PSI - Issue 39

Mahsa Sakha et al. / Procedia Structural Integrity 39 (2022) 792–800 M. Sakha et al. / Structural Integrity Procedia 00 (2019) 000–000

798

7

Set I

Set II

Set IV

Set III

2

2

2

2

1.7

1.7

1.7

1.7

eff c (MPa m)

1.4

1.4

1.4

1.4

1.1

1.1

1.1

1.1

0.8

0.8

0.8

0.8

0.5

0.5

0.5

0.5

0.2

0.2

0.2

0.2

50

100

110

40

Effective fracture toughness K

75

80

0

0

50

50

-50 0 (degrees)

25

-40

20

0

-100

-80

-10

-25

Kink angle

-150

-50

-40

-120

0 15 30 45 60 75 90 (degrees)

0 15 30 45 60 75 90 (degrees)

0 15 30 45 60 75 90 (degrees)

0 15 30 45 60 75 90 (degrees)

Fig. 3. Comparison of experimental data on θ 0 and K c

eff with the predictions of MTS along with the MERR criterion with different assumptions.

Set II

Set III

Set IV

Set I

2

Experimental data MTS MERR

1.75

eff c (MPa m)

MTS: Neglecting T-stress MERR: Neglecting T-stress

1.5

1.25

1

0.75

0.5

80

Effective fracture toughness K

60

40

20

0 (degrees)

0

-20

-40

Kink angle

-60

0 15 30 45 60 75 90 (degrees) -80

0 15 30 45 60 75 90 (degrees)

0 15 30 45 60 75 90 (degrees)

0 15 30 45 60 75 90 (degrees)

Fig. 4. Comparison of experimental data on kink angle, θ 0 , and the effective fracture toughness, K c

eff ), with the predictions of the MTS, modified

MERR in the presence and absence of T-stress.

and modified MERR criteria are equally accurate in their predictions, provided that both theories include the effect of T-stress in the formulation. The introduced modifications must also be applied to the MERR theory, especially for materials which lack comparable values of shear and tensile fracture toughness, or for cases where the effect of T-stress is significant. The MTS criterion may be attractive in the sense that it is simply implemented; however the MERR is superior to MTS in cases where a shear-based failure precedes opening.