An initially unloaded, semi-infinite, stationary crack is assumed to kink or bifurcate at time t=0 and the new crack tip(s) propagate out along a straight line at a constant velocity vCT. A Green’s function, consisting of a dislocation whose Burgers vector is growing linearly with time, that is suddenly emitted from the tip of a stress-free semi-infinite crack and propagates out along the kinked crack line at constant velocity u, is used to form a Cauchy singular integral equation. This equation is solved using standard numerical techniques and the stress-intensity factor is obtained as a function of crack-tip speed vCT and kink angle δ. The bifurcation case is treated in a similar manner. Finally, some conclusions concerning crack initiation and propagation are drawn.

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