第5章螺纹联接和螺旋传动课件

Chapter5Screwjointsandscrewdrive§5－1Screwthread§5－2TypesofScrewthreadandStandardjoint§5－3Pre-tighteningofscrewjoints§5－5Strengthcalculationofscrewjoint§5－7Materialandadmissiblestressofscrewbolt§5－8Measuresofimprovingintensityofscrewboltjoint

§5－9Screwdrive§5－4Loosenesspreventingofscrewjoint§5－6DesignofjointofscrewboltgroupChapter5Screwjointsand1

ⅠFormingofscrewthread§5－1Screwthreadd2Helicalline----thelocusofamovingpointwhichrotatesaroundaxis,andatthesametimemovesalongtheaxisinconstantvelocityonthesurfaceofcylinder。Screwthread----Aplanefiguremovesalongahelicallineandkeepsitselfthroughtheaxisofthecylinderwhenmoving.Thenscrewthreadisformed.ScrewthreadⅠFormingofscrewthread§5－12AccordingtothetypeoftoothofscrewthreadTypesofscrewthreadAccordingtothedirectionofrotationofscrewthreadAccordingtothenumberofhelicallineAccordingtoinsideandoutsidesurfaceofsolidofrotationAccordingtoThefunctionofscrewthreadAccordingtotheshapeofbodyofrevolutionRectanglescrewthreadTrianglescrewthreadTrapeziumscrewthreadHacklescrewthreadAccordingtothetypeoftooth3

Thetypeoftoothofscrewthread

SquarethreadTrianglethreadTrapezoidalthreadButtressthread15º30º3º30º

Thetypeoftoothofscrew4RectanglescrewthreadTrianglescrewthreadTrapeziumscrewthreadHacklescrewthreadright-handthreadleft-handthread

AccordingtothetypeoftoothofscrewthreadTypesofscrewthreadAccordingtothedirectionofrotationofscrewthreadAccordingtothenumberofhelicallineAccordingtoinsideandoutsidesurfaceofsolidofrotationAccordingtoThefunctionofscrewthreadAccordingtotheshapeofbodyofrevolutionRectanglescrewthreadright-ha5RectanglescrewthreadTrianglescrewthreadTrapeziumscrewthreadHacklescrewthreadright-handthreadleft-handthread

single-startthreadmulti-startthreaddouble-startthreadsingle-startthreadPSS=2PPSPS=Pnthread:S=nP

n≤4

AccordingtothetypeoftoothofscrewthreadTypesofscrewthreadAccordingtothedirectionofrotationofscrewthreadAccordingtothenumberofhelicallineAccordingtoinsideandoutsidesurfaceofsolidofrotationAccordingtoThefunctionofscrewthreadAccordingtotheshapeofbodyofrevolutionRectanglescrewthreadright-ha6RectanglescrewthreadTrianglescrewthreadTrapeziumscrewthreadHacklescrewthreadright-handthreadleft-handthreadsingle-startthreadmulti-startthreadexternalthreadinternalthreadscrewpairAccordingtothetypeoftoothofscrewthreadTypesofscrewthreadAccordingtothedirectionofrotationofscrewthreadAccordingtothenumberofhelicallineAccordingtoinsideandoutsidesurfaceofsolidofrotationAccordingtoThefunctionofscrewthreadAccordingtotheshapeofbodyofrevolutionRectanglescrewthreadright-ha7

externalthreadinternalthread

externalinternalthread8RectanglescrewthreadTrianglescrewthreadTrapeziumscrewthreadHacklescrewthreadright-handthreadleft-handthreadsingle-startthreadmulti-startthreadexternalthreadinternalthreadscrewpairAccordingtothetypeoftoothofscrewthreadTypesofscrewthreadAccordingtothedirectionofrotationofscrewthreadAccordingtothenumberofhelicallineAccordingtoinsideandoutsidesurfaceofsolidofrotationAccordingtoThefunctionofscrewthreadAccordingtotheshapeofbodyofrevolutionJointscrewthreadDrivingscrewthreadScrewdriveRectanglescrewthreadright-ha9JointscrewthreadDrivingscrewthread

