毕业设计中起重机的英文翻译起重机的用途与历史文献资料翻译中英文对照翻译.docx
- 文档编号:3444107
- 上传时间:2022-11-23
- 格式:DOCX
- 页数:13
- 大小:33.19KB
毕业设计中起重机的英文翻译起重机的用途与历史文献资料翻译中英文对照翻译.docx
《毕业设计中起重机的英文翻译起重机的用途与历史文献资料翻译中英文对照翻译.docx》由会员分享,可在线阅读,更多相关《毕业设计中起重机的英文翻译起重机的用途与历史文献资料翻译中英文对照翻译.docx(13页珍藏版)》请在冰豆网上搜索。
毕业设计中起重机的英文翻译起重机的用途与历史文献资料翻译中英文对照翻译
中文6433字
第一部位外文原文
标题:
起重机的用途与历史
TheUseandHistoryofCrane
Everytimeweseeacraneinactionweremainswithoutwords,thesemachinesaresometimesreallyhuge,takinguptonsofmaterialhundredsofmetersinheight.Wewatchwithamazementandabitofterror,thinkingaboutwhatwouldhappeniftheloadcomesofforifthemovementofthecranewaswrong.Itisareallyfascinatingsystem,surprisingbothadultsandchildren.Theseareespeciallytowercranes,butinrealitythereareplentyoftypesandtheyareinuseforcenturies.Thecranesareformedbyoneormoremachinesusedtocreateamechanicaladvantageandthusmovelargeloads.Cranesareequippedwithawinder,awireropeorchainandsheavesthatcanbeusedbothtoliftandlowermaterialsandtomovethemhorizontally.Itusesoneormoresimplemachinestocreatemechanicaladvantageandthusmoveloadsbeyondthenormalcapabilityofahuman.Cranesarecommonlyemployedinthetransportindustryfortheloadingandunloadingoffreight,intheconstructionindustryforthemovementofmaterialsandinthemanufacturingindustryfortheassemblingofheavyequipment.
1.Overview
ThefirstconstructioncraneswereinventedbytheAncientGreeksandwerepoweredbymenorbeastsofburden,suchasdonkeys.Thesecraneswereusedfortheconstructionoftallbuildings.Largercraneswerelaterdeveloped,employingtheuseofhumantreadwheels,permittingtheliftingofheavierweights.IntheHighMiddleAges,harborcraneswereintroducedtoloadandunloadshipsandassistwiththeirconstruction–somewerebuiltintostonetowersforextrastrengthandstability.Theearliestcraneswereconstructedfromwood,butcastironandsteeltookoverwiththecomingoftheIndustrialRevolution.
Formanycenturies,powerwassuppliedbythephysicalexertionofmenoranimals,althoughhoistsinwatermillsandwindmillscouldbedrivenbytheharnessednaturalpower.Thefirst'mechanical'powerwasprovidedbysteamengines,theearlieststeamcranebeingintroducedinthe18thor19thcentury,withmanyremaininginusewellintothelate20thcentury.Moderncranesusuallyuseinternalcombustionenginesorelectricmotorsandhydraulicsystemstoprovideamuchgreaterliftingcapabilitythanwaspreviouslypossible,althoughmanualcranesarestillutilizedwheretheprovisionofpowerwouldbeuneconomic.
Cranesexistinanenormousvarietyofforms–eachtailoredtoaspecificuse.Sizesrangefromthesmallestjibcranes,usedinsideworkshops,tothetallesttowercranes,usedforconstructinghighbuildings.Forawhile,mini-cranesarealsousedforconstructinghighbuildings,inordertofacilitateconstructionsbyreachingtightspaces.Finally,wecanfindlargerfloatingcranes,generallyusedtobuildoilrigsandsalvagesunkenships.Thisarticlealsocoversliftingmachinesthatdonotstrictlyfittheabovedefinitionofacrane,butaregenerallyknownascranes,suchasstackercranesandloadercranes.
2.History
AncientGreece
ThecraneforliftingheavyloadswasinventedbytheAncientGreeksinthelate6thcenturyBC.Thearchaeologicalrecordshowsthatnolaterthanc.515BCdistinctivecuttingsforbothliftingtongsandlewisironsbegintoappearonstoneblocksofGreektemples.Sincetheseholespointattheuseofaliftingdevice,andsincetheyaretobefoundeitherabovethecenterofgravityoftheblock,orinpairsequidistantfromapointoverthecenterofgravity,theyareregardedbyarchaeologistsasthepositiveevidencerequiredfortheexistenceofthecrane.
Theintroductionofthewinchandpulleyhoistsoonleadtoawidespreadreplacementoframpsasthemainmeansofverticalmotion.Forthenexttwohundredyears,Greekbuildingsiteswitnessedasharpdropintheweightshandled,asthenewliftingtechniquemadetheuseofseveralsmallerstonesmorepracticalthanoffewerlargerones.Incontrasttothearchaicperiodwithitstendencytoever-increasingblocksizes,GreektemplesoftheclassicalageliketheParthenoninvariablyfeaturedstoneblocksweighinglessthan15-20tons.Also,thepracticeoferectinglargemonolithiccolumnswaspracticallyabandonedinfavorofusingseveralcolumndrums.
Althoughtheexactcircumstancesoftheshiftfromtheramptothecranetechnologyremainunclear,ithasbeenarguedthatthevolatilesocialandpoliticalconditionsofGreeceweremoresuitabletotheemploymentofsmall,professionalconstructionteamsthanoflargebodiesofunskilledlabor,makingthecranemorepreferabletotheGreekpolisthanthemorelabor-intensiverampwhichhadbeenthenormintheautocraticsocietiesofEgyptorAssyria.
