ChaptershaftdesignPPT学习教案

1、会计学1Chaptershaftdesign第1页/共73页第2页/共73页第3页/共73页第4页/共73页第5页/共73页第6页/共73页第7页/共73页按轴线的形状轴可分为：直轴，曲轴和挠性轴。第8页/共73页第9页/共73页第10页/共73页第11页/共73页第12页/共73页第13页/共73页第14页/共73页第15页/共73页第16页/共73页第17页/共73页inchesin gear theofdiameter pitch D inlbin gear on the torqueT rpmin speed n hpin ed transmittbeingpower p where2

2、)-(12 )2/(W1)-(12 / )(63000trotationalDTnPTThe angle between the total force and the tangential component is equal to the pressure angle,of the tooth form. Thus, if the tangential force is known, the radial force can be computed directly from第18页/共73页.25or ,2014.5 typicallyis angle pressure theall.a

3、t force total thecompute toneed no is thereand3)-(12 tantrWW第19页/共73页 load W angle pressure anglehelix the force; tan W where4)-(12 cos/tanrntradialnormalgentialWWntrload Wwhere5)-(12 tanxaxialWWtx第20页/共73页第21页/共73页第22页/共73页第23页/共73页The upper part of the chain is in tension,referred to the tight sid

4、e, and produces the torque on either sprocket.The lower part of the chain, referred to as the slack side, exerts no force on either sprocket.第24页/共73页sprocket theofdiameter pitch D where6)-(12 )2/(DTFcFc acts along the direction of the tight side of the chain. Because of the size difference between

5、the two sprockets, that direction is at some angle from the centerline between the shaft centers. A precise analysis would call for the force,Fc, to be resolved into components parallel to the centerline and perpendicular to it. That is sinF F and cosccyccxFFWhere the angle is the angle of inclinati

6、on of the tight side of the chain with respect to the x-direction第25页/共73页第26页/共73页8)-(12 )2/(Fed transmitt torque thefrom computed becan force drivingnet theof magnitude the7)-(12 N21DTFFFN第27页/共73页BFFF21But unless the two sprockets are radically different in diameter, little error will result from

7、 21FFFBTo determine the bending force,FB, a second equation involving the two forces F1 and F2 is needed. This is provided by assuming a ratio of the tight side tension to the slack side tension. For v-belt drives, the ratio is normally taken to be 5/21FF第28页/共73页11)-(12 FFCdetermined be oconstant t

8、C where10)-(12 2121NBFFFFCFFNBFrom equation (12-9), thenC=1.5FB=1.5FN=1.5T/(D/2) (12-12)第29页/共73页13)-(12 )2/(0 . 20 . 2DTFFNB第30页/共73页第31页/共73页第32页/共73页第33页/共73页第34页/共73页第35页/共73页runner) (sled 6 . 1K(profile) 0 . 2ttKEach of these is to be applied to the bending stress calculation for the shaft, usi

9、ng the full diameter of the shaft. The factors take into account both the reduction in cross section and the effect of the discontinuity.See reference 5第36页/共73页第37页/共73页)fillet (5 . 1)fillet (5 . 2roundedwellKsharpKttReferring to the chart for stress concentration factors in figure A15-1,these valu

10、es correspond to ratio of r/d of approximately 0.03 for the sharp fillet case and 0.17 for the well-rounded for a D/d ratio of 1.50。第38页/共73页第39页/共73页When torsion exists along with bending, or when only torsion exists at a section of interest, the stress concentration factor is not applied to the to

11、rsional shear stress component because it is steady.第40页/共73页第41页/共73页第42页/共73页第43页/共73页shaft. ain stressshear direct or stress,shear verticalstress,shear sionalsteady torfor value thisusecan we14)-(12 / )577. 0()3/(NsNsyyd第44页/共73页第45页/共73页)3/4(,considered be toarefactor ion concentrat stress where

12、section cross theof area A force shearing verticalV 3/4maxmaxAVKwhereAVt第46页/共73页15)-(12 )(433. 0)4()3(0.577SNgives Nfor 577. 03)4(Kgives ,3/ )4(let /577. 0 is thisstress,design a as exp/577. 0577. 0s isshear in strength endurance then the recommed isory energy the distortion the15)-(5 /ntmaxdmaxsnm

13、axVksVKAsolvingNsAVAVknowNsressedsNthenssNtntntdnnnsn第47页/共73页16)-(12 /)(94. 24/DAdiameter. required thedetermine toshaft theofdesign theis objective usualour )(31. 2433. 0)(2ntntntSNVKDbutsNVKSNVKA第48页/共73页But values for vertical shearing stress are rarely reported. As an approximation, we will use

14、 the values for Kt for torsional shear stress when using these equations.第49页/共73页第50页/共73页第51页/共73页19. 0s19. 0s068. 0s068. 0s85. 1Cmm)in (D than250mmless diameters Cinches)in (D10in than less diameters )6 . 7/(Cmm)in (D 50mm than less diameters )3 . 0/(CInches)in (Din 2.0 than lessdiameter DforDfor

15、DforDfor第52页/共73页Table 12-1 reliability factors, CR Desired reliability Reliability factor,CR0.50 1.000.90 0.900.99 0.810.999 0.75第53页/共73页Any stress concentration factor will be accounted for in the design equation developed later. Other factors, not consideration here, that could have an adverse e

16、ffect on the endurance strength of the shaft material, and therefore on the design stress, are temperatures above approximately 400F(200C);variation in peak stress levels above the nominal endurance strength for some periods of time;vibration;residual stresses; case hardening; interference fits; cor

17、rosion; thermal cycling; plating or surface coating; and stresses not accounted for in the basic stress analysis.第54页/共73页RsnnCCss 17)-(12 /Nsnd第55页/共73页第56页/共73页第57页/共73页第58页/共73页1)/3()/sN(konly, first term in the bendingfor factor ion concentrat stress a int,1)/3()/s(Nthen ory.energy the distorsio

18、n for the 3/s use willwe18)-(12 1)/()/(22nt22nys22yyyysnsNroducethensNsss第59页/共73页T/(2S)thereforemodulussection polar theis 16/ Zwhere21)-(12 T/Z is stressshear torsionalthemodulus.section recangular theis 32/DS where20)-(12 M/SisM,moment, bending a todue stress bending theshafts,circular solid,rotating, 3pp3Dfor第60页/共73页24)-(12 433232/Slet 22)-(12 123322322yntyntsTsMkNDDSsNTSsNMK第61页/共73页第62页/共73页第63页/共73页 TTTndPWT3632 . 01055. 910 MPa （7-13） 第64页/共73页第65页/共73页由上式可得轴的直径 3336362 . 01055. 92 . 01055. 9nPAnPnPdTT式中， TA362 . 0/1055. 9可根据不同材料查附表8-1 在计算中，当弯矩相对扭矩很小或只受扭矩时，取较大值，A取较小值；