外文翻譯--夾頭.doc

附錄A外文文獻(xiàn)及其翻譯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.翻譯為了提高微/中尺度元件的生產(chǎn)力，研究人員專注于開發(fā)小型化生產(chǎn)工具，如微機(jī)械工具，這些小型化系統(tǒng)有望節(jié)省能源和易于識(shí)別文字.微制造工具的第一步是小型化相應(yīng)的子系統(tǒng).尤其是微機(jī)械材料，清除過程工具，作為一個(gè)關(guān)鍵子系統(tǒng)，一個(gè)微型主軸單元，必須達(dá)到較高的旋轉(zhuǎn)速度，同時(shí)保持對(duì)微加工功能良好的旋轉(zhuǎn)精度。在發(fā)展微型主軸單元，一個(gè)關(guān)鍵問題是該工具夾緊部分保存在主軸方法的縮減，如傳統(tǒng)的工具夾夾頭，卡盤，液壓卡盤，收縮后接的方法，工具，小型化，可能受到他們本身復(fù)雜的結(jié)構(gòu)和運(yùn)作機(jī)制.夾頭，卡盤，一個(gè)錐形夾頭及夾頭拉設(shè)備，一個(gè)螺絲釘，都必須在微主軸里.此外，包括有限公司，錐形夾頭的原因疊層寬容，這可能會(huì)增加旋轉(zhuǎn)誤差偏移.液壓夾頭主軸內(nèi)有一個(gè)由于對(duì)一個(gè)調(diào)整螺絲和石油路線.這些元素不平衡轉(zhuǎn)子的質(zhì)量需要非軸對(duì)稱結(jié)構(gòu)，增加高旋轉(zhuǎn)速度的革命運(yùn)動(dòng)誤差。最后，收縮接刀柄需要特定的設(shè)備加熱裝置，高溫下松開的工具，設(shè)備過于昂貴，對(duì)于微機(jī)械工具.一個(gè)使用的方式來避免這些問題太大，是把一個(gè)形狀記憶合金（SMA）。形狀記憶合金，最近在各種應(yīng)用，如驅(qū)動(dòng)器，緊固件，骨等7-13。它們是輕量級(jí)的，使用，允許安裝方便，準(zhǔn)確，產(chǎn)量出色的可靠性，并提供防沖擊和雇用一個(gè)工具鉗SMA的振動(dòng).通過良好免疫力，鉗可以簡(jiǎn)化，因?yàn)橹苯犹峁┝薙MA徑向工具鉗的工具支撐.由于這個(gè)簡(jiǎn)單的結(jié)構(gòu)受力，進(jìn)一步小型化是可能的，因此它針對(duì)該離心力.優(yōu)勢(shì)除了免疫效果好，不像一個(gè)夾頭，卡盤，一個(gè)SMA型工具鉗不需要夾頭夾緊力的發(fā)展，這消除了公差層疊，形狀記憶合金基于設(shè)備還