河南理工大学材料力学第十一章 交变应力

1、Mechanics of MaterialsChapter 11 Alternating Stress (Alternating Stress) (Alternating Stress) (Calculation of the fatigue strength of the member under symmetric cycles) (Calculation of the fatigue strength of the member under unsymmetric cycles)(Alternating Stress)APt(Alternating Stress)(Alternating

2、 Stress)静平衡位置静平衡位置tt st max min(Alternating Stress)PP tzAtry sintIrMIyM sint 1 2 3 4 1O(Alternating Stress) (Alternating Stress) 裂纹缘裂纹缘光滑区光滑区粗糙区粗糙区 (Alternating Stress)(Alternating Stress)(Alternating Stress)一个应力循环一个应力循环O t maxminr maxminr max min(Alternating Stress)aO一个应力循环一个应力循环 t max min a a2minm

3、ax a2minmaxm (Alternating Stress)O max min t1maxmin rmax a0m (Alternating Stress)（min1r0maxmin r2maxma O max min=0 t(Alternating Stress)1r0a maxm O max min=0t (Alternating Stress)MPa5610115. 05830042maxmax APMPa2 .5370115. 05580042minmin APMPa1225375612minmaxa MPa54925375612minmaxm 957. 0561537maxmi

4、n r(Alternating Stress) Endurance limit or fatigue limit of a materials(Alternating Stress) max，1 -1 max，2N1N212N max 0Nr (Alternating Stress)PPPPaab 1max,2max, 1max, -1 max，1 max，2N1N212N maxPa(Alternating Stress) (Alternating Stress)0.020.040.060.080.100.120.140.16 0.180MM1 . 1dDRdD1.001.201.401.6

5、01.802.002.202.402.60 KMPa500b 600700800900MPa1000b dr(Alternating Stress)0.020.040.060.080.100.120.140.16 0.180MM2 . 11 . 1dDRdD1.201.401.601.802.002.202.402.602.80 KMPa500b 600700900MPa1000b dr3.003.20800(Alternating Stress)MM22 . 1dDRdD0.020.04 0.06 0.080.10 0.12 0.14 0.160.180drMPa1000b 80090070

6、0600MPa500b K1.201.401.601.802.002.202.402.602.803.003.203.40(Alternating Stress)TTRdD2 . 11 . 1dDMPa1000b 800MPa700b 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.180dr1.201.401.601.802.002.202.401.00 K900(Alternating Stress)0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.180drTTRdD22 . 1dD1.201.401.601.802.

7、002.202.401.00 K2.602.80MPa700b 800MPa1000b 900(Alternating Stress)11)( (Alternating Stress) (Alternating Stress) d)()(11 (Alternating Stress)101 K K 1 rrK 0 (Alternating Stress) (Calculation of the fatigue strength of the member under symmetric cycles)1011 1 Knn1011 1 Knn1max nKn1max nKn1max (Alter

8、nating Stress)f f50f f40r=525. 14050dD125. 0405dr77. 0 MPa1000b 55. 1 KMPa900b 55. 1 KMPa920b 55. 1 K(Alternating Stress)MPa1000b 28. 1 KMPa900b 25. 1 KMPa920b 26. 1)900920(90010025. 128. 125. 1 K81. 0 (Alternating Stress).MMf f50f f40r=5MPa2 .6505. 0328003minmax WM1maxmin r(Alternating Stress) 4 .

9、1 KMPa600 ; 15. 0 ; 4 . 1bdrdD 79. 0 nKn12. 22504 . 15 .6294. 079. 0 1max (Alternating Stress) 107r0.25r0r-1(Alternating Stress) amOamPmaxma rr 11tanminmaxminmaxma (Alternating Stress) amOamPP(Alternating Stress) A20 CbBamOamPP2/2/tan001 m1arr (Alternating Stress) (Calculation of the fatigue strengt

10、h of the member under unsymmetric cycles)sOBHIJCFKGPEALmmaasm, OIPIarGHOH (Alternating Stress)mma1m Krama1 KGHamrmamm GHGHOHnr)(rm1 KGHmrmaGH (Alternating Stress)nn nKn ma1 ma1 Knamrmamm GHGHOHnrmma1m Krama1 KGH(Alternating Stress)3633m1028. 6)04. 0(3232 dWMPa5 .811028. 65126maxmax WM MPa3 .1651maxm

11、in 2 . 051maxmin rmm2截面截面mm40(Alternating Stress)MPa9 .4823 .165 .812minmaxm MPa6 .322minmaxa 05. 04020 ddMPa950b 18. 2 K77. 0 77. 0 (Alternating Stress)21. 49 .482 . 06 .32177. 018. 2430ma1 KnSmaxS62. 65 .81540nn (Alternating Stress)nnnnnn 22 n n(Alternating Stress)R5TTMM50600.40.4MPa3 .81103 .121000MPa3 .81103 .1210006minmin6maxmax WMWM 3633m103 .123205. 032 dW1maxmin r(Alternating Stress)3633m106 .241605. 016 dWt61MPaPa1061106 .24150066maxmax tWT 0min 0maxminmin rMPa5 .302maxa MPa5 .302maxm (Alternating Stress)1 . 0105, 2 . 15060 d