危害室内环境的因素微生物

毕业设计（论文）英文资料翻译MicroShotBlastingofMachineTools学院：西北工业大学明德学院专业：机械设计制造及自动化班级：161003班姓名：王伟学号：指导老师：2015年6月MicroshotblastingofmachinetoolsforimprovingsurfacefinishandreducingcuttingforcesinmanufacturingD.M.Kennedy*,J.Vahey,D.HanneyFacultyofEngineering,DublinInstituteofTechnology,BoltonStreet,Dublin1,IrelandReceived5January2004;accepted3February2004Availableonline13April2004AbstractMicroblastingofcuttingtipsandtoolsisaveryeffectiveandreliablemethodofadvancingthelifeoftoolsundertheactionofturning,milling,drilling,punchingandcutting.Thispaperoutlinesthewaysinwhichmicroblastedtools,bothcoatedanduncoatedhavebenefitedfromshotblastingandresultedingreaterproductivity,lowercuttingforces,improvedsurfacefinishoftheworkpiecesandlessmachinedowntime.Theprocessofmicroblastingisdiscussedinthepaper.Itseffectivenessdependsonmanyparametersincludingtheshotmediaandsize,themechanicsofimpactandtheapplicationoftheshotviathemicroshotblastingunit.Controloftheprocesstoproviderepeatabilityandreliabilityintheshotblastingunitisdiscussed.Comparisonsbetweentreatedanduntreatedcuttingtoolsaremadeandresultsoftoollifeforthesecuttingtipsoutlined.Theprocesshasshowntobeofmajorbenefittotoollifeimprovement.2004ElsevierLtd.Allrightsreserved.Keywords:Microshotblasting;Surfacefinish;Machinetools1.IntroductionManymoderntechniqueshavebeendevelopedtoenhancethelifeofcomponentsinservice,suchasalloyingadditions,heattreatment,surfaceengineering,surfacecoating,implantationprocesses,lasertreatmentandsurfaceshapedesign.Processessuchasthinfilmtechnology,plasmaspraying,vacuumtechniquesdepositingarangeofmulti-layeredcoatingshavegreatlyenhancedthelife,useandapplicationsofengineeringcomponentsandmachinetools.Bombardmentwithmillionsofmicroshotranginginsizefrom4to50lmwithacontrolledprocesscanleadtodramaticoperatinglifeimprovementsofcomponents.StandardshotpeeningwasfirstusedinaproductionprocesstoextendthelifeofvalvespringsforBuickandCadillacenginesintheearly1930s[1,2]butpriortothisitwasawellknownprocessusedbyblacksmithsandswordmakersovertimetoimprovethetoughnessofthecuttingedgesoftheirtoolsandweapons.Today,cuttingtipsandtoolscanbegreatlyimprovedbytheprocessofmicroshotblastingtheirsurfacestoinducecompressiveresidualstresses.Theoperatinglifeoftoolssuchasdrills,turningtips,millingtips,punches,knifeedges,slicers,blades,andarangeofotherworkingpartscanalsobenefitfromthisprocess.Standardcomponents,suchassprings,dies,shafts,cams,anddynamiccomponentsinmachinesandenginescanbeenhancedbythisprocess.Thefatiguelifeofcompressorcomponentsforexample,treatedbyshotpeeninghaveincreaseddramaticallyasreportedbyEckersleyandFerrelli[3].Otherfactorssuchasimprovedfatigueresistance,microcrackclosure,reducedcorrosionandanimprovedsurfacefinishcanalsobedesignedintocomponentsasaresultofthisthepeeningprocess.Notonlycanimprovementsbemadetothesurfacefinishofthecuttingtipsandtoolsbutalsothesurfacefinishoftheworkpiecesmachinedwiththesetoolshaveimprovedasaresultofthistechnique.Engineeringmaterialssuchastoolssteels,carbides,ceramics,coatedcarbides,throughtopolymersandevenrubbers(elastomers)canbenefit.Thekeyrequirementforthisprocessistodevelopanautomatedmicroblastingprocesstofitinsideasprayboothorstandardshotblastingbooth.Shotmaterial,sizeandmass,operatingpressures,operatingvelocities,kineticenergy,densityandcoveragetimewillneedtobeperfectedandoptimisedforarangeofmaterials.Theprocessisalineofsightmethodbutcanbeappliedtocomplexsurfaceshapessuchasthetipsofdrillbits.2.MethodofoperationOneoftheprimarywaysthatcomponentsfailinerviceisthroughfatigue.Thisiscloselyassociatedwithcyclicstressesandacceleratedbytensilestresses,microcrackpropagationandstresscorrosioncracking.Cracksreducethecrosssectionofamaterialandeventuallyitwillfailtosupporttheappliedloads.Onesimplemethodofreducingfailurebyfatigueistoarrestthesetensilestressesbyinducingcompressivestressesintoasurface.Thebenefitsobtainedwithshotpeeningareadirectresultoftheresidualcompressivestressesproducedinacomponent.AtypicalshotstrikingasurfaceisshowninFig.1.AnyappliedtensileloadswouldhavetoovercometheresidualcompressivestressesbeforeacrackcouldinitiateasdescribedbyAlmen[4].Poormachiningofmaterialscanresultinresidualstressesaccruingatthesurface.Roughsurfaceshavedeepernotches,wherecrackscaninitiateduetotensilestressconcentrationsatthesepoints.Manystandardmachiningprocessessuchasgrinding,milling,turning,andcoatingprocessessuchaselectroplatinginduceresidualtensilestressesinsurfacesandthiscanleadtoearlyfailureofcomponents.Furthertensileloadinginservicewouldleadtoearlyfailureandthiscanbepreventedbyshotpeeningandmicroblastingofcomponentsurfaces.Microshotblastingwillchangethefollowinginamaterialssurface:(i)resistancetofatiguefracture;(ii)resistancetostresscorrosion;(iii)achangeinresidualstresses;(iv)modificationofsurfacefinish.Itisacoldworkingprocessinvolvingbombardingpowderssuchasceramics,glassandmetalsofmainlysphericalshapesagainstsurfacesandcanbeusedinconjunctionwithotherprocesses.Themainstagesinvolvedinthisdynamicprocessincludeelasticrecoveryofthesubstrateafterimpact,somepl