Fatigue Crack Paths 2003

Table 2. Crystallographic orientations on grains A, B, C and D.

Grain Orientation matrix

plSalinpes Preθdi(c°)ted Obsθe(°r)ved Observed slip bands Sfcachtmorid Predicted

α (°)

0,92877 -0,17402 -0,32728 111

89,1

80

88

0,494

-0,0126 0,8676 -0,4971 -111

42,0 18,5 -53,4

0,303 0,289 0,491

grainA

11-1

0,37045 0,46581 0,80361 1-11

-0,98973 0,06073 0,12939 111

27,8

0,372

67,8

0,04522 -0,72573 0,68649 -111

-42,6 84,7

-45

0,451 0,456 0,413

64,3

grain B

11-1

90

120,6

0,1356 0,68529 0,71553 1-11

80,0

76

10,7

0,97879 0,09856 -0,17962 111

-84,2

-76

0,422

117,6

8,3

-0,18265 0,81694 -0,54704 -111

67,2 24,5 -46,6

66

0,468 0,333 0,454

grainC

11-1

51,7 84,8

0,09283 0,56824 0,81761 1-11

0,31749 0,66543 -0,67557 111

-80,1

-60

0,260

22,7

-0,94091 0,3096 -0,13723 -111

42,1 -25,7 -82,3

0

0,493 0,381 0,462

34,5 28,5 87,2

grain D

11-1

0,11785 0,67922 0,72441 1-11

In grain A, the 10° difference observed between predicted and observed θ angles is

quite higher than the 5° accuracy previously assumed. One explanation may be that the

crack path correspond to a combination of two slip planes (the one at 89° and another

one). The observation of steps along the crack path (Fig. 8) is in support of this

asumption.

10 μ m

Figure 8. Optical micrography of the local crack path in grain A showing small steps

(indicated by arrows) along the propagation plane.

In grain D, no correlation has been found between the crack path and the local

activated slip planes and the local crack path looks highly tortuous (Fig. 8). This maybe