Asymptotic study of the interfacial crack with friction

We study a model of interfacial crack in which contact of the crack faces obeys a Coulomb law of friction. For such cracks, the possibility that the stress has a stronger singularity than r^{- 1/2} near the tip has been reported. In this paper, we demonstrate that these strong singularities can, in fact, be discarded, because they would assume a backward propagation of the crack. In passing, we prove that near-tip slip is possible in one direction only, which is imposed by the sign of the elastic mismatch. The locking of the stress intensity factor during a non-monotonic cycle of loading is pointed out, as well as the formation of a bubble near the tip under certain loading conditions.