Fatigue Crack Paths 2003

T and T + 1 and K (s; T) the SIF at step T, both at point 5 of the front.

Next section shows how the advance 60(5; T) is obtained in both fatigue and brittle

fracture by a Paris’ type law, involving the SIF. Second section shows howto update this

SIF using Bueckner-Riceweight function theory.

Z

Figure 2: Small (magnified on the figure for the sake of visibility) perturbation of the

crack front .73.

Propagation Laws

In fatigue, propagation can be described by the Paris’ law :

(9a — I C A K" (9T ( )

where deb/(9T denotes the rate (T could be interpreted as “kinematical time”) of crack

advance at any position on the crack front, A Kthe amplitude of the cyclic modeI SIF at

that point, and C and n positive material constants.

This could be written :

K(S;T)))"

(1)

5Q(S;T) I 56011660)

Where ||KO0 (T) I sup K(s; T), dammh)the maximumdistance between step T and

56]:

T + 1.

In brittle fracture, Irwin’s criterion reads :

K < Kc I> no propagation (60 E 0)

K I Kc I> possible propagation (6a 2 0)