JointscrewthreadDrivingscre10RectanglescrewthreadTrianglescrewthreadTrapeziumscrewthreadHacklescrewthreadright-handthreadleft-handthreadsingle-startthreadmulti-startthreadexternalthreadinternalthreadscrewpairAccordingtothetypeoftoothofscrewthreadTypesofscrewthreadAccordingtothedirectionofrotationofscrewthreadAccordingtothenumberofhelicallineAccordingtoinsideandoutsidesurfaceofsolidofrotationAccordingtoThefunctionofscrewthreadAccordingtotheshapeofbodyofrevolutionJointscrewthreadDrivingscrewthreadScrewdriveparallelscrewthreadtaperscrewthreadRectanglescrewthreadright-ha11(1)majordiameterd

与外螺纹牙顶(或内螺纹牙底)相重合的假想圆柱体的直径。(2)minordiameterd1

与外螺纹牙底(或内螺纹牙顶)相重合的假想圆柱体的直径。

(3)pitchdiameterd2

也是一个假想圆柱的直径，该圆柱的母线上牙型沟槽和凸起宽度相等。βd1d2d(4)threadpitchP

相邻两牙在中径线上对应两点间的轴向距离。(5)LeadSS=nP(6)leadangleψ

中径d2圆柱上，螺旋线的切线与垂直于螺纹轴线的平面的夹角

(7)includedangleα

轴向截面内螺纹牙型相邻两侧边的夹角。牙型侧边与螺纹轴线的垂线间的夹角。tgψ=πd2

nP

flankangleβαβψπd2Sψ同一条螺旋线上的相邻两牙在中径线上对应两点间的轴向距PⅡPrimarygeometryparametersofscrewthreadSPP/2P/2

(8)contactheighth

内外螺纹旋合后，接触面的径向高度。h(1)majordiameterd与外螺纹牙顶(或12Themajordiameterofregularscrewthreadsisthenominaldiameter.Thereareavarietyofthreadpitchesofthesamenominaldiameter.Thereintothescrewthreadhavingthemaximalthreadpitchiscalledcoarsethread,andtherestarecalledfinethreads.60˚Precisiongradeofscrewthread:AgradeBgradeCgradeUsinginsuchoccasion:smalltolerance,highestprecision,usingintheoccasionthatthefitispreciseUsinginsuchoccasion:Bearingheavyloadandbeingdisassembledoradjustedfrequentlyorbearingvariableload/fluctuatingloadUsingingeneraljoint,inmostcommonuseCoarsethreadisappliedmostwidely.Theadvantagesoffinethread:leadangleissmall;minordiameterisgreat;thecapabilityofselflockingisgood;anddegreeofstrengthishigh.Thedisadvantagesoffinethread:wearresistanceispoorandeasilywear。Application:thinwallpart,thejointbearingvariableloadandfineregulationmechanismPdCoarsethreaddPFinethreaddPFinethreadThemajordiameterofr13

TrapeziumscrewthreadTrapeziumscrewthreadHacklescrewthread

30º3º30º为了减少摩擦和提高效率，这两种螺纹的牙侧角β比三角形螺纹的要小得多。用于剖分螺母时，梯形螺纹可消除因摩擦而产生的间隙，应用较广。锯齿形螺纹的效率比矩形螺纹高，但只适合单向传动。HacklescrewthreadUsuallyusingintransmission。β=15ºβ=3º

Basicdimensionsofregularcoarsethread、regularfinethreadandtrapeziumscrewthreadvideposttables(orrefertocorrelatedmanualsofmachinedesign).Basicdimensionsofscrewthread:TrapeziumscrewthreadTrapezi14

