机械原理 英汉双语 教学课件 作者 张春林 Chapter 4 Force Analysis of Planar Mechanisms.pptx

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1、Chapter4ForceAnalysisofPlanarMechanism1.ContentsofForceAnalysis1)Knowingtheexternalappliedloads,calculatetheconstraintforceswhichoccurinpairs.Constraintforcescanbeusedtodesignkinematicpairs.2)Knowingtheresistanceactingondrivenlink,calculatetheforcesactingondrivinglink,orknowingthedrivingforce,ca

2、lculatetheresistanceactingondrivenlink.3)Theforceanalysisisthetheoreticalfoundationtocalculatetheefficiency.4)Makeuseoftheforceanalysis,wecandesignsomeselflockingmechanism.4.1Introduction2.MethodsofForceAnalysisTherearetwogeneralmethodsofperformingacompleteforceanalysis：Graphicalforceanalysis&

3、Analyticalforceanalysis.1.InertiaForcesFig.4-1　Inertiaforceandinertiatorqueintoresultantforce(连杆的惯性力与惯性力矩的合成)4.2ForceAnalysisIncludingInertiaForcesinMechanismsFig4-1ashowsaslidercrankmechanism.Becauseoftheconstrainedmotionofthemechanism,accelerations,suchasas2,α2oftheindividuallink2andaC3ofthesl

4、ider3,maybedeterminedfirst,thentheinertiaforcesFi2andtorqueMs2actingonthelink2canbecalculatedrespectively.2.KinetostaticAnalysisofPlanarMechanism(1)KinetostaticanalysisofplanarmechanismbygraphicalmethodExample4-1Fig4-2ashowsaconventionalshapermechanisminwhichtheangularvelocityofthecrankandalldim

5、ensionsoflinksareknown.SupposetheweightoftheramisG5,resistanceactingontheramisFr,andinertiaforceactingontheramisFi5.Theotherweightsandinertiaforcesneednottobeconsidered.DeterminetheinputtorqueMbactingonthedrivinglinkandtheconstraintforcesinpairs.Fig.4-2　Graphicalforceanalysisofsharper(牛头刨床的动态静力分

6、析)Fig.4-3　Analyticalforceanalysis(动态静力分析的解析法)Example4-2Fig4-3showsaslidercrankmechanismusedinalotofmachines,suchasinternalcombustionengineandreciprocatingcompressors.Allthedimensionsoflinks,angularpositionofthecrankandangularvelocityofthecrankareknown.Thekinematicanalysisisfirstperformedalso.(2)K

7、inetostaticanalysisofplanarmechanismbyanalyticalmethod1.FrictioninKinematicPairs(1)FrictioninslidingpairsThefrictioninslidingpairscanbedividedintoplanesurfacefrictionandVsurfacefriction.4.3ForceAnalysisIncludingFricti