PSI - Issue 57

508 Nesrine Majed et al. / Procedia Structural Integrity 57 (2024) 502–509 Nesrine Majed et al./ Structural Integrity Procedia 00 (2019) 000 – 000 7 until the affected depth reaches the value. Figure 7 shows the variation of the fatigue limit of the material as a function of the size of the spherical defect with a variation of its dimension √ from 100 to 900 μm . Experimental results were indicated by Mu et al (2014).

a

b

Figure 7.a shows the Kitagawa diagram for the load ratio = -1. It can be seen obviously that there are two zones: a first plateau zone and a second zone which is characterized by a significant decrease in fatigue limit when the defect size increases. Therefore, it can be concluded that a critical size of the defect is equal to 300 μm . Figure 7.b shows the kitagawa diagram for the load ratio =0.1. It seems that there are also two zones: a first zone characterized by a decrease in fatigue limit when the defect size increases, consequently the fatigue limit is Fig 7. Kitagawa diagram for the cast alloy A357-T6 (a) tension loading, = -1; (b) tension loading, =0.1.