外文翻译--夹头.doc

附录A外文文献及其翻译COLLECTCHUCK1.IntroductionToimproveproductivityinmicro/meso-scalecomponents,researchershavefocusedondevelopingminiaturizedmanufacturinginstruments,suchasmicro-machinetools.Theseminiaturizedsystemsareexpectedtosaveenergyandbeeasilyreconfigurable.Thefirststepinmicro-manufacturinginstrumentsisminiaturizingthecorrespondingsubsystems.Inparticular,micro-machinetoolsformaterial-removalprocesseshave,asakeysubsystem,amicro-spindleunitthatmustachievehighrotationalspeedswhilemaintaininggoodrotationalaccuracyformicro-featuremachining.Indevelopingmicro-spindleunits,acriticalproblemisminiaturizationofthetool-clampingpartthatholdsthetoolinthespindle.Approachesforscalingdownconventionaltoolclamps,suchasthecollet-chuck,hydraulicchuck,andshrink-fitmethods,maybelimitedbytheirinherentlycomplicatedstructuralandoperationalmechanisms.Incollet-chucks,ataperedcolletandcollet-pullingdevice,suchasaspringandascrew,mustbeincludedinthemicro-spindle.Inaddition,ataperedcolletcausestolerancestackup,whichmayincreaserotationerrormotion.Hydraulicchuckshaveanon-axisymmetricstructureinsidethespindleduetotheneedforanadjustingscrewandoilpaths.Theseelementsunbalancetherotormass,increasingrotationerrormotionathigh-speedrevolution.Finally,shrink-fittoolholdersrequirespecificequipmenttoheatthedevicetoahightemperaturetounclampatool,equipmentthatistooexpensiveandtoolargeforusewithmicro-machinetools.Onepossiblewaytoavoidtheseproblemsistoincorporateashapememoryalloy(SMA).SMAshaverecentlybeenusedinvariousapplications,suchasactuators,fasteners,bonefixaters,andsoon713.Theyarelightweight,alloweasyandpreciseinstallation,yieldexcellentreliability,andprovidegoodimmunityagainstshockandvibration.ByemployingSMAforatoolclamp,theclampcanbesimplifiedbecausetheSMAdirectlyprovidestheradialtool-clampingforceonthetoolholder.Duetothissimplestructure,furtherminiaturizationispossible,soithasanadvantageofgoodimmunityagainsttheeffectofcentrifugalforce.Inaddition,unlikeacollet-chuck,anSMA-basedtoolclampdoesnotrequireacollettodevelopclampingforce；thiseliminatesthetolerancestackupthatresultsfromthecollet.TheSMA-baseddevicealsohasanaxisymmetricstructuralconfiguration,unlikeahydraulicchuck,whichminimizestheeffectofmassunbalance.Finally,thetoolclampcanswitchbetweentheclampedandunclampedstatesbyusingasimpledevicetoregulatesmallchangesintemperature,therebyeliminatingtheneedfortheexpensiveheatingequipmentusedinshrink-fitmechanisms.Inthisstudy,wedevelopedatoolclampbasedonSMAforapplicationsinmicro-spindleunits.First,wedevelopedthebasicconfigurationofthetoolclampusinganSMAring,anddescribedtheprincipleofclamping/unclampingthetoolmathematically.Second,weconductedthree-dimensional(3D)finiteelementmethod(FEM)analysestoassessthecharacteristicsoftheclamping/unclampingoperationsandtheeffectofcentrifugalforce.Next,wedesignedandbuiltaprototypeoftheSMA-basedtoolclamp.Then,weexperimentallyevaluatedthetimeneededforclamping/unclampingoperationsandthetool-clampingforce.Finally,weusedtheprototypetoconductamill-machiningtesttoconfirmthatitwasunaffectedbycentrifugalforceathighrotationalspeeds.2.Principle2.1.ShapememoryalloysSMAsareauniqueclassofalloysthatarecharacterizedbytheshapememoryeffect.AnSMAthatisdeformedinalow-temperaturephase,calledthemartensiticphase,canrecoveritsoriginalshapeuponheatingtothereversetransformationtemperature,wheretheSMAenterstheausteniticphase.IftheSMAisimpededbyanexternalmechanicalstructureasitisreturningtoitsoriginalshape,recoverystressesaregenerated.TherelationshipsbetweenstressesandstrainsinSMAmaterialsareafunctionoftemperature15.Inthelow-temperaturephase,SMAshaveasmallerYoungsmodulusandyieldstrengththanathighertemperatures.Thatis,SMAsinthemartensiticphasearemoreeasilydeformedelasticallyorplasticallythanthoseintheausteniticphase.Thus,anSMAsrecoverystresscanbeadjustedbycontrollingtemperature.Basedonthesephenomena,anSMAcanbeusedinatoolclamp.2.2.ConfigurationFig.1showsthestructuralconfigurationofourSMA-basedtoolclamp.Itconsistsofonlytwoparts:atoolholderintheendofthespindle,andaclosedSMAring.Thetoolholderhasacentralholeinwhichatoolisinstalled,andfourlateralslots.TheSMAringisplacedaroundtheoutsideofthetoolholder.Thelocationofthisringisdeterminedbythesurfaceboundarybetweenthedifferentdiametersofthecomponentsofthetoolholder,sotheclampingforceoftheSMAringcanbeprovidedinthedesiredlocationanddirection.ItisimportantthattheSMA-basedtoolclampcannotonlyclampthetoolbutalsounclampwheneveratoolchangeisrequired.Toachieveclamping/unclamping,aninterference-fitbetweenthetoolholderandtheSMAringwasdeveloped.Thisinterference-fitconstrainstherecoveryoftheSMAring,resultinginarecoverystress,sothatarecoveryforceactsonthetoolholder.WhentheSMAisintheausteniticphase,thetoolholeisfurthershrunkbytherecoveryforce.However,whentheSMAisinthemartensiticphase,thetoolholecanreturnalmosttoitsoriginalshapethroughtheelasticforceofthetoolholder,becauseinthisphasetheSMAhasminimalrecoveryabilityandiseasilydeformedbyexternalforces.Inotherwords,intheausteniticphasetheSMAremainsaboveitsreversetransformationtem-perature,ensuringthetoolremainsclamped,andduringthecoolingprocedurethetoolunclampedinthetoolholdercanbeinstalledoruninstalled.翻译为了提高微/中尺度元件的生产力，研究人员专注于开发小型化生产工具，如微机械工具，这些小型化系统有望节省能源和易于识别文字.微制造工具的第一步是小型化相应的子系统.尤其是微机械材料，清除过程工具，作为一个关键子系统，一个微型主轴单元，必须达到较高的旋转速度，同时保持对微加工功能良好的旋转精度。在发展微型主轴单元，一个关键问题是该工具夹紧部分保存在主轴方法的缩减，如传统的工具夹夹头，卡盘，液压卡盘，收缩后接的方法，工具，小型化，可能受到他们本身复杂的结构和运作机制.夹头，卡盘，一个锥形夹头及夹头拉设备，一个螺丝钉，都必须在微主轴里.此外，包括有限公司，锥形夹头的原因叠层宽容，这可能会增加旋转误差偏移.液压夹头主轴内有一个由于对一个调整螺丝和石油路线.这些元素不平衡转子的质量需要非轴对称结构，增加高旋转速度的革命运动误差。最后，收缩接刀柄需要特定的设备加热装置，高温下松开的工具，设备过于昂贵，对于微机械工具.一个使用的方式来避免这些问题太大，是把一个形状记忆合金（SMA）。形状记忆合金，最近在各种应用，如驱动器，紧固件，骨等7-13。它们是轻量级的，使用，允许安装方便，准确，产量出色的可靠性，并提供防冲击和雇用一个工具钳SMA的振动.通过良好免疫力，钳可以简化，因为直接提供了SMA径向工具钳的工具支撑.由于这个简单的结构受力，进一步小型化是可能的，因此它针对该离心力.优势除了免疫效果好，不像一个夹头，卡盘，一个SMA型工具钳不需要夹头夹紧力的发展，这消除了公差层叠，形状记忆合金基于设备还