THE STATISTICS OF CRACK BRANCHING DURING FAST CRACK PROPAGATION

Abstract

We present simple theoretical ideas which allow an understanding of part of the scaling laws recently observed on branched fracture surfaces. Some of these are argued to be common to all critical branched structures, which barely survive when propagating. This is exemplified by numerical results on the directed percolation cluster, which serves as a good toy-model. Finally, we propose a Langevin equation for unbranched cracks in three dimensions, which naturally leads to self-affine structures.