Fatigue Crack Paths 2003

dΠ

(13)

V J

∝

da

R

R= a

At this point, a useful correspondence may be drawn among N

K

, JL, JV and J. Under

i

mixed modeloadings, for a given V-notch, JL,i is to N

i K as JV is to J-integral of a virtual

embedded crack along the bisector.

y

y

R

2 α

2 α

x

x

R

R

L

a =

L

Figure 2. Frame of reference.

The numerical check of Eqs (4) and (12) performed by FE method is reported in

Table 2. The listed results are relative to the specimens showed in Fig. 3. In order to

minimise the computational errors, using the A N S Y Ssoftware it has been performed

accurate mesh with quad 8 elements. The 2α opening angle was equal to 60° and 135°,

respectively. Note that modeII is singular only in the former case.

F = 1000 N

thickness = 1 m m

40

50

[2deαg]

a

K2N i

K1N

L = 10

[MPa m m ] λ − 1

2 α = 60°−135°

60° 11.66

53.72

F = 1 0 0 0 N

40

200

135° 8.71

28.82

Figure 3. Specimens used for FEAs(dimension in mm).