本科畢業(yè)論文-1600鎂合金帶材精整機(jī)組-分條圓盤剪設(shè)計(jì)

1600鎂合金帶材精整機(jī)組-分條圓盤剪機(jī)架設(shè)計(jì))式中——聯(lián)軸器的許用轉(zhuǎn)矩/；T——聯(lián)軸器長期承受的理論轉(zhuǎn)矩/；——聯(lián)軸器工作條件系數(shù)。所以：7.4齒輪機(jī)座的作用及類型為了將電動機(jī)或減速器的扭矩分配給每個(gè)刀盤軸，除電動機(jī)單獨(dú)傳動每個(gè)刀盤軸的情況外，大多數(shù)分條圓盤剪的主傳動系統(tǒng)中都設(shè)有齒輪機(jī)座。因?yàn)辇X輪機(jī)座傳遞的扭矩較大，而中心距又受到刀盤軸中心距的限制，為了滿足強(qiáng)度要求，齒輪的模數(shù)較大（8~45），齒寬較寬（齒寬系數(shù)為1.6~2.4），而齒數(shù)較少，通常為22~44。齒輪機(jī)座的箱體有高立柱式、矮立柱式和水平剖分式三種形式。齒輪機(jī)座通常直接安裝在基礎(chǔ)上，安裝方式有兩種，一種是將整個(gè)底座都安放在基礎(chǔ)上，另一種是由地腳安裝在基礎(chǔ)上。7.5齒輪機(jī)座的結(jié)構(gòu)齒輪機(jī)座由齒輪軸、軸承及軸承座和機(jī)蓋等主要部件組成。由于傳遞的扭矩大，因此傳動軸的直徑很大，相比之下，齒輪的直徑很小，所以一般與傳動軸作成一體，即齒輪軸。齒輪多做成具有漸開線齒形的人字齒，這樣，只能將一根軸的一端在軸向予以固定，而另外一根齒輪必須設(shè)計(jì)成軸向游動的，在運(yùn)轉(zhuǎn)過程中依靠人字齒的嚙合自動定位，從而避免載荷在兩側(cè)斜齒上的不均勻分布。另外，在溫度發(fā)生變化時(shí)，相嚙合的齒輪軸均可自由伸縮，保證正常嚙合。在齒輪機(jī)座中采用雙圓弧齒輪軸，可提高齒輪軸的使用壽命和承載能力，使齒輪軸的外形尺寸減小。齒輪軸的材料為45、40Cr、32Cr2MnMo、35SiMn2MoV、40CrMn2MoV等。由于分條圓盤剪齒輪箱齒輪軸的齒面接觸應(yīng)力很高,應(yīng)采用硬齒面,齒面淬火硬度為HB480~570。齒輪機(jī)座的軸承主要采用滾動軸承，齒輪機(jī)座箱體應(yīng)保證齒輪傳動具有良好的密封性，并具有足夠的剛性，以使軸承具有堅(jiān)固的支撐，為此，應(yīng)盡可能加強(qiáng)箱體軸承處的強(qiáng)度和剛度。由于齒輪箱大多是單件或少量生產(chǎn)，為了降低成本，機(jī)座的箱體采用鍛焊結(jié)構(gòu)或鑄焊結(jié)構(gòu)。

8系統(tǒng)的潤滑8.1潤滑劑的作用機(jī)械零件的表面在接觸的時(shí)候產(chǎn)生相對運(yùn)動，在此過程中，避免不了會產(chǎn)生摩擦。假如潤滑不當(dāng)，效率會下降，并且引起發(fā)熱、振動、噪聲等。由于零件磨損，機(jī)械精度下降，壽命降低，影響了正常工作而發(fā)生早期報(bào)廢。因此，在機(jī)械設(shè)計(jì)中，潤滑是一個(gè)很重要的問題。在機(jī)械的摩擦副中加潤滑劑的主要作用是：減小摩擦因數(shù)，提高機(jī)械效率。減輕磨損，延長機(jī)械使用壽命。液體潤滑劑能帶走摩擦所產(chǎn)生的熱量，使零件的表面工作溫度下降。循環(huán)潤滑能起排污作用。點(diǎn)、線接觸的摩擦表面，油膜能起到緩沖吸振的作用，能夠?qū)⑤d荷分布到較大的面積上，使最大應(yīng)力下降。緩蝕、密封。8.2潤滑方式的選擇8.2.1軸承的潤滑滾動軸承潤滑的作用是降低摩擦阻力、減少磨損、防止銹蝕，同時(shí)還可以起到散熱、減小接觸應(yīng)力、吸收振動等作用?？紤]軸承潤滑時(shí)，選用脂潤滑方式，潤滑膜強(qiáng)度高，能承受較大的載荷，不易流失，容易密封，能防止灰塵等雜物侵入軸承內(nèi)部，對密封要求不高，一次加脂可以維持相當(dāng)長的一段時(shí)間。其缺點(diǎn)是：摩擦損失大，散熱效果差。對于那些不便經(jīng)常添加潤滑劑的部位，或不允許潤滑油流失而導(dǎo)致污染產(chǎn)品的工業(yè)機(jī)械來說，這種潤滑方式十分適宜。潤滑脂的填充量要適中，一般為軸承內(nèi)部空間容積的。8.2.2齒輪傳動的潤滑齒輪在傳動時(shí)，相嚙合的齒面間有相對滑動，因此就要發(fā)生沖突和磨損，添加動力消耗，降低傳動效率。特別是高速傳動，就更要做好齒輪的潤滑。齒輪嚙合面之間需要加入潤滑劑，能夠防止金屬直接碰觸，減小摩擦損耗，還能夠散熱及防銹蝕。因而，對齒輪傳動系統(tǒng)進(jìn)行必要的潤滑，能夠大大改善輪齒的工況，確保運(yùn)轉(zhuǎn)正常及預(yù)期的壽命。通用閉式齒輪傳動，其潤滑方法依據(jù)齒輪圓周速度大小決定。當(dāng)齒輪的圓周速度時(shí)，通常是將大齒輪輪齒浸入油池中進(jìn)行浸油潤滑。這樣，齒輪傳動時(shí)，就把潤滑油帶到嚙合的齒面上，也能將油甩到箱壁上，借以散熱。齒輪浸入油中的深度可視齒輪圓周速度大小決定，對圓柱齒輪一般不宜超過一個(gè)齒高，但一般不該小于10mm。8.2.3滑塊式萬向接軸的潤滑由于滑塊式萬向接軸的摩擦表面不能很好地密封，潤滑油不能很好地保存在摩擦面上。同時(shí)分條圓盤剪的運(yùn)行特點(diǎn)和萬向接軸所處的位置，使其潤滑較為困難，造成滑塊的磨損加快，壽命降低，嚴(yán)重影響分條圓盤剪的作業(yè)率。目前潤滑方式主要是人工定期加注潤滑油和采用自動潤滑油裝置兩種。另外，采用密封油包包覆和內(nèi)存潤滑劑的方式也可以較好地解決潤滑問題。潤滑劑可用潤滑脂或潤滑油。8.2.4齒輪機(jī)座的潤滑分條圓盤剪的齒輪機(jī)座連續(xù)運(yùn)轉(zhuǎn)時(shí)間很長，因此機(jī)座的冷卻與潤滑是很重要的。對于齒輪，采用兩種方式，一種是用側(cè)向噴嘴直接向齒輪嚙合區(qū)噴射潤滑油；另一種是用一排位于上齒輪軸上部的噴油嘴，通過側(cè)擋板向齒輪嚙合區(qū)注油。齒輪箱的軸承通常與齒輪使用同一潤滑系統(tǒng)，在齒輪箱體上應(yīng)有潤滑軸承的油溝。

