广东技术师范学院天河学院本科毕业设计外文翻译译文学生姓名陈剑锋院（系）广东技术师范学院天河学院专业班级机械设计制造及其自动化指导教师蒋文明完成日期2011.12.30外文出处：http://en.wikipedia.org/wiki/Leaf_springLeafspringhistoryTherewereavarietyofleafsprings,usuallyemployingtheword"elliptical"."Elliptical"or"fullelliptical"leafspringsreferredtotwocirculararcslinkedattheirtips.Thiswasjoinedtotheframeatthetopcenteroftheupperarc,thebottomcenterwasjoinedtothe"live"suspensioncomponents,suchasasolidfrontaxle.Additionalsuspensioncomponents,suchastrailingarms,wouldbeneededforthisdesign,butnotfor"semi-elliptical"leafspringsasusedintheHotchkissdrive.Thatemployedthelowerarc,henceitsname."Quarter-elliptic"springsoftenhadthethickestpartofthestackofleavesstuckintotherearendofthesidepiecesofashortladderframe,withthefreeendattachedtothedifferential,asintheAustinSevenofthe1920s.Asanexampleofnon-ellipticleafsprings,theFordModelThadmultipleleafspringsoveritsdifferentialthatwerecurvedintheshapeofayoke.Asasubstitutefordampers(shockabsorbers),somemanufacturerslaidnon-metallicsheetsinbetweenthemetalleaves,suchaswood.Leafspringswereverycommononautomobiles,rightuptothe1970sinEuropeandJapanandlate70'sinAmericawhenthemovetofront-wheeldrive,andmoresophisticatedsuspensiondesignssawautomobilemanufacturersusecoilspringsinstead.Todayleafspringsarestillusedinheavycommercialvehiclessuchasvansandtrucks,SUVs,andrailwaycarriages.Forheavyvehicles,theyhavetheadvantageofspreadingtheloadmorewidelyoverthevehicle'schassis,whereascoilspringstransferittoasinglepoint.Unlikecoilsprings,leafspringsalsolocatetherearaxle,eliminatingtheneedfortrailingarmsandaPanhardrod,therebysavingcostandweightinasimpleliveaxlerearsuspension.Amoremodernimplementationistheparabolicleafspring.Thisdesignischaracterisedbyfewerleaveswhosethicknessvariesfromcentretoendsfollowingaparaboliccurve.Inthisdesign,inter-leaffrictionisunwanted,andthereforethereisonlycontactbetweenthespringsattheendsandatthecentrewheretheaxleisconnected.Spacerspreventcontactatotherpoints.Asidefromaweightsaving,themainadvantageofparabolicspringsistheirgreaterflexibility,whichtranslatesintovehicleridequalitythatapproachesthatofcoilsprings.Thereisatrade-offintheformofreducedloadcarryingcapability,however.Thecharacteristicofparabolicspringsisbetterridingcomfortandnotas"stiff"asconventional"multi-leafsprings".Itiswidelyusedonbusesforbettercomfort.AfurtherdevelopmentbytheBritishGKNcompanyandbyChevroletwiththeCorvetteamongstothers,isthemovetocompositeplasticleafsprings.Typicallywhenusedinautomobilesuspensiontheleafbothsupportsanaxleandlocates/partiallylocatestheaxle.Thiscanleadtohandlingissues(suchas'axletramp'),astheflexiblenatureofthespringmakesprecisecontroloftheunsprungmassoftheaxledifficult.Somesuspensiondesignswhichuseleafspringsdonotusetheleaftolocatetheaxleanddonothavethisdrawback.TheFiat128'srearsuspensionisanexample.Figure1leafspringavarietyofshapesLeafspringmanufacturingprocessMulti-leafspringsaremadeasfllows:1.Shearingofflatbar2.Centerholepunching/Drilling3.EndHeatingprocessforming(hot&coldprocess)1.EyeForming/WrapperForming2.Diamondcutting/endtrimming/widthcutting/endtapering3.Endpunching/endgrooving/endbending/endforging/eyegrinding4.Centerholepunching/Drilling/nibbing4.HeatTreatment1.Heating2.Camberforming3.Quenching4.Tempering5.Surfacepreparation1.Shotpeening/stre...
