Propagation of Slepyan's crack in a non-uniform elastic lattice
  We model and derive the solution for the problem of a Mode I semi-infinite crack propagating in a discrete triangular lattice with bonds having a contrast in stiffness in the principal lattice directions. The corresponding Green's kernel is found and from this wave dispersion dependencies are obtained in explicit form. An equation of the Wiener-Hopf type is also derived and solved along the crack face, in order to compute the stress intensity factor for the semi-infinite crack. The crack stability is analysed via the evaluation of the energy release rate for different contrasts in stiffness of the bonds. 
Michael Nieves, Alexander Movchan, Ian Jones and Gennady Mishuris
math-ph math.MP