毕业外文翻译.docx
- 文档编号:10152561
- 上传时间:2023-05-23
- 格式:DOCX
- 页数:11
- 大小:27.60KB
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
- 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 外文 翻译