汽车专业英语PPT课件-section 4ppt课件Chapte12 3

Section4AutomotiveDesignandManufacturing,Chapter12AutomotiveManufacturing12.1Vehiclearchitecturedesignandmanufacturing12.2InjectionMoulding12.3JoiningForLightweightVehicles,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,NewWords,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,NewWords,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,NewWords,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Withtheincreasingtrendtowardlightweightvehicles,thebodymaterialsforautomobilesarechangingfrommostlylowcarbonsteelstoamixofmaterialsthatincludesbothlowcarbonsteelsandhighstrengthsteels,lightnon-ferrousalloys,suchasaluminumandmagnesiumalloys,andfiberreinforcedpolymers.Theacceptanceofthesematerialswilldependnotonlyontheirstructuralperformanceandmanufacturability,butalsoonthejoiningmethodsthatcanbeusedtoassembletheminarapid,robustandreliablemanner.Thestructuralperformanceofajointdependsonthejoiningmethod,jointgeometryandjointquality.Thejoiningmethodoftendependsonthematerialsbeingjoined,butundermassproductionconditionsitmustalsobequick,lessdependentonfitanddimensionalvariationsofthepartsbeingjoinedandasdefectfreeaspossible.,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Joiningisanimportantconsiderationinthedesignofanautomobile,sincejointsareusuallytheweakestareasinthestructureandtheyareoftenthefailureinitiationlocationsinservice.Joiningbecomesevenmoreimportantasthebodymaterialchangesfromasinglematerialtoamixofmaterials,sincethecompatibilitybetweendifferentmaterialsintermsoftheirmutualjoinability,surfacecharacteristics,corrosion,assemblystresses,etc.mayposemanytechnicalchallengesandneedstobeconsideredinthedesignprocessandselectionofmaterials.Sincehighstrengthsteelsandaluminumalloysareemergingastheprincipalmaterialoptionsforbodyconstructioninthenearfuture,thejoiningmethodsthataremostapplicableforthesetwotypesofmaterialsareconsidered.Thesejoiningmethodscanbedividedintofourcategories:,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Thesejoiningmethodscanbedividedintofourcategories:(i)liquidphaseweldingorfusionwelding,(ii)solidphasewelding,(iii)mechanicaljoiningand(iv)adhesivebonding.Thereareseveraldifferenttechniquesavailableundereachofthesecategories(Table12-1).,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Table12-1Variousjoiningmethodsusedwithsheetmetalsintheautomotiveindustry,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Forexample,liquidphaseweldingorfusionweldingincludesresistancespotwelding(Figure12-4),arcweldingandlaserwelding.Thetwomostcommonmethodsofarcweldingaregasmetalarcwelding(GMAW)(Figure12-5)andgastungstenarcwelding(GTAW)(Figure12-6);buttherearemanyotherformsofarcweldingmethodsthatareusedeitherinspecialcasesorinlimitedapplications.Solidphasewelding,whichisaccomplishedwithoutmeltingthematerials,includesfrictionstirweldingandafewotheremergingtechnologies,suchasmagneticpulseweldingandultrasonicwelding.Mechanicaljoiningincludestheconventionalmechanicalfasteningmethodsusingboltsandnuts,butalsothenewertechniques,suchasself-piercingrivetingandclinching.,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Adhesivebondingisalsoanestablishedmethodofjoining,butacombinationofadhesivejoiningandweldingorrivetingisrelativelynewandisfindingwiderapplication,especiallyinspaceframedesigns.Liquidphaseweldingisperformedbylocallyheatingthematerialstobejoinedtotheirliquidphases,applyingpressuretocreatefusionbondingbetweenthemandallowingthefusionbondedliquidphasetocoolunderpressuretoformthejoining.Theprincipalliquidphaseweldingprocessesusedintheautomotiveindustryareresistancespotweldingandarcwelding.Resistancespotweldingistheprincipaljointingmethodusedforlowcarbonsteelbodyconstruction.,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Figure12-4resistancespotwelding(RSW)process,Chapter11AutomotiveDesign12.3JoiningForLightweightVehicles,Figure12-5Gasmetalarcwelding(GMAW)process,Chapter11AutomotiveDesign12.3JoiningForLightweightVehicles,Figure12-6Tungstengasarcwelding(GTAW),Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Insolidphasewelding,twosheetsofthesamematerialordifferentmaterialsarejoinedbycreatingmetallurgicalbondwithoutmeltingthematerials.Theweldqualityisusuallyexcellent,sinceporosity,grainboundarycrackingandotherproblemscommonlyassociatedwithliquidphaseweldingdonotoccurinsolidphasewelding.Themechanicalproperties,ingeneral,areequaltoorbetterthanthoseobtainedbyliquidphasewelding.Anotheradvantageisthatbynotcreatingamoltenpoolofmaterialwhichshrinkssignificantlyonsolidification,distortionofthepartandresidualstressesafterweldingarerelativelylow.Theprocessisenvironmentallyfriendly,sincenofumesorspatteraregenerated,andtherearenoarcglaresorreflectedlaserbeamstocontendwith.,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Thetwocommonsolidphaseweldingmethodsusedwithsteel,aluminumandavarietyofothermetalsarefrictionstirwelding(Figure12-7),knownasFSW,andfrictionstirspotwelding,knownasFSSW(Figure12-8).BothprocesseswereinitiallydevelopedbyTheWeldingInstitute(TWI)ofUK.FSWwasdevelopedin1991andsincethenithasbeengainingpopularityforweldingaluminumalloysinbothautomotiveandaircraftindustries.FSSWwasdevelopedlaterandisseeingincreasingapplicationsintheautomotiveindustry.Inbothprocesses,thematerialsatthejointarebroughttothesoftenedstatesbythefrictionalheatgeneratedbetweenarotatingweldingtoolandthesheetsorplatestobejoined.Theyhavetheabilitytojoinmaterialsthataredifficulttofusionweld;forexample,the2000and7000-seriesaluminumalloys.AnothermajorbenefitofFSWandFSSWisthereducedenergyconsumption.,Chapter12AutomotiveManufacturing12.3JoiningForLightweightVehicles,Theelectricityconsumptionforfrictionstirweldingaluminumisonly5%ofthatofRSW.SinceFSWdoesnotneedtheuseoflargecurrent,coolant,andcompressedairthatarerequiredforRSW,thetotalenergyconsumptioninFSWissignificantlylow.Self-piercingrivetedjointisshowninFigure12-9.Self-pie