結(jié)論經(jīng)過一個(gè)學(xué)期的學(xué)習(xí)、分析、設(shè)計(jì)，在老師的耐心指導(dǎo)和同學(xué)們的熱情幫助下，我最終完成了1600鎂合金帶材精整機(jī)組-分條圓盤剪機(jī)架設(shè)計(jì)。分條圓盤式剪切機(jī)主要功能是對已經(jīng)軋制過的AZ31鎂合金板進(jìn)行分條。我設(shè)計(jì)的這臺分條圓盤式剪切機(jī)主要是對于刀盤軸的設(shè)計(jì)校核、軸承的選擇校核、電動機(jī)的核算選擇校核、傳動裝置中主要的萬向連接軸和齒輪的計(jì)算校核，部分鍵的計(jì)算，以及對潤滑系統(tǒng)進(jìn)行了分析。在設(shè)計(jì)和核算過程中涉及、運(yùn)用了許多基礎(chǔ)及專業(yè)知識，如：軋鋼機(jī)械設(shè)計(jì)、機(jī)械制造、機(jī)械原理、材料力學(xué)，理論力學(xué)、金屬工藝學(xué)等。對這些知識的應(yīng)用使我大大加強(qiáng)了本專業(yè)知識功底。由于我的水平有限，設(shè)計(jì)中不可避免存在一些不足，在核算、設(shè)計(jì)及繪圖過程中不可避免地出現(xiàn)錯誤，請各位老師給予批評指正。

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外文翻譯Chapter5Edgecracking5.1OverviewofcrackingstudiesEdgecrackingoftenresultsinedgetrimmingtoremovethedamagedmaterialorcancausetheworkpiecetobreakupintherollgap.Insomecasesthequantityofscraphasbeenquotedas6%ormoreforcertainaluminummagnesiumalloys(45).Creatingthesecracksrequiresbothinadequateductilityandsecondarytensilestressontheedge(15).Obviouslyjustliketheneedtopredicttheresultofrolling,edgecrackinghassolicitedresearchtobetterunderstandtheconceptsandcausesassociatedwiththisdefect.Becauserollingisanindustrialprocess,theconcernofexperimentsisinmakingsurethatresultstranslatefromthelabbacktothefactoryfloor.Thisisacomplicatedprocess,especiallyforhotrolling,becauseindustrialmillsaremuchlargerthanthosetypicallyusedforlaboratoryexperiments.Whilegrossgeometryiseasilyscalable,themetallurgicalparametersincludingmicro-structuralandthermalvariablesarenot.Forexample,laboratoryrollingmillsareusuallymuchsmallerthantheonesusedinindustry,thereforetheworkpiecesaresmaller,thiscausesissuesbecausethethermalmassesofthetwodiffer.Thereforetheheatdistributiondiffersbetweenthetwocaseswhichgreatlyeffectsflowstress.ThisproblemhasbeenaddressedbyBurmanbyreheatingthespecimensafteratemperaturedropofmorethan40°Cbelowthatofthefirstrollingpass(46).Accuratelymodelingrollinginthelabhascreatedsomeuniquetestingmethods;forexample,inordertoaccuratelymodelforwardslipconditionsusedincoldrollinganupsettingrollingtestisused.Thishasbeenusedtostudytheeffectofchangingtheforwardslipconditionandcontactconditionseasily.Inthistest,thematerialisdrawnthroughthedeviceusingatensiletestmachine.Thisdeviceonlyreproducescontactconditionsononlyonesideofthestrip(47).Indifferentexperiments,toestimatethecreationoftensilestressesinrolling(whichisrelatedtocrackpropagation),oftentimesagridwouldbeetchedontoamaterialsampleeitheronthesideorbetweentwopiecesofmaterialwhichthenarerivetedtogether.Thesetestpiecesarethenrolled.Afterrolling,thestreamlinedataiscollectedbymeasuringgridchanges.Modelingisthenemployedtoback-trackoutthestresses(46).Instudyingmaterialfactors,oftentimesdifferentmethodsareusedtorevealthemicrostructureofthematerialincluding:opticalmicroscopy,TEM,andx-raydiffraction(48).Thesenotonlyattempttolookatlocationsandmaterialinclusionsthattendtocausecrackingbutattempttotracktheevolutionofthemicrostructureinthesematerials.Tostudyedgecrackingcreatingaccuratefiniteelementmodelshavebecomenecessaryasexperimentsareexpensiveanddifficulttorelatebacktoindustrialconditions.ThemaindebateinusingthismethodisthedamagemodelasdiscussedinChapter4.Perhapsthesimplestmethodattemptedtomodelcrackingisusingstressintensityfactors(49).Thestressintensityfactor(SIF)helpscharacterizesthecracktipandisusedcommonlyinfracturestudies.Thedeterminationofthisfactorisdependentonthesizeofthecrack,geometryofthecrackandpart,theappliedload,andboundaryconditions.Thefactoriscalculatedthencomparedtofracturetoughnessinformation.WhileXieet.al.study,asdescribedhere,providessomeinsightsintoedgecracking,caremustbetaken.TheSIFismainlyvalidforlinearelasticmaterialsandprocesses;inthecaseofrollingdeformationplasticityisinherenttotheprocess(41).Inaddition,SIFanalysisdoesnottakeintoaccountcrackcreationbutonlydealswithcrackpropagation.WhileXie’sstudycouldbeusedtodescribeacoldrollingsituationwithalightpasses,whichmaylimitthezoneofplasticity,thevalidityofthismethodwithhotrollingwouldnotbeappropriate(49).Morerelevanttothedamagemethodusedhere,manyauthorscreateafracturecriterionandsimplydeleteelementswhenthiscriterionismet.Manyfracturecriteriahavebeenproposed;somearebasedoncriticalstrain,criticalstress,orplasticwork(50).OneexampleofthisistheworkofOhandKobayashi(51)wheretheyusetheprincipaltensilestrainsandprincipalcompressivestrain.Theconstantsintheseformulationsaredeterminedbyexperiment.Anexampleisgivenbelow: （5.1）Thiscriteriavalidityislimitedtomaterialinquestion,AA7075-T6andonlyforrollingcases.Themostcomplicateddamagemodel,usedinfiniteelementanalysis,utilizestheideaofvoidvolumefraction.Sinceductilecrackingisbasedontheinitiation,growth,andthenlinkingofvoids,thisisamorephysicalbasedanalysis.Inthistypeofstudythevoidvolumefractionisallowedtoincreaseanddecreaseuntilitreachesacriticalvalueinwhichthematerialfractures.InastudybyRiedeletal.(50)theyattemptedtomodeledgecrackingthiswayusingtheGologanumodel,whichisbasedonthemorecommonlyusedGursonmodel.Theusesofeitherofthesemodelsareproblematicduetomodelcomplexityandadifficulttodeterminesetofmaterialproperties.But,sincethemodelisbelievedtobeclosertothephysicsofthesituationitismorelikelytobevalidoverdifferentstressstates.Thesetypesofmodelsalsoshowtheevolutionofdamagethroughoutthemodel.Therearetwointerestingthingstonoteaboutthisstudy:sincetheyweretryingtorecreatethe45°fracturepatternthatisinherenttoedgecracking1)theyhadpreviouslyusedafracturecriteriontorecreatethepatternand2)theGursonmodelwasunabletocreatethispattern.OnlywhentheyusedtheGologanumodelwhichassumesellipticalvoidshapes(insteadofsphericalones)weretheyabletorecreatethecrackingcondition.5.2Causesofcracking5.2.1MaterialPropertiesAsmentionedatthebeginningofthischapter,oneoftherequiredconditionsforedgecrackingisinsufficientductility.Therefore,studiesofedgecrackinginrollingoftenmeasuredifferentmaterialpropertiesandmicrostructuresandhowthoseparametersaffectductility.Ductilityisinfluencedbytemperature,grainsize,preferredorientationofthematerial,andcompositionofthematerial(1).Thisisespeciallytruewithsecondphaseinclusionswhichshape,size,andstrengthcanbeinitiationpointsforedgecracking(15).Additionallyinhotductility:temperature,strainrate,composition,andpreviousthermalandmechanicaltreatmentsarealsomajorfactorsaffectingductility(48).Themechanismsofcrackgrowthandthereforeductilityinalloysdifferintensiletesttothatofrolling.Sowhenlookingatmaterialsandtheirtensileresponse,somereviewmustbedoneonhowitvaryingcompositionandmicrostructureactuallyeffectspecificaspectsoftheductilecrackprocess.Forexample,inreviewingAl-4.5Cu-3.4Femetalmatrixcomposites,amaterialwhichcontainsrandomlyoriented“needles”ofanintermetalliccompound,thetensiletestindicatesthatthecrackingofparticlescontrolstheductility,butforrolledsamplesvoidnucleation,growthandlinkagecontroltheductility(52).Atomiccrystallinestructurecanplayapartofcrackinglikelihood.Forexample,inlookingatamagnesiumalloyswhichhasahexagonalclosepackedstructuretheratiooflatticeparameters(c/a)effectsprobabilityofcracking;asthisratiocontrolsthelikelihoodofdifferentslipsystemsbeingactivated.Inthesematerials,itwasfoundthatgrainsizehadaweakercorrelationtocrackingthanthelatticeparameterratio.Thiswascausedbytheinterplayofthesetwolatticeparametersandtheirabilitytolimitandorinduceslippingandtwinning.Inaddition,whenthesematerialstwinnedthecrackingresistancevariedonthetypeoftwinform,makingthiscrackingcasemorecomplicated(53).Theexistenceofinclusionsisnotenoughtodetermineductility,butthecompositionsoftheinclusionsmatters.Forexample,inmachiningsteelsthatcontainingnon-metallicinclusionstoimprovemachinabilitysuchasMnSormetallicinclusionssuchasPb,Bi,andSn,theneedtobalancetheeffectsofinclusioninterfaces,whichbothdecreasestheforcerequiredformachiningandincreasesthelikelihoodofcrackingbyinitiatingvoids,isdifficult.ThisstudywasconductedbycomparinginclusionsformedbyPdandBi,inordertoreducePd-S(lead)use,becauseofthehumanandenvironmentalharmthatitcauses.ItwasfoundthatBi-Ssteelsweremoredifficulttorollcomparedtotheleadbasedones.Apparently,thelowmeltingtemperatureandthepoordeformationofBiwiththematrixacceleratestheformationofcracks;soMnisthoughttobeabettersolutiontotheproblem(54).Otherexamplesofmaterialstudiesincludestudyingcompositionsofausteniticstainlesssteelsafterhotrolling.Thesestudiescontainededgecracksofdifferentsizeandfrequency.Thesecracksweresensitivetothecontentandamountofthedeltaferrite.Itisbelievedthatdeltaferriteslowsthemigrationofaustenitegrainboundaryduringsolidificationwhichleadstocorrugatedboundariesresistanttocrackpropagation,becausetheseboundariesactasnucleationsitestoincreaserecrystallizationrates.Thedistributionofthematerialisinhomogeneous,asthehighestferritecontentislocatedinthevicinityoftheplateedge.Thedeltaferritecontentalsoaffectsthedegreeofedgecracksbothinnumberandinsize(48).Contaminationalsocomesintoplayinthecracking.Forexampleinelectricalsheet,oxidationseemstocreatemorecracksofgreaterseverity(55).Oxidationisalsoaffectedbydifferentaddonmaterials.Forexample,theadditionofsulfurcanleadtothedetrimentalformationofoxidesinsteelbillets.OftentimesreducingtheimpactofoxidationrequiresacertainanamountofMntobeaddedtofree-machiningsteels.Theoxideincreasestheprobabilityofcrackformationbycreatingstressconcentrationpoints(54).Hydrogenembrittlementcanalsocausecrackingissuesindifferentmaterials.InAl-Mgalloystheadditionsofsodiummaketheedgespronetocrackingastheadditionofsodiumisknowntoincreasetheamountofhydrogendissolvedinthematerial.Whilethemechanismofhydrogenembrittlementisunknownforaluminum,crackingnucleationisincreasedbyanincreaseinporosityduetohydrogenandotherdissolvedgasses(46).Notallmaterialcontaminationincreasestheprobabilityofedgecrackinginrolling.Inastudyofhotrollingofalloy5182,sodiumandcalciumcontaminationwerereviewed.Whiletheadditionofsodiumiswellknowntoinducecrackingasdiscussedabove;theeffectofcalciumisunderdebate.Ascalciumislikelytobepickedupduringcasting,astudymonitoringcalcium’seffectoncrackingwasperformed.Todosospecificamountsofbothcalciumwereaddedtoaperfectlycastmaterial.Thealloywiththeelevatedcalciumleveldidnotcrack.Whenbothcalciumandsodiumareaddedtothealloy,attypicalconcentrations,theresultingmaterialhadfewerandlessseverecracksafterrolling(45).Ultimately,thematerialmicrostructureandcompositionprovidesnosimpleinsightintothelikelihoodofcrackingandeachcomponentmustbereviewedseparatelyforitseffectoncrackformation.Tensiletestsareoftenaplacetostart,butdifferentmethodsoftestinghavebeendevelopedtobetterreplicaterollingconditionsthatexist.Manyofthesemethodstrytoviewfractureconditionsatdifferenttriaxialities(especiallynegativeones).Methodsincludetheconicalsplaytest(56)andtensileandcompressiontestingofuniquegeometriesexploredbyKweon(33)andBoaetal.(43).Rollingofmaterialisaprocessandduringthatprocessmicrostructureandstrengthevolveovertime.Whilematerialcompositionisthefirststeptodeterminewhatthematerialwillbecome,itisnecessarytolookattheentireprocessandreviewtheductilityofthematerialthrougheachstageinmetalsheetandbarcreation.Thefirststepinmostrollingprocessesistheinitialcast;whetherthematerialisinitiallycastintoaningotorasheetusingacontinuouscastingmethod.Thisisthefirstplacetocombateedgecracking;ascontrollingmeltingandcastingtechniquescanproduceaworkpiecefreeofsurfaceandcenterplaneweakeningfeaturesandprovideinitialductilityofthesample(57).Foranexampleofweakeningfeatures,Graset.al.(58)studiedtheevolutionofbleedsincontinuouscaststeels.Bleedsaresmallsectionsofregionspackedwithintermetallicparticles.Theseareformedassmallbucklesinthematrixareformed,whichfillwithahighlyenrichedmetalmixture,andthensolidifiedrapidly.Thiscreatesmaterialpocketsinthematrixthataremuchharderthanthesurroundingmatrix.EvenwiththesehardparticlescrackingisnotcertainasfoundinGrasstudy,astheparticlesmustbehardenoughtocausevoidnucleationinthematrix.Inthecasesofingotforming(asquotedforAl-Mgalloysbutaccurateforothers)controllingingotreheating,passschedule,ingotsideprofile,edgescalping,castingtechnology,andingotdefectsdirectlyaffectrollingastheseeffectthecreationofweakeningfeaturesandductility(45).Solidificationcannotbeignoredinrolling.Oftensegregationbandsareformedontheoutsideofingotswhichgetpropagatedtotheedgesofsheetmetalwhentheyarerolled.InonestudybyThomsonandBurman(59),whichlookedatsolidificationbandsonindustrialingotsinAl-Mgalloys,theysawthreetypesofcracks:smallcracksthatwerecontainedwithinthesegregationband,largecracksthatstartedinthesegregationbandbutmovedintomaterialbulk,andlargecracksthatstartedoutsidetheband.Inthisstudythemajorityofcrackswerethesmallkindthatwherecontainedinthesegregationbandandwhilethesesmallercrackswerenotsufficientfortheformationoflargercracksitwaswherethemajorityofcracksinitiated.Aftercastingandhomogenization,theheatflow,intermediateannealing,scaling,lubrication,andconditionsoftherollingmillalleffectmicrostructureandcrackingdevelopmentasthematerialmovesthroughtheprocessofedgecracking(57).Forexamplewhenlookingatcontinuouscastmaterials,whichoftenhasmoremicro-defectsandpoortextureevolutionwithheavydeformation,Grasetal.noticedthatafter50%reductionthematerialmicrostructurebecameuniformasdeformationcausedthegrainstorotateinthematerial(58).Rollingstepsarenotabadthingwhenproperlychosen;ascracksarealsoknowntohealincontinuousdeformationaswell.Temperaturecontrolcannotbeignoredasitcaneffectandcreatevariationsinthemicrostructureofthematerial.Inonestudyofnon-orientedelectricalsteelsheet,Hanetal.showedgrainsizesdifferedalongthesheetbecauseofthetemperatureeffectsduringprocessing.Theshortercoolingtimecausedelongatedgrainsintheedgeregion;whilethelongercoolingtimeallowedformoredynamicrecrystallizationtooccurandcausedequiaxedgrainsinthecenteroftheplate.Thelargergrains(andlessenedductility)ontheedgescausedcrackingmorereadilyherethaninthecenteroftheplate(55).AnotherexampleisinanAlcompositematerialwhererollingoftenbreaksupparticlesandrefinesthemtoasmallermicrostructurethatbecomesmoreorderedandorientatedalongtherollingdirection,improvingthestrengthandothermechanicalpropertiesofthematerial(52).5.2.2CreationofTensileEdgeStressesEventhoughrollingisoftenmodeledasaplanestrainprocess,anedgeregionexistswithstressesvaryingacrossthewidthoftherolledmaterial.Withoutmodelingthissection,theunevenlateraldeformationwhichleadstoedgecrackingcannotbestudied(30).Inthisregion,lateralflowcreatesagradualdropoftheinterfacepressureclosetotheedges.Herethematerialdoesdeformlongitudinallybutonlybecauseitisattachedtothebulkofthestrip.Inthisareayieldingoccurswithacombinedeffortofbothcompressiveandsecondarytensilestresses(57).Thesestressesoccuronthefreeedgeaftertherollbitewithamaximumatthecentralsymmetryplane.Notonlydothesetensilestressescauseinhomogeneousdeformationthatresultinconcaveandconvexedgeprofileswhichcaninducestrongertensileforces,butthesetensilestressesaretheonlywayforvoidgrowthtooccur(30).Becausetherestofthestripisincompression,damageisusuallyconfinedtotheedgeregion.Thecreationandtheeffectoftheseedgeswillbediscussedingreaterdetailinthenextchapter.OnewaytocombatthesetensileforcesisfromSaxl(60)whorecommendedtheuseofedgerestraintbarswhichhelpsmaintainsquareedgesandcontainslateralflowwhichoccur--whichaccordingtohisexperimentsworkedwell.5.2.3FinalcommentsItisimportanttorememberthatedgecrackingrequiresbothconditions:lackofductilityandsecondarytensilestresses.Bothoftheseconditionsplayapartintheedgecrackingandoftentimesthespecificlimitingfactormaybedifficulttodetermine.Forexample,inthecaseofedgeshearingwhichcreatesaburrontheedgeoftheworkpiecethatmayinduceanincreaseintensilestresses.Itwasfoundthatcomparinganannealedshearedsampletoanascutmaterialinasecondpassofrolling,theannealedsteeldidnotcrackliketheascutversiondid.Therefore,inthiscase,theworkhardeningofthematerialcreatedbytheshearingprocessplayedamuchlargerpartinthecrackingthantheshapechange(61).Thetworequirementsforedgecrackingdiscussedinlengthinthischapterarenotalwaysthereasonsquotedinliterature.Someauthorshavechosen(57)tocitethreereasons.Thethirdislistedastherollingofanon-squareedgeshape.Thisisnotspecificallyincludedinthiswork,mainlybecausetheeffectofthetensilestressesisbothcreatedandincreasedbytheoverhangingmaterialanditisdifficulttodecouplethesetwoeffects.Whenreviewingliteratureonthepreventionofedgecrackingitisimportanttokeepthesetworequirementsinmind,assomerollingparameterssparkmuchdebateastowhethertheyaffectedgecrackingornot.Forinstance,passsequencehasbeendebated.WhileDoddsandBoddington(15)saysitdoesnotaffectcracking;ThomsonandBurmanhassomeevidencethatitdoes(59).Whilethisdebatewillnotbesettledinthispaper,perhapsitisbettertoreviewtheseissueswiththetworequirementsofcrackinginmind.Inthenextchapter,someofthedifferentrollingparametersandconditionswillbereviewedwiththehopeofprovidingsomeexplanationastotheireffectsonrolling.

Chapter6ProcessParametersandtheireffectonrollingWhilesecondarytensilestressesandgeometricaleffectsarequotedasbeinglessertoductilityforcausingedgecracking,thispaperwillfocusonthesesecondaryissueswhicharefairlyeasytotestusingamodelingmethod.Forthemostpart,thesefactorsaremuchlessstudiedthanthematerialductilityfactors.Themajorfactorsstudiedherearetemperatureandspeedeffects(whicharerelatedtoductility),widthtothicknessratios,edgeshape,friction,andasymmetricrolling(whichareallgeometricaleffects).Whilethereareotherparametersthateffectcracking,theywillnotbediscussedormodeledhere,asthislistisagoodstartofmanyfactorsbelievedtocontributetoedgecrackingotherthanstraightductility.Othergeometricalfeaturesnotconsideredherebutbelievedtocontributetoedgecrackingisthedeviationfromaparallelrollgap,whichcanleadtoawidevarietyofrollingdefectsincludingedgecracking(15).Inaddition,changesinforwardslipcanalsoaffectthelikelihoodofcracking(47).Figure12-Typicaltriaxialityanddamagelegendforthefollowingsection.Intheremainingsectionsofthechapter,predictionsofedgecrackingaremadethroughthemodelandthedamageparametersetupinChapter1andChapter4,respectively.Generallyspeakingthreedifferentsetsofdatawillbeprovidedforeachcase:vonMisesstress,triaxiality,anddamage.Inallcases,theparametersaresetupwiththesamerangeofvaluesforeachsetofcontourplots.Forthedamageandtriaxialityvalues,thecontourplotisalwayssettomodelfromzerotoone(seeFigure12)unlessotherwisenoted.Inthecaseoftriaxiality,thelowerlimitiszerobecausethedamageisbelievedtoonlyaccumulatewhentriaxialityisapositivevalue;theupperlimitwaschosenbecause,whileitdidnotcoverallthepeaks,itgaveagooddistributionofthevalues.Whilenotaddressedhere,sometimewastakentolookattriaxialitiesfrom-1/3toone,aswell,becauseofthelikelihoodthatvaluesgiveninthisrangecouldcausecrackingasdiscussedinChapter4.InFigure13oneofthesegraphsispresented.Astruewithmostofthesecasesofrollingintherollbite,triaxialityvariesmostlyfrom-1/3tooneinthisregion.So,thereforeaneffortshouldbetakeninthefuturetoincludeorevaluatetheeffectsofthe1/3tozerotriaxialityrangeinthedamagemodel.Figure13-Triaxialitygraphedfrom-1/3toone.Inaddition,itshouldbenotedthatthetriaxialityconditionontheedgeisquitedifferentwhencomparedtothecenter(seeFigure14).Thefocusontheedgeregionismainlybecausethisregionproducespositivetriaxialityandthereforedamage.Whilethedamageparameterisdiscrete,theinterpolationofvalueswhenplottedusingtheABAQUScodeleadstographedvaluesthatcanbeoutsideandinthemiddleoftherange.Typicallyiftheregionislightblueorgreen,thiscorrespondswithonenodeyieldingineachelement.CentersectionEdgesectionFigure14-Triaxialityfordifferentsectionsoftherollbite.Generally(unlessotherwisenoted),thevonMisesstressscalecorrespondstoFigure15.Typicallythevaluesarenotcriticaltothediscussionasmuchasthechangesbetweenthevalues.Figure15-TypicalvonMisesstressscaleusedinthefollowingsection.

第五章邊緣裂紋5.1開裂研究的概述邊緣開裂通常以去除材料導(dǎo)致邊緣修整或?qū)е鹿ぜ怏w在輥縫中。在某些情況下，大量廢金屬被引述為6%或更肯定了鋁鎂合金。這些邊緣裂紋的產(chǎn)生需要足夠的延展性和二次拉伸應(yīng)力。顯然，軋制的結(jié)果就需要預(yù)測。邊緣裂紋的研究，更好的理解這個(gè)缺點(diǎn)的概念和相關(guān)原因。因?yàn)檐堉剖枪I(yè)生產(chǎn)方法，實(shí)驗(yàn)關(guān)注的是確保結(jié)果應(yīng)用到生產(chǎn)車間。這是一個(gè)復(fù)雜的過程，特別是對于熱軋，因?yàn)閺氖鹿I(yè)的工廠通常比做實(shí)驗(yàn)的實(shí)驗(yàn)室更大。雖然，總的幾何形狀易于擴(kuò)展，該冶金參數(shù)包括微觀機(jī)構(gòu)和熱變量都沒有。例如，實(shí)驗(yàn)室軋機(jī)通常比在工業(yè)中使用的那些小得多，因此工件較小，因?yàn)閮烧叩臒豳|(zhì)不同這會引起問題。因此，熱分配不同的情況下大大影響了流動應(yīng)力。在實(shí)驗(yàn)室中準(zhǔn)確地模擬軋制，創(chuàng)造了一些獨(dú)特的測試方法。例如：為了準(zhǔn)確地模擬前滑條件，使用冷軋?jiān)囼?yàn)。這已被用來容易地研究影響改變前滑條件和接觸條件。在該實(shí)驗(yàn)中，材料通過使用拉伸試驗(yàn)機(jī)設(shè)備拉出。此裝置僅再現(xiàn)了帶材一側(cè)的接觸條件。在不同試驗(yàn)中，在軋制過程中對拉伸應(yīng)力的估計(jì)（與其裂紋擴(kuò)展有關(guān)）。通常一個(gè)網(wǎng)格將蝕刻到材料樣品的一側(cè)或兩塊材料然后鉚接在一起。然后，將這些試驗(yàn)片進(jìn)行軋制，軋制后通過測量網(wǎng)格變化來收集數(shù)據(jù)流。建模后采用回歸應(yīng)力。在研究物質(zhì)因素中，通常使用不同的方法來揭示材料的微觀結(jié)構(gòu)包括：光學(xué)顯微鏡、透射電子顯微鏡、X射線衍射。這些不僅試圖尋找位置和材料的夾