对磨削的一些观察外文文献翻译、中英文翻译、外文翻译

Grinding-SomeobservationsFortheproductionoffinishedcomponentsofdesiredshape,sizeandaccuracy,machiningisthecommonlyusedmanufacturingprocess.Machiningprocessinvolvestheusageofsingleormultiplepointcuttingtoolstoremovetheunwantedmaterialsformthestockintheformofchips(Komandurai,1993).Amongthevariousmetalcuttingprocessavailable,Grindingisoneoftheimportantmetalcuttingprocessusedextensivelyinthefinishingoperationofdiscretecomponents.Itisaversatileandalsofinishmachiningprocessintheproductionofcomponentsrequiringclosedimensionaltolerances,geometricalaccuraciesandrequiredsurfacefinish(Rajmohanetal.,1994).Mostoftheproductionprocessesareincompletewithoutgrindingprocess.AccordingtoSubramanian(1999),itisamajormanufacturingprocess,whichaccountsforabout25%ofthetotalexpenditureonmachiningoperationsinindustrializedcountries.Almostalltheengineeringcomponentsareprocessedingrindingmachiningmachinesatsomestagesofitsproduction.Grindingisaslowprocessintermsofunitremovalofthestock.Hence,othermethodsareusedfirsttobingtheworkclosetoitsrequireddimensionsandthenitisgroundtoachievethedesiredfinish.Insomeapplications,grindingisalsoemployedforhighermetalremovalrate.Insuchheavydutygrindingoperationsmoreabrasiveisconsumed.Inthesecases,themainobjectiveistoremovemoreamountofmaterialthattooasquicklyandeffectivelyaspossible.Thus,thegrindingprocesscanbeappliedsuccessfullytoalmostanycomponentrequiringprecisionorhardmachininganditisalsooneofthewidelyusedmethodsofremovingmaterialfromtheworkpieceafterhardening.Inordertodecreasethecostandincreasetheproductionrate,thegrindingmachinemustbesettooperatewithintheshortestpossiblegrindingcycletime.Hence,itisoftenimportanttosetthecorrectgrindingmachineparameterssoastoproducepartsofrequiredquality.Theselectionofgrindingparametersifitisdoneonhitandmisstechniquenotonlywastestimebutalsoleadstoaninefficientprocess.Toovercomethisdifficulty,Guptaetal.(2001)intheirworkoptimizedthegrindingprocessparametersusingtheenumerationmethod.Theparametersshouldbeselectedsoastoresultinanoptimalsolution.Selectionofgrindingprocessparametersismadeeasyemployingthe“Expertsystem”.ShajiandRadhakrishnan(2002)analyzedtheprocessparameterssuchasspeed,feed,unfeedandmodeofdressingasinfluentialfactorsontheforcecomponentsandsurfacefinishdevelopedbasedonTaguchi’sExperimentaldesignmethods.FengguoCaoetal.(2003)developedtheconceptofintegratingneuralnetwork,greyrelationalanalysisandgeneticalgorithmfortheoptimizationofprocessparametersinincreased.ExplosiveElectricalDischargeGrindingProcessliesintheproperselectionandintroductionofsuitabledesignofexperimentattheearlieststageoftheprocessandproductdevelopmentcyclessoasobtainqualityandproductivityimprovement.Amongtheexistingtypesofgrindingprocesses,cylindricalgrindingprocessistheone,whichisverywidelyusedinthefinishmachiningofnumberofautomobilecomponentswithsurfacesofrevolution.Incylindricalgrindingprocess,thefrictionalresistanceencounteredbetweentheworkmaterialandthetool,chiptoolinterfaceandtheresistancetodeformationduringshearingofthechipscontributestoriseintemperatureatthecontactzone(Triggeretal.1951).Thetemperaturegeneratedisnotonlyveryhighbutthetemperaturegradientsarealsosevere.Suchtemperaturesofsufficientmagnitudecancauseadversechangesinworkpiecemetallurgicalstructure,lossindimensionalaccuracyandacceleratedwear[or]dullingofthetool(DesRuisseauxandZerkle,1970;TakashiUedaetal.,1985).Inadditiontocausingsurfacedamage,grindingheatmaycausethermalexpansion/distortioninthecomponentgroundandthusadverselyaffecttheattainableaccuracy.MasudaandShiozaki(1974)demonstratedhowgrindingheatinplungesurfacegrindingresultsinout-of-flatnessofthefinishedpart.Betterflatnesswasobtainedwithsmallerdepthsofcutandhigherworkpiecevelocities.Bothofthemcauselessergrindingheatandwithincreasedcoolantflowratethecoolingoftheworkpieceisenhancedandthethermaldistortionisminimized.Chandrsekaretal.(1996)studiedthethermalaspectsofsurfacefinishingprocess.Ingrinding,thelocalizedabrasiveworkpiececontactpressuresandhighslidingspeedproducehightemperaturesattheinterfacebetweenanabrasiveparticleandtheworksurface,aswellasintheworksub-surfacesduetofrictionalheating.Hightemperaturesaretheimportantsourceofdamageonthemachinedsurface.First,thetransienttemperatureandthetemperaturegradientaretheprinciplesourcesforresidualstressesandmicrocrackingongroundsurfaces.Secondly,thelocalizedtemperaturescancausewarpingofthecomponentsbeingmachined,especially,whenitisofsmallsizeandhasarelativelylargesurfaceareatovolumeratio.Thisisaseriousprobleminthefinishingofsmallelectronicdevicessuchasrecordingheads.Thirdly,thishightemperaturecanalsoleadtophasetransformationsinthematerialsbeingmachined.ThenatureofgrindingdamagewassurveyedbyTarasov(1950),whoidentifiedthreemainkindsofgrindingdamage,namelycracking,rehardeningburnandtemperingburn.Duringgrindingofhardenedsteel,ifthesurfacetemperatureoftheworkpieceissufficientlyhigh,thesurfacereaustenizesandisrapidlyquenched.Consequently,thereisaformationofbrittle,untemperedmartensiteatthesurface.Thistypeofthermaldamageisalsocommonlyreferredtoasworkpieceburnandishighlyundesirable(Tarasov,1950;Torrance,1978).Amartensitictypeofphasetransformationalsooccursduringthegrindingoftoughenedzirconia.Here,thetransientmechanicalandthermalstressesgeneratedduringgrindingdrivesthetransformation.Theseformsofthermaldamagechangethemechanical,magneticandelectricalpropertiesoftheworkmaterials.Thelocaltemperaturesplayanimportantroleinthedegradationoftheabrasiveparticlesandthebondingpropertyofthematerial.Theheatgeneratedduringgrindingischaracterizedby,i)Instantaneousconcentratedsource,ii)Highrateofliberation,andiii)Verysmallcontactperiod.Heatassociatedwiththeenergyexpendedbygrindingistransportedawayfromthegrindingzonebytheworkpiece,grindingfluid,grindingchipsandgrindingwheel.Ofparticularinterestisthefractionofthetotalgrindingenergytransportedtotheworkpieceatthegrindingzone,whichcausestheriseinworkpiecetemperatureandpossiblethermaldamage.ForregulargrindingwithconventionalAluminumoxidewheels,theenergypartitiontotheworkpiecetypicallyrangesfrom60-80%dependingontheactualgrindingsituation(MalkinandAnderson,1974;Roweetal.,1995and1997).Onlyafewisolatedattemptshavebeenreportedsofaronexperimentalanalysisofthetemperaturedevelopedatthewheelworkcontactzone,energypartitionratio,graincontacttimeandthermaldamages.Atthispoint,itappearsthatpracticaloptimizationstrategyandreliablemathematicalmodelsarestillrequiredtoanalyzethethermaldamageingrinding.FieldandKahles(1971)investigatedthedissipationofheatingrindingandtheresultinginfluenceonthesurfaceintegrityoftheworkpiece.GuoandMalkin(1992)describedthatdependingonthegrindingconditiontheheatfluxtakespartmainlyviatheworkpieceandleadstoalargethermalloadinginthesurface.Thisthermalloadissuperimposedbymechanicalloadcausingahightemperatureinthesurface.Thisthermo-mechanicalloadcausessomeundesiredalterationsinthesurfacelayer,likecracks,temperedzoneorwhiteetchingareas(WEA).ShawandVyas(1994)gaveanimpressivetheoreticaldescriptionofmetallurgicalchangesingroundsurfaces.Underabusivegrindingconditions,theformationofheat-affectedzonewasobserved.DesRuisseauxandZerkle(1970)analyzedthattheheat-affectedzoneunderabusivegrindingconditionsdamagesthegroundsurfaceofthehardenedsteelveryfrequently.Athermallydamagedcomponentmaythereforeincurasignificantcosttothemanufacturerinfailingqualitystandard.Thus,thethermalphenomenaplayakeyroleintheeconomicsandmechanicsofabrasivemachiningprocesses.Anestimationoftheamountofenergygenerated,worksurfacetemperatureandanunderstandingoftheirroleinmetallurgicalchangesongroundsurfacesarestillchallengingtotheproductionengineers(SoyesandMaris1978).MalkinandFedoseev(1991)analyzedthemethodtopredicttheundesiredalterationstoavoidthermaldamagesingrindinggardenedsteel.Inanycase,thegeneratedheatquantitiesingrindingareconsideredasarestrictingfactor.Theinventionofadvancedgrindingprocesses,whichenabledthesurfacehardeningofsteelparts,wasdescribedforthefirsttimein1994.Insuchoperations,namedgrindhardening,thedissipatedheatingrindingisutilizedtoinducedmartensiticphasetransformationinthesurfacelayerofcomponents(BrinksmeierandBrockhoff,1997).Bettersurfacefinishwithincreasedhardnessatthesurfacebyutilizingtheheatgeneratedduringgrindingispossibleunderoptimumoperatingconditions.Thus,oneoftheareafortheresearcherstoconcernabouttheuniqueoptimalsettingsofgrindingprocessparameters-Depthofcut,Numberofpasses,WheelspeedandworkspeedformaximizingthesurfacehardnessandminimizingthesurfaceroughnesswhilegrindingAISIsteelmaterialswithAl2O3grindingwheels.“Ishikawacauseeffectdiagram”ofmachiningisstudiedtoidentifytheinfluentialprocessparametersthatmayaffectthesurfaceintegrityofgroundedpartsbyRamamoorthyetal.,2001and;Harisinghetal.,2004.Taguchi’sparameterdesignapproachhasbeenusedtoaccomplishtheobjective.Aspecialmathematicaltoolknownasgreyrelationalanalysiscanbeusedwithresponsegraphapproachandsignaltonoiseratioapproachfortheoptimization.Itiswellknownthatphysicalsurfacepropertiescandeterminethelifetimeandthefunctionofhighlyloadedworkpieceandcomponents.Forthisreason,manufacturingindustriesrequireinformationaboutthetechniquestoinfluencethesurfacestateofworkpieceandachieveconsistentproperties(Kegg,1982).Thisinteresthasitsimportanceduetothefactthatmagnitudeoftheresidualstressinterferesonthefatiguestrengthofthematerials(Novasakietal.,1996).Residualsrtessisthemostrepresentativeparametertodescribethequalityofthesurface(Brinksmeieretal.,1982)amongvarioussurfacealterationslikephasetransformations,hardnessvariations,microcracks,grindingburnetc.BanerjeeandChattopadhyay(1987)investigatedthecontrolofresidualstressingrindingbycryogeniccoolingwhichresultsinmuchlesstensileresidualstresses.Kruszynskietal.