材料力学复习例题课堂PPT

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1、12F1F2F3l1l2l3ABCD3F1F2F3l1l2l3ABCDF1FN1)(kN2001N1N1 FFF4F2F1FN2F1F2F3l1l2l3ABCD)(kN1502N2N21 FFFFFFN3)(kN5003NR3N FFFD5FN2=-15kN（-）FN1=20kN（+）FN3=-50kN（-）15+-2050F1F2F3l1l2l3ABCD6FN2=-15kN (-)FN1=20kN（+）FN3=-50kN(-)F1F2F3l1l2l3ABCD)(MPa.N 8 81 17 76 61 11 1AFAB)(MPa.N 6 67 74 42 22 2AFBC)(MPa.N 5 5

2、1101103 33 3AFDC 进行强度校核时一定要找出构件内进行强度校核时一定要找出构件内应力最大的截面，才是危险截面，应力最大的截面，才是危险截面，一般在横截面尺寸较小或内力最大一般在横截面尺寸较小或内力最大的位置上的位置上因因(max-)/=4%5%,因此因此该结构仍是安全的该结构仍是安全的7m102.534-N 1 11 11 1EAlFlABm101.424-N 2 22 22 2EAlFlBCm101.584-N 3 33 33 3EAlFlCD-0.3mm BCCDBllumm10-0.474-CDBCABADllllF1F2F3l1l2l3ABCD8 CABDF 1 12 2

3、3 3xyFA 2 21 10 0NNFFFx 0coscos03N2N1N FFFFFy 9CABDF 1 12 23 3xyFA CABD 1 12 23 3103 3l A1 12 23 3 CABDF 1 12 23 3CABD 1 12 23 31 1l cos3 31 1ll 1 11 11 11 1EAlFlN 3 33 33 33 3AElFl cosN 2 23 33 33 31 1cosNNAEEAFF 11CABDF 1 12 23 33 3l A1 12 23 3 1 1l 2 23 33 32 21 12 21 1coscosNNAEAEFFF 2 21 1NNFF

4、0 03 32 21 1 FFFFNNNcoscos 2 23 33 33 31 1cosNNAEEAFF 2 23 33 33 32 21 1cosNAEEAFF 1213M1M2ABCll14Me1Me2ABCll1Me2CT12Me2CMe1BT2 4kNm2kNm+_15T maxtmaxmaxWT M1M2ABCllMPa5.34)1(1643max DT max16ABCMeAMeBMeC22 14+_MPa84.6416/)12.0(102216/33311t11max1 dTWTMPa3.7116/)1.0(101416/333222t2max2 dTWT17 0 xM1816

5、3maxtmaxmaxDTWTmTD0272.0163max191803218004max0maxmaxDGTGITpmGTD0295.018032420max对于轴而言，其主控因素是刚度，因此由刚度条件算对于轴而言，其主控因素是刚度，因此由刚度条件算出的轴直径会比强度大。该轴除受扭外还受弯曲的作出的轴直径会比强度大。该轴除受扭外还受弯曲的作用，因此在机械设计中，一般按扭矩进行估算，设计用，因此在机械设计中，一般按扭矩进行估算，设计好轴的结构后再按弯扭进行校核。好轴的结构后再按弯扭进行校核。2021)2(12axaqaFS)2()2(1122axaaxqaqaMx122 FEqABCD0.21

6、.612kN806.11005.0RRBAFF23+80kN80kNkN80RS AAFF右 kN80RS ACFFkN80RS BDFFkN80RS左 BBFFkN0S右右BF kN80maxS FFEqABCD0.21.61224mkN162.0RBDFM0MBmkN48maxMmkN162.0RACFM0MAFEqABCD0.21.612mkNqFMRAE.4828.08.011616+4825ACBFa2a203014FRAFRBFa433cm07.112)cm2)(cm4.1(12)cm2)(cm3(zI34maxcm07.11cmcm07.1 yIWzzmaxWMz kN3 aWF

