1600镁合金带材精整机组分条圆盘剪设计

1600镁合金带材精整机组-分条圆盘剪机架设计)式中——联轴器的许用转矩/；T——联轴器长期承受的理论转矩/；——联轴器工作条件系数。所以：7.4齿轮机座的作用及类型为了将电动机或减速器的扭矩分配给每个刀盘轴，除电动机单独传动每个刀盘轴的情况外，大多数分条圆盘剪的主传动系统中都设有齿轮机座。因为齿轮机座传递的扭矩较大，而中心距又受到刀盘轴中心距的限制，为了满足强度要求，齿轮的模数较大（8~45），齿宽较宽（齿宽系数为1.6~2.4），而齿数较少，通常为22~44。齿轮机座的箱体有高立柱式、矮立柱式和水平剖分式三种形式。齿轮机座通常直接安装在基础上，安装方式有两种，一种是将整个底座都安放在基础上，另一种是由地脚安装在基础上。7.5齿轮机座的结构齿轮机座由齿轮轴、轴承及轴承座和机盖等主要部件组成。由于传递的扭矩大，因此传动轴的直径很大，相比之下，齿轮的直径很小，所以一般与传动轴作成一体，即齿轮轴。齿轮多做成具有渐开线齿形的人字齿，这样，只能将一根轴的一端在轴向予以固定，而另外一根齿轮必须设计成轴向游动的，在运转过程中依靠人字齿的啮合自动定位，从而避免载荷在两侧斜齿上的不均匀分布。另外，在温度发生变化时，相啮合的齿轮轴均可自由伸缩，保证正常啮合。在齿轮机座中采用双圆弧齿轮轴，可提高齿轮轴的使用寿命和承载能力，使齿轮轴的外形尺寸减小。齿轮轴的材料为45、40Cr、32Cr2MnMo、35SiMn2MoV、40CrMn2MoV等。由于分条圆盘剪齿轮箱齿轮轴的齿面接触应力很高,应采用硬齿面,齿面淬火硬度为HB480~570。齿轮机座的轴承主要采用滚动轴承，齿轮机座箱体应保证齿轮传动具有良好的密封性，并具有足够的刚性，以使轴承具有坚固的支撑，为此，应尽可能加强箱体轴承处的强度和刚度。由于齿轮箱大多是单件或少量生产，为了降低成本，机座的箱体采用锻焊结构或铸焊结构。

8系统的润滑8.1润滑剂的作用机械零件的表面在接触的时候产生相对运动，在此过程中，避免不了会产生摩擦。假如润滑不当，效率会下降，并且引起发热、振动、噪声等。由于零件磨损，机械精度下降，寿命降低，影响了正常工作而发生早期报废。因此，在机械设计中，润滑是一个很重要的问题。在机械的摩擦副中加润滑剂的主要作用是：减小摩擦因数，提高机械效率。减轻磨损，延长机械使用寿命。液体润滑剂能带走摩擦所产生的热量，使零件的表面工作温度下降。循环润滑能起排污作用。点、线接触的摩擦表面，油膜能起到缓冲吸振的作用，能够将载荷分布到较大的面积上，使最大应力下降。缓蚀、密封。8.2润滑方式的选择8.2.1轴承的润滑滚动轴承润滑的作用是降低摩擦阻力、减少磨损、防止锈蚀，同时还可以起到散热、减小接触应力、吸收振动等作用。考虑轴承润滑时，选用脂润滑方式，润滑膜强度高，能承受较大的载荷，不易流失，容易密封，能防止灰尘等杂物侵入轴承内部，对密封要求不高，一次加脂可以维持相当长的一段时间。其缺点是：摩擦损失大，散热效果差。对于那些不便经常添加润滑剂的部位，或不允许润滑油流失而导致污染产品的工业机械来说，这种润滑方式十分适宜。润滑脂的填充量要适中，一般为轴承内部空间容积的。8.2.2齿轮传动的润滑齿轮在传动时，相啮合的齿面间有相对滑动，因此就要发生冲突和磨损，添加动力消耗，降低传动效率。特别是高速传动，就更要做好齿轮的润滑。齿轮啮合面之间需要加入润滑剂，能够防止金属直接碰触，减小摩擦损耗，还能够散热及防锈蚀。因而，对齿轮传动系统进行必要的润滑，能够大大改善轮齿的工况，确保运转正常及预期的寿命。通用闭式齿轮传动，其润滑方法依据齿轮圆周速度大小决定。当齿轮的圆周速度时，通常是将大齿轮轮齿浸入油池中进行浸油润滑。这样，齿轮传动时，就把润滑油带到啮合的齿面上，也能将油甩到箱壁上，借以散热。齿轮浸入油中的深度可视齿轮圆周速度大小决定，对圆柱齿轮一般不宜超过一个齿高，但一般不该小于10mm。8.2.3滑块式万向接轴的润滑由于滑块式万向接轴的摩擦表面不能很好地密封，润滑油不能很好地保存在摩擦面上。同时分条圆盘剪的运行特点和万向接轴所处的位置，使其润滑较为困难，造成滑块的磨损加快，寿命降低，严重影响分条圆盘剪的作业率。目前润滑方式主要是人工定期加注润滑油和采用自动润滑油装置两种。另外，采用密封油包包覆和内存润滑剂的方式也可以较好地解决润滑问题。润滑剂可用润滑脂或润滑油。8.2.4齿轮机座的润滑分条圆盘剪的齿轮机座连续运转时间很长，因此机座的冷却与润滑是很重要的。对于齿轮，采用两种方式，一种是用侧向喷嘴直接向齿轮啮合区喷射润滑油；另一种是用一排位于上齿轮轴上部的喷油嘴，通过侧挡板向齿轮啮合区注油。齿轮箱的轴承通常与齿轮使用同一润滑系统，在齿轮箱体上应有润滑轴承的油沟。

