Crack Paths 2009

effective 1 was found to enhance it. Very limited influence of mode I on ∆KII

was found

sequential

performed for

for

simulations

but

loading,

here

∆KI=15Mpa√m,∆KII=20Mpa√fomr a much softer ferritic-pearlitic

steel in a previous

study [5] have shown that for such loading, the residual crack tip opening increases

from cycle to cycle. This effect, which would probably be observed in maraging steel at higher ∆KI is likely to reduce crack faces interference and increase ∆KIIeffective.

Note that for similar nominal loading ranges, ∆KI=10Mpa√mand ∆KII=20Mpa√m, variations in the loading path lead to variations in ∆KIeffective from 7.9 to 10Mpa√mand

in ∆KIIeffective

from 11.1 to 20Mpa√m!Such differences in effective loading can produce

differences in crack paths and growth rates.

12 90°out-of-phase mixed-mode+staticmodeI rev rsedmixed-mode sMoedquIeIn+cset tic I ∆KInominal(MPa√m) 2 m

a)

b)

0,246801 0 2 4 6 8 10 246801 9 t- - h se mix d o s r v s i sMoedeI s t 246801 9mrsM 246801 9mrsM

14

16

0,0246 0246

1,12 12 12

0,8

0,0246

mixed-mode+staticmodeI

reversedmixed-modeor90°outof

phase

modeI+staticmodeII

0

5

10

15

20

25

30

∆KIInominal(MPa√m)

Figure 3: Mutual influence of mode I and mode II on the effective fraction of ∆ Kof

the other mode(h=10µm, p=180µm) a) ∆KII=20MPa√amnd b) ∆KI=10MPa√m.

Figure 4: crack paths for a) sequential mixed-mode loading (C1) b) in-phase mixed

mode+ static modeI (D) c) fully reversed 90° out-of-phase mixed-mode (F).

410