircularblades（刀片）similartothoseinacanopener（Fig.16.6）;thisprocessiscalledslitting.Thebladesfolloweitherastraightlineoracircularorcurvedpath.Aslitedgenormallyhasaburr毛刺,whichmaybeplasticallyfoldedoverthesheetsurfacebyrollingthesheetbetweentworolls.,Figure16.6Slittingwithrotaryknives.Thisprocessissimilartoopeningcans.,steelrule钢尺,Softmetals（aswellaspaper,leather,andrubber）canbeblankedwithsteel-ruledies.Suchadieconsistsofathinstripofhardenedsteel,bentintotheshapetobeproduced（aconceptsimilartothatofacookiecutter）andheldonitsedgeonaflatwoodenbase.Thedieispressedagainstthesheet,whichrestsonaflatsurface,anditshearsthesheetalongtheshapeofthesteelrule.,LaserWelding,Figure16.7Productionofanoutersidepanelofacarbody,bylaserbutt-weldingandstamping.Source:

AfterM.GeigerandT.Nakagawa.,ExamplesofLaserWeldedP