PSI - Issue 26

S.M.J. Razavi et al. / Procedia Structural Integrity 26 (2020) 240–245 Razavi et al. / Structural Integrity Procedia 00 (2019) 000 – 000

245

6

L = 1

L = 0

35

35

(a)

(b)

30

30

25

25

20

20

15

15

teta = 0 teta = 15 teta = 30 teta = 45

teta = 0 teta = 15 teta = 30 teta = 45

10

10

Half crack length (mm)

Half crack length (mm)

L = 0

L = 1

5

5

0E+0 1E+5 2E+5 3E+5 4E+5 5E+5 6E+5

0E+0

1E+5

2E+5

3E+5

4E+5

Number of cycles

Number of cycles

Fig. 4. Fatigue crack growth life for different loading conditions

5. Conclusion

The effects of mode mixity on the biaxial loading condition was studied numerically in center cracked cruciform specimens made of 6061-T651 aluminum alloy. All specimens with initial crack angle experienced the mixed mode loading conditions. In the specimens with zero initial angle , the biaxiality ratio of loading didn’t affect the FCG path. For the biaxiality ratio of L = 1 the fatigue crack propagated on its initial angle and the FCG trajectory didn’t changed. The FCG life behavior for the specimen under biaxial loading of L = 1 is unlike the behavior of the specimen under uniaxial. For this loading condition, increasing the initial crack angle decreased the FCG life. The related results are limited to specific biaxiality ratios investigated in this paper; the same approach can be developed to estimate the FCG behavior of cracked specimens under more loading. AFGROW®, Fracture mechanics and fatigue crack growth analysis software tool. Ver 4.12.15.0, LexTech, Inc, 2008. Anderson, P.R.G., Garrett, G.G., 1980. Fatigue crack growth rate variations in biaxial stress fields. International Journal of Fracture 16, R111 – R1116. Ayatollahi, M.R., Razavi, S.M.J., Chamani, H.R., 2014a. A numerical study on the effect of symmetric crack flank holes on fatigue life extension of a SENT specimen. Fatigue & Fracture of Engineering Materials & Structures 37(10), 1153-1164 Ayatollahi, M.R., Razavi, S.M.J., Chamani, H.R., 2014b. Fatigue life extension by crack repair using stop-hole technique under pure mode-I and pure mode-II loading conditions. Procedia Engineering 74, 18-21. Ayatollahi, M.R., Razavi, S.M.J., Yahya, M.Y., 2015. Mixed mode fatigue crack initiation and growth in a CT specimen repaired by stop hole technique. Engineering Fracture Mechanics 145, 115-127. Ayatollahi, M.R., Razavi, S.M.J., Sommitsch, C., Moser, C., 2016. Fatigue life extension by crack repair using double stop-hole technique. materials science forum 879, 3-8. Kitagawa, H., Yuuki, R., Tohgo, K., 1981. Fatigue crack propagation behavior under mixed mode conditions (KI and KII). Transactions of the Japan Society of Mechanical Engineers, Part A 47(424) 1283-1292. Liu, A.F., Dittmer, D.F., 1978. Effect of multi-axial loading on crack growth, technical summary. Air force flight dynamics laboratory report AFFDL-TR-78-175. 1 – 3. Razavi, S.M.J., Ayatollahi, M.R., Sommitsch, C., Moser, C., 2017. Retardation of fatigue crack growth in high strength steel S690 using a modified stop-hole technique. Engineering Fracture Mechanics 169, 226-237. Tanaka, K., Akiniwa, Y., Kato, T., Takahashi, H., 2005. Prediction of fatigue crack propagation path from a pre-crack under combined torsional and axial loading. Transactions of the Japan Society of Mechanical Engineers, Part A 71(704), 607-614. Yuuki, R., Akita, K., Kishi, N., 1989. The effect of biaxial stress state and changes of state on fatigue crack growth behavior. Fatigue and Fracture of Engineering Materials and Structures 12(2), 93 – 103. References