Abstract
On the basis of the local stress criterion, Beremin explained successfully scatter and dependence on temperature and plate thickness in fracture toughness. According to the current fracture model of micro-mechanism, however, initiation of cleavage is controlled not only by the local stress but also by plastic strain to induce cracks of cementites as fracture triggers. Furthermore, the critical fracture stress increases with increase in plastic strain. In the present paper a modification of the Beremin model is proposed to take into account these effects of plastic strain on fracture. The new model can predict the above mentioned characteristics of cleavage fracture as well as the Beremin model. In addition, the new model can explain that fracture initiation points may distribute on either side i.e. a near side or a remote side of the stress maximum around notch tip.
