PSI - Issue 36

Ivan Pidgurskyi et al. / Procedia Structural Integrity 36 (2022) 190–196 Ivan Pidgurskyi, Mykola Stashkiv, Mykola Pidgurskyi et al. / Structural Integrity Procedia 00 (2021) 000 – 000

192

3

N coal

N crack

Fig. 1. Calculation schemes for estimating the fatigue crack growth life N coal during the coalescence stage of two identical coplanar surface cracks and the residual durability of a structural element with the major surface crack formed after the cracks coalescence. 3. Influence of the shape of the contour of identical surface cracks during coalescence on the fatigue crack growth life of the plate under uniaxial tension The coalescence of surface cracks was simulated for two cases. In the first case, surface cracks with small almost identical semi-axes on the surface were modeled: c = 1.25 mm and 1.28 mm and different depths a = 1.0 mm and 1.28 mm (see Table 1). In the second case, larger surface cracks with the same lengths of the semi-axis on the surface c = 5.5 mm and different depths a = 2.2 mm; 5.5 mm; 8.648 mm were modeled. The shape parameter of the merging surface cracks was significantly different: a/c = 0.4; 1.0 and 1.57, respectively (see Table 1).

N crack , cycle ∙ 100% 1.48E+06 4.85

Table. 1. Comparative data on the influence of the contour shape of surface cracks on the durability of samples during coalescence of the cracks.

№

c, mm

a, mm

4 c, mm

a/ 4 c

σ n , MPa

N coal , cycle

a/c

a/t

R

1 2 3

1.25 1.28 1.79

1

0.80 1.00 1.56

0.05

5

0.20 0.25 0.39

150 150 150

0 0 0

7.17E+04* 4.80E+04* 5.27E+04* 6.34E+04* 6.33E+04** 2.15E+04* 2.74E+04**

1.28 2.79

0.064

5.12 7.16

1.29E+06 6.98E+05 2.37E+05 2.37E+05 1.19E+05 1.19E+05 7.60E+04 3.20E+05

3.73 7.55

0.1395

26.80 26.74 18.11 23.03 25.69 28.13 34.71

4

5.5

2.2

0.40

0.11

22

0.10

187.5

0.25

5

5.5

5.5

1.00

0.275

22

0.25

187.5

0.25

6 7 8

5.5

8.648

1.57 0.79 0.60

0.4324

22

0.39 0.20 0.15

187.5

0.25 1.95E+04**

5.26

4.16

0.208 0.565

21.04

- -

0.1

9.00E+04***

18.725 11.3

74.9

-

4.20E+04**** 12.1E+04

* - calculation according to the formula (2) ** - calculation according to the FEM modeling using discrete values of SIF

*** - experiment (Kishimoto et al. (1989)) **** - experiment (Bezensek et al. (2004))