Diameterandpitch,basicdimensionsofcoarsethreadmm30.52.6752.459Nominaldiameter（majordiameter）coarsethreadfinethreadDdthreadpitchPpitchdiameterD2d2minordiameterD2d2threadpitchP40.73.5453.24250.83.5454.1340.350.5615.3504.91881.257.1886.647101.59.0268.3761.25,10.75121.7510.86310.1061.5,1.250.5(14)212.70111.8351.5,116214.70113.835(18)2.516.37615.294202.518.37617.294(20)2.520.37619.29424322.05220.752(27)325.05223.752303.527.72726.2112,1.5,1Note:thenominaldiameterinthebracketisthesecondseriesH=0.866Pd2=d-0.6495Pd1=d-1.0825PD1、d1----minordiameterofinternalandexternalthreadD2、d2----pitchdiameterofinternalandexternalthreadD、d

----majordiameterofinternalandexternalthreadP----threadpitchExampleofmark：M24(regularcoarsethread、diameter24、pitch3)M24X1.5(regularfinethread、diameter24、pitch1.5)PP/8P/8P/8H/4DdD2d2D1d1P/2P/430˚60˚90˚Diameterandpitch,basicdime15

BasicdimensionofregularfinethreadmmPitchPpitchdiameterD2、d2minordiameterD1、d10.35d-1+0.773d-1+0.6210.5d-1+0.675d-1+0.4590.75d-1+0.513d-1+0.1881d-1+0.35d-2+0.9181.25d-1+0.188d-2+0.6471.5d-1+0.026d-2+0.3762d-2+0.701d-3+0.8353d-2+0.052d-4+0.752Basicdimensionofregularf16

BasicdimensionoftrapeziumscrewthreadmmExampleofmark：Tr48X8(trapeziumscrewthread，diameter48，pitch8)Threadtoothheight牙顶clearance

nominaldiameterdpitchdiameter

minordiameterofinternalthreadpitchPh3=H4

ac1stseries2ndseriesD2d2D1

126.50.590、10085、95d-6d-12105.50.540、70、8038、42、65d-5d-1086.50.548、5246、50d-4d-842.250.2516、2018d-2d-452.750.2524、2822、26d-2.5d-562.250.532、3630、34d-3d-6InternalthreadExternalthreaddPR1R2D1D4H1D2d2d3acac30˚

H4R2Basicdimensionoftrapeziu17

dd2d1PGasthreadusingscrewsealRegularfinethreadgasthreadGasthreadnotusingscrewseal（shellofcylindricalpipeα=55˚）Gasthreadusingscrewseal（shellofconicalpipeα=55˚）60˚conicalgasthreadNominaldiameter---nominaldiameterofpipehole强调与普通螺纹不同55˚55˚Gasthreadnotusingscrewsealdd2d1Pφ2φdd2d1PGasthreadusingscr18

§5－2TypesofscrewjointandstandardjointerⅠ

Basic

typesofscrewjointBoltedjointBasictypes

eaal1l1可承受横向载荷。Remaininglengthofthreadl1ReamedholeboltClearancebetweenholeandbodyofscrewStaticloadl1>=(0.3~0.5)d;Variableloadl1>=0.75d;Reamedholeboltl1≈0;用于经常拆装易磨损之处。

ddShockloadorbendingloadl1≥d;Extensionelongationofthreada=(0.2~0.3)d;Distancebetweentheaxisofboltandtheedgee=d+(3~6)mm§5－2Typesofscrewjoint19

ScrewjointScrewingdepthinthebaseH，Whenthematerialofscrewholeis：aeeStudjoint件厚，允许拆装。SteelorbronzeH=d;Castiron

