PSI - Issue 38

Benaouda Abdellaoui et al. / Procedia Structural Integrity 38 (2022) 116–131 Benaouda Abdellaoui et al / Structural Integrity Procedia 00 (2021) 000 – 000

128

13

2 = 10 6 . 2,5 10 + 10 5 . ( ∑ ( + 0,25) 10 =12 =2,5 3 = 10 6 . 2,5 10 + 10 5 . ( ∑ ( + 0,25) 10 =9 =2,5

Here is the calculation for pivot 2 and 3

) + 81 000 . 5,75 10 = 9,636 . 10 12 (8)

(9)

) + 56 153 . 5 10 = 1,884 . 10 12

The order of magnitude of the endurance limit at 10 6 cycles is estimated by: ( = 10 6 ) = ( 2 + 3 2. ) 1 = ( 9,636 . 10 12 + 1,884 . 10 12 2 . 10 6 ) 1 1 0 = 4,74 (10) The result on pivot 4 confirms the estimate of the endurance limit given to us by the results obtained from the locati method [9] on pivot 2 and 3. Failure analyses have been performed on fatigue samples. For all tested specimen, the crack is located in a branch at the level of a section change zone as it may be seen in Fig. 11 to Fig. 13. There is no significant plastic deformation or necking ( local section reduction) phenomenon. Fracture surfaces were investigated.

Fig. 11. Pivot 2 crack

Fig. 12. Pivot 3 failure