毕业外文翻译.docx

毕业外文翻译.docx

《毕业外文翻译.docx》由会员分享，可在线阅读，更多相关《毕业外文翻译.docx（11页珍藏版）》请在冰点文库上搜索。

毕业外文翻译

毕业外文翻译

英文资料

Suspension

Suspensionisthetermgiventothesystemofsprings,shockabsorbersandlinkagesthatconnectsavehicletoitswheels.Suspensionsystemsserveadualpurpose–contributingtothecar'sroadholding/handlingandbrakingforgoodactivesafetyanddrivingpleasure,andkeepingvehicleoccupantscomfortableandreasonablywellisolatedfromroadnoise,bumps,andvibrations,etc.Thesegoalsaregenerallyatodds,sothetuningofsuspensionsinvolvesfindingtherightcompromise.Itisimportantforthesuspensiontokeeptheroadwheelincontactwiththeroadsurfaceasmuchaspossible,becausealltheforcesactingonthevehicledosothroughthecontactpatchesofthetires.Thesuspensionalsoprotectsthevehicleitselfandanycargoorluggagefromdamageandwear.Thedesignoffrontandrearsuspensionofacarmaybedifferent.

LeafspringshavebeenaroundsincetheearlyEgyptians.

Ancientmilitaryengineersusedleafspringsintheformofbowstopowertheirsiegeengines,withlittlesuccessatfirst.Theuseofleafspringsincatapultswaslaterrefinedandmadetoworkyearslater.Springswerenotonlymadeofmetal,asturdytreebranchcouldbeusedasaspring,suchaswithabow.

Horsedrawnvehicles

Bytheearly19thcenturymostBritishhorsecarriageswereequippedwithsprings;woodenspringsinthecaseoflightone-horsevehiclestoavoidtaxation,andsteelspringsinlargervehicles.Theseweremadeoflow-carbonsteelandusuallytooktheformofmultiplelayerleafsprings.[1]

TheBritishsteelspringswerenotwellsuitedforuseonAmerica'sroughroadsofthetime,andcouldevencausecoachestocollapseifcorneredtoofast.Inthe1820s,theAbbotDowningCompanyofConcord,NewHampshiredevelopedasystemwherebythebodiesofstagecoachesweresupportedonleatherstrapscalled"thoroughbraces",whichgaveaswingingmotioninsteadofthejoltingupanddownofaspringsuspension（thestagecoachitselfwassometimescalleda"thoroughbrace"）

Automobiles

Automobileswereinitiallydevelopedasself-propelledversionsofhorsedrawnvehicles.However,horsedrawnvehicleshadbeendesignedforrelativelyslowspeedsandtheirsuspensionwasnotwellsuitedtothehigherspeedspermittedbytheinternalcombustionengine.

In1903MorsofGermanyfirstfittedanautomobilewithshockabsorbers.In1920Leylandusedtorsionbarsinasuspensionsystem.In1922independentfrontsuspensionwaspioneeredontheLanciaLambdaandbecamemorecommoninmassmarketcarsfrom1932.[2]

Importantproperties

Springrate

Thespringrate（orsuspensionrate）isacomponentinsettingthevehicle'srideheightoritslocationinthesuspensionstroke.Vehicleswhichcarryheavyloadswilloftenhaveheavierspringstocompensatefortheadditionalweightthatwouldotherwisecollapseavehicletothebottomofitstravel（stroke）.Heavierspringsarealsousedinperformanceapplicationswheretheloadingconditionsexperiencedaremoreextreme.

Springsthataretoohardortoosoftcausethesuspensiontobecomeineffectivebecausetheyfailtoproperlyisolatethevehiclefromtheroad.Vehiclesthatcommonlyexperiencesuspensionloadsheavierthannormalhaveheavyorhardspringswithaspringrateclosetotheupperlimitforthatvehicle'sweight.Thisallowsthevehicletoperformproperlyunderaheavyloadwhencontrolislimitedbytheinertiaoftheload.Ridinginanemptytruckusedforcarryingloadscanbeuncomfortableforpassengersbecauseofitshighspringraterelativetotheweightofthevehicle.Aracecarwouldalsobedescribedashavingheavyspringsandwouldalsobeuncomfortablybumpy.However,eventhoughwesaytheybothhaveheavysprings,theactualspringratesfora2000 lbracecaranda10,000 lbtruckareverydifferent.Aluxurycar,taxi,orpassengerbuswouldbedescribedashavingsoftsprings.Vehicleswithwornoutordamagedspringsridelowertothegroundwhichreducestheoverallamountofcompressionavailabletothesuspensionandincreasestheamountofbodylean.Performancevehiclescansometimeshavespringraterequirementsotherthanvehicleweightandload.

Mathematicsofthespringrate

Springrateisaratiousedtomeasurehowresistantaspringistobeingcompressedorexpandedduringthespring'sdeflection.ThemagnitudeofthespringforceincreasesasdeflectionincreasesaccordingtoHooke'sLaw.Briefly,thiscanbestatedas

where

Fistheforcethespringexerts

kisthespringrateofthespring.

xisthedisplacementfromequilibriumlengthi.e.thelengthatwhichthespringisneithercompressedorstretched.

Springrateisconfinedtoanarrowintervalbytheweightofthevehicle,loadthevehiclewillcarry,andtoalesserextentbysuspensiongeometryandperformancedesires.

