Abstract
Subcritical crack branching along the primary austenite grains during the plane-strain fracture toughness test of ultra high strength low-alloyed steels was simulated by a computer procedure using the two-dimensional Voronoi cells as the grain network. The corresponding crack tip shielding effect was calculated. Results confirm that mainly this effect can be considered to be responsible for the observed increase in K_Ic of coarse grain structures obtained by the application of high austenitizing temperatures. The predicted amount of shielding is comparable with that of the previously published models based on a regular hexagonal grain network.

Key words
low-alloyed steels, subcritical crack branching

Full text not available