Mixed-mode cleavage front branching at a high-angle grain boundary

In a previous study it was observed that a cleavage front can penetrate through a high-angle grain boundary in either regular or irregular mode. In this article, we report the third mode, which has a self-similar characteristic. In this mode, the cleavage front branches into a number of segments and the breakthrough points are in clusters, which can be regarded as the combination of regular and irregular processes. A first-order analysis is performed to estimate the boundary fracture resistance.