7、WFazz26zF1=9kNF2=4kNACBD1m1m1m80y1y2202012027FRAFRBF1=9kNF2=4kNACBD1m1m1mkN52R.FA kN510R.FB mkN5.2 MCmkN4 MB MPa2.27t1maxtIyMzB MPa2.46c2maxcIyMzB MPa8.28t2maxtIyMzC 80y1y22020120z-+4 kNm2.5 kNm28lABxF29xlwABxF()()(1)M xF lx ()(2)EIwM xFlFx 21 (3)2FxEIwFlxC 2312(4)26FlxFxEIwxCC 3021 (3)2FxEIwFlxC 23

8、12(4)26FlxFxEIwxCC 0,0 0,0 xwxw120 0CC22FxEIwFlx 2326FlxFxEIw 31BwmaxmaxxlyAF（）222max|22x lFlFlFlEIEIEI max maxw（）3max|3x lPlwwEI 32（）|0.00242Bx lrad （）|0.0805Bx lwwmm 33BqFACaaF=AB+ABq 2()4A FFaEI 3()6CFFawEI 45()24CqqawEI 3()3A qqaEI 34()()AA FA q2(34)12aFqaEI 435()246CqaFawEIEI qFF=+AAABBBCaaq 2(

9、)4AFFaEI 3()6CFFawEI 45()24CqqawEI 3()3AqqaEI 35l=400mmF2=2kNACa=0.1m200mmDF1=1kNBF2BCDA=+F2BCaF2BCDAM=+F1=1kNADCF2=2kNCABB36l=400mmF2=2kNACa=0.1m200mmDF1=1kNB 21116BF lEI 211116CBF l awaEI 20B 3223CF awEI 2333BMllaFEIEI 22333CBF lawaEI+F2BC图图2图图3+F2BCDAM=图图1F1=1kNDC37 212163BF lF laEIEI 2321221633C

10、F l aF aF a lwEIEIEI44441284()643.14 (8040)1064 188 10 mIDd F2=2kN=+图图1图图2l=400mmACa=0.1m200mmDF1=1kNBF1=1kNDBC图图3F2BDAMACCF238 23261225.19 10 m1633CF l aF aF a lwEIEIEI 212-40.4400200()1632101880163 +0.42310BF lF laEIEI maxwwll 65max5.19 10 m10 mww 4max0.423 100.001 3940A alA50,70,0 xyyx41依据约定可知：两个

11、角度依据约定可知：两个角度 中绝对中绝对值小的那一个确定值小的那一个确定429.10)70(50222tan0 yxxy 5 562625 527270 0.xA A MPaMPa)(minmax9 96 62 26 62 22 22 22 2xyyxyx MPa,MPa9 96 60 02 26 63 32 21 1 612)96(26231max4243FACD1.2m1.2mB30FFRAyFRAxFyxFNAB3002.14.230sin 0N FFMABAFFAB NFFFFFFAyyAxx5.00866.00RR MPa,MPa9 96 60 02 26 63 32 21 1 44

12、xFN图图FRAxxM图图F/445AFAFAx866.0R zzAyWFWF6.02.1Rmax MPa37.946.0866.0maxc zWFAFFACD1.2m1.2m30BFFRAyFRAxFyxFNAB3046yzz0z15050150150350FF47yzz0z15050150150350FF48nnFNMyyFFMFFy22N105.4210)5.735(yzz0z1505015015049MPa15NFAF nnFNMyyzz0z1505015050)(MPa53105.74250maxt FIzMyy)(MPa53105.124251maxc FIzMyy 5050150

13、150yzz0z1拉拉nnFNMy5153105.742515tmaxtmaxt FF5050150150yzz0z1拉拉压压nnFNMy5253105.12425cmaxcmaxc FAF5050150150yzz0z1拉拉压压nnFNMy535430mm20mmyz1p99E m0058.002.003.0)02.003.0(1213 AIiyy55m0087.0 AIizz15.0 zy 30mm20mmyz11586 zzzyyyilil kN5.8922crcr zEAAF 56ABCF0.60.30.8570 CM0 06 60 09 90 0 .sin.N FF8.06.08.0sin22 FF27272 2.N 1P99E 4dAIi ABCF0.60.30.858180 ils257ab 12 MPa214cr bakN268NcrcrFnAFstFF27.2N ABCF0.60.30.859