机械原理英文试题及答案

机械原理英文试题及答案

I.Multiple-choiceQuestions(10questions,2pointseach)1.Whichofthefollowingisahigherpairinmechanicalengineering?A.SlidingpairB.RevolutepairC.GearpairD.Prismaticpair2.Thedegreeoffreedomofaplanarmechanismiscalculatedbytheformula:A.\(F=3(n-1)-2P_{L}-P_{H}\)B.\(F=2(n-1)-3P_{L}-P_{H}\)C.\(F=3(n-1)-P_{L}-2P_{H}\)D.\(F=2(n-1)-P_{L}-3P_{H}\)3.Acammechanismismainlyusedto:A.TransmitpowerB.ConvertrotarymotiontolinearmotionC.IncreasespeedD.Reduceforce4.Inafour-barlinkage,iftheshortestlinkplusthelongestlinkislessthanorequaltothesumoftheothertwolinks,andtheshortestlinkisfixed,themechanismiscalled:A.Double-rockermechanismB.Crank-rockermechanismC.Double-crankmechanismD.Noneoftheabove5.Thefunctionofaflywheelinamachineisto:A.StoreandreleaseenergyB.IncreasethespeedofthemachineC.ReducethefrictionD.Changethedirectionofmotion6.Therelativevelocityoftwopointsonarigidbodyinpurerotationis:A.ZeroB.EqualtotheproductofangularvelocityanddistancebetweenthepointsC.InfinityD.Noneoftheabove7.Thecontactratioingearsisdefinedas:A.TheratioofthelengthofthearcofcontacttothecircularpitchB.TheratioofthecircularpitchtothelengthofthearcofcontactC.TheratioofthemoduletothecircularpitchD.Theratioofthebasepitchtothecircularpitch8.Amechanismwithonedegreeoffreedomhas:A.OneinputmotionisrequiredtocompletelyspecifyitsmotionB.TwoinputmotionsarerequiredtocompletelyspecifyitsmotionC.ThreeinputmotionsarerequiredtocompletelyspecifyitsmotionD.Noinputmotionisrequired9.Inareciprocatingengine,thepiston'smotionisanexampleof:A.RectilinearmotionB.CircularmotionC.CurvilinearmotionD.Oscillatorymotion10.Whichofthefollowingisnotabasickinematicpair?A.ScrewpairB.CylindricalpairC.Hooke'sjointpairD.Spring-damperpairAnswers:1.C2.A3.B4.C5.A6.B7.A8.A9.A10.DII.Multiple-choiceQuestions(Morethanoneanswer)(10questions,2pointseach)1.Thefollowingpairsarekinematicpairs:A.SlidingpairB.Belt-pulleypairC.Ball-and-socketpairD.Cam-followerpair2.Factorsaffectingtheefficiencyofamechanisminclude:A.FrictionB.InertiaforcesC.ElasticdeformationD.Manufacturingerrors3.Characteristicsofagoodgearsysteminclude:A.HighefficiencyB.ConstantspeedratioC.LownoiselevelD.Largepower-to-weightratio4.Inacam-followersystem,thetypesoffollowermotioncanbe:A.UniformmotionB.SimpleharmonicmotionC.CycloidalmotionD.Exponentialmotion5.Thepartsofafour-barlinkageare:A.FrameB.CrankC.ConnectingrodD.Rocker6.Thefunctionsofagovernorare:A.TomaintainaconstantspeedoftheengineB.TocontrolthefuelsupplyC.ToadjusttheloadontheengineD.Toincreasetheenginepower7.Theadvantagesofusingaflywheelare:A.ReducingspeedfluctuationsB.ImprovingthestabilityofthemachineC.AbsorbingshockloadsD.Savingenergy8.Thefollowingcanbeusedtoanalyzethemotionofamechanism:A.GraphicalmethodB.AnalyticalmethodC.NumericalmethodD.Experimentalmethod9.Thekinematicinversionsofafour-barlinkagecanresultin:A.Crank-rockermechanismB.Double-crankmechanismC.Double-rockermechanismD.Slider-crankmechanism10.Ingearsystems,differenttypesofgearsare:A.SpurgearsB.HelicalgearsC.BevelgearsD.WormgearsAnswers:1.A,B,C,D2.A,B,C,D3.A,B,C,D4.A,B,C5.A,B,C,D6.A,B7.A,B,C,D8.A,B,C,D9.A,B,C10.A,B,C,DIII.TrueorFalseQuestions(10questions,2pointseach)1.Ahigherpairhaspointorlinecontactbetweentheelements.