结论经过一个学期的学习、分析、设计，在老师的耐心指导和同学们的热情帮助下，我最终完成了1600镁合金带材精整机组-分条圆盘剪机架设计。分条圆盘式剪切机主要功能是对已经轧制过的AZ31镁合金板进行分条。我设计的这台分条圆盘式剪切机主要是对于刀盘轴的设计校核、轴承的选择校核、电动机的核算选择校核、传动装置中主要的万向连接轴和齿轮的计算校核，部分键的计算，以及对润滑系统进行了分析。在设计和核算过程中涉及、运用了许多基础及专业知识，如：轧钢机械设计、机械制造、机械原理、材料力学，理论力学、金属工艺学等。对这些知识的应用使我大大加强了本专业知识功底。由于我的水平有限，设计中不可避免存在一些不足，在核算、设计及绘图过程中不可避免地出现错误，请各位老师给予批评指正。

参考文献[1]李忠盛,潘复生,张静.AZ31镁合金的研究现状和发展前景[J].金属成形工艺,2004,22(1)：54-57.[2]苌群峰,李大永,彭颖红,等.AZ31镁合金板材温热冲压数值模拟与实验研究[J].中国有色金属学报,2006,16(4):580-585.[3]黄佳.金属带材圆盘分切断面分析及分切过程数值模拟仿真[D].广东：广东工业大学，2012.[4]熊雪英,王玉明,傅东旭,等.金属材料纵切分条加工排刀程序开发应用[C].上海：2001.[5]许体武.圆盘剪剪切过程数值模拟及工艺优化[D].马鞍山：安徽工业大学,2013.[6]贾海亮.圆盘剪剪切过程的有限元模拟和实验研究[D].太原：太原科技大学,2010.[7]寻鑫,蒋新华,许思猛.基于S7-200的高精度纵剪分条机控制系统的设计[J].机电技术,2013,5(4):2-4.[8]张蒙.圆盘剪力能参数的计算方法与选择[J].冶金设备，2010(Z1):1-13.[9]孔繁华,杨大中,杨富伟.切边圆盘剪的力能参数计算[J].一重技术，1999,4:15-24.[10]潘嘉强,路家斌,阎秋生.圆盘剪分切工艺有限元仿真研究[J].机电工程技术，2012,41(10):117-122.[11]张弘,罗恺.圆盘剪切机电机的选择计算[J].科技创新导报，2015(7):242-244.[12]张金兰,夏长发.中小型电机选型手册[M].北京：机械工业出版社，1998.[13]滚动轴承圆锥滚子轴承型号查询目录[S].[14]唐增宝,常建娥.机械设计课程设计（第4版）[M].武汉：华中科技大学出版社，2011.[15]陆凤仪,钟守炎.机械设计[M].北京：机械工业出版社，2010.[16]黄庆学.轧钢机械设计[M].北京：冶金工业出版社,2007.[17]HL型弹性柱销联轴器基本参数和主要尺寸(GBT5014-85)[S].[18]Maastricht-Eindhoven,Maastricht.Therotatingdiscasadevicetostudytheadhesivepropertiesofendothelialcellsunderdifferentialshearstresses[J].journalofmateriaisscience,1994,361-367.[19]V.P.Sankevich.rotarydiskshearswithmechanized[E].186-187.[20]A.P.Koshka.Increasingtheproductivityofstripslittingdiskshears420[J].NovosibirskMetallurgicalWorks,577-580.[21]E.Ya.Filatov,V.E.Pavlovskii,V.N.Belokurov,etal.Machineforfatiguetestingofspecimensandpartswithvariationofthebendingmoment,torque,andshearingforce[M].409-414[22]YasumasaChino,T.Furuta,M.Hakamada,etal.FatiguebehaviorofAZ31magnesiumalloyproducedbysolid-staterecycling[J].jmatersci,2006,317:3229-3232

外文翻译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.

第五章边缘裂纹5.1开裂研究的概述边缘开裂通常以去除材料导致边缘修整或导致工件解体在辊缝中。在某些情况下，大量废金属被引述为6%或更肯定了铝镁合金。这些边缘裂纹的产生需要足够的延展性和二次拉伸应力。显然，轧制的结果就需要预测。边缘裂纹的研究，更好的理解这个缺点的概念和相关原因。因为轧制是工业生产方法，实验关注的是确保结果应用到生产车间。这是一个复杂的过程，特别是对于热轧，因为从事工业的工厂通常比做实验的实验室更大。虽然，总的几何形状易于扩展，该冶金参数包括微观机构和热变量都没有。例如，实验室轧机通常比在工业中使用的那些小得多，因此工件较小，因为两者的热质不同这会引起问题。因此，热分配不同的情况下大大影响了流动应力。在实验室中准确地模拟轧制，创造了一些独特的测试方法。例如：为了准确地模拟前滑条件，使用冷轧试验。这已被用来容易地研究影响改变前滑条件和接触条件。在该实验中，材料通过使用拉伸试验机设备拉出。此装置仅再现了带材一侧的接触条件。在不同试验中，在轧制过程中对拉伸应力的估计（与其裂纹扩展有关）。通常一个网格将蚀刻到材料样品的一侧或两块材料然后铆接在一起。然后，将这些试验片进行轧制，轧制后通过测量网格变化来收集数据流。建模后采用回归应力。在研究物质因素中，通常使用不同的方法来揭示材料的微观结构包括：光学显微镜、透射电子显微镜、X射线衍射。这些不仅试图寻找位置和材料的夹