兰大《工程力学ii材料》春在线作业Engineering mechanics ii materialspring online homework.docx

兰大《工程力学ii材料》春在线作业Engineering mechanics ii materialspring online homework.docx

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兰大《工程力学ii材料》春在线作业Engineeringmechanicsiimaterialspringonlinehomework

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）13springonlinehomework3

Totalscore:

100testtime:

--

Singletopicselection

Multiplechoice

Trueorfalse

（atotalof10questions,40points.）

Theneutralaxisandtheexternalforceofthecrosssectionoftheeccentricpullbarareattheoppositesideofthe（）.

A.axisofsymmetry

B.Crosssectioncore

C.Principalaxisofinertia

D.Themaininertiaaxis

Fullmarks:

4points

2.Thefollowingconclusionsaboutthegeneralperformanceofmaterialmechanicsarecorrect（）.

A.Thetensilestrengthofbrittlematerialislowerthanthatofitscompressiveability

B.Thetensilestrengthofbrittlematerialishigherthanthatofitscompressiveability

C.thetensilecapacityofplasticmaterialishigherthanthatofcompressivestrength

D.Thetensilestrengthofplasticmaterialishigherthanthatofshearresistance

Fullmarks:

4points

3.Themaximumpositivestressinthecrosssectionofthebeambendingis（）.

A.Neutralaxis

B.symmetryaxis

C.Onthefaredgeoftheneutralaxis

Fullmarks:

4points

4.Thethrustbearingundertheactionofspaceforceisbinding（）.

A.two

B.three

C.four

D.six

Fullmarks:

4points

Inastaticsystem,therearethreeredundantconstraints,andthesystemisinanindefinitenumberoftimes（）.

A.threetimes

6B.

1C.

D.Notsure

Fullmarks:

4points

6.Thecross-sectionareaofthesuspensionrodwiththesamelengthandweightisA2andA1,andthemaximumaxialforceandstressofthetwobarsareN1,N2,sigma1andsigma2,respectively.

A.N1N2,sigma1==sigma2

B.N1indicatesN2,1=sigmasigma2

C.N1=N2,sigma1indicatesasigma2

D.N1indicatesN2,sigma1indicatesasigma2

Fullmarks:

4points

7.Thestressstateofeachpointinthecrosssectionexcepttheneutralaxisis（）.

A.one-way

B.twoto

ThreetoC.

D.Dependingonthecircumstances

Fullmarks:

4points

3mainstresssigma1=24MPa,sigma2=0MPa,sigma3=-36mpa,materialpoissonratio?

=0.25.Theequivalentstressofthedangerouspointiscalculatedbythesecondstrengththeory.Thesigmar2is（）MPa.

A.33

B.24

C.-36

D.60

Fullmarks:

4points

9.TheAnglebetweenthetwomainplanesofplanestressstateis（）.

A.45degrees

B.90degrees

C.60degrees

D.180degrees

Fullmarks:

4points

10.Inthecalculationformulaofthebendingofthebeam,EIdenotes（）

A.Torsionalrigidity

B.Compressivestiffness

C.Flexuralrigidity

D.Tensilestiffness

Fullmarks:

4points

Spring13,autumn,theengineeringmechanics（II）（material）13springonlinehomework3

Theanswerisnotuploaded,forreviewanduse,ifyouneedtheanswer,pleaselookatmyregistrationnametofindthetotalscoreofthetest:

100testtime:

--

Singletopicselection

Multiplechoice

Trueorfalse

（atotalof5questions,20points.）

1.Intheeccentriccompressionofthebar,thefollowingconclusionsarecorrect（）.

A.Ifthecenterofthecentripetalforceislocatedatthecoreofthecrosssection,thereisnotensilestressinthebar

B.Ifthecenterofthecentripetalforceislocatedontheedgeofthecoreofthesection,thereisnotensilestressinthebar

C.

Ifthecenterofthecentripetalforceislocatedontheedgeofthecoreofthecrosssection,thenormalstressatleastonepointinthecrosssectionofthebarisequaltozero

D.Ifthecenterofthecentripetalforceislocatedatthecoreofthecrosssection,thetransversesectionoftheneutralaxiswillbedividedintotworegions:

tensionandcompression

Fullmarks:

4points

2.Themarkingdistanceofthespecimenbeforethetensiletestisl,andthecross-sectionalareaisA.Duringloading,theinstantaneousloadmeasuredisP;Theinstantaneouslengthofthemarkerdistanceisl1,theinstantaneouscrosssectionalareaisA1,andthefollowingconclusioniscorrect（）.

