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