Fracture energy effect on spall signal

Numerical simulations of flying plate impact test usually show discrepancies between the calculated and observed velocity vs time plot under spalling conditions. Very often these differences are ascribed either to the constitutive model or to the numerical scheme. In this paper it is shown that, at least in the case of ductile metals, these differences can be the understood as the presence of a dissipation process during fracturing due to the viscous separation of spall fracture plane surfaces. An advanced CDM model for ductile metals has been used in order to simulate soft spall in metals and standard fracture mechanics concepts have been used to estimate the fracture energy dissipated during the separation of the fracture surfaces.