Crack Paths 2009

applied max net-section stresses for low and high specimens. It is noteworthy that

t K

t K

the low specimens at the peak stress levels of 420 and 450 M P aexperienced gross

net-section yielding.

15.0

)

m

LowKt

( m

High Kt

z o n e s i z e

10.0

p clasti

5.0

N o t c h

0.0

100.0 150.0 200.0 250.0 300.0 350.0 400.0 450.0 500.0

Appliedstressat net-section(MPa)

Figure 6. Notch plastic zone sizes for low and high .tK

A N A L Y S I S O F S P E C T R U MF C G F O R D I F F E R E N T STRESS

C O N C E N T R A TFIAOCNT O R S

For all three types of specimens under the spectrum loading, F C Gdata were measured

by QF. Huynh et al. [18] analyzed the F C Gdata using the L E F Mapproach and found

the conventional geometry factors failed to correlate the growth rate. Figure 7(a) is the

curves of crack growth rate vs crack length from the notch root of the high specimens t K

at the peak net-section stress of 155 MPa. As can be seen, similar to F C Gfrom notches

under the C Aloading, there are also two “V” shaped curves when cracks are small near

the notch root under the spectrum loading. But, the other three curves seem not

influenced by the notch root plastic zone. More importantly, Figure 7(b) demonstrates

for all five high specimens at the higher peak stress level of 250 MPa, that crack t K

growth rates increase proportionally with crack size, indicating there is no anomalous

behavior of F C Gdue to the notch plastic zone.

F C GRatevs a for High Kt at 155M P a

1.0E-01

S F H )

F C GRate vs a for High Kt at 250 M P a

1.0E-02

1.0E-01

/SFH )

m m /

t (

1.0E-03

1.0E-02

reat , d a / d

m

t ( m

1.0E-04

d a / d

1.0E-03

1.0E-05

reat ,

G r o w t h

1.0E-06

1.0E-04

G r o w t h

1.0E-07

1.0E-03

1.0E-02

1.0E-01

1.0E+00 1.0E+01

1.0E+02

1.0E-05

Crack length, a (mm)

1.0E+00

1.0E+02

1.0E-03

1.0E-02

1.0E-01

1.0E+01

Cracklength, a ( m m )

(a) at the peak load level of 155 M P a (b) at peak load level of 250 M P a

Figure 7. F C Grate vs crack length from notch root for high . t K

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