PSI - Issue 52

Akihide Saimoto et al. / Procedia Structural Integrity 52 (2024) 323–339 A. Saimoto et al. / Structural Integrity Procedia 00 (2023) 000–000

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The e ff ect of the angle α between the material principal axis and the physical coordinate system on the SIF was plotted in Fig.7 for the case where h / b is fixed at 1.0. In the case of material type I-1, which is most close to a homogeneous isotropic material, SIFs are independent of the angle α for both modes I and II and maintain almost a constant level. On the other hand, for materials type II and type III, which are more anisotropic, the SIF strongly depends on the angle α . The dependence seems quite complicated. F I tends to reach a maximum value when α is near 60 ◦ and 150 ◦ . It was found that the range of variation of F II is about 1 / 5 that of F I . The value of F II varies with angle α , but was always positive. This indicates a tendency for the two parallel cracks to propagate in the direction of increasing their distance rather than merging from each other. The e ff ect of a ratio h / b on the SIF was plotted in Fig.8 for the case where the angle between the material principal axis and the physical coordinate system α is fixed at 60 ◦ .As h / b increases, F I approaches 1.0 and F II converges to 0.0 for all materials. This means that the interference e ff ect disappears as the distance between the two cracks increases, approaching a single crack condition. In the limit where the ratio h / b approaches zero, the two cracks behave as a single crack, and the value of F I can be considered to asymptotically approach 0.5, independent of the type of material and the value of angle α .

1.300

0.075

0.050

1.200

0.025

1.100

0.000

-0.025

A'

B'

1.000

A B

-0.050

0.900

-0.075

0.1

1

10

0.1

1

10

Fig. 9. Normalized SIFs F A

I and F A II at outer crack tip A for α = 0 ◦ condition for the problem of step cracks (Fig.5(b)).

1.300

0.100

0.075

1.200

0.050

1.100

0.025

0.000

1.000

A'

B'

-0.025

A B

0.900

-0.050

0.800

-0.075

0.1

1

10

0.1

1

10

Fig. 10. Normalized SIFs F A

I and F A II at outer crack tip A for α = 60 ◦ condition for the problem of step cracks (Fig.5(b)).