Crack tip fields for rapidly growing cracks in viscoplastic materials

A fast propagating crack in a visco-plastic material of Perzyna-type is considered by two different methods. First, the problem of an semi-infinite crack in an infinite plate is examined. An analytical investigation leads to a system of ordinary differential equations, which is solved numerically by a multiple shooting-method. To I,rove the physical significance of the resulting crack tip fields a mixed Finite Element formulation is introduced in the second part which is applied to the boundary value problem of a running crack in an infinite strip under steady state conditions. Results regarding to the extension of the dominance zone are presented.