H=(1.25~1.5)dAluminiumalloy

H=(1.5~2.5)dDepthofscrewholeH1=H+(2~2.5)P;DepthofdrillingH2=H1+(0.5~1)d;Parametersl1、e、aisthesameasbolt’sl1l1HHH1H1H2H2结构简单，省了螺母，不宜经常拆装，以免损坏螺孔而修复困难。d§5－2TypesofscrewjointandstandardjointerⅠBasic

typesofscrewthreadjointBoltedjointBasictypesScrewjointScrewingdepthi20

holdingscrewjointholdingscrewjoint

ScrewjointStudjoint§5－2TypesofscrewjointandstandardjointerⅠBasic

typesofscrewthreadjointBoltedjointBasictypesholdingscrewjointholdingsc21

ⅡScrewthreadfastenerboltScrewthreadfastenerStructureofboltLL0dhexagonheadLdL0SmallhexagonheadⅡScrewthreadfastenerboltS22dL0L1LL1-----lengthofoneendfittinginthebaseL0-----lengthofanotherendfittinginthenutstudⅡScrewthreadfastenerboltScrewthreadfastenerdL0L1LL1-----lengthofoneen23EndstructureHeadendstructureScrew、holdingscrewstudⅡScrewthreadfastenerboltScrewthreadfastenerEndstructureHeadendstructur24

foundationbolt

HoistingboltSpecialscrewthreadjointTtypeboltScrew、holdingscrewstudⅡScrewthreadfastenerboltScrewthreadfastenerfoundationboltHoistingbol25hexagonnutFlathexagonnutThickhexagonnutroundnut用于经常拆装易磨损之处。用于尺寸受限制之处。国标罗列有六十余种不同结构的螺母NutSpecialscrewthreadjointScrew、holdingscrewstudⅡScrewthreadfastenerboltScrewthreadfastenerhexagonnutFlathexagonnutThi26

Othernuts：Othernuts：27

Othernut：Othernut：28washerplainwasherthinplainwasherAtypeplainwasher

Btypeplainwasher

BevelwasherSpringwasherclampingwasherusingbyroundnutFunction:toincreasethebearingareainordertodecreasepressure,toavoidscratchingthesurfacewhiletighteningup,topreventlooseness.NutSpecialscrewthreadjointScrew、holdingscrewstudⅡScrewthreadfastenerboltScrewthreadfastenerwasherplainwasherthinplainw29§5－3Pre-tighteningofscrewthreadjointPre-tighteningforce：themajorityofscrewthreadjointneedtobetightenedwhilefittinginordertobearloadbeforesupportingserviceload.Thisloadiscalledpre-tighteningforce.Theaimofpre-tightening:toenhancethereliabilityandtightnessofjoint,topreventappearanceofgaporrelativemoveafterbearingload.Principleofdeterminationofpre-tighteningforce:thepre-tighteningstressaftertighteningupisnotmorethanthe80percentofthematerial’slimitofyieldingss.

ⅠOverview一般螺纹联接在装配时都必须拧紧，这时螺纹联接受到预紧力的作用。对于重要的螺纹联接，应控制其预紧力，因为的大小对螺纹联接的可靠性，强度和密封均有很大影响。Carbonsteelbolt:Qp≤(0.6~0.7)σsA1Alloysteelbolt:Qp≤(0.5~0.6)σsA1A1---theareaofminimumlifesection，A1≈πd21/4§5－3Pre-tighteningofscrewt30ⅡtighteningtorqueT1—conquerresistancetorquewhilerelativelyrotatingT2—conquerfrictionresistancetorqueonthesupportingareaofnutIfaxialforceisFa或预紧力（不受轴向载荷）fc—frictioncoefficient.whilehavingnolubrication：fc=0.15rf—radiusofsupportingarea

rf=(dw+d0)/4Simplifiedformula：适用于M10~M60的粗牙螺纹，f’=0.15,fc=0.15,

T≈0.2FadFaFa是由联接要求决定的，为了发挥螺栓的工作能力和保证预紧

可靠，应取：Generaltorque：

Notice:Forimportantjoint,theM12boltshouldbeadoptedtothebestofone'sabilities.Td0ddwⅡtighteningtorqueT1—conquer31

measuringtorquespannerControlmethodsofpre-tighteningforce:联接用三角形螺纹都具有自锁性，在静载荷和工作温度变化不大时，不会自动松脱。但在冲击、振动和变载条件下，预紧力可能在某一瞬时消失，联接仍有可能松动。高温下的螺栓联接，由于温度变形差异等，也可能发生松脱现象（如高压锅），因此设计时必须考虑防松。即防止相对转动。FfixedtorqueSpanner通常螺纹联接拧紧是凭工人的经验来决定的，重要螺栓则必须预紧力进行精确控制。LS1)dependonexperience；2)measuringtorqueSpanner；3)fixedtorqueSpanner；4)Measuringelongationamount。LMLSmeasuringtorquespannerCont32