()2.Thedegreeoffreedomofaspatialmechanismiscalculatedinthesamewayasaplanarmechanism.()3.Acammechanismcanonlyconvertrotarymotiontolinearmotion.()4.Inafour-barlinkage,iftheshortestlinkisnotfixed,itcanneverbeadouble-crankmechanism.()5.Aflywheelcancompletelyeliminatespeedfluctuationsinamachine.()6.Therelativeaccelerationoftwopointsonarigidbodyinpuretranslationiszero.()7.Thecontactratioingearsshouldbeassmallaspossibletoreducewear.()8.Amechanismwithzerodegreeoffreedomisastaticstructure.()9.Inareciprocatingengine,theconnectingrodhasbothlinearandangularmotion.()10.Ascrewpairisalowerpair.()Answers:1.T2.F3.F4.T5.F6.T7.F8.T9.T10.TIV.Short-answerQuestions(4questions,5pointseach)1.Whatisthesignificanceofthedegreeoffreedominamechanism?Answer:Thedegreeoffreedomindicatesthenumberofindependentinputmotionsrequiredtocompletelyspecifythemotionofamechanism.Ithelpsindesigningandanalyzingmechanisms,determiningiftheycanperformthedesiredmotion,andunderstandinghowmanyactuatorsareneededtocontrolthemechanism'smovement.2.Explaintheconceptofkinematicinversion.Answer:Kinematicinversionistheprocessoffixingdifferentlinksofakinematicchainonebyone.Whendifferentlinksarefixed,therelativemotionsbetweentheotherlinkschange,resultingindifferenttypesofmechanisms.Forexample,differentinversionsofafour-barlinkagecangivecrank-rocker,double-crank,ordouble-rockermechanisms.3.Whatarethemainfunctionsofacam-followersystem?Answer:Acam-followersystemismainlyusedtoconverttherotarymotionofthecamintoadesiredlinearoroscillatorymotionofthefollower.Itcanbedesignedtoachievevariousmotionprofilessuchasuniform,harmonic,orcycloidalmotion,andiswidelyusedinengines,machinesforautomation,etc.4.Whyisaflywheelusedinamachine?Answer:Aflywheelstoresenergyduringtheperiodwhentheinputenergyismorethantherequiredoutputenergyandreleasesitwhentheinputenergyisless.Itreducesspeedfluctuations,improvesthestabilityofthemachine,andcanalsoabsorbshockloads,makingthemachineoperatemoresmoothly.V.DiscussionQuestions(4questions,5pointseach)1.Discusstheadvantagesanddisadvantagesofdifferenttypesofgears(spur,helical,bevel,worm).Answer:Spurgearsaresimpleandeasytomanufacture,withhighefficiencybutcanbenoisy.Helicalgearshavesmootheroperationandhigherload-carryingcapacitybutproduceaxialforces.Bevelgearsareusedforchangingthedirectionoftheshaft,buttheirdesignandmanufacturingarecomplex.Wormgearscanachievehighgearratiosinacompactspacebuthaverelativelylowefficiency.2.Analyzethefactorsthataffecttheefficiencyofamechanism.Answer:Frictionisamajorfactor,asitdissipatesenergy.Inertiaforcescancauseadditionalenergylossesduringaccelerationanddeceleration.Elasticdeformationofcomponentsmayleadtoenergystorageandreleaseinaninefficientway.Manufacturingerrorscanalsoaffectthesmoothoperationandthustheefficiencyofthemechanism.3.Howcanweimprovetheperformanceofacam-followersystem?Answer:Wecans