  Dynamic Mode III interfacial fracture in a dissimilar square-cell lattice,
composed of two contrasting mass-spring lattice half-planes joined at an
interface, is considered. The fracture, driven by a remotely applied load, is
assumed to propagate at a constant speed along the interface. The choice of the
load allows the solution of the problem to be matched with the crack tip field
for a Mode III interfacial crack propagating between two dissimilar continuous
elastic materials. The lattice problem is reduced to a system of functional
equations of the Wiener-Hopf type through the Fourier transform. The derived
solution of the system fully characterises the process. We demonstrate the
existence of trapped vibration modes that propagate ahead of the crack along
the interface during the failure process. In addition, we show as the crack
propagates several preferential directions for wave radiation can emerge in the
structured medium that are determined by the lattice dissimilarity. The energy
attributed to the wave radiation as a result of the fracture process is studied
and admissible fracture regimes supported by the structure are identified. The
results are illustrated by numerical examples that demonstrate the influence of
the dissimilarity of the lattice on the existence of the steady failure modes
and the lattice dynamics.
