THE INFLUENCE OF GRAIN-SIZE, TEMPERATURE AND STRESS STATE ON BRITTLE-FRACTURE OF STEEL

The influence of grain size on brittle fracture properties was investi gated in low and medium carbon contents (0.1 and 0.48%) steels. The re sults indicated that resistance against brittle fracture evaluated by standard Charpy V-notch test in comparison with dynamic fracture tough ness may give contradictory information about influence of microstruct ure. In presented paper, it is pointed out at connection of that findi ng with expressively different temperature dependence of plastic zone size at initiation of brittle fracture in the notched specimens agains t the specimens with fatigue crack.