PSI - Issue 28

Yifan Li et al. / Procedia Structural Integrity 28 (2020) 1140–1147 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1145

6

0.6

0.3

0.0

-0.3

-0.6

T*

-0.9

-1.2

D/W=0.4 D/W=0.5 D/W=0.6

-1.5

2 a /W=0.8

0

10

20

30

40

50

60

70

 (  )

(c) T * Fig. 5. Dimensionless parameters versus orientation angle for different preset hole diameters: (a) dimensionless parameter Y I , (b) dimensionless parameter Y II , (c) dimensionless parameter T * . It can be observed from Figs. 4 and 5 that when is equal to zero, Y II = 0 and the specimen is subjected to pure mode I loading. The dimensionless parameter Y I decreases as the orientation angle increases, but the mode II geometry factor Y II has the opposite tendency. Pure mode II fracture, by definition, occurs when the mode I stress intensity factor K I =0 and the mode II stress intensity factor K II ≠0 (Ayatollahi and Zakeri 2017). From Figs. 4(a) and 5(a), it can be seen that the mode I geometry factor Y I becomes equal to 0 when the orientation angle increasing to a specific value, so this type of specimen can be used to conduct a series of fracture tests for the full range of mode mixities including pure mode I and pure mode II. For larger orientation angles, Y I decreases to a negative value and the specimen is considered to be subjected to compression shear loading. It can be seen from Figs. 4(c) and 5(c) that T * can obtain both positive and negative values. T * is negative for pure mode II conditions in most cases and approaches positive value by decreasing the orientation angle. The orientation angles for pure mode II fracture vary with the relative crack length 2 a /W and hole diameter to plate length ratio D/W is shown in Fig. 6. As can be seen from this figure, the orientation angle II increases by increasing the relative crack length 2 a /W at a constant ratio D/W. It can be also seen from these curves that the orientation angle II decreases when the hole diameter to plate length ratio D/W enhances in a fixed crack length ratio 2 a /W.

D/W=0.4 D/W=0.5 D/W=0.6

68

66

64

  ()

62

60

58

0.4

0.5

0.6

0.7

0.8

0.9

2 a /W Fig. 6. The orientation angle II for different values of 2 a /W and D/W.