联接用三角形螺纹都具有自锁性，在静载荷和工作温度变化不大时，不会自动松脱。但在冲击、振动和变载条件下，预紧力可能在某一瞬时消失，联接仍有可能松动而失效。高温下的螺栓联接，由于温度变形差异等，也可能发生松脱现象（如高压锅），因此设计时必须考虑防松，即防止相对转动。Functionsofloosenesspreventing：1.LoosenesspreventingusingadditionalfrictionfeltcylinderlocknutSpringwasheroppositeverticalnut§5－3LoosenesspreventingofscrewjointLoosenesspreventing—topreventrelativerotationofscrew-pair联接用三角形螺纹都具有自锁性，在静载荷和工作温度变化不大时33

cotterpin&hexagonslottednutseriesconnectionsteelwire2.Loosenesspreventingusingspecialelement

clampingwasherbyroundnut

clampingwashercotterpin&hexagonslotted343.Other

loosenesspreventingfunctions1~1.5PTopunch2-3dotsusingpunchpinloosenesspreventingbypuncheddotsloosenesspreventingbyagglutinateLayingbondon3.Otherloosenesspreventing35§5－5StrengthcalculationofscrewjointMainfailureformsBoltbearingtensilestressplasticdeformation螺纹部分fatiguefractureBoltsbearingshearstressshearingcrash螺杆和孔壁的贴合面fracture--axialvariableloadOftendismountedwear§5－5Strengthcalculationo36

螺栓与螺母的螺纹牙及其他各部尺寸是根据等强度原则及使用经验规定的。采用标准件时，这些部分都不需要进行强度计算。所以，螺栓联接的计算主要是确定螺纹小径d1，然后按照标准选定螺纹公称直径d及螺距P等。ⅠStrengthcalculationoflooseboltjointStrengthcondition：Informula:d1----threadminordiametermm，

[σ]—allowablestressⅡStrengthcalculationoftightenedboltjointFaFa力除以面积Designformula：装配时须要拧紧，在工作状态下可能还需要补充拧紧。1.Tightenedboltjointonlybearingpre-tighteningforce2.tightenedboltbearingaxialload3.tightenedboltbearingshearingforce装配时不须要拧紧螺栓与螺母的螺纹牙及其他各部尺寸是根据等强度原则及使用经验37BoltbearsdualactionofaxialtensileloadF0andfrictiontorqueT1Tensilestress：Strengthoftightenedboltjointonlybearingpre-tighteningforceTorsionshearstress：ForM10-M64commonsteelscrewthread,itcanbeadopted:tgρ’≈f’=0.17，d2/d1=1.04-1.08,tgρ’≈0.5so：

τ≈0.5σ分母为抗剪截面系数Calculatedstress：由此可见，对于M10—M64普通螺纹的钢制紧螺栓联接，在拧紧时，虽然同时承受拉伸和扭转的联合作用，但在计算时，可以只考虑拉伸强度计算，并将预紧力增大30%来考虑扭转的影响。Intensitycondition:Boltbearsdualactionofaxia38

Whilebearingtransverseworkingload,thefrictiononthejointfacegeneratingbypre-tighteningloadF0shouldbemorethantransverseloadF.C---reliabilitycoefficient,usuallyisC=1.1~1.3Pre-tighteningloadF0