ThefirstunequivocalliteraryevidencefortheexistenceofthecompoundpulleysystemappearsintheMechanicalProblems(Mech.18,853a32-853b13)attributedtoAristotle(384-322BC),butperhapscomposedataslightlylaterdate.Aroundthesametime,blocksizesatGreektemplesbegantomatchtheirarchaicpredecessorsagain,indicatingthatthemoresophisticatedcompoundpulleymusthavefounditswaytoGreekconstructionsitesbythen.
AncientRome
TheheydayofthecraneinancienttimescameduringtheRomanEmpire,whenconstructionactivitysoaredandbuildingsreachedenormousdimensions.TheRomansadoptedtheGreekcraneanddevelopeditfurther.Wearerelativelywellinformedabouttheirliftingtechniques,thankstoratherlengthyaccountsbytheengineersVitruvius(DeArchitectura10.2,1-10)andHeronofAlexandria(Mechanica3.2-5).TherearealsotwosurvivingreliefsofRomantreadwheelcranes,withtheHateriitombstonefromthelatefirstcenturyADbeingparticularlydetailed.
ThesimplestRomancrane,theTrispastos,consistedofasingle-beamjib,awinch,arope,andablockcontainingthreepulleys.Havingthusamechanicaladvantageof3:
1,ithasbeencalculatedthatasinglemanworkingthewinchcouldraise150kg(3pulleysx50kg=150),assumingthat50kgrepresentthemaximumeffortamancanexertoveralongertimeperiod.Heaviercranetypesfeaturedfivepulleys(Pentaspastos)or,incaseofthelargestone,asetofthreebyfivepulleys(Polyspastos)andcamewithtwo,threeorfourmasts,dependingonthemaximumload.ThePolyspastos,whenworkedbyfourmenatbothsidesofthewinch,couldalreadylift3000kg(3ropesx5pulleysx4menx50kg=3000kg).Incasethewinchwasreplacedbyatreadwheel,themaximumloadevendoubledto6000kgatonlyhalfthecrew,sincethetreadwheelpossessesamuchbiggermechanicaladvantageduetoitslargerdiameter.Thismeantthat,incomparisontotheconstructionoftheEgyptianPyramids,whereabout50menwereneededtomovea2.5tonstoneblockuptheramp(50kgperperson),theliftingcapabilityoftheRomanPolyspastosprovedtobe60timeshigher(3000kgperperson).
However,numerousextantRomanbuildingswhichfeaturemuchheavierstoneblocksthanthosehandledbythePolyspastosindicatethattheoverallliftingcapabilityoftheRomanswentfarbeyondthatofanysinglecrane.AtthetempleofJupiteratBaalbek,forinstance,thearchitraveblocksweighupto60tonseach,andonecornercorniceblockevenover100tons,allofthemraisedtoaheightofabout19m.InRome,thecapitalblockofTrajan'sColumnweighs53.3tons,whichhadtobeliftedtoaheightofabout34m(seeconstructionofTrajan'sColumn).
ItisassumedthatRomanengineersliftedtheseextraordinaryweightsbytwomeasures(seepicturebelowforcomparableRenaissancetechnique):
First,assuggestedbyHeron,aliftingtowerwassetup,whosefourmastswerearrangedintheshapeofaquadranglewithparallelsides,notunlikeasiegetower,butwiththecolumninthemiddleofthestructure(Mechanica3.5).Second,amultitudeofcapstanswereplacedonthegroundaroundthetower,for,althoughhavingalowerleverageratiothantreadwheels,capstanscouldbesetupinhighernumbersandrunbymoremen(and,moreover,bydraughtanimals).ThisuseofmultiplecapstansisalsodescribedbyAmmianusMarcellinus(17.4.15)inconnectionwiththeliftingoftheLateranenseobeliskintheCircusMaximus(ca.357AD).Themaximumliftingcapabilityofasinglecapstancanbeestablishedbythenumberoflewisironholesboredintothemonolith.IncaseoftheBaalbekarchitraveblocks,whichweighbetween55and60tons,eightextantholessuggestanallowanceof7.5tonperlewisiron,thatispercapstan.Liftingsuchheavyweightsinaconcertedactionrequiredagreatamountofcoordinationbetweentheworkgroupsapplyingtheforcetothecapstans.
MiddleAges
DuringtheHighMiddleAges,thetreadwheelcranewasreintroducedonalargescaleafterthetechnologyhadfallenintodisuseinwesternEuropewiththedemiseoftheWesternRomanEmpire.Theearliestreferencetoatreadwheel(magnarota)reappearsinarchivalliteratureinFranceabout1225,followedbyanilluminateddepictioninamanuscriptofprobablyalsoFrenchorigindatingto1240.Innavigation,theearliestusesofharborcranesaredocumentedforUtrechtin1244,Antwerpin1263,Bruggein1288andHamburgin1291,whileinEnglandthetreadwheelisnotrecordedbefore1331.
Generally,verticaltransportcouldbedonemoresafelyandinexpensivelybycranesthanbycustomarymethods.Typicalareasofapplicationwereharbors,mines,and,inparticular,buildingsiteswherethetreadwheelcraneplayedapivotalroleintheconstructionoftheloftyGothiccathedrals.Nevertheless,botharchivalandpictorialsourcesofthetimesuggestthatnewlyintroducedmachinesliketreadwheelsorwheelbarrowsdidnotcompletelyreplacemorelabor-intensivemethodslikeladders,hodsandhandbarrows.Rather
- 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:
- 毕业设计 起重机 英文翻译 用途 历史文献 资料 翻译 中英文 对照