機(jī)械基礎(chǔ)試題及答案英語1.Whencalculatingthestressconcentrationfactor(Kt)forasteppedshaftwithafilletradiusof2mmandadiameterratioof1.5,whichofthefollowingformulasismostaccurateforestimatingKtinastaticloadingscenario?(Answer:B)A.Kt=1+(D/d-1)

B.Kt=1.5+0.35(r/d)

C.Kt=2.0-0.1(r/D)

D.Kt=(D/d)22.Agearpairhasamoduleof4mm,apressureangleof20°,andacenterdistanceof100mm.Whatisthesumofthenumberofteeth(z1+z2)forthetwogears?(Answer:C)A.20

B.30

C.50

D.703.Ahydraulicsystemoperatesatapressureof15MPa.Ifthepistonareais0.02m2,whatisthetheoreticalforceoutputinkN?(Answer:A)A.300

B.150

C.75D.304.Whichtypeofbearingismostsuitableforhigh-speed,low-loadapplicationswith

minimalaxialmovement?(Answer:D)A.TaperedrollerbearingB.CylindricalrollerbearingC.NeedlerollerbearingD.Deepgrooveballbearing5.A4-strokeinternalcombustionenginehasaboreof80mm,astrokeof100mm,andoperatesat2000RPM.Whatisthesweptvolumeperminuteinliters?(Answer:B)A.8.04B.16.08

C.32.16

D.64.326.Whenselectingamaterialforashaftsubjectedtoalternatingbendingstresses,whichpropertyismostcritical?(Answer:C)

A.HardnessB.DuctilityC.FatiguestrengthD.Thermalconductivity7.Ahelicalcompressionspringhasawirediameterof5mm,ameancoildiameterof30mm,and10activecoils.IfG=80GPa,whatisthespringrate(k)inN/mm?(Answer:A)A.12.7

B.25.4

C.50.8

D.101.68.Whichcouplingtypeisbestsuitedforconnectingtwoshaftswithslightmisalignmentandangulardisplacement?(Answer:D)

A.RigidcouplingB.FlangecouplingC.OldhamcouplingD.Universaljoint9.Abeltdrivesystemusesaflatbeltwithacoefficientoffrictionof0.3andawrapangleof180°.Whatisthemaximumtensionratio(T1/T2)beforeslippingoccurs?(Answer:C)A.1.5

B.2.0

C.2.5

D.3.010.Acylindricalpressurevesselhasaninnerdiameterof500mmandoperatesat5MPa.Iftheallowablestressis120MPa,whatistheminimumrequiredwallthicknessinmm?(Answer:B)

A.5B.10C.15D.2011.Whichthreadprofileprovidesthehighesttensilestrengthforagivendiameter?(Answer:A)A.Squarethread

B.V-threadC.AcmethreadD.Buttressthread12.Amachinecomponentissubjectedtoafluctuatingstressrangingfrom50MPato150

MPa.UsingtheGoodmancriterion,iftheultimatetensilestrengthis400MPaand

endurancelimitis200MPa,whatisthefactorofsafety?(Answer:D)A.1.2

B.1.5

C.1.8

D.2.113.Ageartrainconsistsofa20-toothpiniondrivinga60-toothgear.Iftheinputspeedis1200RPM,whatistheoutputspeedinRPM?(Answer:B)A.300

B.400

C.600

D.90014.Whichlubricationmethodismosteffectiveforreducingfrictioninhigh-speedjournalbearings?(Answer:C)

A.GreaselubricationB.Boundarylubrication

C.Hydrodynamiclubrication

D.Solidfilmlubrication15.Acantileverbeamoflength1missubjectedtoapointloadof500Natitsfreeend.Iftheflexuralrigidity(EI)is2×10?N·m2,whatisthemaximumdeflectioninmm?(Answer:A)

A.6.25B.12.5C.25.0D.50.016.Whichmaterialpropertydeterminestheresistancetoplasticdeformationundercompressiveloads?(Answer:B)

A.ToughnessB.YieldstrengthC.Elasticmodulus

D.Poisson’sratio17.Ahydraulicpressexertsaforceof50kNonapistonwithadiameterof100mm.WhatisthepressureinthesysteminMPa?(Answer:C)A.5B.6.37

C.7.96

D.1018.Whichtypeofchainiscommonlyusedinconveyorsystemsforheavy-duty

applications?(Answer:A)A.Rollerchain

B.Silentchain

C.LeafchainD.Flat-topchain19.Athreadedfastenerhasapitchof2mmandrequires5turnstofullyengage.Whatistheaxialadvanceinmm?(Answer:D)A.2

B.5

C.8

D.1020.Aflywheelwithamassof50kgandaradiusofgyrationof0.5mrotatesat300RPM.WhatisitskineticenergyinkJ?(Answer:B)A.1.84

