外文翻译--故障的分析、尺寸的决定以及凸轮的分析和应用-精品Word下载.doc
- 文档编号:15271537
- 上传时间:2022-10-29
- 格式:DOC
- 页数:19
- 大小:168.51KB
外文翻译--故障的分析、尺寸的决定以及凸轮的分析和应用-精品Word下载.doc
《外文翻译--故障的分析、尺寸的决定以及凸轮的分析和应用-精品Word下载.doc》由会员分享,可在线阅读,更多相关《外文翻译--故障的分析、尺寸的决定以及凸轮的分析和应用-精品Word下载.doc(19页珍藏版)》请在冰豆网上搜索。
INTRODUCTION
Itisabsolutelyessentialthatadesignengineerknowhowandwhypartsfailsothatreliablemachinesthatrequireminimummaintenancecanbedesigned.Sometimesafailurecanbeserious,suchaswhenatireblowsoutonanautomobiletravelingathighspeed.Ontheotherhand,afailuremaybenomorethananuisance.Anexampleisthelooseningoftheradiatorhoseinanautomobilecoolingsystem.Theconsequenceofthislatterfailureisusuallythelossofsomeradiatorcoolant,aconditionthatisreadilydetectedandcorrected.
Thetypeofloadapartabsorbsisjustassignificantasthemagnitude.Generallyspeaking,dynamicloadswithdirectionreversalscausegreaterdifficultythanstaticloads,andtherefore,fatiguestrengthmustbeconsidered.Anotherconcerniswhetherthematerialisductileorbrittle.Forexample,brittlematerialsareconsideredtobeunacceptablewherefatigueisinvolved.
Manypeoplemistakinglyinterpretthewordfailuretomeantheactualbreakageofapart.However,adesignengineermustconsiderabroaderunderstandingofwhatappreciabledeformationoccurs.Aductilematerial,howeverwilldeformalargeamountpriortorupture.Excessivedeformation,withoutfracture,maycauseamachinetofailbecausethedeformedpartinterfereswithamovingsecondpart.Therefore,apartfails(evenifithasnotphysicallybroken)wheneveritnolongerfulfillsitsrequiredfunction.Sometimesfailuremaybeduetoabnormalfrictionorvibrationbetweentwomatingparts.Failurealsomaybeduetoaphenomenoncalledcreep,whichistheplasticflowofamaterialunderloadatelevatedtemperatures.Inaddition,theactualshapeofapartmayberesponsibleforfailure.Forexample,stressconcentrationsduetosuddenchangesincontourmustbetakenintoaccount.Evaluationofstressconsiderationsisespeciallyimportantwhentherearedynamicloadswithdirectionreversalsandthematerialisnotveryductile.
Ingeneral,thedesignengineermustconsiderallpossiblemodesoffailure,whichincludethefollowing.
——Stress
——Deformation
——Wear
——Corrosion
——Vibration
——Environmentaldamage
——Looseningoffasteningdevices
Thepartsizesandshapesselectedalsomusttakeintoaccountmanydimensionalfactorsthatproduceexternalloadeffects,suchasgeometricdiscontinuities,residualstressesduetoformingofdesiredcontours,andtheapplicationofinterferencefitjoints.
Camsareamongthemostversatilemechanismsavailable.Acamisasimpletwo-memberdevice.Theinputmemberisthecamitself,whiletheoutputmemberiscalledthefollower.Throughtheuseofcams,asimpleinputmotioncanbemodifiedintoalmostanyconceivableoutputmotionthatisdesired.Someofthecommonapplicationsofcamsare
——Camshaftanddistributorshaftofautomotiveengine
——Productionmachinetools
——Automaticrecordplayers
——Printingmachines
——Automaticwashingmachines
——Automaticdishwashers
Thecontourofhigh-speedcams(camspeedinexcessof1000rpm)mustbedeterminedmathematically.However,thevastmajorityofcamsoperateatlowspeeds(lessthan500rpm)ormedium-speedcamscanbedeterminedgraphicallyusingalarge-scalelayout.Ingeneral,thegreaterthecamspeedandoutputload,thegreatermustbetheprecisionwithwhichthecamcontourismachined.
DESIGNPROPERTIESOFMATERIALS
Thefollowingdesignpropertiesofmaterialsaredefinedastheyrelatetothetensiletest.
Figure2.7
StaticStrength.Thestrengthofapartisthemaximumstressthatthepartcansustainwithoutlosingitsabilitytoperformitsrequiredfunction.Thusthestaticstrengthmaybeconsideredtobeapproximatelyequaltotheproportionallimit,sincenoplasticdeformationtakesplaceandnodamagetheoreticallyisdonetothematerial.
Stiffness.Stiffnessisthedeformation-resistingpropertyofamaterial.Theslopeofthemoduluslineand,hence,themodulusofelasticityaremeasuresofthestiffnessofamaterial.
Resilience.Resilienceisthepropertyofamaterialthatpermitsittoabsorbenergywithoutpermanentdeformation.Theamountofenergyabsorbedisrepresentedbytheareaunderneaththestress-straindiagramwithintheelasticregion.
Toughness.Resilienceandtoughnessaresimilarproperties.However,toughnessistheabilitytoabsorbenergywithoutrupture.Thustoughnessisrepresentedbythetotalareaunderneaththestress-straindiagram,asdepictedinFigure2.8b.Obviously,thetoughnessandresilienceofbrittlematerialsareverylowandareapproximatelyequal.
Brittleness.Abrittlematerialisonethatrupturesbeforeanyappreciableplasticdeformationtakesplace.Brittlematerialsaregenerallyconsideredundesirableformachinecomponentsbecausetheyareunabletoyieldlocallyatlocationsofhighstressbecauseofgeometricstressraiserssuchasshoulders,hole
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 外文 翻译 故障 分析 尺寸 决定 以及 凸轮 应用 精品
![提示](https://static.bdocx.com/images/bang_tan.gif)