机制材料力学试卷A答案.doc

《机制材料力学试卷A答案.doc》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、2008机制材料力学试卷A一、（20）5.83Theworkingstressesforthemanufacturedwoodbeamare10MPainbendingand1.0MPainshear.Determinethelargestallowablevalueoftheloadintensityw0.Solution5(a)DesignforshearThemaximumshearforceisthefirstmomentofthecross-sectionalareaabovetheneutralaxisis3themomentofinertiaof

2、thecross-sectionalabovetheneutralaxisis3--------P1634(b)DesignforbendingThenormalstress4Sothelargestallowablevalueoftheloadintensity1二、（20）TheoverhangingbeamABCcarriestheuniformlydistributedloadbetweenitssupportsandtheconcentratedloadPatendC.DeterminethedisplacementofthebeamattheC,b

3、ysuperposition.5Accordingtodeflectionformulasforbeams,weknow，5，541三、（20）8.27Thecrosssectionsofthemembersofthepin-jointedstructureare200-mmsquare.FindthemaximumcompressivestressinmemberBDE.15SolutionThemaximumcompressivestressinmemberBDE5四、（20）8.110Determinethesmallestallowablediamet

4、eroftheshaftthatcarriesthethreepulleys.Theworkingstressesareσw=18ksiandτw=8ksi.NeglecttheweightsofthePulleysandtheshaftaswellasthestressduetothetransverseshearforce.SolutionAccordingthesupport,weknowthereisthelargestbendingmomentoccursatC,thelargesttorqueoccursinsegmentBC.Showinthef

5、igure.，FBY=938.33(lb)，FDY=1511.67(lb)C点弯矩和扭矩：，D点弯矩和扭矩：，B点弯矩和扭矩：，7AtDsection,wehave，Therefore,thestressatthebottomofthesectionare44DrawtheMohr’scircleAccordingtoMohr’scircle,wehaved=2.119(in.)4Settleit,wegetd=2.397(in.)五、（20）Forthetrussshowninthefigure(a),thecrosssectionofbarCDisshow

6、inFig.(b),usingAISCcolumnspecificationswithE=200GPaandσyp=250MPa.,determinethemaximumsafevalueofP.Assumethatcross-bracingpreventsthejointsfromdeflectingperpendiculartotheplaneofthetruss.SolutionDeterminetheforceFcxDeterminethemomentofinertiaofthecross-sectionalareaaboutthez-axisthem

7、omentofinertiaArea，Theslendernessratioofa1600mmx2400mmrectangleTheleastradiusofgyrationwithz-axis24Theslendernessratio4Fortheslendernessratioislessthan,sothattheconcretecolumnisofintermediatelength.Theseequationsyieldthefactorofsafety4andtheworkingstress4Thelargestallowableaxialload

8、thusbecomesaccordin