Crack Paths 2009

εx/εy=0

1

εx/εy=0.5

0.8

0.6

0.4

0.2

0

A

-0.2

0.02W

a)

b)

s/(2ρ/π)

0

0.5

1

Figure 2.a) Meshin the crack area. b) Normalised strain distribution along a crack

with a half-circular tip for uniaxial and biaxial loading, respectively.

R E S U L TASN DDISCUSSION

Several simulations are performed with different combinations of threshold values and

degrees of biaxiality. In most cases, crack growth during 2000 load cycles is followed

giving a final crack length of approximately 0.02W. The crack pattern and the growth

rate of the cracks branches are studied.

Crack paths

A selection of the resulting crack patterns from the simulations is shown in Table 1 for different combinations of threshold value, εth, and degree of biaxiality, x∞ y∞ ε ε / . Many

different patterns are obtained, both unbranched and branched. For high values of x∞ y∞ ε ε / crack branching seems to be promoted in most cases, and vice versa. This could

be expected since the strain distribution for larger stress biaxiality along the crack front

is less concentrated to the very tip than for a crack subjected to a dominating

perpendicular external load direction. Figure 2.b shows the normalised strain distribution along a crack with a half-circular tip for uniaxial ( x∞ y∞ ε ε / =0) and biaxial

x∞ y∞ ε ε / =0.5), respectively. The point A indicates where the circular part of the

loading (

crack surface changes into the straight, see also Fig. 1.a. With biaxial loading, the

strains do not decrease as much as for the uniaxially loaded crack, since the horisontal

load comtribute to the straining of the crack flanks significantly more than to the strain

at the very front of the crack. With the same threshold value as for the uniaxial case, a

larger part of the crack surface will dissolve, and toghether with the lower decline of

strains with biaxial load, thus, leading to broader and more blunt crack tip. This will in

turn make it more possible to reach a situation where the strain distribution shows two

maximaand branching may occur.

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