SpringratestypicallyhaveunitsofN/mm（orlbf/in）.Anexampleofalinearspringrateis500 lbf/in.Foreveryinchthespringiscompressed,itexerts500 lbf.Anon-linearspringrateisoneforwhichtherelationbetweenthespring'scompressionandtheforceexertedcannotbefittedadequatelytoalinearmodel.Forexample,thefirstinchexerts500 lbfforce,thesecondinchexertsanadditional550 lbf（foratotalof1050 lbf）,thethirdinchexertsanother600 lbf（foratotalof1650 lbf）.Incontrasta500 lbf/inlinearspringcompressedto3 incheswillonlyexert1500 lbf.

Thespringrateofacoilspringmaybecalculatedbyasimplealgebraicequationoritmaybemeasuredinaspringtestingmachine.Thespringconstantkcanbecalculatedasfollows:

wheredisthewirediameter,Gisthespring'sshearmodulus（e.g.,about12,000,000lbf/in²or80GPaforsteel）,andNisthenumberofwrapsandDisthediameterofthecoil.

Wheelrate

Wheelrateistheeffectivespringratewhenmeasuredatthewheel.Thisisasopposedtosimplymeasuringthespringratealone.

Wheelrateisusuallyequaltoorconsiderablylessthanthespringrate.Commonly,springsaremountedoncontrolarms,swingarmsorsomeotherpivotingsuspensionmember.Considertheexampleabovewherethespringratewascalculatedtobe500 lbs/inch,ifyouweretomovethewheel1 inch（withoutmovingthecar）,thespringmorethanlikelycompressesasmalleramount.Letsassumethespringmoved0.75 inches,theleverarmratiowouldbe0.75to1.Thewheelrateiscalculatedbytakingthesquareoftheratio（0.5625）timesthespringrate.Squaringtheratioisbecausetheratiohastwoeffectsonthewheelrate.Theratioappliestoboththeforceanddistancetraveled.

Wheelrateonindependentsuspensionisfairlystraight-forward.However,specialconsiderationmustbetakenwithsomenon-independentsuspensiondesigns.Takethecaseofthestraightaxle.Whenviewedfromthefrontorrear,thewheelratecanbemeasuredbythemeansabove.Yetbecausethewheelsarenotindependent,whenviewedfromthesideunderaccelerationorbrakingthepivotpointisatinfinity（becausebothwheelshavemoved）andthespringisdirectlyinlinewiththewheelcontactpatch.Theresultisoftenthattheeffectivewheelrateundercorneringisdifferentfromwhatitisunderaccelerationandbraking.Thisvariationinwheelratemaybeminimizedbylocatingthespringasclosetothewheelaspossible.

Rollcouplepercentage

Rollcouplepercentageistheeffectivewheelrates,inroll,ofeachaxleofthevehiclejustasaratioofthevehicle'stotalrollrate.RollCouplePercentageiscriticalinaccuratelybalancingthehandlingofavehicle.Itiscommonlyadjustedthroughtheuseofanti-rollbars,butcanalsobechangedthroughtheuseofdifferentsprings.

Avehiclewitharollcouplepercentageof70%willtransfer70%ofitssprungweighttransferatthefrontofthevehicleduringcornering.Thisisalsocommonlyknownas"TotalLateralLoadTransferDistribution"or"TLLTD".

Weighttransfer

Weighttransferduringcornering,accelerationorbrakingisusuallycalculatedperindividualwheelandcomparedwiththestaticweightsforthesamewheels.

Thetotalamountofweighttransferisonlyaffectedby4factors:

thedistancebetweenwheelcenters（wheelbaseinthecaseofbraking,ortrackwidthinthecaseofcornering）theheightofthecenterofgravity,themassofthevehicle,andtheamountofaccelerationexperienced.

Thespeedatwhichweighttransferoccursaswellasthroughwhichcomponentsittransfersiscomplexandisdeterminedbymanyfactorsincludingbutnotlimitedtorollcenterheight,springanddamperrates,anti-rollbarstiffnessandthekinematicdesignofthesuspensionlinks.

Unsprungweighttransfer

Unsprungweighttransferiscalculatedbasedontheweightofthevehicle'scomponentsthatarenotsupportedbythesprings.Thisincludestires,wheels,brakes,spindles,halfthecontrolarm'sweightandothercomponents.Thesecomponentsarethen（forcalculationpurposes）assumedtobeconnectedtoavehiclewithzerosprungweight.Theyarethenputthroughthesamedynamicloads.TheweighttransferforcorneringinthefrontwouldbeequaltothetotalunsprungfrontweighttimestheG-Forcetimesthefrontunsprungcenterofgravityheightdividedbythefronttrackwidth.Thesameistruefortherear.

Suspensiontype

Dependentsuspensionsinclude:

∙Satchelllink

∙Panhardrod

∙Watt'slinkage

∙WOBLink

∙Mumfordlinkage

∙Liveaxle

∙Twistbeam

∙Beamaxle

∙leafspringsusedforlocation（transverseorlongitudinal）

Thevarietyofindependentsystemsisgreaterandincludes:

∙Swingaxle

∙Slidingpillar

∙MacPhersonstrut/Chapmanstrut

∙UpperandlowerA-arm（doublewishbone）

∙multi-linksuspension

∙semi-trailingarmsuspension

∙swingingarm

∙leafsprings

Armouredfightingvehicle