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ID:238795
大小:2.93 MB
页数:42页
时间:2017-07-12
《模具专业英语 毕业论文外文文献翻译》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、外文文献EnglishforDie&MouldLesson1DrawingOperationThreebentflangesareshowninFig.1-1,Thefirstone(Fig.1-la)isthesimplestraightbend.Thestretchflangeandshrinkflange(Fig.1-lbandc,respectively)involveaplasticflowofmetalthatdoesnottakeplaceinastraight-bendflange.Thisplasticflowo
2、radjustmentofmetalischaracteristicofalldrawingoperations.Stressesareinvolvedthatexceedtheelasticlimitofthemetalsoastopermitthemetaltoconformtothepunch.However,thesestressescannotexceedtheultimatestrengthwithoutdevelopingcracks.Ifthestretchflange(Fig.1-lb)isconsideredt
3、obeasectionofacirculardepressionthathasbeendrawn,themetalinarcaamusthavebeenstretchedtoa'a'.Theactionisathinningoneandmustbeuniformtoavoidcracks.Intheshrinkflange(Fig.1-lc)theactionisjusttheopposite,andthemetalintheflangeisthickened.Mostdrawnpartsstartwithaflatplateof
4、metal.Asthepunchisforcedintothemetal,severetensilestressesareinducedintothesheetbeingformed.Atthesametimetheouteredgesofthe,sheetthathavenotengagedthepunchareincompressionandundesirablewrinklestendtoform.Thismustbecounteractedbyablankholderorpressureplate,whichholdsth
5、eflatplatefirmlyinplace.Inasimpledrawingoperationofrelativelythickplatestheplatethicknessmaybesufficienttocounteractwrinkling.Thismaybedoneinasingle-actingpressasshowninFig.1-2.Additionaldrawsmaybemadeonthecup-shapedpart,eachoneelongatingitandreducingthewallthickness.
6、Mostdrawing,involvingtheshapingofthinmetalsheets,requiresdouble-actingpressestoholdthesheetinplaceasthedrawingprogresses.Pressesofthistypeusuallyhavetwoslides,onewithintheother.Oneslidecontrollingtheblank-holdingringsmovestothesheetaheadoftheothertoholditinplace.Thisa
7、ctionisillustratedinFig.1-3.Themotionoftheblank-holdingslideiscontrolledbyatoggleorcammechanisminconnectionwiththecrank.Hydraulicpressesarewelladaptedfordrawingbecauseoftheirrelativelyslowaction,closespeedcontrol,anduniformpressureFig.1-4showsasectionaldiagramofaninve
8、rteddrawingdie.Thepunchisstationaryandismountedonthebedofthepress.Asthediedescends,theblankiscontacted;thenasitsdownwardmove
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