：f---frictioncoefficient,forsteelandcastiron,itis

f=0.1~0.15m---thenumberofjointface上图m=1,下图m=2Iff=0.15，C=1.2,m=1,then：F0

≥8F→configurationdimensionisgreatFFFF/2F/2F0F0F0F0Whilebearingtransversewo39

FF/2F/22.Intensityof

tightenedboltbearingaxialloadImprovemeasure：a.Adoptkey,sleeve,pintobeartransverseload.螺栓仅起连接作用b.Adoptreamedholebolthavingnoclearance.Tosupposethatthepressureofliquidisp,boltnumberisZ,thentheaverageloadofeachboltaroundthecylinderbodyis:p·πD2/4F

=ZpFFD

FF/2F/22.Intensityoftight40

LoadingdeformingEspecialnote,axialload:F2≠F0+FAfteraddingpre-tighteningforce→elongationofboltisλb0→shorteningofjointedpieceisλm0AfterloadingF:ThetotalelongationamountofboltincreasedtoTotaltensileforceis：TheshorteningofjointedpiecedecreasedtoTheremnantpre-tighteningforcedecreasedto:F1

Obviously:F1<F0被联接件放松了∆λ+λb0λm0-∆λ

LoosenessstatePre-tightenedstateλb0F0F0λm0FFF0F0FFFFF2F2F2=F+F1∆λF1F1∆λ

LoadingEspecialnote,axial41

λb0∆λJointerdeformingforceBoltdeformingforce∆Fb∆FmBoltdeformingforceF2F1FF0F0λm0F0λb0λC0arctgCbarctgCmλb0∆λJointerdeformingforceB42

forceBoltdeformingarctgCb

---relativestiffnesscoefficientF=∆Fb+∆Fm=(Cb+Cm)∆δCb+CmCbF2=F0+FCb+CmCbF1=F0

–F

1-F1=F0-∆F=F0

-Cm∆δF2=F0

+∆Fb=F0

+Cb∆δCb+CmF∆λ=FF2∆FbF0∆λthen：Table5-4bolt’srelativestiffnesscoefficientTypeofwashermetalwasherorwithoutwasherleathercoppersheetrubber0.2~0.30.70.80.9Cb+CmCb∆FmF1forceBoltdeformingarctgCb433.

tightenedboltbearingshearingforce这种联接是利用铰制孔用螺栓抗剪切来承受载荷的。螺栓杆与孔壁之间无间隙，接触表面受挤压。在联接结合面处，螺栓杆则受剪切。Extrusionintensityconditionofboltandholewallis:Shearingintensityconditionofboltis:F－workingshearingforceofbolt,itsunitisN;LminReamedboreboltFFd0Itshouldbedesignedtobe:Lmin≥1.25d0d0－diameterofbolt’sshearingsurface(itcanbediameterofbolthole),itsunitismm;Lmin－theminimumofheightbetweenboltandholewall,itsunitismm;3.tightenedboltbearingshea44§5－6Designofjointofscrewboltgroup在设计螺栓组联接时，关键是联接的结构设计。它是根据被联接件的结构和联接的用途，确定螺栓数目和分布形式。▲inordertobeconvenienttoprocessingandsymmetricallylayingbolts,ensureloadinguniformlyonthejointsurface,thegeometryshapeofjointfaceisusuallydesignedtobesimpleaxialsymmetrygeometryshape:ⅠStructuredesignofscrewboltgroupjointBasicprinciple:Boltisusedingroupinmajorityofmachine.circularity

circularringrectangle

rectanglerimtriangle§5－6Designofjointofscrew45▲Boltlayingshouldmakeeachboltbearloadreasonably

FFForreamedboreboltjoint,don’tlaymorethan8boltsinlineinparallelwiththedirectionofserviceloadlestloaddistributingistoouneven.

