Modeling of impact-induced spall fracture and post spall behavior of a circular plate

The ductile spall fracture and post-spall behavior of a circular target plate after impact with a flyer plate having small diameter, is modeled by means of a viscoplastic constitutive theory that includes the microvoid volume fraction as a scalar material damage variable. Incorporation of the damage parameter permits description of rate-dependent, hardening, compressible inelastic deformation and ductile fracture, where local fracture is defined in terms of a critical microvoid volume fraction. Multidimensional axisymmetric strains are developed where, because of the edge effect of the smaller flyer plate, nonplanar as well as planar waves are generated. Numerical simulations demonstrate the destructive effect of increasing the velocity of impact. They also illustrate the influence of varying the viscosity parameter associated with the microvoid growth on the development of damage. The change in location of the spall fracture caused by reduction of the flyer plate thickness is shown, as is the fragmented behaviour of the target up to 50 μs after initiation of the spall fracture.