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126alternativestressfatigue§26-1§26-22§26-3§26-4§26-5§26-6326§261262261262263tS4263stresscyclestressratior()minminmaxmaxSrSSS=≤26la()maxminmaxminSrSSS=≥26lbmeanStressSm2minmaxmSSS+=(262)(stressamplitude)Sa2minmaxmSSS=(263)maximumStressammaxSSS+=264minimumstressminmaSSS=-(265)symmetricalreversedcycleSmax=Smin,,maxam01SSSr==-=,,fluctuatingcycleSmin=00=rstaticalstress01amminmax====SSSSr,,5SSsStAFNx=s()zzIyM-=sPIMxrt=nominalstressllll264aslipbands264b264c2652646265dislocation104m~107mmicrocrack104m,macrocrack2662667endurancelimit267a267b267(SmaxNSN268SN268SN269abSN8269SN269aSN269bSNSNrSrS1SN107SN2×107§),KtnmaxtSSK=(266),SmaxSnsttKK→;tttKK→9efectivestressconcentrationfactor11f--='SSK2671-S1'-SSnotchsensitivityfactorq()ft11KqK=+-2686~10mm2613e()1d1--=sse2691-s()d1-s26910b()11--=ssbb26101-s()bs1-1§2611SmaxNlgSlgN2611N0(106)lgSlgN11CNSimi=2611mCSiNiSiNilgSlgNN0SNalternativestresswithequalamplitudenn](2612)nn[n]1.3[n]=1.51.8[n]=1.82.5nr=1ms=0maxass=0m=tmaxatt=af1ssebssKn-=261312aft1ttebtKn-=2614sntn11--tsftfsKKebSNSNSNSmax=SaebafSSKSNS=ebafSSKN(2612a)SaSaSNN2612b13alternativestresswithvaryingamplitude2613ab2613damagecumulativedamage1426142614abS1N1S2N2BD2614aS1FAE13n1=N1/3ES2EFS2F13n2=N232614bEFC→→EFlineartheoryofcumulativedamage1945MinerMAS1N=NlN=n1WW1111NnWW=(a)S2222NnWW=bSii=12niiiNnWW=(i=1,2,k)cWk=+++L21(2615)abc1511=∑=kiiiNn(2616)MinerCriterioniiNnSii12,klllll11=∑=kiiiNnSimmiS11=∑=kiimiimiNSnSdCNSimi=lgSlgN2610Cm2610BN0S101NSm-(d)imiNS∑=-=kiimimnSNS10111(e)(S1)1101-==∑SnSNmkiimi261716mkiiminSNS∑==10e12618NmaxmkiimieSNnSSNNS⎥⎥⎦⎤⎢⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛=∑=10max2619eSSn1-=(2620)SexmkiimxiNnNNKKnma1ma0fs1afs1ssssebssebs⎥⎥⎦⎤⎢⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛==∑=--2621maxmkiimmaxifNnNNKntttebttt⎥⎥⎦⎤⎢⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛=∑=-1012622[]nn≥s2623a[]nn≥t2623bl(k)SiS1S1lSinilSmaxlSNmN0lN[261]1s()26151-s=400MPam=9N0=3×1061550h,fsK=1.2170.1==bemaxs=500Mpa500500max1=ss,500450max2=ss,500400max3=ssNniTinTN151TT1=Nn,152TT2=Nn,1512TT3=Nn50hN=(50×60×60×15)=0.27×1072621031s.=n∑==kiiiNn1118NiniSiN∑==⋅kiiiNnNN1112624N∑=⋅=kiiiNnNN111(2625),NiSNSini/NN2616ni/NTTTNni/,TinSiNT2616[262]MPaisNi()5501500510100504802080045050500410125000380275000MPaisNi()510300019450120038080000as=480MPa?n4144332211=+++NnNnNnNnN1=10500,n1=30001s=510MPaN2=50500,n2=120002s=450MPaN3=275000,n3=800003s=380MPaN4=20800,n4=?4s=480MPa1208002750008000050500120001005030004=+++nas=480MPan4=3598reliabilityNSNlgSlgN261720505050501068standarddeviationupN=106'NS0.920.92'NS8up=12121)!1(2)12()1(33640621112753+⎟⎟⎠⎞⎜⎜⎝⎛---+++-+-=--nnuuuuuRnnpnppppLp(2626)up1R84.13up30.76'NSR=99.9N=10688up2618up=0up=1up=3508419999992618CRreliabilityfactorCR8413CR=0.92;999CR=076Rfs1CKSeb-aRfs1sSCKSneb-=(2627)SN1988707622llr=l01SmSaI199523261B1aFP2bFP261262B1am2bAC3cda4dB26-2263as=400MPa450MPa500MPa2.41051.61059104112526126420MPaNT=5750iasTinNiiiasMPaTinNi150019.0103247561.1610434231402.10104436213604.701045287100001.551056212460008.701057137140000∞863302500∞2426519MPaNT=115091iasTinNiiiasMPaTinNi1350115.61042332807.4104329814001.31054254136002.810552011000001.251066149460000∞7961400000∞8443025000∞