reasonableunreasonableb)Whenboltjointbearbendingmomentortorque,thelocationofboltsshouldneartheedgeofjointsurfacetolessenloadofbolt.▲Boltlayingshouldmakeeach46

dhD▲thearrangeofboltsshouldhavereasonablespace,edgedistancetoguaranteespannerroomage.c)Whenbearingaxialloadandbiggishtransverseloadinthesametime,thepartresistingshearingshouldbeadoptedtoenduretransverseload.60˚CCEE60˚扳手空间的尺寸见有关标准。ABdhD▲thearrangeofbolts47▲forthesakeofindexandscribingconvenientlywhiledrillingaroundthecircle,thenumberofboltdistributingonthesamecircleisusuallychose:

Forsuchimportantjointaspressurevesseletc.ofwhichcompactnessisdemandedhigh,spacebetweenboltsshouldbelessthanthevaluerecommendedbythetablebelow.t0Spacebetweenboltst0workingpressure(MPa)7d4.5d4.54d3.53dt0(mm)≤1.61.6~44~1010~1616~2020~30d4,6,8etcevennumber.Thematerial,diameterandlengthofboltsinthesamegroupshouldbeuniform.▲forthesakeofindexandscr48

保证被联接件，螺母和螺栓头支承面平整，并与螺栓轴线相互垂直。对于在铸、锻件等的粗糙表面上安装螺栓时，应制成凸台或沉头座。当支承面为倾斜表面时，应采用斜面垫圈等。▲toavoidboltbearingadditionalbendingload.Adoptingdummycluborcounterborecuttingbearingsurface

BearingsurfaceisnotsmoothBearingsurfaceinclineAdoptingbevelwasher保证被联接件，螺母和螺栓头支承面平整，并与螺栓轴线相49ⅡLoadanalysisofjointofboltgroup▲theaimofloadanalysis:Accordingtothestructureofjointandtheconditionofloading,theboltloadingmostheavilyanditsloadshouldbefoundout,sothattheintensityofboltjointcanbecalculatedout.▲hypothesismadeinloadanalysis:

a)thematerial,diameter,lengthandpre-tighteningloadofallboltsarethesame.c)jointsurfaceremainsplaneafterloading.

▲typesofloadanalysis:b)symmetrycenterofboltgroupandcentreoffigureofjointsurfacearematchedtogether.BearingtorqueBearingtransverseloadBearingaxialloadBearingupsettingmomentMⅡLoadanalysisofjointofbo50

（1）forreamedboreboltjoint,workingshearingloadofeachboltis:（2）Forcommonboltjoint,accordingtothedemandthatthemaximumoffrictiongeneratingbetweenjointsurfacesafterpre-tightenedmustmorethanorequaltotransverseload,thereis:Informula:zisthenumberofbolts.图示为由四个螺栓组成的受横向载荷的螺栓组联接。1．JointofboltgroupbearingtransverseloadorKsisskidpreventioncoefficient,indesignitcanbechoseas:Ks=1.1-1.3.ReamedboreboltF∑F∑F∑F∑Commonbolt（1）forreamedboreboltjoin51

TO

O采用普通螺栓和铰制孔用螺栓组成的螺栓组受转矩时的受力情况是不同的。2．Jointofboltgroupbearingtorque

Adoptingcommonbolt,itdependsonthefrictiongeneratingbetweenjointsurfacestoresistthetorqueT.

Adoptingreamedborebolt,itdependsonactionofshearingofboltandextrusionbetweenboltandholewalltoresistthetorqueT.TrmaxFmaxr1fF0fF0r2riFi假设底板受载仍为平面，则螺栓的剪切变形量与距离成正比，F=Kri剪切力与距离r的比值为常数TOO采用普通螺栓和铰制孔用螺栓组成的螺栓组受转矩时的受523．Jointofboltgroupbearingaxialload

IfthetotalaxialloadFΣactingonboltgroupisparallelwiththeaxisofboltandthroughthesymmetrycenter,loadingoneachboltisequal.Workingloadofeachboltis:

Usually,eachboltalsobearspre-tighteningload.Ifthepre-tighteningloadF1isguaranteed,thetotalloadofeachboltF2is:F2=F1+Fp

