Crack Paths 2009

slight increase in C T O Acan be seen in the steady state region suggesting that both

treatments have altered the toughness. This can be seen more clearly when the data is

plotted as a cumulative probablity of CTOA,shown in Figure 7. The data is plotted

only for the steady state region (between 5 m mand 2 5 m min this case). Plateauing of the

curve is a result of the stablising and destablising of data at the beginning and end of the

steady state region. This format emphasises the increase in C T O Awith both burnishing

configurations and confirms that this treatment increases the resistance to tearing.

18

Control

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5.00

10.00

15.00

20.00

25.00

30.00

Stripe

Corridor

d e g )

C T O A(

Crack Length (mm)

Figure 6 C T O Aresistance for two burnished patterns and the control specimen,

burnishing was at 2.12kN in both cases

12468020

)

ilit y ( %

por b a b

C u m u la t iv e

Control

SCotrriipdeor

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

C T O A(deg)

Figure 7 Cumulative probability curves for two burnished patterns and the control

specimen, burnishing was at 2.12kN in both cases

958