The emission of dislocations from crack tips: A critical assessment

The analytical treatment of dislocation emission at crack tips based on the Peierls concept is critically reviewed. Most treatments are based on the balance of stresses and must make a number of simplifying assumptions. Of special importance is to obtain the correct atomic interaction potential in the emission plane. In the literature, there exist some inconsistencies when combining the continuum concept of linear elastic fracture mechanics with the atomistic considerations of the Peierls model. It is also important to include the energy of ledge formation. Both aspects have a considerable influence on the critical stress intensity for dislocation emission and modify the γus criterion of Rice. It is shown that these shortcomings can be overcome by treating dislocation emission as a variational problem of the crack energy.