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1、兰大《工程力学(II)(材料)》13春在线作业3（Engineeringmechanics(II)(material)13springonlinehomework3）Spring13,autumn,theengineeringmechanics(II)(material)13springonlinehomework3Totalscore:100testtime:--SingletopicselectionMultiplechoiceTrueorfalse(atotalof10questions,
2、40points.)Theneutralaxisandtheexternalforceofthecrosssectionoftheeccentricpullbarareattheoppositesideofthe().A.axisofsymmetryB.CrosssectioncoreC.PrincipalaxisofinertiaD.ThemaininertiaaxisFullmarks:4points2.Thefollowingconclusionsaboutthegeneralperfor
3、manceofmaterialmechanicsarecorrect().A.ThetensilestrengthofbrittlematerialislowerthanthatofitscompressiveabilityB.ThetensilestrengthofbrittlematerialishigherthanthatofitscompressiveabilityC.thetensilecapacityofplasticmaterialishigherthanthatofcompres
4、sivestrengthD.ThetensilestrengthofplasticmaterialishigherthanthatofshearresistanceFullmarks:4points3.Themaximumpositivestressinthecrosssectionofthebeambendingis().A.NeutralaxisB.symmetryaxisC.OnthefaredgeoftheneutralaxisFullmarks:4points4.Thethrustbe
5、aringundertheactionofspaceforceisbinding().A.twoB.threeC.fourD.sixFullmarks:4pointsInastaticsystem,therearethreeredundantconstraints,andthesystemisinanindefinitenumberoftimes().A.threetimes6B.1C.D.NotsureFullmarks:4points6.Thecross-sectionareaofthesu
6、spensionrodwiththesamelengthandweightisA2andA1,andthemaximumaxialforceandstressofthetwobarsareN1,N2,sigma1andsigma2,respectively.A.N1N2,sigma1==sigma2B.N1indicatesN2,1=sigmasigma2C.N1=N2,sigma1indicatesasigma2D.N1indicatesN2,sigma1indicatesasigma2Ful
7、lmarks:4points7.Thestressstateofeachpointinthecrosssectionexcepttheneutralaxisis().A.one-wayB.twotoThreetoC.D.DependingonthecircumstancesFullmarks:4points3mainstresssigma1=24MPa,sigma2=0MPa,sigma3=-36mpa,materialpoissonratio?=0.25.Theequivalentstress
8、ofthedangerouspointiscalculatedbythesecondstrengththeory.Thesigmar2is()MPa.A.33B.24C.-36D.60Fullmarks:4points9.TheAnglebetweenthetwomainplanesofplanestressstateis().A.45degreesB.90degreesC.60degreesD.180degreesFullmarks:4points10.Inthecalculationform