DF∑FF3．Jointofboltgroupbearing53

倾覆力矩M作用在联接接合面的一个对称面内，底板在承受倾覆力矩之前，螺栓已被拧紧并承受预紧力F0且被拉伸，地基有均匀的压缩。在作用M后，接触面绕o-o线转动一个角度，左边的地基被放松，而螺栓被进一步拉伸；右边的螺栓被放松，而地基被进一步压缩。Thetorquegeneratedbythetensileforceofsingleboltis:F1F0

F0

σp

(

F

0cause)F2mσp2(

F1mcause)σp1(

F1cause)LiLmaxOOxxOMMMi=FiLi假设底板受载仍为平面，则螺栓受力与螺栓中心到螺栓组排列中心的距离成正比。Loadborebyboltisnproportiontodistance:4．Jointofboltgroupbearingupsettingmoment倾覆力矩M作用在联接接合面的一个对称面内，底板在承54

F1m

强调是基座上的压力Fm

F2m

F1

F

F2

C2

Loadanalysisofsinglebolt:Om

force

deformationOb

CompositetorqueloadingontheflankofmotherboardandupsettingtorqueMbalance,then:Whileloadingnoupsettingmoment,actionspotisA.∑Mi=0WhileloadingupsettingmomentM:ActionpointofleftboltmovedtoB1

andC1ActionpointofrightboltmovedtoB2

and

C2

左边螺栓总拉力增加，右边螺栓总拉力减小。F2

F2m

C1

B2

B1

求得最大工作载荷A

F0

F1m强调是基座上的压力FmF2mF1FF2C55Totaltensileforceofbolt:Topreventjointsurfacebeingcrushedwherepressureisbiggestorappearingclearancewherepressureisleast,itisrequired:Table8-5allowableextrusionstressofmaterialofjointsurfaceMaterialsteelcastironconcretebrick(groutcrack)wood[σ]p(Mpa)0.8σs(0.4~0.5)σB2.0~3.01.5~2.02.0~4.0直接引用前面的结论Totaltensileforceofbolt:56§5－7material&allowablestressofboltⅠMaterialofscrewthreadjointerUsualmaterialofbolt,screw:Q215、Q235、35、45etccarbonsteel；Specialuse(antimagnetic,electricconduction):specialsteel,copperalloy,aluminumalloyetc.Thecapabilitygradeofboltdividedinto10level.3.64.64.85.6586.88.89.810.912.9作为标准零件，螺纹联接件是按其性能等级选用的。对于一定性能等级的螺纹联接件应具备一定的强度极限。Usingintheoccasionofimpactandvibration:15Cr、40Cr、30CrMnSietcalloysteel.Washer:：Q235、15、35washer：65Mn§5－7material&allowables57Chooseprinciple:Commonuse:about4.8gradeboltisusuallychose;Importantoccasion:highercapabilitygradeboltshouldbechose;

8.8gradeboltisoftenchoseinthepressurevessel.Thecapabilitygradeofnutisdividedinto7level.456891012Chooseprinciple:Thecapabili58ⅡAllowablestressofscrewthreadjointer

Allowablestressofscrewthreadjointerisrelatedwithloadcharacter(staticandvariableload),assemblingcondition(loosenessjointandtightenjoint),materialandstructuredimension.Allowabletensilestress:Allowableshearstressandextrusionstress--jointerissteel--jointiscastironSτ,Sp---safetyfactor,theirvaluesvideinfratableⅡAllowablestressofscrewth59

Table5-11safetyfactorSofboltjointCarbonsteel5~44~2.52.5~2Carbonsteel12.5~8.58.58.5~12.5M6~M16M16~M30M30~M60M16~M16M16~M30M30~M60LoadtypestaticloadvariableloadLoosenessboltjoint1.2~1.7Alloysteel5.7~55~3.43.4~3Alloysteel10~6.86.86.8~101.2~1.51.2~1.5(Sa=2.5~4)steel：Sτ=2.5，Sp=1.25，ste