(1991)madeanattempttopredictresidualstressesingrindingofmetalswiththeaidofanewgrindingparameter.Hucker(1994)showedthattherewasaquantitativerelationbetweentheeffectivework-surfacetemperatureandtheresidualstressproducedongroundsurfacesofhardenedsteels.X-raydiffractiontechniqueswereusedtomeasuretheresidualstresses.ItwasreportedthatCBNgrindingisfoundtoproducecompressivestressatthesurfaceincontrasttoAl2O3grinding.However,manyoftheresearchesprovedthatundertheconditionsofmartensiticformation(roughgrinding)compressiveresidualstressesareformedwhengroundwithAl2O3wheel.BrockhoffandBrinksmeier(1997)intheircomprehensiveviewongrindhardeningfundoutthatcompressiveresidualstressesareexistingintheWhiteEtchingAreas,whichcontinueintotheareaofetchablemartensiteandwhicharecompensatedbylowtensileresidualstressesinagreaterdistancefromthesurface.LitmannandWulff(1955)foundthatforhardenedsteels,whichhavebeenburnedduringgrinding,theworkpiecesub-surfaceconsistsofarehardenedzonenearthesurfaceandasoftenedtemperedzonebeneathit.Thiswouldsuggestthattheonsetofburningischaracterizedbytheformationofausteniteoversomeportionoftheworkpiecesub-surface.Rehardeningatthesurfaceoccursbyacicularmartensite(thatappearsintheformofparallelneedleswithinformeraustenitegrains)formationasthecoolermaterialinthebulkoftheworkpiecequenchesthesurface.Thisreferstophasetransformationingrinding.Aftergrindingunderidealconditions,thegroundsurfacewillbecrackfreeandwillexhibitcompressiveresidualstressesfavorableforcorrosionresistanceandlonglifeundercyclicloadingconditions.Incontrast,manygrindingconditionsaresuchthatthesurfaceproducedsufferstensilestresses,sub-surfacecrackingandoxidationleadingtofailureinsurface.Inordertostrikeabalancebetweenqualityandstrengthingroundedpartsitisdesirabletohaveacontrolovertheresidualstress.Thisnecessitatesadetailedstudyofthefreework-surfacetemperature,amountofheatgeneratedandthemagnitudeofresidualstressformed.对磨削的一些观察为了使在零部件的生产中达到预期的形状、尺寸和精度，机械加工被广泛运用于生产加工工艺中。机械加工过程中会运用到一个或多个切削工具，来去除工件上不需要的部分，使之成为切屑。在众多已应用的金属切削工艺中，磨削加工是金属加工工艺常用于零件最终加工的重要加工工艺之一。它用途广泛，也经常用于尺寸公差、几何精度和表面精度要求高的零件的机械加工工艺中。绝大多数产品的生产工艺中都少不了磨削加工。根据Subramanian的统计数据，在工业国家的生产支出中，磨削加工占了25%，处于主要地位。几乎所有的工程零件在其生产的某些阶段会在磨削机床上加工。在工件的单元切削中，磨削加工是一个缓慢的过程。因此，在工件开始加工时，一般采用其他的加工方式使工件达到与要求相近的精度，然后采用磨削完成加工。在某些应用中，磨削也具备更高的金属切削效率。在如重载磨削中，更多的磨料会被消耗，在这些情况下，尽可能快而有效去除更多的金属材料是主要的目标。因而，磨削加工能成功地用于任何高精度或难加工零件的加工过程中，并且它也是可广泛应用于硬化表面材料去除的加工工艺之一。Shaw曾报告称，磨削加工是存在很多相关变量的复杂工艺，而这些相互作用的变量是同磨削方式所决定的。在平面磨削中所产生的几何形状会受到如下因素的影响：砂轮因素：砂轮直径、磨粒类型和尺寸、砂轮等级、砂轮构造、粘结剂、敷料工艺、砂轮的平衡等级等。工件因素：加工表面硬度、构造、化学特征等。机床因素：主轴和工作台刚度、阻尼、动力特性等。加工参数：砂轮转速、进给量、背吃刀量、磨削液等。为了减少消耗，提高生产效率，磨削机床必须设定加工时间处于最短的可能磨削周期内。因此，设置正确磨削机床参数对获得需要的精度往往非常重要。如果磨削参数选择不符合技术要求，就会导致时间浪费效率低下。为了解决这个问题，Gupta在他们的研究中，采用列表的方法来使磨削参数最优化。参数的选取应使工作方案最优化，当采用“专家系统”时，磨削工艺参数的选取就变得容易了。Shaji和Radhakrishnan在Tagudhi的实验设计方法基础上分析了砂轮转速、进给量、背吃刀量、敷料的方式对磨削力的构成、表面加工的影响。FengguoCao提出了一体化神经网络、灰色相关分性分析、遗传算法的概念，来对工艺参数进行优化提高。爆炸式电火花磨削工艺正是立足于对最早工艺阶段和产品开发周期的合理实验设计的选择推广上，来获得品质和效率的提升。在已有的磨削工艺形式中，外加磨削广泛应用于汽车回转零件的表面加工中。在外圆，产生于工件材料与刀具之间的摩擦阻力，刀具表面的剪切变形抗力会使得接触区域的温度上升。产生的温度很高并且分布很不均匀，这样剧烈的高温会使工件的金相结构发生不利的改变，使其尺寸精度丧失，并且加速刀具钝化。除了导致表面损坏，磨削热也会使工件在磨削过程产生热膨胀或热变形，从而对工件精度产生不利的影响。Masuda和Shiozaki阐述了磨削热如何寻到工件表面变得不平整。当采用较小的切深和更高的切削速度时，会获得更高的平面度。同时，也能减少磨削热的产生。再加快冷却液的流动速率，使工件冷却效果加强，能使热变形减小。Chandrsekar研究了表面加工过程的热效应。在磨削过程中，局部的接触应力和高的滑动速度会在工件和磨削刃接触面产生高温，同时在次层面产生摩擦热。高温是造成已加工表面损坏的重要因素。首先，分布不均匀的瞬态高温是工件残余应力和表面微裂纹的主要来源。第二，局部高温会使已加工的部分发生形变。尤其是对尺寸较小却具有较大体积比率的工件，变形尤为严重，这对于某些小型电子设备如电磁记录头的加工，是一个很严峻的问题。第三，高温会导致已加工材料的物相发生改变。Tarasov对磨削操作的性质做了调查研究，确定了三种主要的损伤类型，分别是开裂，二次淬火烧伤和高温烧伤。在磨削硬质的钢材时，如果表面温度过高，就会发生表面再次奥氏体化，并急速冷却，从而在工件表面会形成具有的回火马氏体。这种形式的热损伤也是觉的工件烧伤形式，需要避免。在更质氧化锆的磨削过程中，也会发生类似马氏体类型的物相变化。这种变化是同磨削过程中产生的瞬态机械应力和热应