PSI - Issue 59

Jesús Toribio et al. / Procedia Structural Integrity 59 (2024) 90–97 Jesús Toribio / Procedia Structural Integrity 00 ( 2024) 000 – 000

94

5

i

j

k

  

  

b a

a

h x

  

  

  

  

2

7

2

    0 0 0 i j k

Y

M

O

O



(10)

O

ijk

D

O

where a O /b O is the crack aspect ratio to fatigue pre-crack, a H /b H is the same factor after HE, and the values of M ijk are given by Shin and Cai (2004) and reproduced in Table 4. Regarding a O /b O , previous studies confirm that for the values of dimensionless crack length used in this study ( a O /D  0.30, cf. Table 3), fatigue pre-crack aspect ratio ( a O /b O ) is close to 0.78 (Athanassiadis et al., 1981; Caspers et al., 1986). Consequently, this value was used to calculate Y O according to eq. (10). On the other hand, it was observed experimentally in fracture surface of samples submitted to hydrogen damage that TTS zone can be fitted to an elliptic shape (Fig. 3) and, therefore, it seems to be adequate to use eq. (9) in order to obtain the value of Y H .

Fig. 2. Crack characterization (Shin and Cai, 2004).

Fig. 3. The TTS zone modelled as a semi-elliptical crack.

4. Model results In the present paper, the values of SIF in harsh environment ( K H ) are analyzed in different cracked wires where the shape of the TTS region varied from a semicircular shape ( a H /b H =1) to a limit case of a TTS region of straight