Crack Paths 2009

C T O Afrom displacementfields

50

45

y

5.1 and9.6 a

35 40

5.1 and11.8a

y -

(deg )

30

-2.9 and1 4 a

y

25

y

- 5.1 and9.6 b

C T O A

20

5.1 and11.8b

y -

15

105

y -

2.9 and14 b

-25

-20

-15

-10

-5

0

5

10

15

20

-5

Distance from crack tip (mm)

Figure 12: 2D plot of C T O Avalues shown in Figure 11

Results from the calculation of C T O Afrom displacement field measurements have

shown that it is possible to obtain consistent C T O Adata from full field displacement data

measured using DIC. However, adequate measures need to be taken to discriminate data

affected by extensive plasticity close to the crack path and the measurement length effect

discussed earlier. The accuracy and consistency of the C T O Aobtained from the DIC

measured displacements and extraction of data has allowed for C T O Ato be used as a

realistic measure of tearing toughness. Figure 13 demonstrates the capability of the

technique to be able to discriminate the change in tearing toughness caused by material anisotropy which in this particular case was significant.

Cumulative distribution plot of steady state C T O A

100

90

80

TL

70

Probabilit y ( % )

60

50

LT

40

30

20

10

0

3

4

5

6

7

8

9

10

11

C T O A(deg)

Figure 13: Cumulative distribution plot of C T O Avalues illustrating anisotropy

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