建筑

河南科技大学毕业论文----学号201153230400061-1-附：英语材料翻译Material1MachineElementsHoweversimple,anymachineisacombinationofindividualcomponentsgenerallyreferredtoasmachineelementsorparts.Thus,ifamachineiscompletelydismantled,acollectionofsimplepartsremainssuchasnuts,bolts,springsgears,camsandshaftsthebuildingblockofallmachinery.Amachineelementis,therefore,asingleunitdesignedtoperformaspecificfunctionandcapableofcombiningwithotherelements.Sometimescertainelementsareassociatedinpairs,suchasnutsandboltsorkeysandshafts.Inoterinstances,agroupofelementsiscombinedtoformasubassembly,suchasbearings,couplings,andclutches.Themostcommonexampleofamachineelementisagear,which,fundamentally,isacombinationofwheelandthelevertoformatoothedwheel.Therotationofthisgearonahuborshaftdrivesothergearsthatmayrotatefasterorslower,dependinguponthenumberofteethonthebasicwheels.Otherfundamentalmachineelementshaveevolvedfromwheelandlever.Awheelmusthaveashaftonwhichitmayrotate.Thewheelisfastenedtotheshaftswithcouplings.Theshaftmustrestinbearings,maybeturnedbyapulleywithabeltorachainconnectingittoapulleyonasecondshaft.Thesupportingstructuremaybeassembledwithboltsorrivetsorbywelding.Properapplicationofthesemachineelementsdependsuponknowledgeoftheforceonthestructureandthestrengthofthematerialsemployed.Theindivedaulreliabilityofmachineelementsbecomesthebasisforestimatingtheoveralllifeexpectancyofacompletemachine.Manymachineelementarethoroughlystandardized.Testingandpracticalexperiencehaveestablishedthemostsuitabledimensionsforcommonstructuaralandmechanicalparts.Throughstandardization,uniformityofpracticeandresultingeconomicsareobtained.Notallmachinepartsinusearestandardized,however.Intheautomotiveindustryonlyfasteners,bearings,bushings,chains,andbeltsarestandardized.Crankshaftsandconnectingrodsarenotstandardized.河南科技大学毕业论文----学号201153230400061-2-GearsGearsarevitalfactorsinmachinery:Oneorthefirstmechanisminventedusinggearswastheclock.Infact,aclockislittlemorethanatrainofgears.Considerablestudyandresearchhavebeenmadeongearsnrecentyearsbecauseoftheirwideuseunderexactingconditions.Theyhavetotransmitheavierloadsandrunathigherspeedsthaneverbefore.Theengineersandthemachinistsallconsidergearingtheprimeelementinnearlyallclassesofmachinery.SpurGearsSpurgearsareusedtotransmitpowerandrotarymotionbetweenparallelshafts.AscanbeseeninFig.Theteethaercutparalleltotheaxisoftheshaftonwhichthegearsaremouted.Thesmalleroftwogearsinmeshiscalledthepinion.andthelargeriscustomarilydesignatedasthegear.Inmostapplicationsthepinionisthedrivingelementwhereasthedrivenelement.HelicalGearsFigshowshelicalgearsinmesh.Thepairshownismountedonparallel,themostcommonsituationforwhichhelicalgearsareused.However,helicalgearsaresometimesusedfornon-parallel,non-intersectingshaftapplications.Whenusedinthismanner,theyareknownascrossedhelicalgears.Figillustratesapairofcrossedhelicalgearsinmesh.Spurgearsareusedforlowspeedapplicationandthosesituationswherenoisecontrolisnotaproblem.Useofhelicalgearsisindicatedwhenapplicationinvolveshighspeeds,largepowertransmission,orwherenoiseabatementisimportant.Whereasspurgearshavetheirteethcutparalleltothegearaxis,helicalgearteetharecutintheformofhelicesmakingaconstantanglewithrespecttothegearaxis.WormGearsAlthoughcrossedhelicalgearscanbeusedforapplicationsinvolvingnon-parallel,non-intersectingshafts,theyareratherlimitedintheirloadtransmissioncapacith.Inaddition,largespeedratios,ontheordrofsay200to1couldnotbereasonablyachievedinonereductionbecauseofthesizeofgearrequired.Forexample,ifthesmallergearhad20teeth,thelargerwouldhavetohave4000teeth.Amuchmorefeasiblesolutiontotheproblemwouldbetheuseofawormgearset.河南科技大学毕业论文----学号201153230400061-3-AwormgearsetsuchasshowninFigconsistsoftheworm,whichisverysimilartoascrew,andthewormwheel,whichisahelicalgear.Theshaftsuponwhichthewormandthegeararemountedareusually90degreesapart.Oneoftheadvantagesassociatedwiththeuseofwormgearsisthatthetoothengagementoccurswithouttheshockprevalentinothergeartypes.Infactthemeshingoftwoteethoccurswithaslindingactionwhich,whileresultinginveryquietoperation,mayproduceoverheating.BevelGearThemostimportanttypeofgearusedtotransmitpowerbetweennon-parallelorintersectingshaftsisthebevelgear.Bevelgearscanperhapsbebestdescribedasbeingconicalgears,becausetheyarecutonconicalblanks.Therearethreeprimarytypesofbevelgears:straightbevelgears,spiralbevelgearsandHypoidbevelgears.Material2Technologiesofmetal-cutting1.DrillingandBoringDrilling,abasicmachineshoptechniqueconsistsofcuttingaroundholebymeansofarotatingdrill.boring,ontheotherhand,involvesthefinishingofaholealreadydrilledorcoredbymeansofarotating,offsetandsingle-pointtool.Fig.8-1showsthedrillingmachine.2.millingMillingmeansmachiningapieceofmetalbybringitintocontactwitharotatingcuttingtoolwhichhasmultiplecuttingedges.Therearemanytypesofmillingmachinesdesignedforvariouskindsofwork.forexample,verticalmillingmachineandhorizontalmillingmachineandNCmillingmachine,Fig.8-2showshorizontalmillingmachine.3.GrindingGrindingconsistsofshapingapieceofworkbybringingitintocontactwithar