Abstract：For mixed mode I-II cracks, the plastic zone distribution around crack tips is analyzed theoretically. Two groups of parameters which can be used to evaluate the effect of stress state on crack fracturing are introduced, and the local plastic deformation is considered. In this study, we adopt the following two assumptions: (1) cracks propagate in the direction in which the plastic core region boundary is the shortest to the crack tip; (2) once the radius from crack tip to the shortest plastic core region boundary reaches the critical radius, the crack start to propagate. Based on these assumptions, a new fracture criterion is developed, and the comparisons with the existing fracture criterions and the experimental results are conducted. The results show a well-de?ned correlation between the experimental data and the results according to the new fracture criterion. In addition, some discussions on the limitations of the criterions which are established just by single KIC or single KIIC and the necessity of considering the crack tip’s stress state are presented.
2013, Vol. 34 
