Fatigue Crack Paths 2003

amount of detailed, empirical information is available on the transition, for example in

Ref. [27].

Figure 12. Transition to slant crack growth under fatigue loading.

Figure 13. ModeIII crack with element of ModeIbranch crack.

Figure 14. Section through twist crack perpendicular to crack growth direction.

Twist Cracks

In the presence of ModeIII displacements on an initial crack a ModeI branch crack can

only intersect the initial crack at one point. This is shown in Fig. 13 for a pure ModeIII

initial crack. Under a loading which includes Mode III a number of Mode I branch

cracks may be initiated along the initial crack front and, as crack growth proceeds, these

may link up to produce what is called a ‘twist’ crack, [2, 11, 30]. Figure 14 shows a