论文CK6145主轴箱体加工工艺及精细镗夹具设计Word文档下载推荐.docx

论文CK6145主轴箱体加工工艺及精细镗夹具设计Word文档下载推荐.docx

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毕业设计（论文）外文翻译

毕业设计（论文）题目：

CK6145主轴箱体加工

工艺及精细镗夹具设计

外文题目：

ScrewedConnections

译文题目：

螺纹连接

系（部）：

专业班级：

学生姓名：

指导教师：

2010年9月26日

ScrewedConnections

Theprincipalrequirementforcorrectfunctioningofscrewedconnectingisthatthethreadsmustbefreebendingandshearingstresses.

Aboltlooselymountedintheholesoftheclampedpartsandsubjectedtotheactionoftransverseforcesinforms.Withafullelfinlotionofclearanceatboltsectionsnearthejointmoreshearstressesarise.Furthermoretheboltissujectedtotensionduetowhichitelongatesunderthedisplacemengtofthepulledpart.

Allthesestressesareaddedtothetensilestressesinducedinthebolrduringthepreliminarytightening.Asaresult,intheboltbodyacomplexstateofstressoccurs,producedbythesimultaneousactionofbingding,shearingandtensionforces,thebolt’sstrengthabruptlydrops.

Aserewed-inbolthasstillworseworkingconnditionswheninitscriticalsectionathreadoscut,averystrongstressconcentrationappears.Moseunfavorableisthecaseofthebendinngofastrdscrewedhomeinaholebottom.AsonthepreviouscaseherethestressconcentrationoccursinthesectionwherethethreadcomesTothecriticalsectionoccursinthesectionwherethethreadcomestothecriticalsectionplane.

Alsounfavorablearetheworkingconditionsforthematerialonthethreadedhoesoftightenedcomponents.Thetransverseforces,actingatthejointmwedgeoutthethreadsofthescrewedhole,producinghigherlocalberingstresseswhichweakenthethreadandloosenthefitnessofthescrewedstem,[articularluunderalternatingloads.

Theproblemofstrengtheningtightenedconnectionistoeliminatrthecomplexstressedstatrinthefasteningelementsandtoassureconditonsinwhichtheseelementswouldoperateonlyintensionundertheinfluenceofpreliminarytighteningandworkingforces.Transverseactingforcesmustbetakenupbyadditionalshearload-carryingelements.

Letusconsiderthecaseofacantileveredrod,screwedinahousing.Design1isobviouslyunsatisfactory,becausethemaximumbendingmomentfromthetransverseforcePistheweakenedthreadedportion.Highstressesattheembedmentpointinherentinthecantilevermaketherodbendandcrushthethreadsintheholeandontherod.

Provisionofashoulderinthetighteningareahelpslittle,sincetheshoulderthrustisnearlyparalleltothedirectionofbindingdisplacementandthedeformationisresistedonlybythefrictionforcesarisingatthethrustfacewhentightening.

Inthemorecorrectdesigns3and4,therodhasacylindricalortaperedsectionwhichcloselyfitsthehousingholeandefficientlyimpedestransversestrictalignmentofthethreadedandplainsections,theendofthescrewmusthaveclearance.

THEbestaredesign5and6,whichgaveacylindricalortaperedfittingsectioninthehousing.INtheiscasethethreadsarecompletelyrelievedfrombendingandtakeuponlythetighteningtension.

Figure55billustratesvariousmethodsoffixingacaststandloadedwithatransverseforcetoahousing.Version7isabsolutelyincorrect:

thefasteningstudissubjectdtobendingforceandshearingforce.Version8isalittlebetter:

herethestandisalignedbytheplainstudportion.Intheimprovedversion9thestudhasacenteringcylinder,whichcloselyfitsintotheholesofthehousingandstand.Indesign11bythestandcenteringshoulder.

Illustratedinfig.55carevariousmethodsoftakingupshearingstressesinacounterbalanceunitjointloadedwithatorque.Desing12and17arewrong,andtheresttoamoreorlessdegreeprovidecorrectoperatingconditionsforbolts.

Bindingofboltsisoftentheresultoftheirincorrectpositioningrelatedtotheactingloads.Thebracketindesign22hastwoerrors:

lackinganelementtakinguptheshearstressesandthebindingoftheboltstemsduetotheoff-centreapplicationoftheaxialload.UndertheactionofforcePthebrackettendstoturnaboutpointA.Withtherelationshipspresentedinthefigure,theforceactingupomeachboltisN=P1/2b=1.7P.TheboltissubjectedtobendingbyamomentM=Nd/2wheredisthediameterofthebolthead.

Withtheflangeturning90º

theloadupontheboltbecomespracticallycentral.Sinceinthegivencaseonlyoneboltisactive,theforceappliedtotheblotstillremainsrathergreat.Theintroductionofatriangularflangeinnowayenhancesthejointstrength,astheaddedboltsdonottakepartinthework.INtherationalalternative25twoboltsareactive.TheforceactinguponrachoftheboltsisthusreducedtoN=P.Theboltsheavingisforestalledbymeansofthebracketcenteringshoulder.Indesign26thebaseareaisenlargedand,asaresult,theboltloadisreducedtoN=0.7P.

Fasteningelementsareofrenbentduetothedistortionofthesupportsurfaces