Crack in a lattice waveguide

We consider some structures where the harmonic ‘feeding’ wave localized at the crack faces can force the crack to grow. First, we present some results related to a lattice with a high-contrast layer, where the wave speed is larger than in the ambient matrix. The analytical solution obtained for the steady-state regime, where the crack speed is independent of the wave amplitude, is used to determine the energy relations and the wave-amplitude-dependent position of the crack front relative to the feeding wave. The corresponding numerical simulations confirmed the existence of the steady-state regime within a range of the wave amplitude. For lager amplitudes the simulations revealed a set of ordered crack-speed oscillation regimes, where the average crack speed is characterized by a stepwise dependence on the wave amplitude. We show that the related cluster-type wave representation allows the average crack speeds to be determined analytically. We also show the connection between the cluster representation and the ‘local’ crack-speeds within the cluster. As an example of a continuous system, where the crack can uniformly grow under the localized harmonic wave, an elastic flexural plate is considered. Both symmetric and antisymmetric fracture modes are examined.