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1、《机械原理（双语）》课程试卷2得分评阅教师一、Checkpoint(markyouranswerontheanswersheetbyTrueorFalse)(20points2points/each)1．ThelinkswithinamechanismcanhavedeterminedrelativemotionsifandonlyiftheDOFofthemechanismisgreaterthanzeroandequaltothenumberofthedrivinglinks()2.Duringthegroupdividingofmechanism
2、,iftheDOFofthegroupiszero,thenthegroupiscalledAssurgroup()3.Anythreeindependentlinksingeneralplanemotionmusthavethreeinstantcentres,thethreeinstantcentresmaylieonacommonstraightline.()4.IfamechanismcomplywiththeGrashof’scriterion,thenthemechanismmusthaveacrank.()5.Arotorisstatic
3、allybalancedifithasbeendynamicallybalanced.()6.Inthevelocitypolygon,Thevectorconnectingtheanytwopointsexceptpointprepresentsrelativevelocitybetweenthemandthedirectionisoppositetothevelocity’symbol()7.Theanalysiswithdynamicstaticisanalysisofthemechanismforcewithexceptionoftheiner
4、tiaforce,applyingintothecaseoflowvelocitymechanism.()8.Inacrank-rockermechanism,therockerDCreachesitstwolimitingpositionsDC1andDC2.ifthecrankABisadriver,thenthelimitingpositionsarecalleddeadpoints.()9.Thepressureangleremainsthesameatallpointsonthetoothprofilesoftherack(ak=a),whi
5、chisalsocalledthenormalpressureangle.()10.Thetransmissionratioofwormgearing(wormisdriver)canbecalculatedbytheformulai12=d2/d1()得分评阅教师二.CalculatethedegreeoffreedomofthemechanismasshowninFig(10points)1B得分评阅教师三.FortheplatecammechanismwithtranslatinginlinerollerfollowerasshowninFig,
6、thecamcontouriscircle(theradiusr=100mm),theradiusofrollerrR=10mm,OC=20mm,thecamrotatesatanticlockwise.1).Drawoutthepitchcurveofthecammechanism2).Findouttheradiusofprimecirclerp=?3).Findouttheliftoffollowerh=?4).Forthepositionshown,indicatepressureangleα5).Forthepositionshown,ind
7、icatedisplacements(20points)OC2四.Designanoffsetslider-crankmechanismby得分评阅教师graphicmethod.Theoffseteis16mm.ThecoefficientKoftravelspeedvariationistobe1.2.TheworkingstrokeHoftheslideristobe50mm(15points)3得分评阅教师五.Apairofstandardspurinvolutegearshasamoduleof10mm,0pressureangleα=20,
8、transmissionratioi12=2.thenumbersofteethz1=30.1
