Probabilistic Fatigue Life Prediction Method for Notched Specimens Based on the Weakest-link theory

Transcription

1 Mechnicl Science nd Technology for erospce Engineering Februry Vol o Weibull Weibull Weibull - Weibull TC4 5% 1% 9% Weibull O Probbilistic Ftigue Life Prediction Method for otched Specimens Bsed on the Weest-lin theory Hu Xuteng Xin Pengpeng Song Yingdong College of Energy nd Power Engineering Stte Key Lbortory of Mechnics nd Control of Mechnicl Structures njing University of eronutics nd stronutics njing 2116 bstrct probbilistic ftigue life prediction method for notched specimens ws estblished bsed on the weest-lin theory nd Weibull ftigue life distribution of smooth specimen. Weibull equivlent stress ws derived nd ftigue filure probbility for notched specimen ws formulted bsed on the weest-lin theory nd ftigue strength distribution of smooth specimen. ccording to the reltionship between the Wler equivlent stress nd the chrcteristic ftigue life the chrcteristic life of notched specimen cn be clculted bsed on the Weibull e- quivlent stress. Finlly the life distribution of notched specimens cn be obtined bsed on the ftigue life distribution of smooth specimen. This method ws evluted by the probbilistic ftigue life prediction of TC4 lloy notched specimens nd the prediction result ws compred with the locl stress-strin method. The result shows tht the locl stress-strin method ws very conservtive the method presented in this pper cn predict more ccurtely. The predicted life with 5% filure rte grees well with the test men tested life of TC4 lloy notched specimens. The predicted life with 1% nd 9% filure rte re mostly within the sctter bnd of 2 compred to the test men life. Key words ftigue of mterils crc initition probbility Weibull distribution stress concentrtion ZB xthu@ nu. edu. cn

2 2 165 S- ε- Weibull / P f = 1 - exp - ( 2 * Weibull Tylor 1 * Susmel 2 Ymshit n Δ P r i P r i = exp - ( 1 = exp - ( * n [ Δ * ] Schweiger Weibull m Δ 7 8 Schweiger P r = m P r i Δ = TC4 exp - Δ = exp - m Δ = exp - * * Weibull 4 4 Weibull 9 Weibull Wler Weibull P f = 1 - exp - [ ] 1 Weibull m * * 1 Wler

3 w = 1-1 -γ 5 w Wler P r = n P r i * - n ( w i { [ Δi ] } i i Δ i = n exp - w i Δi * = - w γ Wler 4 Wler w 12 P r = exp - ( w Weibull [ * ] 6 * l Δ i Δ i Δ i i i Δ i Weibull P P r i i i Δ i = exp - ( f = 1 - exp w i [ Δi [ - ( * ] 13 * ] 7 * Weibull w i Δ i Wler * 13 2 exp 8 * 13 Δ i P r = exp - 1 ( w d 12 [ ] 9 * 13 P f = 1 - exp - 1 d w 1 11 Wler - - * - * - Weibull 63. 2% * Weibull = ' f * -b 14 - w = 1 [ w 1 / d ] 11 * = ' f -b 15 1 P f - w = 1 - exp - ( - = * -b 16 w 12 * * 2 b P f = 1 - exp[ - ( * ] 17

4 w = w Wler γ = = /b Wler Weibull - w 14 * 13 2 Wler - 12 K t = 3 TC TC4 3 = - 1 TC TC4 3 4 =. 1 = TC4 Wler -

5 TC4 Weibull Weibull 12 TC4 Weibull = - 1 Weibull ~ 1 5 TC4 Weibull Weibull Weibull 6 TC4 TC TC4 1 /MP TC4 Weibull * 11 Weibull - w 11 Weibull Weibull 11 Weibull n Weibull - w = 1 n w i 1 / [ Δi ] 22 TC4. 1 mm 7 5 TC4 Weibull TC4 Weibull TC4-1 - = 4647 * TC4 TC4 Chboche = /b = 3. 2 / ~ 1 5 TC4 22 TC4 Weibull 2

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