Crack Paths 2009

ij S versus the uncracked ligament W / b i were estimated

The separation constants

from the constant separation parameter region in Fig. 4. The straight line fits through

()

) / l oSgi( ilWojgb−curve for the tension specimen is

these points and the slope of the

the mixed mode plastic

p l η factor for the value of W / a=0.4…0.6 (Fig. 5).

0,08

0,04

0,00

gSi j

o

n=10

0

o

-0,04

lo

15

o

30

o

45

-0,08

o

60

o

75

-0,12

-0,36

-0,24

-0,20

-0,40

-0,32

-0,28

log(bi/W)

versus

( ) i j S l o g

log( W) b/ i

for different angles of an inclined

Figure 5. Variations of

crack under tension.

pl η and

The calculated plastic

CODplη factors decrease with the increase of the crack

θ (Fig. 6). The results obtained by Smith et al. [2] show similar trends

orientation angle

of the mixed mode p l η factor for the single edge notch tension specimens (SENT) of

A508 Class 3 forged steel subjected to combination of modes I and II. It should be

pointed out that the mixed mode plastic

p l η factor is a function of both the crack angle

orientation and the strain hardening exponent. The calculated mixed mode plastic CODplη factor is also changed with the crack orientation angle (not shown), but

pl η over the whole domain of the angleθ.

CODplη exceeds the value of

At the same time, to characterise the mixed I+II mode loading, it was recommended

to employ the mixity ratio which was defined through the applied elastic parameter

e M [ 7 ]

KK

(1)

= M arctan2π e

⎟⎟⎠⎞⎜⎜⎝⎛ II

460