Crack Paths 2006

concentrations in terms of corner points, and the effect of this strikes plane 3, being

closest to the simplified area, the worst. It is also expected that a longer last segment l

reduce the effects of the simplifications since the stress concentration at the crack tip

gets further away from the simplified area.

Comparison of the resolved shear stresses

In the second part of the comparison between the three models, an analysis of the

resolved shear stress at the nucleation points in front of the crack at maximumload was

performed. The stresses were calculated along the same three planes at the possible

nucleation positions, corresponding to the first investigation, and the results are seen in

Fig. 6.

2.05

2

1.95

2

1.9

1.95

1.85

1.9

1.8

3. 11.7885 78

4.

3

4

5

6

7

8

9

11..6775 67

5

6

7

8

9

crack segments

2.

crack segments

3

4

1.

1.15 -100-10

3

4

5

6

7

8

9

=6 : correct model model with three crack segments m t four crack seg 16 cor ect mode o e h thr crac mo h four rack l b s u<¡ b c rdec oh t e t fou ack 6 o ect l o h ra m r

-0.71

-0.72

--00..67987654 987654

crack segments

-0-.015 -.15

6 crack segments 6 7 k t 7

3

4

5

8

9

Figure 6. Nucleation stress,

slip, as function of number of crack segments for the three

different models for two different lengths, l, of the last crack segment.

slip, is calculated along plane 1 in Fig. 1.2 as

In Fig. 6.1 the resolved shear stress,

function of the number of crack segments describing the crack. It is seen that the model

with four crack segments shows excellent agreement with the values from the correct