A.Whendrawingthestress-straincurve,itsverticalcoordinateisequaltoP/A,andthex-coordinateisepsilon=（l1-l）/l

B.Whendrawingthestress-straincurve,itsverticalcoordinateisdenotedbysigma=P/A1,andthex-coordinateisepsilon=（l1-l）/l

C.IfthemaximumloadthatcanbebornebeforethefractureisPb,thestrengthlimitofthematerialisPb/A

D.IfthemaximumloadthatcanbebornebeforethefractureisPb,thestrengthlimitofthematerialisPb/A1

Fullmarks:

4points

3.Fortherectangularcross-sectionbeam,thefollowingconclusioniscorrect（）.

A.Atthepointwherethemaximumpositivestressoccurs,theshearstressmustbezero

Atthepointwherethemaximumshearstressoccurs,thepositivestressmustbezero

C.beaminthepointofmaximumnormalstressandmaximumnouploadhomeworkanswer,firstforyoureview,ifyouneedtoanswerthespecificlookatmyregisterednameforshearstresspointmustbeonthesamesection

D.Thereisnopossibilityofsuchacrosssectioninthebeam,whichisthatthemaximumnormalstressandmaximumshearstressappearonthissection

Fullmarks:

4points

4.Thefollowingconclusionsarecorrect（）.

A.Althoughthesurfaceoftheexternalforceplaneisnotparalleltoanyofthecentralaxisofthecrosssection,thebeamwillproduceAcombineddeformationofplanebendingandtorsion

B.Theneutralaxisinthecrosssectionoftheobliquecurvatureisastraightlinethroughthecenterofthecurve

C.Whetheritisflatoroblique,theneutralaxiswilldividethecrosssectionintotwoareasoftensionandcompression

D.Stretch（compression）andbentcompositedeformationbars,wherethesexualaxisisastraightlinethatdoesnotpassthroughtheshapeoftheheart,butitalwaysdividesthecrosssectionintotworegionsoftensionandcompressionthatareunequalinsize

Fullmarks:

4points

5.Inthestrutofeccentricstretching（compression）,thefollowingconclusionsarecorrect（）.

A.Theinternalforcesonallcrosssectionsarethesame

Thestressstateofeachpointinthecrosssectionisunidirectionalstressstate

C.Theneutralaxisonthecrosssectionisastraightlinethroughthecenter

D.Theneutralaxisisastraightlinethatdoesnotpassthroughthecentroid.Itmaybelocatedinthecrosssectionoroutsidethecrosssection,butitisnotpossibletobetangenttotheperimeterofthesection

Fullmarks:

4points

Spring13,autumn,theengineeringmechanics（II）（material）13springonlinehomework3

Totalscore:

100testtime:

--

Singletopicselection

Multiplechoice

Trueorfalse

（10questions,40points.）

Whentheformulaofbendingandpositivestressofthebeamisderived,thephysicalrelationsigma=Eepsilonisapplied,whichistheassumptionthattheelasticdeformationofthebeamandthelongitudinallayerarenotpressed.

A.mistakes

B.right

Fullmarks:

4points

2.

Thecenterofmassofthehomogeneousobjectisitsshape.

A.mistakes

B.right

Fullmarks:

4points

3.Bendingdeformationbeam,maximumdeflectionoccurs,mustbethemaximumturningpoint.

A.mistakes

B.right

Fullmarks:

4points

4.Theabilityofthemembertomaintainbalanceintheoriginalgeometryiscalledthestabilityofthecomponent.

A.mistakes

B.right

Fullmarks:

4points

5.Theinfluenceof"stressconcentration"shouldbeconsideredintherodpartsmadeofbrittlematerials.

A.mistakes

B.right

Fullmarks:

4points

6.Whentherodispuretorsion,thereisonlytheshearstressinthebar,andthereisnopositivestress.

A.mistakes

B.right

Fullmarks:

4points

7.EIistheflexuralrigidityofthebeam,anditsmosteffectiveandreasonablemethodistoswitchtobettermaterials.

A.mistakes

B.right

Fullmarks:

4points

8.Whenthetransverseforceisbent,themaximumshearstressonthecrosssectiondoesnotoccurontheneutralaxisofthecrosssection.

A.mistakes

B.right

Fullmarks:

4points

9.Thetorsionalaxis,thelargestofwhichisthemaximumshearstress.

A.mistakes

B.right

Fullmarks:

4points

10.Thelesscriticalstressofthepressurebar,thelessunstableitis.

A.mistakes

B.right

Fullmarks:

4points

Thehomeworkanswerisnotuploaded,foreveryonetoreviewanduse,ifyouneedtheanswertothespecificlookofmyregisteredname