B.3.68

C.7.35

D.14.721.Whichbearingarrangementismostsuitableforsupportingaxialloadsinboth

directions?(Answer:C)A.Single-rowdeepgrooveballbearing

B.Double-rowangularcontactbearing

C.ThrustballbearingD.Taperedrollerbearing22.Asteelrodwithadiameterof20mmissubjectedtoatensileloadof40kN.WhatisthestressinMPa?(Answer:A)A.127

B.254

C.318

D.63623.Whichgearmaterialcombinationisleastlikelytocausegalling?(Answer:D)A.Steel-steel

B.Brass-steel

C.Bronze-steel

D.Nylon-steel24.AV-beltdriveoperateswithagrooveangleof40°andacoefficientoffrictionof0.25.Whatisthemaximumtensionratio(T1/T2)fornoslipping?(Answer:B)A.2.1

B.3.2C.4.5

D.5.825.AcylindricalshaftismadeofAISI1040steelwithayieldstrengthof350MPa.Iftheshaftissubjectedtoatorqueof500N·mandabendingmomentof300N·m,whatisthefactorofsafetyusingthemaximumshearstresstheory?(Answer:C)A.1.5

B.2.0

C.2.5

D.3.026.Whichtypeofcouplingcompensatesforaxialmisalignmentbutnotangularmisalignment?(Answer:A)

A.Flexiblecoupling

B.RigidcouplingC.UniversaljointD.Oldhamcoupling27.Apressurereliefvalveissettoopenat8MPa.Ifthesystempressurerisesto10MPa,whatpercentageofthepressureisrelieved?(Answer:D)A.20%

B.50%

C.80%

D.100%28.Ahelicalgearhasahelixangleof15°andanormalpressureangleof20°.Whatisthetransversepressureangle?(Answer:B)A.18.3°

B.20.6°

C.22.1°

D.24.7°29.Whichlubricationregimeoccurswhentheload-carryingsurfacesarecompletely

separatedbyafluidfilm?(Answer:C)A.BoundarylubricationB.MixedlubricationC.HydrodynamiclubricationD.Elastohydrodynamiclubrication30.Aspring-loadedsafetyvalveisdesignedtoopenat0.7MPa.Ifthevalvediscareais500mm2,whatisthespringforcerequiredinN?(Answer:A)A.350

B.700C.1050

D.140031.Whichthreadprofileisself-lockingunderverticalloads?(Answer:B)A.Squarethread

B.V-threadC.AcmethreadD.Buttressthread32.Ashafttransmits10kWat1500RPM.WhatisthetorqueinN·m?(Answer:C)A.5.3B.10.6

C.63.7

D.127.333.Asimplysupportedbeamoflength3mcarriesauniformlydistributedloadof2kN/m.WhatisthemaximumbendingmomentinkN·m?(Answer:B)A.2.25

B.4.5C.6.75

D.9.034.Whichmaterialiscommonlyusedforhigh-temperatureapplicationsinturbineblades?(Answer:D)

A.CarbonsteelB.Aluminumalloy

C.TitaniumalloyD.Nickel-basedsuperalloy35.Agearpumpdelivers0.001m3/satapressureof10MPa.WhatisthepoweroutputinkW?(Answer:A)

A.10B.20C.30D.4036.Whichbearingtypeismostsensitivetomisalignment?(Answer:A)

A.CylindricalrollerbearingB.SphericalrollerbearingC.TaperedrollerbearingD.Deepgrooveballbearing37.Ahydrauliccylinderwithaboreof100mmandastrokeof500mmoperatesat5MPa.WhatisthemaximumforceinkN?(Answer:C)A.19.6

B.39.2

C.58.9

D.78.538.Whichthreadseriesisusedforgeneral-purposefastenersinthemetricsystem?(Answer:B)A.UnifiedNational

B.ISOmetricC.BritishStandard

D.Whitworth39.Aflywheelrotatesat600RPMandhasamomentofinertiaof2kg·m2.WhatisitskineticenergyinJ?(Answer:A)A.395

B.790C.1580

D.316040.Whichlubricanttypeisbestforreducingwearingeardrives?(Answer:D)A.MineraloilB.SyntheticoilC.GreaseD.EP(extremepressure)additive41.Apressurevesselhasasphericalendwitharadiusof200mmandoperatesat3MPa.WhatisthehoopstressinMPa?(Answer:B)A.15

B.30

C.45

D.6042.Whichcouplingtyperequiresprecisealignmentofshafts?(Answer:A)A.Rigidcoupling

B.Flexiblecoupling

C.Universaljoint

D.Oldhamcoupling43.Ahelicalspringhasaspringrateof50N/mmandiscompressedby20mm.WhatisthestoredenergyinJ?(Answer:C)

A.5B.10C.100

D.20044.Whichmaterialpropertydeterminestheabilitytoabsorbenergybeforefracture?(Answer:D)A.HardnessB.Elasticmodulus

C.Yieldstrength

D.Toughness45.Abeltdrivesystemhasadriverpulleydiameterof200mmandadrivenpulleydiameterof100mm.Ifthedriverspeedis1000RPM,whatisthedriv