1Tel Aviv University, Tel Aviv, Israel
2Institute for Industrial Mathematics, Beer Sheva, Israel
3Clarkson University, Potsdam, New York, U. S. A.
Plane, periodic, square-cell and triangular-cell lattices are considered. The lattices are assumed to consist of point particles connected by mass-less viscoelastic bonds. Homogeneous and inhomogeneous problems for dynamic crack propagation, as a consequence of breaks of the bonds, are studied. The unbounded square-cell lattice as well as a square-cell lattice strip is used for the fracture mode III, while the unbounded triangular-cell lattice is used for the fracture modes I and II. Dependences for the global/local energy-release-rate ratio, stresses and elongation of the breaking bonds as well as the crack opening displacement are derived. Comparative results for the energy release rate are obtained for viscoelastic lattices, homogeneous viscoelastic materials, elastic lattices and homogeneous elastic materials. The energy release ratios are found which show the influence of viscosity, discreteness, cell size, strip width and crack speed on wave-viscous resistances.